An optoelectronic aiming method based on an oscillating slit

Abstract

The present application belongs to the field of optical measurement, and discloses an oscillating slit-based photoelectric aiming method, which is characterized in that: when the photoelectric aiming light spot is chopped by the two inner edges of the slit at the same time, the two signals are zero after passing through the multiplier and integrator of the phase-locked due to the inconsistency between the chopping frequency of the slit and the reference frequency of the reference signal source, and aiming is performed. The present application solves the problem of accurate aiming in the field of angle measurement, and realizes accurate aiming in the wide wave band of ultraviolet-visible-infrared. The device is small in size, easy to install and integrated, and can be used to realize the aiming function in other measurement fields, and has a wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of optical measurement technology and relates to an optoelectronic aiming method based on an oscillating slit. Background Technology

[0002] Traditional photoelectric aiming is often limited by human eye fatigue and the limitation of visible light, resulting in significant defects. However, the photoelectric aiming method based on the front slit utilizes the change in electrical signal inside the detector when the front slit passes through a circular light spot. This change can be used for automated photoelectric aiming. At the same time, based on this change, we can easily design devices and algorithms to improve aiming accuracy or sensitivity.

[0003] Photoelectric aiming methods have important applications in precision angle measurement. Currently, various types of photoelectric aiming technologies have been researched and developed to meet different testing needs across different operating wavelengths and with varying degrees of precision. The mainstream methods currently include the CCD method and the direct alignment method.

[0004] The CCD method uses image algorithms to calculate the centroid coordinates of the laser spot on the photosensitive surface array of the CCD by collecting pixel values. The CCD is then aligned with the center of the spot using these coordinates. The advantage of the CCD method is its high accuracy, but its disadvantage is that the response wavelength range is narrow, mostly reaching only the visible to near-infrared wavelength range.

[0005] The direct alignment method of the detector relies on the trend of the voltage change of the internal response of the detector when it passes through the light source, which first increases and then decreases. The peak value of the curve is used to align the light spot. Its advantage is a wide response wavelength range. However, since this method relies on the coordinates when the first derivative of the curve is zero, its accuracy and sensitivity largely depend on the magnitude of the second derivative of the curve, that is, how fast the curve changes. Summary of the Invention

[0006] (I) Purpose of the Invention

[0007] The purpose of this invention is to address the issue that aiming methods in angle measurement generally have poor sensitivity and are limited by wavelength bandwidth. This invention provides a method to increase the accuracy of photoelectric aiming and expand the response wavelength range, based on the general limitations of aiming methods in angle measurement, which are often restricted by wavelength bandwidth. This method relies on the changing pattern of the electrical signal from the lock-in amplifier module when the light signal passes through the oscillating slit to achieve photoelectric aiming, thereby improving aiming sensitivity and accuracy. It also improves existing measurement methods by utilizing detector switching to meet the requirements of wide-band (ultraviolet-visible-infrared) aiming.

[0008] (II) Technical Solution

[0009] To solve the above-mentioned technical problems, the present invention provides a photoelectric aiming device based on an oscillating slit, comprising: a turntable 1, an oscillating slit 2, a detector 3, a measurement module, and a host computer 7; the turntable 1 includes a mounting platform fixed at the center and an annular platform rotating around the mounting platform, a measurement sample block is arranged on the mounting platform, and the oscillating slit 2 and detector 3 are arranged on the annular platform. The detector 3 is located on the light-emitting side of the oscillating slit 2, and the detector 3 is connected to the measurement module, which is connected to the host computer 7. The light reflected by the sample block is chopped by the oscillating slit 2 and received by the detector 3, and then pre-amplified and phase-locked amplified by the measurement module. The processed data is sent to the host computer 7, which determines the position where the annular platform rotates to align the light with the oscillating slit 2.

[0010] The detector 3 is provided in multiple ways, each corresponding to a different wavelength band. Multiple detectors 3 are arranged on the same rotating wheel. By switching different detectors, optical pulse signals under different wavelength bands can be detected.

[0011] The detector 3 consists of three units arranged in a triangle. Different aiming bands are selected by switching between them via an internal motor, enabling wide-band measurement from ultraviolet to visible to infrared.

