CN104427253A - Camera light intensity automatic regulating apparatus - Google Patents

Abstract

The invention belongs to the technical field of photogrammetry, and in particular relates to a camera light intensity automatic adjustment device. It includes a camera, a fixed polarizer, a tachometer, a hollow shaft motor, a rotating polarizer and supporting circuits; a graphics acquisition and processing computer collects image information and solves background gray values; a gray signal acquisition circuit collects gray signals and inputs them to The comparison circuit 2 compares with the set target gray value; the comparison value is used as the speed loop setting value after passing through the proportional adjustment circuit; the rotation speed of the hollow shaft motor is obtained by the measurement of the tachometer, and is input to the comparison circuit after being collected by the tachometer signal acquisition circuit. Circuit 1, the speed value is compared with the set value of the speed loop, and the motor speed deviation is obtained through calculation; the deviation signal is calculated by the control circuit to form a control signal, which is transmitted to the motor drive circuit to drive the hollow shaft after passing through the power amplifier circuit The motor rotates; this process is carried out cyclically, and the angular position of the hollow shaft motor is continuously corrected to realize the control of the deflection angle of the polarizer.

Description

A camera light intensity automatic adjustment device

technical field

The invention belongs to the technical field of photogrammetry, and in particular relates to a camera light intensity automatic adjustment device.

Background technique

Photogrammetry technology has been widely used in science and technology and industrial production. However, optical measurement has strict requirements on the background light. It is necessary to strictly control the background light intensity or improve the image quality by adjusting the lens aperture. However, in the occasion where the background light changes rapidly with time, in order to avoid the phenomenon of being too dark or too bright and ensure the image acquisition effect, it is necessary to design a special automatic light intensity adjustment mechanism. The commonly used adjustment methods are the aperture adjustment method and the polarizer adjustment method, but the change of the aperture needs to be realized by adjusting the lens, but photogrammetry needs to calibrate the lens distortion of the camera, and changing the lens will affect the calibration effect and reduce the measurement accuracy.

The dimming structure utilizing the polarization principle has a good effect, and the adjustment range of the light intensity is large. The structure of the polarizer is formed by two polarizers close together, one of which is fixed, and when the other rotates, the angle between the two polarizers will change. Natural light is an electromagnetic wave with the polarization characteristic of a transverse wave. Assuming that the light vector A vibrating in the plane, the amplitudes in the x and y directions are A _x and A _y respectively, the vibration phase difference is δ, and the angle between the maximum polarization transmission direction PM and the x axis after passing through the first polarizer is θ, and let Pm be the direction orthogonal to PM. As shown in Figure 1.

Assuming that the maximum amplitude transmittance of an ideal polarizer is 1 and the minimum amplitude transmittance is 0, the transmitted light intensity is: $\mathrm{E.}\left(\mathrm{\θ}\right){=A}_x^2{\cos }^2\mathrm{\θ}+A_{\mathrm{the\; y}}^2{\sin }^2\mathrm{\θ}+2A_x{A}_{\mathrm{the\; y}}\cos \mathrm{\θ}\sin \mathrm{\θ}\cos \mathrm{\δ}$

$<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}{\mathrm{<span\; class="notranslate">\; cos</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; the\; y</span>}}{\mathrm{<span\; class="notranslate">\; sin</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 2</span>}\sqrt{{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; the\; y</span>}}}\mathrm{<span\; class="notranslate">\; cos</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}\mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}\mathrm{<span\; class="notranslate">\; cos</span>}\mathrm{<span\; class="notranslate">\; \&delta;</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

Put the polarizer P1 in the optical path as a polarizer, set the natural light intensity as E ₀ , at this time, the projected light intensity E in any direction becomes linearly polarized light, namely:

$\mathrm{<span\; class="notranslate">\; E.</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

Put the polarizing plate P2 in the optical path as an analyzer, and the angle between the transmission direction P2 and P1 is θ, thus forming a quarter-wave plate. At this time, E(θ)=E ₂ in formula (1), A _x =A1, A _y =0, substituting into the transmitted light intensity formula (1), get:

${\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; cos</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

Right now: ${\mathrm{E.}}_2={\mathrm{E.}}_1{\cos }^2\mathrm{\&theta;}=\frac{1}{2}{\mathrm{E.}}_0{\cos }^2\mathrm{\&theta;}---\left(4\right)$

Among them, A1 and _E1 are the light amplitude and light intensity after passing through the polarizer P1, and _E2 is the light intensity after passing through the analyzer P2, as shown in Figure 2.

