EP2283461A1

EP2283461A1 - Image processing device for detecting contrast transition, particularly in a machine tool

Info

Publication number: EP2283461A1
Application number: EP09745607A
Authority: EP
Inventors: Wolfgang Niehsen; Thilo Koeder; Joachim Platzer
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2008-05-14
Filing date: 2009-03-16
Publication date: 2011-02-16
Also published as: US20110122243A1; DE102008001760A1; CN102027506A; WO2009138274A1; JP5264996B2; RU2010150846A; JP2011523808A

Abstract

An image processing device for detecting contrast transition comprises a digital imaging unit as an optical sensor unit, the digital sensor signals of which are processed in an evaluation unit.

Description

title

Image processing device for contrast transition detection, in particular in a machine tool

The invention relates to an image processing device for contrast transition detection according to the preamble of claim 1.

State of the art

In DE 10 2005 005 348 Al is a

Image processing device described in a motor vehicle, via which the position of the vehicle is to be determined in the lane, wherein in the case of leaving the target lane a warning signal is emitted. The image processing device comprises a video camera which generates an analog video signal from the lane, which is evaluated in an evaluation unit. The evaluation unit comprises a filter with a differentiator and a threshold circuit, wherein the video signal for contrast transition detection in the differentiator is subjected to a differentiation and the signal generated in this manner in the threshold circuit is compared with a reference value. If the differentiated signal exceeds the assigned reference value, then a contrast transition is detected, which indicates the exceeding of a lateral lane marking, whereupon the warning signal is generated.

The use of the video camera is a considerable cost, whereby the uses are limited accordingly. Disclosure of the invention

The invention is based on the object to provide an inexpensive image processing device with easy-to-implement means.

This object is achieved with the features of claim 1. The dependent claims indicate expedient developments.

The image processing device according to the invention is used for contrast transition detection, a preferred field of application being machine tools, in particular hand-guided machine tools, such as e.g. hand-held jigsaws. By means of the image processing device, a desired track or setpoint line can be detected, which is the machine in which the

Image processing device is installed, should follow. In the case of use in a machine tool, the setpoint track may be a setpoint or tear line on the workpiece to be machined, along which the machining with the tool of the

Machine tool to be done. The preferred application is therefore in hand-held machine tools, which in principle also semi-stationary or stationary machine tools come into consideration.

Further fields of application are the use in vehicles, in particular for setpoint track detection, by

Road markings are detected using the image processing device. In addition, an application in household appliances is conceivable, which are equipped with a tool for processing an object, such as electric kitchen appliances, the image processing device detects, for example, the contrast between a cutting line and the adjacent areas and generates a warning signal in the event of deviation from the desired line is that can be brought to the display and incidentally can also be used to switch off the device. The image processing device for contrast transition detection comprises an optical sensor unit, which is designed as a digital image capture unit and generates a line and column-shaped digital image in the form of digital sensor signals which are to be fed to a downstream evaluation unit. In the evaluation unit, the sensor signals are analyzed, wherein in particular signal changes are determined, since these characterize a contrast transition in the recorded image, which serves to recognize the desired track or the leaving of the target track. As digital

Image capture unit is in particular a digital camera into consideration, which due to the limited field of application and the task of having to transmit only contrasts, can be made relatively simple. For example, a relatively low resolution with a reduced number of pixels may suffice.

Due to the low quality requirements, other digital imaging units may be used, such as optical sensors such as optical sensors. Mouse sensors or the like.

The evaluation unit connected downstream of the digital image acquisition unit can either be used to process analog

In principle, an alternative and a cumulative execution of both analog and digital signal processing comes into consideration.

In the case of analog signal processing, the evaluation unit comprises a digital-to-analog converter to which the digital sensor signals of the image acquisition unit can be supplied as input variables and which converts the digital signals into analog signals. These can then be known per se

Be analyzed and evaluated in the evaluation, for example, in one of the evaluation associated with the - A -

Digital-to-analog converter downstream differentiator, in which a differentiation of the signals is performed. The differentiation of the signals achieves an amplification of the brightness transitions which characterize a contrast transition. In a comparator also assigned to the evaluation unit, a comparison of the signal determined in the differentiator can then be carried out with a reference variable, wherein a contrast transition is detected if the brightness difference in the signal exceeds a reference value. By changing this reference value, the sensitivity of the evaluation can be adjusted.

