WO2011085123A1

WO2011085123A1 - Automated handling of electro-optical transducers used in lcd test equipment

Info

Publication number: WO2011085123A1
Application number: PCT/US2011/020409
Authority: WO
Inventors: Kent Nguyen; Kaushal Gangakhedkar; Neil Nguyen; Steve Aochi; Ngan Do
Original assignee: Photon Dynamics, Inc.
Priority date: 2010-01-08
Filing date: 2011-01-06
Publication date: 2011-07-14
Also published as: JP3180834U; TWM527544U; KR200476873Y1; TW201140087A; CN202903959U; KR20120006369U

Abstract

An LCD test system includes inspection heads, holders, a stage assembly and means for securing electro-optical transducer elements to the inspection heads. The one or more holders are adapted to house electro-optical transducer elements. The holders are placed on the stage assembly which is adapted to transfer the electro-optical transducer elements to the inspection heads using a computer control system. The LCD test system may also include cleaning stations and a stage assembly adapted to hold and move the cleaning stations. The cleaning stations are adapted to receive and house the electro-optical transducer elements.

Description

AUTOMATED HANDLING OF ELECTRO-OPTICAL TRANSDUCERS

USED IN LCD TEST EQUIPMENT

CROSS-REFERENCES TO RELATED APPLICATIONS

[0001] The present application claims benefit under 35 USC 1 19(e) of U.S. provisional application number 61/293,579, filed January 8, 2010, entitled "AUTOMATED HANDLING OF ELECTRO-OPTICAL TRANSDUCERS USED IN LCD TEST EQUIPMENT," the content of which is incorporated herein by reference in its entirety.

BACKGROUND

[0002] The present invention relates to the machines for the electrical inspection of Thin Film Transistor (TFT) arrays used in Liquid Crystal (LC) or Organic Light Emitting Diode (OLED) Displays. [0003] In the manufacturing of flat panel liquid crystal displays various inspection stages are performed in order to identify defects in the manufactured displays. One type of inspection is electrical inspection of Thin Film Transistor arrays used in the displays. An example of such an array tester is Array Checker AC5080 commercially available from Photon Dynamics, Inc. an Orbotech Company of San Jose, CA. [0004] The array tester (alternatively referred to herein as "Array Checker" or "AC") may identify defects in LC displays through use of a Voltage Imaging ® test apparatus and method as described, for example, in US Patents 4,983,911 , 5,097,201, and 5,124,635. Because LC displays are comprised of an array of pixels, when the LC display is driven electrically, some pixels associated with defects may behave electrically differently than the normal pixels, and thus such differences may be detected using a voltage imaging® sensor.

[0005] These voltage imaging ® sensors typically rely on electro-optical transducers, which in turn may be based on LC materials (such as Nematic Curvilinear Aligned Phase or Twisted Nematic molecules) or other electro-birefringent crystals (e.g. Pockels Crystals, such as LiTa03 or LiNb03). In the case of Orbotech's Array Checker, the electro-optical material is affixed to a glass carrier weighing about 5 lbs., on which it is sandwiched between a transparent electrode and a reflective film. The resulting assembly is referred to as a

"Modulator", identified in Figure 1A using reference numeral 10. Referring to Figure IB, modulator 10 is installed in a modulator air bearing mount 20 attached to an optical lens assembly 40 topped by an imaging sensor (such as a CCD camera) 60. An illuminator 80 is attached to camera 60. The constituted assembly is referred to as Voltage Image Optical System (VIOS) 100 - as shown in Figure 1.

[0006] Figure 2A and Figure 2B are front and top views, respectively, of a schematic drawing of the modulator air bearing mount 20. Referring to Figure 2 A, during inspection, the modulator is placed at a small enough distance from the TFT glass panel 210 under test to ensure substantial capacitive coupling between the electro-optical transducer (modulator) and the pixel electrodes on the panel. This distance, typically around 25-80 um, is maintained by an air bearing using a number, e.g. 3, of injectors 220 with adjustable flows. A modulator sense feedback analog signal 225 measures the bias voltage applied to the transparent electrode on the electro-optical material. The modulator mount includes a set of clamps 230 that can grab and position or release the modulator. The clamps are adapted to be

pneumatically actuated to secure the modulator to the inspection head. Figures 2A and 2B also show a modulator receiving recess 235 in float plate 240. The float plate is secured to modulator mount 250. Furthermore, each modulator may have its own RFID tag 260 which can be sensed by an RFID reader 270 on the inspection head. [0007] Access to modulators or similar electro-optical transducer assemblies in array test systems is required for a number of reasons, such as:

1) Removal/Installation of electro-optical transducer elements;

2) Cleaning of the sensing (panel-side) surface of the electro-optical transducer elements to remove particles and other debris interfering with the testing process and possibly damaging the panel under test, as well as to optimize the lifetime of the transducer elements themselves;

3) Adjustment of the air bearing settings in order to ensure a modulator is level above a plate under test and flies at the correct height. Typically this adjustment is done after every modulator exchange or whenever an adjustment is needed to maintain proper signal strength and uniformity.

