CN117676343A - Exposure control method for point laser optical measuring device - Google Patents
Exposure control method for point laser optical measuring device Download PDFInfo
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- CN117676343A CN117676343A CN202311362331.5A CN202311362331A CN117676343A CN 117676343 A CN117676343 A CN 117676343A CN 202311362331 A CN202311362331 A CN 202311362331A CN 117676343 A CN117676343 A CN 117676343A
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Abstract
The invention discloses an exposure control method of a point laser optical measuring device, which comprises the following steps: initializing exposure parameters, and setting an image target gray value and a gray value minimum deviation range to form a gray value interval; collecting a current frame image and calculating the maximum gray value of the current frame image; judging whether the maximum gray value is in a preset gray value interval, if so, not changing the exposure time, and collecting the next frame of image; if not, adjusting the exposure time; calculating the exposure time which is required to be set for reaching the target gray value by adopting a PID algorithm; the exposure time determined by calculation is set as the exposure time parameter of the next frame, and the next frame image is acquired.
Description
[ field of technology ]
The invention belongs to the technical field of measurement, and particularly relates to an exposure control method of a point laser optical measurement device.
[ background Art ]
Optical measurement devices (e.g., industrial cameras) are widely used in the fields of aerospace, automotive manufacturing, construction, engineering, etc. due to their advantages of high precision, non-contact, automation, low cost, etc. The spot laser optical measuring device is mainly applied to the field of industrial detection, the application scene environment is complex, and proper exposure parameters are needed for obtaining high-precision stable measured values. There are also some methods for adjusting exposure parameters, such as automatic exposure methods, but the automatic exposure function requires the sensor to detect and adjust the ambient brightness and the target reflection signal in real time, and in some fast-changing measurement applications, the convergence speed is too slow, and the measurement result may be inaccurate due to too many times of adjusting the exposure parameters. In addition, the dynamic response range of the existing automatic exposure method is small, and in practice, for a larger dynamic range, the image sensor may need a longer exposure time to capture a darker signal. For smaller dynamic ranges, the image sensor may select a shorter exposure time to avoid oversaturation of the signal. The image sensor may provide a wider measurement range and better measurement sensitivity if the dynamic range is extended. Therefore, how to adjust the exposure parameters of the spot laser optical measurement device is a problem that needs to be solved in the industry.
[ invention ]
The invention aims to provide an exposure control method of a spot laser optical measuring device, which is used for controlling the exposure of the spot laser optical measuring device to obtain a high-precision stable measured value.
In order to achieve the above object, the exposure control method of the spot laser optical measuring device disclosed by the invention comprises the following steps:
step 1: initializing exposure time, and setting a target gray value of an image and a minimum deviation range of the gray value to form a gray value interval;
step 2: collecting a current frame image and calculating the maximum gray value of the current frame image;
step 3: judging whether the current maximum gray level is in a preset gray level interval or not, if the current maximum gray level is in the gray level interval, not changing the exposure time, and collecting the next frame of image; if the current maximum gray is not in the gray value interval, calculating the exposure time which is required to be set up to the target gray value by adopting a PID algorithm;
step 4: and updating the exposure time parameter and collecting the next frame of image.
According to the above main feature, if the calculated exposure time exceeds the set threshold upper limit, the exposure time is set to the maximum value; if the calculated exposure time exceeds the set threshold lower limit, the exposure time is set to a minimum value.
According to the main characteristics, the PID algorithm is adopted to calculate the exposure time increment delta u (k) which needs to be adjusted, wherein delta u (k) =k p *(e k -e k-1 )+k i *e k +k d *(e k -2e k-1 +e k-2 ) Wherein k is p For the k-th order proportional control coefficient, k i For the k-th integral control coefficient, k d E is the kth differential control coefficient k The k-th deviation.
Judging whether the current maximum gray value is in a preset gray value interval according to the main characteristics, and determining an exposure time output value by a nonlinear control algorithm, wherein the nonlinear control algorithm formula is as followsIn e 0 Is the minimum deviation.