[0012] The measurement module includes a lock-in amplifier 6, a preamplifier 4, and a reference signal source 5 that generates a square wave with the same frequency as the oscillating slit 2. The electrical signal detected by the detector 3 is amplified by the preamplifier 4 and then enters the lock-in amplifier 6. At the same time, the square wave reference signal generated by the reference signal source 5 is input into the lock-in amplifier 6 as a reference signal.

[0013] The oscillating slit 2 is controlled by a sinusoidal AC signal generated by a reference signal source 5, and the frequency of the sinusoidal AC signal of the reference signal source 5 is the natural frequency of the oscillating slit 2.

[0014] The oscillating slit 2 includes a tuning fork 8, a coil 9, a magnet 10, and a slit 11. A slit 11 is fixed on the right arm of the tuning fork 8, and the width of the slit 11 is smaller than the diameter of the light spot. A coil 9 is fixed in the hollow part of the left arm of the tuning fork 8, and two magnets 10 with the same poles are fixed on both sides of the coil 9. When the frequency of the alternating current of the coil 9 is consistent with the natural frequency of the tuning fork 8, the slit 11 begins to oscillate with the oscillation of the tuning fork 8, and the amplitude of its oscillation is limited by the amplitude of the alternating current in the coil 9.

[0015] The oscillating slit 2 is arranged vertically, and the reference signal source 5 controls the oscillating slit 2 to oscillate left and right.

[0016] The electrical signal output by the lock-in amplifier 6 is acquired by the acquisition card and then sent to the host computer 7. As the ring stage rotates, the data read by the host computer 7 changes in a manner similar to the trend of a sine function, first rising to a maximum point, then falling to a negative minimum point, and finally returning to zero. During the rotation of the ring stage, the light is first chopped at one inner edge of the oscillating slit 2, and the frequency of the light pulse is the same as the frequency of the reference signal, so the signal rises. As the ring stage continues to rotate, when the light is in the middle of the oscillating slit 2, the light is chopped at both inner edges of the oscillating slit 2, and the frequency of the light pulse is twice the frequency, which is the largest difference from the reference frequency, so the data is zero. As the ring stage continues to rotate, when the light is in the inner edge of the other side of the oscillating slit 2, the chopped frequency is the same as the reference frequency, and the data drops to the negative maximum value. When the ring stage moves to the position where the data detected by the host computer 7 is zero, it is the position where the light is aligned with the oscillating slit 2. The acquired data curve is fitted, and its intercept with the horizontal axis angle axis is the position to be aimed.

[0017] The present invention also provides a photoelectric aiming method based on an oscillating slit, comprising the following steps:

[0018] Step 1: First, input the starting angle and voltage threshold on the host computer interface to determine the prerequisites for judging the trend of the acquired curve signal;

[0019] Step 2: The computer controls the ring stage to move to the input starting angle via the control card.

[0020] The next step is to control the circular stage to scan forward in large steps, searching for the general trend and waveform characteristics of the signal to see if it matches the sinusoidal signal collected by the host computer during the rotation of the circular stage. The identification of this sinusoidal signal mainly begins with the following two feature identification steps.

[0021] Step 3: First, control the ring stage to scan forward in large steps to search for the first signal feature. Specifically, determine whether the signal voltage acquired at this time is greater than the positive threshold voltage or less than the negative threshold voltage, and whether the waveform feature of the signal meets the first feature, i.e., a peak or a trough. If the condition is met, continue to scan forward in large steps to search for the next waveform feature of the signal, i.e., execute step 4. If the condition is not met, continue to execute step 3, i.e., scan forward in large steps to search for the first waveform feature of the signal.

[0022] Step 4: Control the ring stage to continue moving forward and search for the second signal feature;

[0023] When determining the waveform characteristics of the second acquired signal, the second waveform characteristic should be the opposite of the first waveform characteristic. That is, if the first waveform characteristic is a peak characteristic, then the second characteristic is a trough characteristic. Specifically, it is determined whether the voltage value is greater than a positive voltage threshold (corresponding to a peak) or less than a negative voltage threshold (corresponding to a trough).