In the case of digital evaluation can be dispensed with the digital-to-analog converter, since the sensor signals are already present in digital form at the output of the optical imaging unit. The analysis and evaluation in the evaluation unit takes place in this case, for example via a logic gate, e.g. an AND gate, in which various digital signals, which originate from the image acquisition unit, are linked in a logical manner, wherein for the presence of a

Contrast transition, the result of the logical link must correspond to a certain value or must be within a defined normal range. Basically, however, as an alternative to the logic gate and the processing of the digital signals in a microcontroller is possible, for example, with a

Interrupt-on-change function is equipped. Finally, the evaluation of the digitally received signals can also be carried out via a so-called edge filter, which may be part of the evaluation unit. In any case, it can be ascertained via the evaluation in the evaluation unit whether a contrast transition characteristic of a desired track takes place within the viewed image section. In the digital evaluation, the sensitivity can also be adjusted by masking low-order bits, which can be masked, for example, by a corresponding configuration in the

Tristate registers already performed on the hardware side can be, so no additional computational effort is required.

Further advantages and expedient embodiments can be taken from the further claims, the description of the figures and the drawings. Show it:

1 is a perspective view of a executed as a hand-held jigsaw machine tool, with a

Image processing device is equipped to detect a target line to follow the tool of the jigsaw,

2 is a schematic representation of a section of a roadway with different degrees of contrast and associated signals of the image processing device,

3 shows the evaluation of the sensor signals generated in a digital camera via an analog evaluation unit,

4 shows the evaluation of the digital sensor signals in a digital evaluation unit.

In the machine tool 1 shown in Fig. 1 is a hand-held jigsaw 2, which has in a housing 3, an electric drive motor for driving movement of the running saw blade 8 working tool 7, wherein the saw blade 8 performs a lifting movement according to arrow 16. The

Saw blade 8 is guided by a base plate 4 which is connected to the housing 3 and is placed on a workpiece 5 to be machined during machining. The workpiece 5 is provided with a marking 9, which represents a tear or target line along which the processing is to take place via the jigsaw 2. To hold the jigsaw 2, a handle 10 is provided on the housing 3, the switching on and off takes place via a switch 11. The saw blade 8 is held in a tool holder 12.

In a front region of the housing 3, a digital camera 18 is arranged, via which the working area can be detected, which lies directly in front of the saw blade 8. The feed or working direction is marked with arrow 6, accordingly, the area covered by the digital camera 18 is in the direction of arrow 6 in front of the saw blade 8.

The jigsaw 2 is designed as a semi-automatic tool and has in addition to the electric drive motor, which is responsible for the lifting movement of the saw blade 8, further actuators 13 and 14 for adjusting the saw blade, so that the saw blade within the adjustment automatically the target line 9 on the Workpiece 5 can follow. A first actuator 13 is located in the upper part of the housing 3 above the tool holder 12 and allows a rotation or pivoting of the saw blade 8 about the saw blade longitudinal axis according to arrow 15. The second actuator 14 is located in the lower part of the jigsaw 2 and allows a translational and / or rotational movement of the saw blade 8 transversely to the feed direction 6, whereby a pendulum movement of the saw blade can be adjusted.

All actuators in the jigsaw 2, so the electric drive motor and the two actuators 13 and 14 are set via control signals of a control unit 17, which receives as input the signals of the digital camera 18 and from the received signals control signals for acting on the drive motor or the actuators generated. About the sensor device representing a digital camera 18, the control unit 17 and acting as actuators actuators 13 and 14 and the drive motor, a closed loop is achieved. During operation of the jigsaw, the target line 9, which is recorded on the upper side of the workpiece 5, is detected via the digital camera 18. The digital camera 18, together with the control and control unit 17, the image processing device for contrast transition detection between the target line 9 and the adjacent areas of the workpiece. 5

Instead of a digital camera, it is also possible to use other optical image acquisition units which are designed digitally and deliver corresponding digital signals. Such an additional digital sensor is exemplified by reference numeral 19.

In Fig. 2, a section of the work area of the jigsaw is shown immediately in front of the saw blade. The working area is located on the upper side of the workpiece 5 to be machined, wherein the marking, which represents the desired line for the tool, is identified by the reference numeral 9. The nominal line 9 has a strong contrast to the immediately surrounding regions of the workpiece 5.

In addition, a strip 30 is present on the upper side of the workpiece 5 parallel to the reference line 9, which has a lower contrast with respect to the surrounding areas of the upper side of the workpiece 5 than the reference line 9. The strip 30 represents, for example, a disturbance in the surface of the workpiece , but it can also be a shadow or the like. Based on the different contrasts of nominal line 9 and strip 30, the mode of operation will be described below.