[0008] The above processes currently involve intensive manual handling of the electro- optical elements and hence require physical access to the inspection heads inside the system. However, as the size of the glass on which the displays are fabricated increases, so does the size of the equipment used in the fabrication process, among which are the array test systems. Also, in order to keep the throughput adequate, the number of inspection heads increases as the glass size increases. For instance, Gen5 (1100 mm x 1300 mm) AC systems use a single VIOS, while GenlO (2850 mm x3050 mm and larger) uses 4. The increase in the size of the systems and the number of heads makes direct access to the electro-optical transducers increasingly difficult, as illustrated in Figure 3, which is a schematic diagram of an Array Test system 300. For systems handling glass substrates larger than Gen8, it is practically impossible for an operator to safely reach all VIOS 100 inspection heads (3 or more) from the side of the systems. This is especially true for systems using a gantry-style architecture (such as Orbotech Gen8 Array Checkers) since they generally use high risers 310 (typically made of granite) on which the main gantry beam 320 travels in the longitudinal direction of the glass on either side. Access from the front of the system is impossible due to the presence of the glass loader robot chamber 330, on that side. The back of the system is the only point where operators can safely stand inside the environmental chamber 340 enclosure

surrounding the tool (provided the stage are disabled properly by an interlock system), but even there it is very difficult to reach the inspection heads due to the presence of subsystems, such as electronics cabinets 350 or probe configuration stations 360 (used to configure the subsystem delivering the electrical driving signals to the panel under test to the layout being inspected). Note that in split access systems, rear access is impossible, but side access is easier since there are no system-length risers

[0009] Another issue related to manual handling of electro-optical transducer elements and the mounts in which they are installed are the issues of safety and damage. The more an operator has to work in close physical proximity of the inspection heads, the larger the chance of injury due collisions with moving parts on the system - Note that the VIOS heads on AC systems have a moving mass of approximately 200 lbs, develop accelerations of 1.7 G and speeds up in excess of 1 m/s! Also, an operator may drop an electro-optical transducer element onto the plate under inspection, the tiled chuck 370 or other parts of the system, thereby causing damage to the plate, transducer element and/or system.

[0010] Figure 4 is a flow chart of the modulator exchange procedure 400, as known in the prior art. As shown in figure 4, conventionally the replacement of modulators (or similarly, the installation of new modulators) in AC systems is done by selecting 405 a VIOS inspection head, launching 410 the exchange sequence from a control computer's graphical user interface and moving 415 the selected VIOS head on which the exchange is to take place to an accessible area. Subsequently, a first operator places 420 a receptacle under the modulator (alternatively referred to herein as electro-optical transducer element or merely transducer) to be removed - if any is present - while a foot-actuated mechanical switch is being pressed by a second operator to open or release 425 the clamp (element 230 in Figures 2 A and 2B) holding the modulator. The first operator receives 430 the modulator which drops into the receptacle. The second operator may release the foot switch remotely thus closing 435 the modulator clamps. Then a receptacle with the new modulator is placed 440 underneath the empty modulator mount by the first operator. Thereafter, the foot switch is pressed again by the second operator remotely to open 445 the modulator clamps. Next, the first operator manually loads 450 the modulator into the mount. Next, the second operator releases the foot switch, which remotely closes 455 the clamps to grab the new modulator in the mount. Testing inspection may then resume 460 via the GUI once it is safe to proceed.

[0011] In array test systems relying on electro-optical transducers, the transducer needs to be kept at small (dependent on the transducer type and mode of operation, for instance around 50 um) and uniform distance above the panel under test to ensure capacitive coupling between the two while preventing touchdown. This is typically ensured by means of an air bearing with multiple air injectors (elements 220 in Figures 2A-B) incorporated into the mount holding the transducer element or modulator. Commonly, 3 injectors (positioned at the corners of an equilateral triangle) are used since 3 points define a plane. The flow through each of the injectors is individually controlled to raise (increased flow) or lower (decreased flow) the modulator at that point. In general, this adjustment is done when the inspection head is lowered ("gapped") onto the first site of the plate under test. For the adjustment, a signal detected on the imaging sensor is typically used. For instance, in prior Array Checker systems, leveling is done by manually adjusting the flow at each injector individually to obtain either the desired raw detected signal at the gaping position (I-bias) or the desired difference of the I-bias signal and the signal recorded with the head raised as close as possible to a target height value. In previous generation array tester systems, the flow adjustment at each air injector was done using manually adjustable valves to control the pressure at each of the injectors.

BRIEF SUMMARY

[0012] In accordance with one embodiment of the present invention, a computerized method for automatic handling of an electro-optical transducer element used in a LCD test system includes, in part, placing the electro-optical transducer element in a holder positioned on a stage assembly, changing the position of the stage assembly relative to an inspection head so as to mount the electro-optical transducer element to the inspection head, and transferring the electro-optical transducer element from the holder to the inspection head.

[0013] In accordance with various embodiments of the present invention, the computerized method for automatic handling of an electro-optical transducer element used in the LCD test system also includes, in part, aligning the inspection head to the holder, vertically moving the inspection head towards the holder, and vertically moving the holder towards the inspection head. In another embodiment, the method includes, verifying the presence of the electro- optical transducer element on the inspection head and on the holder before and after transferring the electro-optical transducer. In another embodiment, the electro-optical transducer element is placed in a receptacle to prevent human contact.

[0014] In accordance with one embodiment of the present invention, an LCD test system includes, in part, one or more inspection heads, one or more holders, a stage assembly, one or more electro-optical transducer elements, a clamp, and a computer control system. The holders are adapted to house the electro-optical transducer elements. The stage assembly is adapted to hold the holders, and to transfer the electro-optical transducer elements from the holders to the inspection heads. The clamp is adapted to secure the electro-optical transducer elements to the inspection heads.