[0024] If the feature determination in step 4 is also satisfied, then the signal trend collected by the host computer will conform to the sinusoidal signal trend, indicating that the approximate location of the zero point has been found by the system. The next step, step 5, is to perform a more refined scan;

[0025] Step 5: Perform a fine scan; In order to aim at this precise position, move the ring stage in the opposite direction back to the symmetrical position at the other end near the zero point, and then search and collect data forward in smaller steps.

[0026] Step 6: After data acquisition, the next step is to perform curve fitting on the discrete data points and calculate the precise angle values. The fitting method is the least squares method, and the specific formula is as follows:

[0027]

[0028]

[0029] In the formula, x i The x-coordinate angle value of the i-th point, y j Let represent the ordinate voltage value of the i-th point, where N is the number of data points, a represents the slope of the fitted line, b represents the intercept, and represents the fitted angle and voltage value. When fitting a straight line, the intercept - b / a is the desired angular position.

[0030] (III) Beneficial Effects

[0031] The photoelectric aiming method based on oscillating slits provided by the above technical solution has the following advantages:

[0032] Beneficial effects:

[0033] (1) When moving through the ring stage or translation stage, the optical pulse frequency of the oscillating slit changes from one-fold frequency to two-fold frequency and then back to one-fold frequency compared with the frequency of the reference PWM wave. This causes the phase-locked signal to change from positive to negative or from negative to positive. By finding the intercept of the horizontal axis of this curve, the position of photoelectric aiming can be found.

[0034] (2) Since this method relies on the intercept method for solution, and the error source of the direct aiming method is limited by the magnitude of the second derivative, this method has higher sensitivity and accuracy than the direct aiming method. Furthermore, since the response wavelength of CCD is generally in the visible to near-infrared range, this technology can achieve a wider range of measurement requirements (ultraviolet-visible-infrared) by switching detectors compared to the CCD method. At the same time, the device structure on which this method is based is small, easy to install, and easy to integrate into other measuring devices. Attached Figure Description

[0035] Figure 1 This is a schematic diagram illustrating the relationship between sampling time and the acquired signal.

[0036] Figure 2 This is a diagram of an aiming device on which the present invention is based.

[0037] Figure 3 This is a structural diagram of oscillating slit 2.

[0038] Figure 4 This is a schematic diagram showing the position of the light spot as the slit moves.

[0039] Figure 5 Figures A, B, C, and D in the figure represent data from repeatable experiments. Detailed Implementation

[0040] To make the objectives, contents, and advantages of the present invention clearer, the specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples.

[0041] This embodiment of the photoelectric aiming method based on an oscillating slit is applicable to various wavelengths from ultraviolet to visible to infrared. This method is based on... Figure 2 The aiming device shown includes: a turntable 1, an oscillating slit 2, a detector 3, a measurement module, and a host computer 7. The turntable 1 includes a fixed mounting platform at the center and a rotating ring platform located around the mounting platform. A measurement sample is arranged on the mounting platform, and the oscillating slit 2 and detector 3 are arranged on the ring platform. The detector 3 is located on the light-emitting side of the oscillating slit 2. The detector 3 is connected to the measurement module, and the measurement module is connected to the host computer 7. The light reflected from the sample is chopped by the oscillating slit 2 and received by the detector 3. Then, the measurement module performs pre-amplification and phase-locked amplification processing. The processed data is sent to the host computer 7, which determines the position where the ring platform rotates to align the light with the oscillating slit 2.

[0042] There are multiple detectors 3, each corresponding to a different wavelength band. Multiple detectors 3 are arranged on the same rotating wheel. By switching between different detectors, the optical pulse signal detection can be performed for different wavelength bands.

[0043] The measurement module includes a lock-in amplifier 6, a preamplifier 4, and a reference signal source 5 that generates a square wave with the same frequency as the oscillating slit 2. The electrical signal detected by the detector 3 is amplified by the preamplifier 4 and finally enters the lock-in amplifier 6. At the same time, the square wave reference signal generated by the reference signal source 5 also enters the lock-in amplifier 6.

[0044] The oscillating slit 2 is controlled by a sinusoidal AC signal generated by the reference signal source 5, and the frequency of the sinusoidal AC signal of the reference signal source 5 is the natural frequency of the oscillating slit 2.

