DE10323317A1 - Car object detection or distance measurement optical system path folding unit uses silicon micromirror reflectors - Google Patents

Abstract

A car object (O) detection or distance measurement optical system path folding unit (1) has a pulsed laser diode light source (4) and synchronized detector (8) linked (2) by controllable silicon micromirror reflectors (3). Includes an INDEPENDENT CLAIM for use of the system to read bar codes in supermarket cash register systems.

Description

The The invention relates to a device for deflecting the beam path in an optical system and the use of such Contraption.

at optical systems, such as B. Distance measuring systems in vehicle technology or checkout systems at supermarket checkouts, where an evaluation of a light beam reflected from an object often rotating polygon mirrors with a plurality of with one certain angle inclined mirror surfaces applied. The rotating polygon mirror makes an areal Area scan achieved.

adversely in systems with rotating polygon mirrors, on the one hand, that for the Storage of the polygon mirror an expensive, almost free of play and robust precision mechanics needed and on the other hand that due to the rough application area in vehicle technology due to vibration, engine noise, body resonance, Road bumps, potholes considerable mechanical forces act on the relatively heavy construction, which is negative affect measurement accuracy and system life.

Out A large number of such systems are known from the prior art, where a beam of light through a rotating polygon mirror is distracted.

For example, in the DE 101 39 237 A1 describes a device with a detector element for receiving a light beam reflected from an object with means for deflecting the reflected light beam onto the detector element, in which a rotating polygon mirror with a plurality of mirror surfaces inclined at a certain angle is provided as means for deflecting the reflected light beam is, wherein the detector element is arranged in the direction of the axis of rotation of the polygon mirror and for focusing the reflected light beam on the detector element is assigned to each mirror surface of the polygon mirror, which rotates synchronously with the polygon mirror. The rotating optics amplify the inertial forces that are already acting on the rotating polygon mirror, so that the requirements for precision and robustness of the bearings are increased even further.

Out DE 197 49 926 A1 and DE 197 49 923 A1 Laser scanning recording devices are known in which the laser light emitted by a laser light source is reflected on a polygon mirror for scanning a light-sensitive recording medium. The recording devices described are used in laser printers and are intended to compensate for changes in the reflectance of the reflecting surfaces of the polygon mirror by controlling the power of the laser diode.

Farther are from the field of application of laser television for laser beam deflection Silicon micromirrors (so-called torsion actuators) are known. An overview of such Silicon micromirrors are available on the website http://www.infotech.tuchemnitz.de/~zfm/forschung/mikrospiegel.html as well as the dissertation "Ein Novel microactuator for one- and two-dimensional deflection of Light " at the Department of Electrical Engineering at the Gerhard Mercator University Comprehensive University Duisburg by Dipl.-Phys. Harald Schenk. Such micromirrors have with a flat mirror surface maximum deflection angle from 2 ° to 5 ° static or 10 ° to 40 ° in resonance on. The control for the external steering of the beam path takes place through electrostatic excitation.

outgoing the present invention is based on this prior art the task of a device for deflecting the beam path in an optical system, in particular in a system for distance measurement or for the detection of objects in a selectable Area to indicate a moving vehicle that can be manufactured inexpensively is, no precision storage needed high wear resistance, high reliability and has a long service life and is insensitive to mechanical Is and can be regulated with little energy.

According to the Task solved by a device with the features of claim 1 and uses the device according to the invention according to claim 8; advantageous developments are the subject of Dependent claims.

The device according to the invention for deflecting the beam path in an optical system, in particular in a system for distance measurement or for the detection of objects in a selectable Area around a moving vehicle comprises at least one light source, at least one detector element and at least one deflection element for deflecting the light beam, using a silicon micromirror as the deflecting element is provided.

For distance measurement or for detection The light source emits a light beam from objects in the vicinity of the device in a known manner. The light source can be, for example, a laser diode or a gas discharge lamp with an upstream polarization filter. The use of monochromatic or polarized light increases the reliability of object detection.