The working area is recorded by the digital image acquisition unit, which supplies various signals which are analyzed and evaluated in an evaluation unit. As with YO (LSB) to Y7 (MSB) for the bit valence within a row on the one hand and the numbers 1 to 95 for different columns on the other hand, provides the digital

Image capture unit a digital, row and column-shaped grid, each grid space is occupied by the value "0" or the value "1". "1" stands for a recognized contrast, with "0" no contrast could be detected. The target line 9 is assigned the value "1" in all Y values due to the relatively high contrast across the entire width, whereas the strip 30 is assigned the value "1" only in the Y values Y0, Y1 and Y2, the other Y values Y3 to Y7, on the other hand, assume the value "0".

FIG. 3 shows the data record determined from FIG. 2 which is supplied to an evaluation unit 31 operating in an analog manner. The evaluation unit 31 is in particular part of the control unit or control unit 17 (FIG. 1).

The evaluation unit 31 according to FIG. 3 comprises a processor or a latch 32, a digital-to-analog converter 33 and a differentiator 34. The digital data supplied to the evaluation unit 31 are converted in the digital-to-analog converter 33 into analog signals, which are subsequently connected downstream Differentiator 34 are subjected to a differentiation. In the differentiation, differences in a change in the waveform are amplified, whereas constant signals in the differentiation provide no output values. This results in the signal curve labeled "Status", which has a deflection in each case in the transition between the strip 30 or the reference line 9 and the directly adjacent regions of the workpiece top side, since the contrast of the strip 30 is less than the contrast of the reference line 9, Accordingly, the deflections associated with the strip 30 are also smaller than the deflections associated with the reference line 9. The signals can be evaluated by determining whether or not the signals are to be supplied from the differentiator 34 and which is likewise part of the evaluation unit the rash is large enough that a contrast is detected which is assigned to the target line, whereas the signal is lower, the contrast is correspondingly lower and it can be determined accordingly that this contrast does not belong to the target line.

In Fig. 4 is another embodiment of a

Evaluation unit 31 shown, however, in contrast to Fig. 3 is not working on an analog basis, but on a digital basis. The evaluation unit 31 alternatively comprises either a logic gate 35 or a microcontroller 36. The logic gate is designed as an AND gate, for example, which only leads to a result "1" if all Y values assume the value "1". Since this is not the case with respect to the strip 30, the logic gate 35 for the strip 30 furnishes the result value "0", whereas for the reference line 9 the result value "1" is supplied since all the Y values of the

In this way, it is possible to differentiate between a sufficient contrast with respect to the reference line 9 and an insufficient contrast with respect to the strip 30.

In the embodiment as a microcontroller 36, the signals are processed numerically. Here, reference values can be specified, whereby the sensitivity is to be set via the height of the reference values.

Another possibility is an embodiment of the digital evaluation unit 31 with an edge filter into consideration.

Claims

claims

1. Image processing device for contrast transition detection, in particular in a machine tool (1), with an optical sensor unit, the sensor signals of an evaluation unit (31) can be fed, in the signal changes for detecting a contrast transition can be determined, characterized in that the optical sensor unit as a digital image capture unit ( 18) is executed, whose digital sensor signals are processed in the evaluation unit (31).

2. Image processing device according to claim 1, characterized in that the digital image capture unit is a digital camera (18).

3. Image processing device according to claim 1 or 2, characterized in that the evaluation unit (31) comprises a digital-to-analog converter (33) in which the digital sensor signals are convertible into analog signals.

4. Image processing device according to claim 3, characterized in that the evaluation unit (31) comprises a digital-to-analog converter (33) connected downstream differentiator (34).

5. Image processing device according to claim 4, characterized in that the differentiator (34) is associated with a comparator, via which a comparison of the difference in the (34) detected signal with a reference variable is feasible.

6. Image processing device according to one of claims 1 to 5, characterized in that the evaluation unit (31) comprises a logic gate (35) in which the digital sensor signals are to be evaluated.

7. Image processing device according to one of claims 1 to 6, characterized in that the evaluation unit (31) comprises a microcontroller (36), in which the digital sensor signals are to be evaluated.

8. Image processing device according to one of claims 1 to 7, characterized in that the evaluation unit (31) comprises an edge filter, in which the digital sensor signals are to be evaluated.

9. Image processing device according to one of claims 1 to 8, characterized in that in the digital sensor signals associated with the evaluation unit (31) low-order bits are masked in an adjustable manner.

10. A method of operating the image processing device according to one of claims 1 to 9, wherein the contrast transition detection is used for detecting a target track.