[0045] The oscillating slit 2 is arranged vertically, and the reference signal source 5 controls the oscillating slit 2 to oscillate left and right.

[0046] The electrical signal output by the lock-in amplifier 6 is acquired by the data acquisition card and then sent to the host computer 7. As the ring stage rotates, the data read by the host computer 7 changes in a manner similar to the trend of a sine function, first rising to a maximum point, then falling to a negative minimum point, and finally returning to zero. Figure 1 As shown.

[0047] The reason for the changing trend of the data read by the host computer 7 is as follows: During the rotation of the ring stage, initially only one inner edge of the oscillating slit 2 is chopping light, and the frequency of the light pulse is the same as the frequency of the reference signal, so the signal rises; as the ring stage continues to rotate, when the light is in the middle of the oscillating slit 2, both inner edges of the oscillating slit 2 are chopping light, so the frequency of the light pulse is twice the frequency, which is the largest difference from the reference frequency, so the data will be zero; as the ring stage continues to rotate, when the light is in the inner edge of the other side of the slit, the chopping frequency is the same as the reference frequency, and the data drops to the negative maximum value; when the ring stage moves to the position where the data detected by the host computer 7 is zero, it is the position where the light is aligned with the oscillating slit 2. By fitting the curve of the collected data, its intercept with the horizontal axis angle axis is the position to be aimed.

[0048] The structure of oscillating slit 2 is as follows Figure 3 As shown, the assembly includes: a tuning fork 8, a coil 9, a magnet 10, and a slit 11. The tuning fork 8 has its own natural oscillation frequency; it will only begin to oscillate when an external force of left-right swaying is applied, satisfying its natural frequency. A slit 11 is fixed to the right fork arm of the tuning fork 8, and the width of the slit 11 is smaller than the diameter of the light spot. A coil 9 is fixed in the hollow center of the left fork arm of the tuning fork 8, and two magnets 10 with the same poles are fixed on both sides of the coil 9, generating a uniform magnetic field that ensures uniform force on the tuning fork 8. When alternating current is applied to the coil 9, the force on the tuning fork 8 changes. When the frequency of the alternating current in the coil 9 matches the natural frequency of the tuning fork 8, the slit 11 begins to oscillate along with the tuning fork 8, and the amplitude of its oscillation is limited by the amplitude of the alternating current in the coil 9.

[0049] Based on the aforementioned photoelectric aiming device, in order to achieve precise aiming, this invention also provides a photoelectric aiming method based on an oscillating slit. This method utilizes the characteristic that when the photoelectric aiming spot is simultaneously chopped by the inner edges of both sides of the slit, the chopping frequency of the slit and the reference frequency of the reference signal source are inconsistent, resulting in the output signal of these two signals being zero after passing through a phase-locked loop multiplier and integrator. This method is used for aiming. Figure 2As shown, the oscillating slit 2 is located in front of the detector 3 for chopping. There are three detectors 3 arranged in a triangle. They use an internal motor to switch between different aiming bands, enabling wide-band measurements from ultraviolet to visible to infrared. The electrical signal from the detector 3 enters the preamplifier 4, is amplified, and then fed into the lock-in amplifier 6. The reference signal source 5, when powered on, outputs an AC sinusoidal signal with the same natural frequency as the oscillating slit 2 to control its oscillation. Simultaneously, it outputs a square wave pulse signal of the same frequency as the reference signal, which enters the lock-in amplifier 6. The signal received on the computer 7 is obtained from the signal from the lock-in amplifier via AD conversion by the acquisition card.

[0050] The photoelectric aiming method based on the oscillating slit in this embodiment specifically includes the following steps:

[0051] Step 1: First, input the starting angle and voltage threshold on the host computer interface to determine the prerequisites for judging the trend of the acquired curve signal;

[0052] Step 2: The computer controls the ring stage to move to the input starting angle via the control card.

[0053] The next step is to control the circular stage to scan forward in large steps, searching for the general trend and waveform characteristics of the signal to see if it matches the sinusoidal signal collected by the host computer during the rotation of the circular stage. The identification of this sinusoidal signal mainly begins with the following two feature identification steps.