According to the main characteristics, the proportional coefficient, the integral coefficient and the differential coefficient in the PID algorithm are set in sections according to different exposure time intervals, and by using different coefficients in different exposure time intervals, better control performance can be obtained, stability and convergence speed are improved, and the exposure time intervals are set to be 0-100us, 100-200us, 200-400us, 400-800us and more than 800 us.
Compared with the prior art, the invention has the following excellent technical effects: firstly, the adjusting speed is high, and by using the method, the proper exposure parameters can be adjusted only by a few frames; second, the adaptability is strong, through the condition of automatic adjustment exposure parameter, avoid overexposure and underexposure, the image sensor can adapt to the environment automatically to provide reliable and unanimous measurement performance, thereby realize stable measuring result.
[ description of the drawings ]
Fig. 1 is a schematic diagram of functional blocks of a spot laser optical measuring device embodying the present invention.
Fig. 2 is a gray scale image acquired by a point laser optical measurement device embodying the present invention.
Fig. 3 is a flow chart of an exposure control method of the spot laser optical measuring device for implementing the invention.
[ detailed description ] of the invention
Referring to fig. 1, a schematic functional block diagram of a spot laser optical measuring device according to the present invention includes the following modules:
the laser emission module is responsible for generating and emitting laser beams and comprises a laser diode, a laser modulation circuit and other components, and is used for generating high-intensity and stable laser beams;
the receiver module is used for receiving the laser beam reflected from the target object, and comprises an image sensor (CMOS chip), an optical filter, a signal amplifying circuit and other components, and is used for receiving and converting the optical signal into an electric signal;
the control circuit module is responsible for controlling the laser transmitting and receiving processes, including circuits such as laser power control, laser modulation, amplifier control and the like, and is used for ensuring the stability and reliability of laser transmitting and receiving;
the processor module is responsible for processing the received electric signals, performing signal processing and data processing, and comprises an analog-to-digital converter, a digital signal processor and other components, and is used for converting the analog electric signals into digital signals and performing filtering, gain control, data decoding and other processes;
and the output module is used for outputting the processed displacement measurement result data.
As shown in fig. 2, the gray scale formed by the point laser optical measuring device is one-dimensional, and the image formed by the other image sensor is two-dimensional data, so the exposure control method of the point laser optical measuring device of the present invention controls the exposure based on the maximum gray scale value.
Referring to fig. 3, a flow chart of a method for controlling exposure of a spot laser optical measuring device according to the present invention is shown, wherein the method for controlling exposure of a spot laser optical measuring device comprises the following steps:
initializing exposure time, and setting a target gray value of an image and a minimum deviation range of the gray value to form a gray value interval;
collecting a current image, and calculating the deviation e (k) between the maximum gray value of a kth frame image and a set target value;
judging whether the maximum gray value is in a preset gray value interval, determining an exposure time output value through a nonlinear control algorithm, wherein the nonlinear control algorithm formula is as followsIn e 0 Is the minimum deviation. If the current gray level deviation |e k |≤|e 0 I, not adjusting the exposure time; if the current gray level deviation |e k |＞|e 0 I, adjusting the exposure time increment deltau (k);
calculating an exposure time increment Deltau (k) according to an incremental PID algorithm, the exposure time increment Deltau (k) =k p *(e k -e k-1 )+k i *e k +k d *(e k -2e k-1 +e k-2 ) Wherein k is p For the k-th order proportional control coefficient, k i For the k-th integral control coefficient, k d E is the kth differential control coefficient k Is the kth deviation; the proportional coefficient, the integral coefficient and the differential coefficient are set in a segmented mode according to different exposure time intervals, better control performance can be obtained by using different coefficients in different exposure time intervals, stability and convergence speed are improved, and the exposure time intervals are set to be 0-100us, 100-200us, 200-400us, 400-800us and more than 800 us.