[0015] In accordance with some embodiments of the present invention, the stage assembly is further adapted to carry probe contact assemblies. The holders are adjustable in a multitude of directions to enable adjusting of the plane of the electro-optical transducer elements to the inspection heads. The holders have a vertical compliance to reduce any residual

misalignments between the inspection heads and the electro-optical transducer elements. The holders include one or more alignment fiducials. A camera on the inspection heads is adapted to view the alignment fiducials to enable alignment of the holders to the camera. Sensors are adapted to verify the presence and proximity of the electro-optical transducer elements in the holders and on the inspection heads. The sensors are optionally proximity sensors and/or RFID readers. The clamp is optionally a pneumatically actuated clamp.

[0016] In accordance with one embodiment of the present invention, a computerized method of cleaning an electro-optical transducer of an LCD test system includes, in part, conveying a first stage assembly with at least one cleaning station to a second stage assembly, moving a position of the second stage assembly relative to the first stage assembly, positioning the electro-optical transducer element in the cleaning station, and delivering a first gas flow to loosen and remove particles from a surface of the electro-optical transducer element. The second stage assembly includes, in part, at least one inspection head and at least one electro-optical transducer element.

[0017] In accordance with some embodiments of the present invention, the computerized method of cleaning an electro-optical transducer of an LCD test system also includes, in part, bringing the inspection head in alignment with the cleaning station, vertically moving the inspection head toward the cleaning station, vertically moving the cleaning station towards the inspection head, and/or verifying the proximity of the electro-optical transducer element to the cleaning station prior to initiating the cleaning process. In other embodiments, the first gas in the gas flow includes, in part, clean dry air or nitrogen, or is ionized to enable removal of particles attracted by electrostatic attraction.

[0018] In accordance with some embodiments of the present invention, the computerized method of cleaning an electro-optical transducer of the LCD test system includes, in part, dispensing the water from several jets and delivering air or a second gas from one or more nozzles to dry the electro-optical transducer element after dispensing the water. The method further includes, in part, aligning the electro-optical transducer element to the cleaning station using one or more alignment fiducials disposed on the cleaning station as well as a camera disposed on the inspection head. The method further includes, in part, verifying the proximity of the electro-optical transducer element to the cleaning station using one or more sensors prior to delivering the first gas. The method further includes, in part, verifying the proximity of the electro-optical transducer element to the cleaning station using the sensors prior to delivering the first gas.

[0019] In accordance with some embodiments of the present invention, the computerized method of cleaning an electro-optical transducer of the LCD test system includes, in part, adapting the first stage assembly to carry probe contact assemblies. The method further includes adjusting the plane of the electro-optical transducer element with respect to the inspection head by adjusting the cleaning station in several directions. The method further includes reducing the residual misalignments between the inspection head and the electro- optical transducer element by having a vertical compliance in the cleaning station.

[0020] In accordance with one embodiment of the present invention, an LCD test system includes, in part, an inspection head, at least one cleaning station, and a stage assembly adapted to hold and move the cleaning station. The cleaning station is adapted to receive and house an electro-optical transducer element. The cleaning station includes, in part, one or more nozzles for delivering a first gas flow to the surface of the electro-optical transducer element to loosen and remove particles from its surface.

[0021] In accordance with some embodiments of the present invention, the first gas in the gas flow may be clean dry air or nitrogen, or ionized to enable removal of particles attracted by electrostatic attraction. The cleaning station includes, in part, several jets adapted to dispense water and nozzles adapted to deliver air or a second gas to dry the electro-optical transducer element after dispensing the water. The stage assembly is further adapted to carry probe contact assemblies. The cleaning station is adjustable in several directions to enable adjustment of the plane of the electro-optical transducer element with respect to the inspection head. The cleaning station has a vertical compliance to reduce residual misalignments between the inspection head and the electro -optical transducer element. The cleaning station may include, in part, one or more alignment fiducials. The inspection head includes, in part, a camera. The system includes, in part, one or more sensors adapted to verify the proximity of the electro-optical transducer element to the cleaning station prior to delivering the first gas.

[0022] In accordance with one embodiment of the present invention, a computerized method for remotely adjusting a distance between an electro-optical transducer element of an LCD test system and a panel under test, includes, in part, positioning the electro-optical transducer element above .the panel under test, and remotely controlling a flow and a pressure of a gas injected through one or more orifices. The gas flow is used to position the electro- optical transducer element within a known vertical distance from the panel.

[0023] In accordance with some embodiments of the present invention, the computerized method for remotely adjusting a distance between an electro-optical transducer element of an LCD test system and a panel under test, also includes, in part, adjusting the vertical distance using a closed loop control system until target signal values are detected on an image sensor on an inspection head. The method further includes, in part, controlling the flow and pressure of the gas at each of the orifices by selecting one of several fixed orifice flow control valves coupled to each of the orifices using a solenoid valve. The method further includes, in part, performing the adjustment at various locations or at the start of every panel test. The method further includes, in part, selecting the first fixed orifice flow control valve first and selecting the second fixed orifice flow control valve if required. The first fixed orifice flow control valves includes, in part, a narrower orifice than the second fixed orifice flow control valve. [0024] In accordance with some embodiments of the present invention, the computerized method for remotely adjusting a distance between an electro-optical transducer element of an LCD test system and a panel under test includes, in part, adapting the inspection head to hold the electro-optical transducer element of the LCD system. The method further includes, in part, preventing backflow by using a check valve coupled between each of the fixed orifice flow control valves and the orifices.