The The light beam is reflected by objects in the area and subsequently detected by the detector element. For example, as a detector element a so-called CCD sensor can be used. In the beam path of the Arranged in a light beam, the device also comprises at least a deflecting element for deflecting the light beam.

in principle the deflecting element can alternatively be used for two different purposes or used cumulatively.

To the one is possible with the deflecting element or an arrangement of several deflecting elements to influence the light beam before sending it out in such a way that greater Area around it is illuminated.

For this is by means of one or more deflecting element with the light beam the surroundings are scanned in one or two dimensions or the light beam is scattered. For this purpose, the deflection element or the arrangement of deflection elements on one located before the light beam emerges from the device Position arranged in the beam path. That of one in the lighting area reflected object is reflected by the detector element captured and then the distance in a known manner, for example using the runtime method of the reflecting object and / or the existence of a Object detected.

To the others can improve sensitivity and measurement accuracy the device the incident reflected light by means of a Deflecting elements or an arrangement of deflecting elements are bundled in such a way that it is fed to the detector element. For this purpose, the deflection element or the arrangement of deflection elements on one in front of the detector element lying position in the beam path. That reflected Light is detected by the detector element and then how processed as described above.

Both possibilities the arrangement of the or the deflecting element are also cumulative in a device can be used so that the light beam before exiting out of the device by a first deflecting element or a first Arrangement of deflection elements is scattered or a selectable area scans the surroundings and the reflected light after re-entering into the device by a second deflection element or a second arrangement is guided by deflection elements onto the detector element.

The The light beam is preferably deflected instead of mechanically elaborate polygon mirror construction using a silicon micromirror (a so-called torsion actuator) or an arrangement of such Silicon micro-mirrors. These provide the deflecting element in the device Alternatively, the silicon micromirror on an ASIC or semiconductor element formed deflection element. By controlling the silicon micromirror or mirrors by means of electrostatic Suggestion for directing the beam path can be done easily Way a controlled system can be realized so that the given Target deflection range can be controlled and controlled. For this purpose, the deflected beam z. B. checked at at least two reference points and distracted more or less depending on the current result. Here, by applying a predetermined deflection voltage in a test or initialization phase determines at what value the deflection voltage those that limit the target deflection range or a reference deflection angle forming reference points are reached. Subsequently, continuously using a Any voltage swing between the determined values for the deflection voltage Deflection range or deflection angle can be set.

The Advantages achieved with the invention are in particular that due to the simple structure of the device using a Silicon micromirror as a deflecting element is a particularly cost-effective one System for measuring distance or for detecting objects in a selectable Area around a moving motor vehicle is possible because there is no precision mechanics in the form of bearings etc. he is required. Furthermore, the device a higher one wear resistance because the moving parts have a significantly lower weight across from have a polygon mirror system, whereby the influence of the inertial forces a negligible small size shrinks. The system is less prone to failure and exhibits greater reliability and longer Lifespan than conventional Systems because it is less sensitive to mechanical disturbances. The device is simple and can be regulated with little energy expenditure and realizes a continuous deflection of the light beam.

The device can be used for all types of optical recognition devices, such as scanner cash registers, merchandise management systems, files or libraries tion systems, pre-crash systems or electronic drawbars for use on motor vehicles, etc. are used.

embodiments the invention will be explained in more detail with reference to a drawing. In this demonstrate:

1 a device for deflecting a radiation path, in which a plurality of individually controllable silicon micromirrors are arranged in a position in the beam path before the light beam emerges from the device,

2 an alternative embodiment for a device for deflecting a radiation course, in which a plurality of individually controllable silicon micromirrors are arranged at a position in front of the detector element in the beam path, and

3 a diagram for setting a reference deflection angle by means of an adjustable deflection voltage on the silicon micromirror.

each other Corresponding parts have the same reference symbols in all figures Mistake.