However, in current applications for adjusting the light intensity of polarizers, the angle between polarizers is often relatively fixed, so real-time and quantitative adjustment of light intensity cannot be achieved.

Contents of the invention

In order to improve the adjustment accuracy and real-time performance of the adjustment system, the invention proposes a camera light intensity automatic adjustment device, which introduces the closed-loop automatic control technology based on speed and position feedback into the light intensity adjustment based on the polarizer, and realizes the motor Fast response and smooth operation, to achieve the experimental effect of constant incident light intensity of the camera and constant gray scale of the image in the test area.

In order to achieve the above object, the technical scheme adopted in the present invention is:

A device for automatically adjusting light intensity of a camera includes a camera, a fixed polarizer, a tachometer, a hollow shaft motor, a rotating polarizer and supporting circuits; The shaft is fixed, and the optical axis of the hollow-shaft motor and the camera is adjusted to be coaxial. When the hollow-shaft motor rotates, the angle between the rotating polarizer and the fixed polarizer changes, so that the incident light intensity of the camera can be adjusted, and the speedometer can measure it in real time. The rotational speed of the hollow shaft motor is converted into an analog electrical signal and transmitted to the graphics acquisition and processing computer; the supporting circuit includes a graphics acquisition and processing computer, a grayscale signal acquisition circuit, a comparison circuit 1, a comparison circuit 2, a ratio adjustment circuit, and a tachometer Signal acquisition circuit, control circuit, power amplifier circuit, motor drive circuit; the computer for graphic acquisition and processing is connected to the camera to collect image information and solve the background gray value; the gray signal acquisition circuit and computer for graphic acquisition and processing Connect, collect the grayscale signal and input it to the comparison circuit 2 to compare with the set target grayscale value; the comparison value is used as the set value of the speed loop after passing through the proportional adjustment circuit; After being collected by the motor signal acquisition circuit, it is input to the comparison circuit 1, and the speed value is compared with the set value of the speed loop to obtain the motor speed deviation; the deviation signal is calculated by the control circuit to form a control signal, which is passed through the power amplifier circuit After that, it is transmitted to the motor drive circuit to drive the hollow shaft motor to rotate; this process is cyclical, and the angular position of the hollow shaft motor is continuously corrected to achieve the purpose of controlling the deflection angle of the polarizer.

The tachometer signal acquisition circuit, the comparison circuit 1, the control circuit, the power amplifier circuit, and the motor drive circuit constitute a rate loop, which is used for local feedback correction of the hollow shaft motor: on the one hand, the friction of the shaft system in the loop is suppressed, On the other hand, if the bandwidth allocation is reasonable, the speed loop feedback can be designed as a deep negative feedback to improve the characteristics of the object, reduce the difficulty of the hollow shaft motor's own characteristics on the design of the main loop control system, and make the system have a certain degree of robustness.

The graphics acquisition and processing computer, the grayscale signal acquisition circuit, the comparison circuit 2, the ratio adjustment circuit, the comparison circuit 1, the control circuit, the power amplification circuit, and the motor drive circuit constitute a position loop, and the feedback value and the set value of the grayscale are used to form a position loop. The comparison realizes the calculation of the deviation. According to the calculation result, the control error of the polarizer structure is sent to the control system of the hollow shaft motor to ensure the follow performance of the set gray value.

The supporting circuits are all implemented in digital form by single-chip microcomputers, the signal acquisition circuit of the speed measuring machine is composed of A/D, the grayscale signal acquisition circuit is composed of serial ports, and the operation of the comparison circuit 1, the comparison circuit 2 and the control circuit The unit is composed of a single-chip microcomputer. The control signal output by the control circuit is output to the drive circuit through D/A, and various state data enters the single-chip microcomputer through DIO. Calculation of various functions such as protection and judgment of status.