[0025] In accordance with one embodiment of the present invention, an LCD test system includes, in part, an electro-optical transducer element, one or more orifices on the electro- optical transducer element for injecting gas, and a computer adapted to control the flow and pressure of the gas. The gas flow is used to position the electro-optical transducer element within a known vertical distance from a panel under test.

[0026] In accordance with some embodiments of the present invention, the LCD test system also includes, in part, a closed loop control system adapted to automatically adjust the vertical distance until target signal values are detected on an image sensor. The inspection head is adapted to hold the electro-optical transducer element of the LCD system. Several fixed orifice flow control valves are coupled to each of the orifices to control the flow and pressure of the gas. A solenoid valve is coupled to the fixed orifice flow control valves and is adapted to select one of the fixed orifice flow control valves. A first fixed orifice flow control valve includes, in part, a narrower orifice than a second fixed orifice flow control valve. Another embodiment includes, in part, a check valve coupled between each of the fixed orifice flow control valves and the orifices to prevent backflow. The solenoid valve is adapted to first select the first fixed orifice flow control valves and to select the second fixed orifice flow control valves if required. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A is a schematic diagram of a modulator, as known in the prior art.

[0028] Figure IB is a schematic diagram of a Voltage Imaging Optical System (VIOS), as known in the prior art.

[0029] Figure 2A is a front view schematic drawing of modulator air bearing mount, as known in the prior art.

[0030] Figure 2B is a top view schematic drawing of modulator air bearing mount, as known in the prior art. [0031] Figure 3 is a schematic diagram of an Array Test system, highlighting access issues, as known in the prior art.

[0032] Figure 4 is a flow chart of the modulator exchange procedure, as known in the prior art. [0033] Figure 5 is a schematic drawing of an Automatic Modulator Exchange, in accordance with one embodiment of the present invention.

[0034] Figures 6A and 6B are front and top views, respectively, of a modulator exchange pod, in accordance with one embodiment of the present invention.

[0035] Figure 7A is a flow chart describing the sequence for an automated unloading of a modulator, in accordance with one embodiment of the present invention.

[0036] Figure 7B is a flow chart describing the sequence for an automated loading of a modulator, in accordance with one embodiment of the present invention.

[0037] Figures 8A and 8B are front and top views, respectively, of a modulator cleaning station, in accordance with one embodiment of the present invention. [0038] Figure 9 is a flow chart of a sequence used to automatically clean a modulator, in accordance with one of the embodiments of the present invention.

[0039] Figures 10A and 10B show a number of components of the remote air bearing control pneumatics and the automation controls, in accordance with one embodiment of the present invention.

DETAILED DESCRIPTION

[0040] In order to facilitate access to the inspection heads of large array test systems, such as generation 7 inspection heads and beyond, and in order to prevent injuries to operators and damage to equipment, glass substrates and electro-optical transducer elements in array test systems, embodiments of the present invention provide automated handling of the electro- optical transducer elements in such systems, including, in part, loading/unloading, cleaning, and air bearing adjustment by improving the accuracy and repeatability of the adjustment as well as reducing the time required to perform this operation. To achieve the above objectives, embodiments of the present invention provide, among other advantages, an (i) automatic modulator exchanger; (ii) an automatic modulator clean station, and (iii) a remote adjustment of modulator air bearing, as described in detail below. Automatic Modulator Exchange (AME)

[0041] Figure 5 is a schematic drawing of an AME 500, in accordance with one

embodiment of the present invention. As described in detail below, among other advantages, AME 500 overcomes the access issues as well as the safety and damage risks inherent in conventional systems by automatically exchanging electro-optical transducer elements on Array Test Systems. To achieve this, AME 500 includes a number of exchange pods disposed on one of the gantry stages carrying the signals driving the panels during inspection. These gantry stages are referred to herein as probe bars (PB) and are adapted to carry probe contact assemblies that deliver the electrical driving signals to the panel under test. In one

embodiment, there are two PBs per Array Checker system. The modulator exchange pods 520 are typically placed on the rear PB 530, positioned at the rear extremity of its travel range. With this configuration, modulators can be placed into, or retrieved from, the exchange pods (alternatively referred to herein as holder) with minimal risk to operator and equipment. The number of exchange pods may depend on the number of inspection heads. In one embodiment, there is one exchange pod per head. In another embodiment, there are fewer exchange pods than there are heads. In yet other embodiments, there are 2 exchange pods for 3 heads.

[0042] Figures 6A and 6B are front and top views, respectively, of a schematic drawing of a modulator exchange pod 520, in accordance with one embodiment of the present invention. Modulator exchange pod 520 is shown as having a receptor ring 610 adapted to receive a modulator 10. In some embodiments, exchange pod 520 includes secondary modulator receptacle, holder or case, such as carrying case 620 that receives the modulator so as to prevent human contact. Receptor ring 610 is positioned on top of an adjustable base 630 that may be adjusted with sufficient range (e.g. up to 250 um) in all 6 degrees of freedom to make it coplanar with each air-bearing mount, in which the modulators are placed. The final adjustments can be locked in by means of leveling screws or bolts and locking nuts 640. Furthermore, the receptor ring has a built-in vertical compliance by means of o-rings 645 placed between ring 610 and adjustable base 630, allowing it to take up or reduce any residual misalignments between the plane of the modulator in the pod and the plane of the modulator mount. The receptor ring has 3 locating or alignment pins 650, as shown, to accurately locate the modulator inside the pod, and to prevent lateral motion of the modulator (or its receptacle holder 620) in the pod during the exchange process.