[0054] Step 3: First, control the ring stage to scan forward in large steps to search for the first signal feature. Specifically, determine whether the signal voltage acquired at this time is greater than the positive threshold voltage or less than the negative threshold voltage, and whether the waveform feature of the signal meets the first feature, i.e., a peak or a trough. If the condition is met, continue to scan forward in large steps to search for the next waveform feature of the signal, i.e., execute step 4. If the condition is not met, continue to execute step 3, i.e., scan forward in large steps to search for the first waveform feature of the signal.

[0055] Step 4: Control the ring stage to continue moving forward and search for the second signal feature;

[0056] When determining the waveform characteristics of the second acquired signal, the second waveform characteristic should be the opposite of the first waveform characteristic. That is, if the first waveform characteristic is a peak characteristic, then the second characteristic is a trough characteristic. Specifically, it is determined whether the voltage value is greater than a positive voltage threshold (corresponding to a peak) or less than a negative voltage threshold (corresponding to a trough).

[0057] If the feature determination in step 4 is also satisfied, then the signal trend collected by the host computer will conform to the sinusoidal signal trend, indicating that the approximate location of the zero point has been found by the system. The next step, step 5, is to perform a more refined scan;

[0058] Step 5: Perform a fine scan; In order to aim at this precise position, move the ring stage in the opposite direction back to the symmetrical position at the other end near the zero point, and then search and collect data forward in smaller steps.

[0059] Step 6: After data acquisition, the next step is to perform curve fitting on the discrete data points and calculate the precise angle values. The fitting method is the least squares method, and the specific formula is as follows:

[0060]

[0061]

[0062] In the formula, x i The x-coordinate angle value of the i-th point, y j Let represent the ordinate voltage value of the i-th point, where N is the number of data points, a represents the slope of the fitted line, b represents the intercept, and represents the fitted angle and voltage value. When fitting a straight line, the intercept - b / a is the desired angular position.

[0063] Figure 4 The diagram shows the repeatability results of multiple measurements at different wavelengths (500nm, 700nm, 800nm, 1000nm). As can be seen from the diagram, the repeatability reaches the second level, indicating that the photoelectric aiming device has basic application value.

[0064] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A photoelectric aiming device based on an oscillating slit, characterized in that, include: Turntable (1), oscillating slit (2), detector (3), measurement module, host computer (7); Turntable (1) includes a fixed mounting platform in the center and a rotating ring platform located around the mounting platform. Measurement samples are arranged on the mounting platform, and oscillating slit (2) and detector (3) are arranged on the ring platform. Detector (3) is located on the light-emitting side of oscillating slit (2). Detector (3) is connected to the measurement module, and the measurement module is connected to the host computer (7). The light reflected by the sample is chopped by the oscillating slit (2) and received by the detector (3). Then, the measurement module performs pre-amplification and phase-locked amplification. The processed data is sent to the host computer (7). The host computer (7) determines the position where the ring platform rotates to align the light with the oscillating slit (2). The measurement module includes a lock-in amplifier (6), a preamplifier (4), and a reference signal source (5) that generates a square wave with the same frequency as the oscillating slit (2). The electrical signal detected by the detector (3) is amplified by the preamplifier (4) and then enters the lock-in amplifier (6). At the same time, the square wave reference signal generated by the reference signal source (5) is input to the lock-in amplifier (6) as a reference signal. The oscillating slit (2) is controlled by a sinusoidal AC signal generated by a reference signal source (5), and the frequency of the sinusoidal AC signal of the reference signal source (5) is the natural frequency of the oscillating slit (2). The oscillating slit (2) is arranged vertically, and the reference signal source (5) controls the oscillating slit (2) to oscillate left and right; The electrical signal output by the lock-in amplifier (6) is acquired by the acquisition card and then enters the host computer (7). As the ring stage rotates, the data read by the host computer (7) changes in a manner similar to the trend of a sine function, first rising to the highest point, then falling to the lowest negative point, and finally returning to zero. During the rotation of the ring stage, the light is first cut off on one side of the inner edge of the oscillating slit (2). The frequency of the light pulse is the same as the frequency of the reference signal, and the signal rises. When the ring stage continues to rotate and the light is in the middle of the oscillating slit (2), the light is cut off on both sides of the inner edge of the oscillating slit (2). The frequency of the light pulse is twice the frequency, which is the largest difference from the reference frequency, and the data is zero. When the ring stage continues to rotate and the light is in the inner edge of the other side of the oscillating slit (2), the cutting frequency is the same as the reference frequency, and the data drops to the negative maximum value. When the ring stage moves to the position where the data detected by the host computer (7) is zero, it is the position where the light is aligned with the oscillating slit (2). The collected data curve is fitted, and the intercept of the curve with the horizontal axis angle axis is the position to be aimed.