The beneficial effects obtained by the present invention are:

The camera light intensity automatic adjustment device based on the dual-loop automatic control system of the present invention is realized based on the principle of polarizers. The light intensity of the measured area is sensed by the camera, and the speed measuring machine, the hollow shaft motor, the camera, the image acquisition computer, and the adjustment control circuit are used. Together they form an adjustment device, which introduces the automatic control technology based on speed and position feedback into the adjustment of the polarizer to realize the automatic adjustment of the incident light intensity of the camera and keep the brightness of the collected image constant without being affected by the background light intensity. The experimental results show that when the background light intensity of the measured object changes drastically, it can quickly and automatically adjust the incident light intensity of the camera to achieve a constant light intensity, and the camera image can always be stable at the set gray value, with fast response speed and gray deviation. Not greater than 1.

Description of drawings

Fig. 1 is the schematic diagram I of polarization principle;

Fig. 2 is the schematic diagram II of the polarization principle;

Fig. 3 is a schematic diagram of the camera light intensity automatic adjustment device of the present invention;

In the figure: 1. Camera; 2. Adjusted incident light; 3. Lens; 4. Fixed polarizer; 5. Speed measuring machine; 6. Hollow shaft motor; 7. Rotating polarizer; 8. Original incident light.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

As shown in Figure 3, the camera light intensity automatic adjustment device of the present invention comprises a camera 1, a fixed polarizer 4, a tachometer 5, a hollow shaft motor 6, a rotating polarizer 7 and supporting circuits; the fixed polarizer 4 is installed in On the lens 3 of the camera 1, the rotating polarizer 7 is fixed to the inner shaft of the hollow-shaft motor 6, and the optical axis of the hollow-shaft motor 6 and the camera 1 is adjusted to be coaxial. When the hollow-shaft motor 6 rotates, the rotating polarizer 7 and the fixed The included angle between the polarizers 4 changes to realize the adjustment of the incident light intensity of the camera 1, and the tachometer 5 measures the rotating speed of the hollow shaft motor 6 in real time, and converts it into an analog electrical signal and transmits it to a graphics acquisition and processing computer; the supporting circuit includes Graphics acquisition and processing computer, grayscale signal acquisition circuit, comparison circuit 1, comparison circuit 2, ratio adjustment circuit, tachometer signal acquisition circuit, control circuit, power amplification circuit, motor drive circuit; said graphics acquisition and processing computer and camera Connect, collect image information and solve the background gray value; the gray signal acquisition circuit is connected with the graphics acquisition and processing computer, collect the gray signal and input it to the comparison circuit 2 to compare with the set target gray value; compare the value After passing through the proportional adjustment circuit, it is used as the set value of the speed loop; the speed of rotation of the hollow shaft motor 6 is measured by the tachometer 5, and after being collected by the tachometer signal acquisition circuit, it is input to the comparison circuit 1, and the speed value is consistent with the set value of the speed loop Comparing and calculating the motor speed deviation; the control circuit calculates the deviation signal to form a control signal, which is transmitted to the motor drive circuit to drive the hollow shaft motor 6 to rotate after passing through the power amplifier circuit; The angular position of the shaft motor 6 realizes the purpose of controlling the deflection angle of the polarizer.

The basic function of each circuit is as follows:

Speed loop: sequentially composed of tachometer signal acquisition circuit, comparison circuit 1, control circuit, power amplifier circuit, and motor drive circuit; it is mainly used for local feedback correction of hollow shaft motor 6 . On the one hand, the friction of the shaft system in the loop is suppressed. On the other hand, if the bandwidth allocation is reasonable in design, the speed loop feedback can be designed as deep negative feedback. For the loop, local feedback improves the object characteristics and reduces the hollow space. The difficulty of the design of the main loop control system due to the characteristics of the shaft motor 6 makes the system have certain robustness.

Position loop: sequentially composed of graphics acquisition and processing computer, grayscale signal acquisition circuit, comparison circuit 2, proportional adjustment circuit, comparison circuit 1, control circuit, power amplifier circuit, and motor drive circuit; through grayscale feedback value and setting The comparison of the values realizes the calculation of the deviation amount, and the control error of the polarizer structure is obtained according to the calculation result, which is sent to the control system of the hollow shaft motor 6 to ensure the following performance of the set gray value.