In 1 is a device 1 for deflecting a radiation path (hereinafter briefly deflection device 1 called) shown, in which a deflecting element 2 it is provided that the at least one adjustable silicon micromirror in its position 3 comprises and at one before the light beam emerges from the deflection device 1 lying position is arranged in the beam path.

The deflector 1 includes a light source 4 whose generated light L first falls within the deflection device 1 on the silicon micromirror 3 of the deflecting element 2 , Depending on the type and design of the deflecting element 2 , in particular depending on the degree of resolution or the size of the space to be detected, comprises the deflecting element 2 as shown, multiple silicon micromirrors 3 , which can be arranged in rows and / or columns in the manner of a matrix.

The individual silicon micromirrors 3 are about control lines 6 statically aligned so that from the light source 4 emitted light L from each silicon micromirror 3 is distracted in a different direction. This ensures that a larger area of the deflection device 1 surrounding room is illuminated. The deflection of the individual silicon micromirrors 3 can advantageously be adapted to the current situation, for example a changed direction of travel of a vehicle.

Alternatively, the silicon micromirrors 3 can also be controlled dynamically, so that, for example, the space to be monitored is scanned in line form with the emitted light L. In this embodiment, the deflection device 1 become less silicon micromirrors 3 required, however, the room to be monitored is then not permanently fully illuminated, but only partially illuminated.

After being distracted by the silicon micromirror 3 sends the deflector 1 the light L off.

Does that happen from the deflector 1 light L emitted in this way onto an object O which is located within the illuminated room, the light L is partially reflected by this object O The reflected light LR returns to the deflector 1 back and meets an associated detector element there 8th , The detector element 8th has a data interface 10 , via which a measurement signal representing the reflected light LR can be read out and fed to a data acquisition and processing unit for further processing in a manner not shown in any more detail. In this way, with the help of a data acquisition and processing device, not shown, for example an on-board computer of a vehicle, based on that of the detector element 8th determined brightness values, the presence of an object O in the illuminated room can be recognized.

In an advantageous embodiment of the invention, the light source transmits 4 Light pulses so that the distance of the object O can also be determined on the basis of the propagation time of the light L and / or the reflected light LR. It is also advantageous to read the detector element 8th with the emission of light L through the light source 4 synchronize so that interference from external light is prevented.

The described deflection device 1 can advantageously be used in motor vehicles with so-called pre-crash systems or so-called electronic drawbars, ie systems for maintaining a constant distance from a vehicle in front. It can also be used in scanner registers, merchandise management systems, file or library management systems, for example to identify bar codes. For this, the silicon micromirrors 3 of the deflecting element 2 advantageously controlled dynamically so that the space of interest is continuously scanned.

In 2 is a deflector 1 shown in which one of an arrangement of several one controllable silicon micromirror 3 existing deflection element 2 on one in front of the detector element 4 lying position is arranged in the beam path.

That from the light source 4 generated light 11 emerges directly from the deflection device without distraction 1 out. If necessary, the light beam can go through a light source, not shown 4 belonging lens arrangement are scattered, so that the best possible illumination of the room to be monitored is achieved by the emitted light L.

Does that happen from the deflector 1 light L emitted in this way onto an object O which is located within the illuminated room, the light L is partially reflected by this object O The reflected light LR returns to the deflector 1 back and hits there inside the deflector 1 on the silicon micromirror 3 of the deflecting element 2 , With the deflecting element 2 it can be, for example, an ASIC or a semiconductor element on which a silicon micromirror 3 is arranged.

