Large-aperture Flat Element Residual Transmittance and Reflectance and Non-uniformity Measuring Device

Abstract

The present invention discloses a measuring device for the remaining transmittance and non-uniformity of a large-aperture flat element, which relates to the measurement of the transmittance and non-uniformity of an optical element. The purpose is to solve the technical problem in the prior art that the final measurement error is relatively large due to large systematic errors. Compared with the traditional double-light-path measurement method, a reference high-reflection mirror is introduced into the optical path in this application and used as the object for comparative measurement; since the transmittance of the introduced reference high-reflection mirror is in-situ calibrated in the optical path, it improves the progress of systematic error measurement; combined with the calculation formulas for the remaining transmittance and remaining reflectance, the remaining transmittance of the calibrated reference high-reflection mirror is multiplied in both calculation formulas, thereby greatly reducing the random error and further improving the measurement accuracy.

Description

Technical Field

[0001] The inventor belongs to the field of optical detection technology, and is related to the measurement of the transmittance, reflectance and non-uniformity of optical elements, in particular to a device for measuring the residual transmittance, reflectance and non-uniformity of large-aperture flat elements. Background Art

[0002] With the development of fields such as aviation, aerospace and astronomy, the requirements for the quality and precision of optical systems have been increased. Especially for devices such as high-power solid-state lasers, in addition to the requirement that the coating reflectance of optical elements reaches 99.8%, the spatial uniformity is also required to reach 0.1%.

[0003] To measure the reflectance of thin films or optical elements, currently, commercial spectrophotometers are mainly used, such as Hitachi, Shimadzu in Japan, Agilent, PE in the United States, etc. Currently, commercial spectrophotometers are mainly used to measure the reflectance of liquids or small-aperture elements. The general accuracy of transmittance measurement is ±0.1%, and the general accuracy of reflectance measurement is ±0.3%. The measurement accuracy of spectrophotometers is limited, and it is impossible to measure large-aperture elements.

[0004] Abroad, Sanders and others in China, such as Li Bicheng, proposed methods such as optical resonators for the transmittance or reflectance of high-reflection or high-transmission elements. This method is mainly used for extremely high reflectance measurement, generally requiring the reflectance or transmittance to reach more than 99.9% to ensure the signal-to-noise ratio of the decay signal.

[0005] Zhejiang University in China and others developed a set of large-aperture transreflectometer for measuring the transmittance or reflectance of large-aperture optical elements. Its basic principle is still the spectrophotometry principle, so its measurement accuracy is still equivalent to that of spectrophotometers.

[0006] Hou Xiqi and others from the 205th Research Institute of the Ordnance Industry in China proposed a high-reflectance and high-transmittance optical measurement device. This device can be used for the high-precision measurement of the high reflectance and transmittance of optical elements, a method and device for measuring the high transmittance, high reflectance and non-uniformity of large-aperture flat elements, and the measurement accuracy is about 0.1%.

[0007] The invention patent application with the application number 202211232772.9 discloses a method for measuring the reflectivity uniformity of a large-aperture reflective optical element based on a large-size laser beam and a matrix detector. The measurement system includes a pulsed laser 1, a collimating and beam-expanding optical component 2, a front plano-concave high-reflection cavity mirror 3 and a rear plano-concave high-reflection cavity mirror 5, a measured reflective optical element 4, an imaging optical component 6, a CCD array detector 7, a signal generator 8, a delay control device 9 and a computer 10. Using the pulsed light cavity ring-down technology, the TEM fundamental mode laser beam output by the pulsed laser 1 forms a large-size laser beam through the collimating and beam-expanding optical component 2. The position of the optical element in the optical component 2 is adjusted so that the expanded laser beam matches the mode of the optical resonant cavity composed of two plano-concave high-reflection cavity mirrors (front cavity mirror 3 and rear cavity mirror 5) and the measured reflective optical element 4. The laser beam is coupled into the optical resonant cavity from the front cavity mirror and the laser beam output from the rear cavity mirror is imaged on the CCD array detector 7 by the imaging optical component 6 to obtain the light field intensity distribution of the laser beam output from the optical resonant cavity. The light field intensity distribution detected by the CCD detector is sent to the computer 10 for data analysis to obtain the reflectivity uniformity distribution of the measured reflective optical element in the laser irradiation area.

[0008] This technical solution can achieve fast full-aperture complete coverage imaging of the reflectivity uniformity distribution of large-aperture reflective optical elements, and the imaging results have very high spatial resolution. However, in the traditional double optical path, the element to be measured is directly measured, and its systematic error is large, resulting in a large final measurement error. Summary of the Invention

[0009] The purpose of the present invention is to solve the technical problem that the final measurement error is large due to the large systematic error in the prior art. The present application provides a device for measuring the residual transmittance and non-uniformity of a large-aperture flat element, which can realize the comparative measurement of the residual transmittance, greatly reduce the random measurement error, and greatly improve the measurement accuracy.

[0010] The present invention specifically adopts the following technical solutions to achieve the above purpose:

[0011] A device for measuring the residual transmittance and non-uniformity of a large-aperture flat element includes a laser, a stable power meter, a collimating lens, a polarizer, a beam splitter, a reference high-reflection mirror, a reference high-reflection lens translation stage, a sample two-dimensional translation stage, a sample rotation stage, a small hole aperture, a reflecting mirror, a CCD camera, a detector two, a detector horizontal translation stage, a detector rotation stage, a detector one, an amplifier circuit one, a synchronous acquisition card, an amplifier circuit two, and an industrial control computer; the reference high-reflection mirror is placed on the reference high-reflection lens translation stage, the sample two-dimensional translation stage is placed on the sample rotation stage, and the small hole aperture, the reflecting mirror, the CCD camera, the detector two, and the detector horizontal translation stage are all placed on the detector rotation stage and rotate together with the detector rotation stage; the synchronous acquisition card is connected to the industrial control computer;

[0012] The laser generated by the laser passes through a power stabilizer, a collimating lens, and a polarizer in sequence and then is incident on a beam splitter. The beam splitter divides it into reference light I1 and measurement light I2. Among them, the reference light I1 enters detector 1, is converted into a voltage signal by amplifier circuit 1, and then is collected by a synchronous acquisition card and recorded by an industrial control computer. The measurement light I2 is incident on the center position of detector 2, is converted into a voltage signal by amplifier circuit 2, and then is collected by a synchronous acquisition card and recorded by an industrial control computer.