Adjusting the exposure time of the acquired next frame image by using the exposure time increment delta u (k), namely, setting the exposure time to be the maximum value if the calculated exposure time exceeds the upper limit of a set threshold (the upper limit of the threshold is automatically set according to the different frame rates at the beginning); if the calculated exposure time exceeds the set threshold lower limit, the exposure time is set to a minimum value.
And setting the exposure time determined by calculation as an exposure time parameter of the next frame, and collecting the image of the next frame.
The parameters of the control performance in the PID algorithm are proportional coefficient, integral coefficient and differential coefficient. If the response speed needs to be improved, the proportionality coefficient can be adjusted; if steady state errors need to be eliminated, the integral coefficient can be adjusted; the differential coefficient may be adjusted if improved stability is desired. Determination of values of proportional, integral, differential coefficients, i.e. k, by multiple experiments p ,k i ,k d Is described in more detail in this prior art, and is not described in detail here.
Compared with the prior art, the invention has the following excellent technical effects: firstly, the adjusting speed is high, and by using the method, the proper exposure parameters can be adjusted only by a few frames; second, the adaptability is strong, through the condition of automatic adjustment exposure parameter, avoid overexposure and underexposure, the sensor can adapt to the environment automatically to provide reliable and unanimous measurement performance, thereby realize stable measuring result.
It will be understood that equivalents and modifications will occur to those skilled in the art in light of the present invention and their spirit, and all such modifications and substitutions are intended to be included within the scope of the present invention as defined in the following claims.
Claims (5)
1. An exposure control method of a point laser optical measuring device comprises the following steps:
step 1: initializing exposure time, and setting a target gray value of an image and a minimum deviation range of the gray value to form a gray value interval;
step 2: collecting a current frame image and calculating the maximum gray value of the current frame image;
step 3: judging whether the current maximum gray level is in a preset gray level interval or not, if the current maximum gray level is in the gray level interval, not changing the exposure time, and collecting the next frame of image; if the current maximum gray is not in the gray value interval, calculating the exposure time which is required to be set up to the target gray value by adopting a PID algorithm;
step 4: and updating the exposure time parameter and collecting the next frame of image.
2. The spot laser optical measuring device exposure control method according to claim 1, wherein: setting the exposure time to a maximum value if the calculated exposure time exceeds a set threshold upper limit; if the calculated exposure time exceeds the set threshold lower limit, the exposure time is set to a minimum value.
3. The spot laser optical measuring device exposure control method according to claim 1, wherein: calculating the exposure time increment delta u (k) required to be adjusted by adopting a PID algorithm, wherein delta u (k) =k p *(e k -e k-1 )+k i *e k +k d *(e k -2e k-1 +e k-2 ) Wherein k is p For the k-th order proportional control coefficient, k i For the k-th integral control coefficient, k d E is the kth differential control coefficient k The k-th deviation.
4. The spot laser optical measuring device exposure control method according to claim 1, wherein: judging whether the current maximum gray value is in a preset gray value interval, determining an exposure time output value through a nonlinear control algorithm, wherein the nonlinear control algorithm formula is as followsIn e 0 Is the minimum deviation.
5. The spot laser optical measuring device exposure control method according to claim 1, wherein: the proportional coefficient, the integral coefficient and the differential coefficient are set in segments according to different exposure time intervals, and by using different coefficients in different exposure time intervals, better control performance can be obtained, stability and convergence speed are improved, and the exposure time intervals are set to be 0-100us, 100-200us, 200-400us, 400-800us and more than 800 us.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202311362331.5A CN117676343A (en) | 2023-10-19 | 2023-10-19 | Exposure control method for point laser optical measuring device |
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| CN202311362331.5A CN117676343A (en) | 2023-10-19 | 2023-10-19 | Exposure control method for point laser optical measuring device |
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| CN117676343A true CN117676343A (en) | 2024-03-08 |
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