[0043] In order to locate the exchange pod (and hence the modulator placed in it) with respect to the inspection head, an alignment reticle 660 (alternatively referred to herein as alignment fiducial or mark) is mounted on each side of the receptor ring. The alignment mark can be viewed with an optical camera attached to the side of the inspection head. The correct X, Y and Theta positions of the stages involved in the exchange (the VIOS X stage and the rear PB gantry in the case of the AC systems) can be adjusted according to the recorded reticle positions and the (known) offset between the centers of the optical camera system and the modulator air bearing mount (i.e., the inspection optics).

[0044] A number of sensors, placed on the exchange pod as well as the inspection head, allow for monitoring of the exchange process and prevent collisions. In some embodiment of the present invention, three proximity sensors are used on each pod. A first proximity sensor, referred to as modulator proximity sensor 670, senses the presence of a modulator in the receptor ring. A second proximity sensor, referred to as modulator present sensor 680, senses the presence of a modulator as it is being loaded (e.g. from the modulator mount on the inspection head). A third proximity sensor, referred to as case sensor 690 senses the secondary modulator receptacle, holder or case (if used) on the exchange pod. Furthermore, if each modulator is outfitted with its own RFID tag, the RFID reader on the inspection head may be used to confirm the success of the modulator exchange and track modulators during exchange. The modulator's sense feedback analog signal can also be used to confirm the success of the modulator exchange.

[0045] Figure 7 A is a flow chart 750 describing the sequence for an automated unloading of a modulator, in accordance with one embodiment of the present invention. The front PB (not carrying the exchange pods) may be parked 752 at the front of the system. The main gantry, carrying the inspection heads, can be moved 754 to a predetermined longitudinal (Y-) exchange position, for example the rear extremity of its travel (this can minimize exchange time). The gantry can also be kept in its current position. The inspection heads (which are mounted on X/Z stage combos) with modulators that need to be exchanged are moved 756 up in the Z-direction and to predetermined lateral (X-) exchange positions. These X positions should correspond to the X-position of the exchange pods on the rear PB. The Z-position should correspond to the focus of the camera used to view the alignment marks, assuming there is no mechanical interference between the inspection heads and the exchange pods. The rear PB (carrying exchange pods, which should be empty - this can be verified 758 using the proximity sensors) is moved 760 underneath the main gantry and the alignment mark positions are recorded 762 (if they do not fall in the field of view of the optical cameras used to view them, a spiral search routine can be used 764). [0046] Based on the recorded positions, the Y direction, and Theta or Z-position of the rear PB and the X-position of the inspection heads can be adjusted 766. The inspection heads are lowered 768 to the exchange position height (this can be determined 770 by a presence sensor, as described above), and the modulator is released 772 onto the exchange pod. Once the presence of the modulator in the pod is confirmed 774 using the presence sensors, the inspection heads are raised 776 again and the rear PB is moved in Y direction to the rear extremity of its travel. An operator can now remove 778 the modulators that were removed from the inspection heads.

[0047] In some embodiments, the modulator mount clamps used to grab or release the modulators, are actuated by a button situated on the outside of an environmental chamber in which the tester is placed.

[0048] Figure 7B is a flow chart 700 describing the sequence for an automated loading of a modulator, in accordance with one embodiment of the present invention. In the following it is assumed that the modulator has been unloaded from the inspection head, using, for example, the sequence shown in flowchart 750 and described above. Referring to figure 7B, the automated loading of a modulator is achieved by first selecting 702 a VIOS inspection head , and launching 704 the automatic exchange sequence from a control computer's Graphical User Interface. Next, the inspection heads and rear PB axis move 706 to a predefined location for load/unload access (analogous to unloading steps 1-3 above). The operator installs and aligns 708 the modulator with the receptacle into the corresponding exchange pod on the rear PB. The operator exits 710 the system enclosure and continues the process sequence when safe.

[0049] Next, the system automatically checks 712 the presence of the modulator in the exchange pod using the sensors. If the modulator is not present in the pod, the process sequence aborts 732. If the modulator is successfully detected in the pod by the sensors, the rear PB gantry moves 714 underneath the main gantry at a predefined exchange location. Next, the system auto-aligns 716 the inspection head, main gantry and rear PB using the alignment mark on the pod and the optical camera on the inspection head (analogous to unloading step 4 above). If the auto-alignment fails, the process sequence aborts 732. If the auto-alignment is successful, the inspection head gradually lowers 718 to the exchange height (analogous to unloading step 5 above). The system checks 720 the proximity of the modulator to mount the modulator to the inspection head using the sensors. If proximity check 720 fails, the process sequence aborts 732. If the proximity check succeeds, the operator remotely actuates the modulator clamps on the modulator mount on the inspection head grabbing 722 the modulator from the pod. In an alternate embodiment the system automatically actuates the modulator clamps grabbing the modulator from the pod without operator intervention.

[0050] Next, the system automatically verifies 724 using sensors to confirm the modulator is clamped successfully by the inspection head. If clamp check 724 fails, the process sequence aborts 732. If the modulator is clamped successfully, the inspection head lifts 726. Next, the inspection heads and PB axes move 728 to predefined locations for load/unload access. Then, the operator enters 730 the system enclosure to remove the empty receptacle from the rear PB gantry. [0051] The entire modulator exchange process is controlled by computer. There are at least three main components to the control software, namely motion control, alignment, and user interface. The motion control component of the software ensures the axes involved move to the correct positions for exchange in the correct sequence. The motion control also involves interlocks to prevent one axis from colliding with another one. The alignment control of the software determines the offset of the alignment reticles with respect to the center of the field of view of the optical cameras and determines the corrections in stage positions for modulator exchange accordingly. The user interface component of the software enables the user to operate the different stages of the exchange process (e.g. motion, alignment, load/unload) safely for each head. Automatic Modulator Cleaning Station (AMCS)

[0052] Conventional cleaning of modulators in AC systems involves removing the modulator from its mount; cleaning with a solvent-imbibed optical wipe and placing it back in again.