The individual silicon micromirrors 3 are about control lines 6 statically aligned so that the reflected light LR from different spatial directions from each silicon micromirror 3 on the detector element 8th is directed. This ensures that reflected light LR is detected from the entire room to be monitored. The deflection of the individual silicon micromirrors 3 can advantageously be adapted to the current situation, for example a changed direction of travel of a vehicle. 3 shows an example of a diagram for setting a reference deflection angle α formed by reference points RP1, RP2 on the basis of a silicon micromirror 3 deflection voltage U applied to the control line 6 , By applying the deflection voltage U in a test phase, it is determined at which value of the deflection voltage U the reference points RP1, RP2 of the reference deflection angle α have been reached. In operation of the deflector 1 By changing the deflection voltage U, any reference deflection angle α can then be set continuously or stepwise by means of a voltage swing between the determined values of the deflection voltage U for the reference points RP.

Alternatively or additionally, the silicon micromirrors can be used 3 can also be controlled dynamically, so that reflected light LR incident from different directions of the room to be monitored is, for example, scanned in a line shape. In this embodiment, the deflection device 1 become less silicon micromirrors 3 required, however, reflected light LR incident from different directions of the room to be monitored is then not permanently completely, but always only partially detected.

After being distracted by the silicon micromirror 3 the reflected light LR strikes the detector element 8th , The detector element 8th has a data interface 10 , via which a measurement signal recorded from the reflected light LR can be read out and fed to a data acquisition and processing unit for further processing. In this way, with the aid of a data acquisition and processing device, not shown, for example an on-board computer of a motor vehicle, based on that of the detector element 8th determined brightness values, the presence of an object O in the illuminated room can be recognized.

The deflector 1 can also have two deflection elements 2 comprise, one of which before the light beam exits the deflection device 1 lying position is arranged in the beam path and the other on one in front of the detector element 8th lying position is arranged in the beam path.

The described deflection device 1 can advantageously be used in motor vehicles with pre-crash systems or so-called electronic drawbars, ie systems for maintaining a constant distance from a vehicle in front. It can also be used in scanner registers, merchandise management systems, file or library management systems, for example to identify bar codes. For this, the silicon micromirrors 3 of the deflecting element 2 advantageously controlled dynamically so that the space of interest is continuously scanned.

The deflector 1 is inexpensive to manufacture, requires no precision storage, has high wear resistance, high reliability and a long service life and is insensitive to mechanical disturbances and can be regulated with little energy consumption.

1

deflector

2

deflecting

3

Silicon micromirror

4

light source

6

control lines

8th

detector element

10

Data Interface

L

sent out light

LR

reflected light

O

object

RP1, RP2

reference points

U

deflection

α

Reference deflection angle

Claims (11)

Contraption ( 1 ) for deflecting the beam path in an optical system, in particular in a system for measuring distance or for detecting objects in a selectable area around a moving vehicle, comprising at least one light source ( 4 ), at least one detector element ( 8th ) and at least one deflection element ( 2 ) for deflecting the light beam, the deflecting element ( 2 ) at least one silicon micromirror ( 3 ) having. Device according to claim 1, characterized in that the deflecting element ( 2 ) an arrangement of several individually controllable silicon micromirrors ( 3 ) includes. Device according to claim 1 or 2, characterized in that a deflecting element ( 2 ) is arranged at a position in the beam path before the light beam emerges. Device according to one of claims 1 to 3, characterized in that a deflecting element ( 2 ) in front of the detector element ( 8th ) lying position is arranged in the beam path. Device according to one of the preceding claims, characterized in that the light source ( 4 ) is a laser diode. Device according to one of the preceding claims, characterized in that the light source ( 4 ) is operated pulsating. Device according to one of the preceding claims, characterized in that the reading of the detector element ( 8th ) synchronized or synchronized with the emission of light (L) by the light source ( 4 ) he follows. Using a device ( 1 ) according to one of claims 1 to 7 for the detection of objects (O) in a selectable space. Using a device ( 1 ) according to one of claims 1 to 7 for measuring the distance between the device ( 1 ) and an object in the room (O). Using a device ( 1 ) according to one of claims 1 to 7 for recognizing characteristic features of an object (O) located in space. Using a device ( 1 ) according to one of claims 1 to 7 for identification of a bar code.