2. The photoelectric aiming device based on an oscillating slit as described in claim 1, characterized in that, The detector (3) is provided in multiple ways, each corresponding to a different wavelength band. Multiple detectors (3) are arranged on the same rotating wheel. By switching different detectors, optical pulse signals under different wavelength bands can be detected.

3. The photoelectric aiming device based on an oscillating slit as described in claim 2, characterized in that, The detector (3) has three units arranged in a triangle. Different aiming bands are selected by switching the internal motor to achieve wide-band measurement from ultraviolet to visible to infrared.

4. The photoelectric aiming device based on an oscillating slit as described in claim 3, characterized in that, The oscillating slit (2) includes: a tuning fork (8), a coil (9), a magnet (10), and a slit (11); a slit (11) is fixed on the right arm of the tuning fork (8), and the slit width (11) is smaller than the diameter of the light spot; a coil (9) is fixed in the hollow on the left arm of the tuning fork (8), and two magnets (10) with the same pole are fixed on both sides of the coil (9). When the frequency of the alternating current of the coil (9) is consistent with the natural frequency of the tuning fork (8), the slit (11) begins to oscillate with the oscillation of the tuning fork (8), and the amplitude of its oscillation is limited by the amplitude of the alternating current in the coil (9).

5. A photoelectric aiming method based on an oscillating slit, performed using the photoelectric aiming device described in claim 4, characterized in that, The photoelectric aiming method includes the following steps: Step 1: First, input the starting angle and voltage threshold on the host computer interface to determine the prerequisites for judging the trend of the acquired curve signal; Step 2: The computer controls the ring stage to move to the input starting angle via the control card; The next step is to control the circular stage to scan forward in large steps, searching for the general trend and waveform characteristics of the signal to see if it matches the sinusoidal signal collected by the host computer during the rotation of the circular stage. The identification of this sinusoidal signal mainly begins with the following two feature identification steps. Step 3: First, control the ring stage to scan forward in large steps to search for the first signal feature. Specifically, determine whether the signal voltage acquired at this time is greater than the positive threshold voltage or less than the negative threshold voltage, and determine whether the waveform feature of the signal meets the first feature, i.e., a peak or a trough. If the condition is met, continue to scan forward in large steps to search for the next waveform feature of the signal, i.e., execute step 4. If the condition is not met, continue to execute step 3, i.e., scan forward in large steps to search for the first waveform feature of the signal. Step 4: Control the ring stage to continue moving forward and search for the second signal feature; When determining the waveform characteristics of the second acquired signal, the second waveform characteristics should be the opposite of the first waveform characteristics. That is, if the first waveform characteristics are peak characteristics, then the second characteristics are trough characteristics. The determination process is as follows: determine whether the voltage value is greater than the positive voltage threshold or less than the negative voltage threshold. Step 5: Perform a fine scan; move the ring stage in the opposite direction back to the symmetrical position at the other end near the zero point, and then search and collect data forward with smaller steps each time; Step 6: After data acquisition, perform curve fitting on the discrete data points and calculate the precise angle values; the fitting method is the least squares method, and the specific formula is: In the formula, represents the x-th i The x-coordinate angle value of the y-th point represents the x-coordinate angle value of the y-th point. i The ordinate voltage value of each point is given, where N is the number of data points, a represents the slope of the fitted line, b represents the intercept, and represents the fitted angle and voltage value. When fitting a straight line, the intercept - b / a is the angle position to be aimed at.

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