[0053] An AMCS, in accordance with one embodiment of the present invention, overcomes the access issues as well as the safety and damage risks inherent to the current manual procedure by enabling an automated way of cleaning electro-optical transducer elements on Array Test Systems. Figures 8A and 8B are front and top views, respectively, of a schematic drawing of a modulator cleaning station 540, in accordance with one embodiment of the present invention. Modulator cleaning station 800 includes a receptor ring 810, adapted to receive modulator 10 from an inspection head, and one or more nozzles 840 adapted to inject

(continuously or pulsed ionized air or N2, which loosens particles that may be present on the surface due to electrostatic attraction. Following the cleaning operation, the cleaning station is maintained at negative pressure by means of a vacuum seal 820 placed in the cleaning space 830 between the receptor ring and modulator 10, thereby removing any particles loosened through the ionization. The ionized air is supplied through inline ionizers and nozzles 840 mounted into the cleaning station; the vacuum is supplied through separate orifices (not shown). Air (or N2) and vacuum supplies can be turned on or off via computer- controlled solenoids 842 and 844 respectively. The direction of cleaning gas flow 846 is indicated by thick arrows in Figure 8A. In addition, wipers with clean room cloth rollers can be installed in the AMCS for wiping the detecting surface of the modulator. Alternatively, cleaning of the modulator can be done by means of de-ionized water, supplied by jets installed in the cleaning stations and subsequent drying using (heated) clean dry air or Nitrogen supplied by nozzles in the same stations.

[0054] The cleaning stations may be similar to the modulator exchange pods. In one embodiment, the cleaning stations include alignment pins 850, alignment fiducials 860 and proximity sensors 870. Some embodiments of the present invention include multiple cleaning stations 540, as illustrated in Figure 5. Some embodiments of the present invention include equal number of cleaning stations and inspection heads. In some embodiments, the cleaning components performing the cleaning operations may be integrated into the modulator exchange pods. In yet other embodiments, the components used for cleaning are separate from the components used for exchanging the modulators and are mounted on a front probe bar (element 510 in Figure 5). [0055] Figure 9 is a flow chart 900 of a sequence used to automatically clean a modulator, in accordance with one embodiment of the present invention. As illustrated in Figure 9, cleaning a modulator is done by selecting 902 the VIOS head to be cleaned and launching 904 the automatic cleaning sequence from a control computer's GUI. The operation sequence of the cleaning process is similar to that of the exchange process. [0056] The rear PB (not carrying the cleaning stations) parks at the rear of the system. The inspection heads (which are mounted on X/Z stage combos on the main gantry) with selected modulators moves up in the Z-direction and to predetermined lateral (X-) "cleaning" positions. These X positions correspond to the X-position of the cleaning pods on the front PB. The Z-position corresponds to the focus of the camera used to view the alignment marks, assuming there is no mechanical interference between the inspection heads and the cleaning stations. The main gantry may move to a pre-determined "cleaning" position, e.g. above the front PB, or can be kept in its current position. The front PB (carrying exchange pods) moves 906 underneath the main gantry (if not already there) and the alignment mark positions are recorded (if the do not fall in the field of view of the optical cameras used to view them, a spiral search routine can be used). Based on the recorded positions, the Y and Theta position of the front PB and the X-position of the inspection heads can be adjusted during auto- alignment 908. If the auto-alignment fails, the process sequence aborts 918. If the auto- alignment is successful, the inspection heads gradually lower 910 into the cleaning stations. Next, the system checks 912 the proximity of the modulator mounted to the cleaning station (this can be determined by the presence sensor, as described above), but the modulator is not released. If proximity check 912 fails, the process sequence aborts 918. If the proximity check succeeds, the cleaning process starts 914. After the cleaning is done, the inspection process resumes 916 normally.

[0057] Note that, as in the exchange case, the entire process is computer controlled including the actuation and timing of the air and vacuum involved in the cleaning.

Remote adjustment of modulator air bearing

[0058] In accordance with one embodiment of the present invention, the access issues as well as the safety and damage risks inherent to the current manual procedure are overcome by enabling remote control over the flow at each injector by using two fixed orifice flow control valves - one with a narrow orifice, the other with a wide orifice. At each injector, selection of the orifices is done through a dedicated solenoid valve upstream. The range of air flow in each injector channel can thus be increased compared to existing designs and remotely switched under computer control between high and low flow ranges flowing through the corresponding wide and narrow orifices. The details of the remote air bearing control pneumatics and the automation controls in an embodiment of the invention are shown respectively in Figures 10A and 10B. The height of the modulator above the panel under test can be finely adjusted by controlling the orifices and the air-pressure through software. This adjustment can be done remotely by the operator or can be automated without operator intervention. Algorithms iteratively increase or decrease the air bearing pressures in small increments until the gapping targets are met. The algorithm first selects a low air flow through the narrow orifice to determine if the gapping target is met and then selects the wide orifice for high air flow if required to increase the air flow to meet the target. Thus, the gas flow may be used to position the electro-optical transducer element within a known vertical distance from the panel. Using this form of automation enables more frequent adjustments of the air bearing at various locations or at the start of every panel tested (for instance on the first site of every panel instead of merely the first site of every plate of panels where the plate includes multiple panels), enabling more accurate gap control over the plate and optimizing modulator life time.