The supporting circuits are all realized in digital form by single-chip microcomputer. The tachometer signal acquisition circuit is composed of A/D, the gray signal acquisition circuit is composed of a serial port, the comparison circuit 1, the comparison circuit 2 and the operation unit of the control circuit are composed of a single-chip microcomputer, and the control signal output by the control circuit is passed through D/A is output to the drive circuit, and various state data enters the single-chip microcomputer through DIO, and the single-chip microcomputer completes the calculation of various functions such as speed acquisition, grayscale data reception, rotation angle calculation, digital signal processing, abnormal signal protection, and state discrimination.

Claims (4)

1. A camera light intensity automatic adjustment device, characterized in that: the device includes a camera (1), a fixed polarizer (4), a tachometer (5), a hollow shaft motor (6), a rotating polarizer (7) and supporting circuit; the fixed polarizer (4) is installed on the lens (3) of the camera (1), the rotating polarizer (7) is fixed to the inner shaft of the hollow shaft motor (6), and the hollow shaft motor (6) is connected to the The optical axis of the camera (1) is adjusted to be coaxial, and when the hollow shaft motor (6) rotates, the angle between the rotating polarizer (7) and the fixed polarizer (4) changes to realize the adjustment of the incident angle of the camera (1) The light intensity and tachometer (5) measure the rotational speed of the hollow shaft motor (6) in real time, and convert it into an analog electrical signal and transmit it to the graphics acquisition and processing computer; the supporting circuit includes a graphics acquisition and processing computer, a grayscale signal acquisition circuit, a comparison Circuit 1, comparison circuit 2, ratio adjustment circuit, tachometer signal acquisition circuit, control circuit, power amplifier circuit, motor drive circuit; the graphic acquisition and processing computer is connected with the camera, collects image information and solves the background gray value; The grayscale signal acquisition circuit is connected with the graphics acquisition and processing computer, and the grayscale signal is collected and input to the comparison circuit 2 to compare with the set target grayscale value; the comparison value is used as the set value of the speed loop after passing through the proportional adjustment circuit; The rotational speed of the hollow shaft motor (6) is measured by the tachometer (5), and is collected by the signal acquisition circuit of the tachometer, and then input to the comparison circuit 1, and the speed value is compared with the set value of the speed loop to obtain the motor speed deviation ;The deviation signal is calculated by the control circuit to form a control signal, which is transmitted to the motor drive circuit to drive the hollow shaft motor (6) to rotate after passing through the power amplifier circuit; the process is cyclic, and the angle of the hollow shaft motor (6) is continuously corrected Position, to achieve the purpose of controlling the deflection angle of the polarizer. 2. The camera light intensity automatic adjustment device according to claim 1, characterized in that: said tachometer signal acquisition circuit, comparison circuit 1, control circuit, power amplification circuit, and motor drive circuit constitute a rate loop for hollow Shaft motor (6) performs partial feedback correction: on the one hand, the friction of the shaft system in the loop is suppressed; on the other hand, if the bandwidth allocation is reasonable, the speed loop feedback can be designed as deep negative feedback to improve the characteristics of the object and reduce the hollow shaft The difficulty of the design of the main loop control system due to the characteristics of the motor (6) makes the system have certain robustness. 3. The camera light intensity automatic adjustment device according to claim 1, characterized in that: said graphic acquisition and processing computer, grayscale signal acquisition circuit, comparison circuit 2, ratio adjustment circuit, comparison circuit 1, control circuit, power The amplifying circuit and the motor drive circuit form a position loop, and the calculation of the deviation is realized by comparing the feedback value of the gray level with the set value, and the control error of the polarizer structure is obtained according to the calculation result, and sent to the control system of the hollow shaft motor (6) , to ensure the following performance of the set gray value. 4. The camera light intensity automatic adjustment device according to claim 1, characterized in that: said supporting circuits are all realized in digital form by single-chip microcomputers, said tachometer signal acquisition circuit is composed of A/D, and said grayscale signal Acquisition circuit is made up of serial port, and the operation unit of described comparison circuit 1, comparison circuit 2 and control circuit is made of single-chip microcomputer, and the control signal that control circuit outputs is sent to driving circuit through D/A, and various state data enters single-chip microcomputer through DIO, and single-chip microcomputer Completing the calculation and status identification of various functions such as speed acquisition, grayscale data reception, rotation angle calculation, digital signal processing, and abnormal signal protection.