[0059] Figure 1 OA shows the remote air bearing control pneumatics 1000, in accordance with one embodiment of the present invention. A flight drawer 1005 supplies 3 injector flow lines, A-C, coupled to respective flow control valves 1010, 1015 and 1020 which couple each respective channel's air flow thru respective wide or narrow orifice lines thru cable track 1025. Each flow channel's pair of lines are coupled thru respective wide and narrow orifices 1030 and 1035 in the VIOS 100, thru air couplings to respective flow lines A-C on modulator mount 20. The flight drawer provides a remotely controlled pressure range for each injector channel. The pressure in each channel is fed to the flow control valve that directs the pressurized air to either the wide or narrow fixed orifice corresponding to high or low air flow ranges respectively. The flow from the fixed orifices is then directed to the modulator mount that holds the modulator. The air then flows into the modulator air bearing nozzles A, B and C. A check valve 1037 downstream of each orifice is used to isolate the unused wide or narrow leg in each injector channel to prevent additional backflow air volume from affecting the air bearing stiffness.

[0060] Figure 10B shows the remote air bearing automation controls 1050, in accordance with one embodiment of the present invention. A Delta-Tau 34AA-2 controller 1055 couples control signals A-C and AGND to one set of flight components per VIOS 100 via respective optically isolated power transistors 1060-1070 which drive flow control valves 1010, 1015 and 1020. +V power is supplied to each flow control valve from the flight drawer. Each flow control valve is normally adapted to couple air flow from the flight drawer 1005 to the narrow orifice unless one of the three control signals A-C is activated to send the air flow to the wide orifice.

Claims

WHAT IS CLAIMED IS: 1. A computerized method for automatic handling of an electro-optical transducer element used in a LCD test system, the computerized method comprising:

placing the electro-optical transducer element in a holder positioned on a stage assembly using the computer;

changing position of said stage assembly relative to an inspection head so as to mount the electro-optical transducer element to the inspection head using the computer; and transferring the electro-optical transducer element from the holder to the inspection head using the computer.

2. The computerized method of claim 1 wherein the electro-optical transducer element is placed in a receptacle to prevent human contact.

3. The computerized method of claim 1 wherein the inspection head is aligned to the holder using the computer.

4. The computerized method of claim 1 wherein the inspection head is vertically moved towards the holder using the computer.

5. The computerized method of claim 1 wherein the holder is vertically moved towards the inspection head using the computer.

6. The computerized method of claim 1 wherein the presence of the electro-optical transducer element on the inspection head and on the holder is verified by the computer before and after transferring the electro-optical transducer.

7. An LCD test system comprising:

one or more inspection heads;

one or more holders adapted to house one or more electro-optical transducer elements;

a stage assembly adapted to hold the one or more holders, said stage assembly further adapted to transfer the one or more electro-optical transducer elements from the one or more holders to the one or more inspection heads using a computer control system; and a clamp adapted to secure the one or more electro-optical transducer elements to the one or more inspection heads.

8. The system of claim 7 wherein the stage assembly is further adapted to carry probe contact assemblies.

9. The system of claim 7 wherein the one or more holders are adjustable in a plurality of directions to enable adjusting of the plane of the one or more electro-optical transducer elements to the one or more inspection heads.

10. The system of claim 7 wherein the one or more holders has a vertical compliance to reduce any residual misalignments between the one or more inspection heads and the one or more electro-optical transducer elements.

1 1. The system of claim 7 wherein the one or more holders include one or more alignment fiducials and wherein a camera disposed on the one or more inspection heads is adapted to view the alignment fiducials to enable alignment of the one or more holders to the camera.

12. The system of claim 7 wherein said system further comprises one or more sensors adapted to verify the presence and proximity of the one or more electro-optical transducer elements in the one or more holders and on the one or more inspection heads.

13. The system of claim 12 wherein the one or more sensors are proximity sensors and/or RFID readers.

14. The system of claim 7 wherein the clamp is a pneumatically actuated clamp.

15. A computerized method of cleaning an electro-optical transducer of an LCD test system, the computerized method comprising:

conveying a first stage assembly having disposed thereon at least one cleaning station to a second stage assembly using the computer, said second stage assembly comprising at least one inspection head and at least one electro-optical transducer element;

moving a position of the second stage assembly relative to the first stage assembly using the computer;

positioning the at least one electro-optical transducer element in the at least one cleaning station using the computer; and

delivering a first gas flow to loosen and remove particles from a surface of the at least one electro-optical transducer element using the computer.

16. The computerized method of claim 15 wherein the at least one inspection head is brought in alignment with the at least one cleaning station using the computer.

17. The computerized method of claim 15 wherein the at least one inspection head is vertically moved toward the at least one cleaning station using the computer.

18. The computerized method of claim 15 wherein the at least one cleaning station is vertically moved towards the at least one inspection head using the computer.

19. The computerized method of claim 15 wherein the proximity of the at least one electro-optical transducer element to the at least one cleaning station is verified prior to initiating the cleaning process using the computer.

20. The computerized method of claim 15 wherein the first gas in the gas flow is selected from a group consisting of clean dry air or nitrogen.

21. The computerized method of claim 15 wherein the first gas in the gas flow is ionized to enable removal of particles attracted by electrostatic attraction.

22. The computerized method of claim 15 further comprising:

dispensing water from a plurality of jets using the computer; and delivering air or a second gas from one or more nozzles to dry the at least one electro-optical transducer element after dispensing the water using the computer.

23. The computerized method of claim 15 wherein the first stage assembly is further adapted to carry probe contact assemblies.

24. The computerized method of claim 15 further comprising adjusting the plane of the electro-optical transducer element with respect to the at least one inspection head by adjusting the at least one cleaning station in a plurality of directions.

25. The computerized method of claim 15 further comprising reducing residual misalignments between the at least one inspection head and the electro-optical transducer element by having a vertical compliance in the at least one cleaning station.

26. The computerized method of claim 15 further comprising aligning the at least one electro-optical transducer element to the at least one cleaning station using one or more alignment fiducials on the at least one cleaning station and a camera disposed on the at least one inspection head using the computer.

27. The computerized method of claim 15 further comprising verifying the proximity of the at least one electro-optical transducer element to the at least one cleaning station using one or more sensors prior to delivering the first gas using the computer.

28. An LCD test system comprising:

an inspection head;

at least one cleaning station adapted to receive and house an electro-optical transducer element; and

a stage assembly adapted to hold and move the at least one cleaning station, wherein the at least one cleaning station comprises one or more nozzles for delivering a first gas flow to the surface of the electro-optical transducer element to loosen and remove particles from a surface of the electro-optical transducer element.

29. The system of claim 28 wherein the first gas in the gas flow is selected from a group consisting of clean dry air or nitrogen.

30. The system of claim 28 wherein the first gas flow is ionized to enable removal of particles attracted by electrostatic attraction.

31. The system of claim 28 wherein the at least one cleaning station comprises a plurality of jets and nozzles, said jets adapted to dispense water, said nozzles adapted to deliver air or a second gas to dry the electro-optical transducer element after dispensing the water.

32. The system of claim 28 wherein the stage assembly is further adapted to carry probe contact assemblies.

33. The system of claim 28 wherein the at least one cleaning station is adjustable in a plurality of directions to enable adjustment of the plane of the electro-optical transducer element with respect to the inspection head.

34. The system of claim 33 wherein the at least one cleaning station has a vertical compliance to reduce residual misalignments between the inspection head and the electro-optical transducer element.

35. The system of claim 28 wherein said at least one cleaning station comprises one or more alignment fiducials, wherein said inspection head comprises a camera.

36. The system of claim 28 wherein said system comprises one or more sensors adapted to verify the proximity of the electro-optical transducer element to the at least one cleaning station prior to delivering the first gas.

37. A computerized method for remotely adjusting a distance between an electro-optical transducer element of an LCD test system and a panel under test, the computerized method comprising:

positioning the electro-optical transducer element above the panel under test using the computer; and

remotely controlling, using the computer, a flow and a pressure of a gas injected through one or more orifices, said gas flow being used to position the electro-optical transducer element within a known vertical distance from the panel.

38. The computerized method of claim 37 wherein the vertical distance is adjusted using a closed loop control system until target signal values are detected on an image sensor disposed on an inspection head adapted to hold the electro-optical transducer element of the LCD system using the computer.

39. The computerized method of claim 37 wherein the flow and pressure of the gas at each of the one or more orifices is controlled by selecting one of a plurality of fixed orifice flow control valves coupled to each of the one or more orifices using a solenoid valve using the computer.

40. The computerized method of claim 38 wherein said adjustment is performed at various locations or at the start of every panel test using the computer.

41. The computerized method of claim 39 wherein a first one of the plurality of fixed orifice flow control valves comprises a narrower orifice than a second one of the plurality of fixed orifice flow control valves.

42. The computerized method of claim 39 wherein backflow is prevented by using a check valve coupled between each of the plurality of fixed orifice flow control valves and the one or more orifices.

43. The computerized method of claim 41 wherein the first one of the plurality of fixed orifice flow control valves is selected first and the second one of the plurality of fixed orifice flow control valves is selected if required using the computer.

44. An LCD test system comprising:

an electro-optical transducer element;

one or more orifices disposed on the electro-optical transducer element for injecting a gas; and

a computer adapted to control the flow and pressure of the gas, said gas flow being used to position the electro-optical transducer element within a known vertical distance from a panel under test.

45. The system of claim 44 wherein said LCD system further comprises a closed loop control system adapted to automatically adjust the vertical distance until target signal values are detected on an image sensor disposed on an inspection head adapted to hold the electro-optical transducer element of the LCD system.

46. The system of claim 44 wherein said LCD system further comprises: a plurality of fixed orifice flow control valves coupled to each of the one or more orifices to control the flow and pressure of the gas; and

a solenoid valve coupled to the plurality of fixed orifice flow control valves, the solenoid valve adapted to select one of the plurality of fixed orifice flow control valves.

47. The system of claim 46 wherein a first one of the plurality of fixed orifice flow control valves comprises a narrower orifice than a second one of the plurality of fixed orifice flow control valves.

48. The system of claim 46 wherein said LCD system further comprises: a check valve coupled between each of the plurality of fixed orifice flow control valves and the one or more orifices to prevent backflow.

49 . The system of claim 47 wherein the solenoid valve is adapted to first select the first one of the plurality of fixed orifice flow control valves and to select the second one of the plurality of fixed orifice flow control valves if required.