[0013] When using this measuring device for measurement, the specific steps are as follows:

[0014] Step S1, measurement of the remaining transmittance of the reference high reflector

[0015] Place the reference high reflector on the translation stage of the reference high reflector lens, and measure the remaining transmittance T before and after the reference high reflector is moved into the optical path respectively:

[0016]

[0017] Among them, F1 represents the light intensity before the reference high reflector is moved in, and F2 represents the light intensity after the reference high reflector is moved in;

[0018] Step S2, zero calibration

[0019] Adjust detector 2 so that the light spot is incident on the center position of detector 2. Keep the reference high reflector in the optical path and perform zero calibration. Collect the voltage signals V1 and V2 converted by amplifier circuit 1 and amplifier circuit 2 respectively at this time to obtain the zero calibration parameter K:

[0020]

[0021] Step S3, measurement of the remaining transmittance

[0022] Remove the reference high reflector, place the element to be measured on the two-dimensional translation stage of the sample, and move it into the optical path. Adjust the attitude of the element to be measured through the two-dimensional translation stage of the sample so that the surface of the element to be measured is parallel to the two-dimensional translation stage of the sample;

[0023] Rotate the angle of the element to be measured through the sample rotating stage so that the incident angle on the element to be measured meets the measurement requirements; at this time, collect the voltage signals V`1 and V`2 converted by amplifier circuit 1 and amplifier circuit 2. The remaining transmittance P of the element to be measured is expressed as:

[0024]

[0025] Step S4, measurement of the remaining reflectance

[0026] Adjust the position of the second detector through the detector horizontal translation stage and the detector rotation stage so that the light spot is incident on the center position of the second detector; at this time, collect the converted voltage signals V``1 and V``2 of the first and second amplifier circuits, and the remaining transmittance M of the component to be measured is expressed as:

[0027]

[0028] Step S5, non-uniformity measurement

[0029] Move the component to be measured horizontally and vertically through the sample two-dimensional translation stage to obtain the remaining reflectance and / or remaining transmittance at different positions of the component to be measured, so as to calculate the non-uniformity of the component to be measured.

[0030] Furthermore, the CCD camera is located at the conjugate position of the second detector.

[0031] The beneficial effects of the present invention are as follows:

[0032] 1. In the present invention, compared with the traditional double-light-path measurement method, a reference high-reflection mirror is introduced into the optical path in this application and used as a comparison measurement object; since the transmittance of the introduced reference high-reflection mirror is in-situ calibrated in the optical path, it improves the progress of system error measurement; combined with the calculation formulas of the remaining transmittance and the remaining reflectance, the calibration reference high-reflection mirror's remaining transmittance is multiplied in the calculation formulas, thereby greatly reducing the random error and further improving the measurement accuracy.

[0033] 2. In the present invention, in order to adapt to different ranges of remaining reflectance or transmittance, the reference element can be replaced, and reference elements with different ranges of low transmittance can be selected to adapt to the remaining transmittance and reflectance of different components to be measured, greatly reducing the requirements for the dynamic range of the detector.

[0034] 3. In the present invention, a CCD is introduced at the conjugate position in front of the detector in the optical path. By monitoring the change in the position of the light spot and combining it with the two-dimensional guide rail and the component attitude adjustment mechanism, the attitude leveling under the component measurement state can be realized without introducing other position judgment devices, achieving the in-situ attitude leveling of the component, improving the measurement efficiency, and saving the equipment development cost. Description of the Drawings

[0035] Figure 1 is the optical path diagram of the present invention;

[0036] Among them, the reference numerals are: 1, laser; 2, power stabilizer; 3, collimating lens; 4, polarizer; 5, beam splitter; 6, reference high reflector; 7, reference high-reflection lens translation stage; 8, sample two-dimensional translation stage; 9, sample rotation stage; 10, small aperture diaphragm; 11, mirror; 12, CCD camera; 13, detector two; 14, detector horizontal translation stage; 15, detector rotation stage; 16, detector one; 17, amplifier circuit one; 18, synchronous acquisition card; 19, amplifier circuit two; 20, industrial control computer. Specific embodiments

[0037] This embodiment provides a measuring device for the residual transmittance and non-uniformity of a large-aperture flat element, as Figure 1 shown. The device includes a light source system, a detection system, a spot position positioning system, and a rotation stage system.

[0038] The light source system includes a laser 1, a power stabilizer 2, a collimating lens 3, and a polarizer 4. The laser 1 is a semiconductor continuous laser, and the semiconductor continuous laser can output monochromatic laser light. The power stabilizer 2 can be used to stabilize the laser power. The collimating lens 3 can be used to collimate the laser light to achieve long-distance beam transmission. The polarizer 4 can be used to adjust the deflection state of the output light.

[0039] The detection system includes a detector one 16, an amplifier circuit one 17, a detector two 13, an amplifier circuit two 19, a synchronous acquisition card 18, and an industrial control computer 20. Both the detector one 16 and the detector two 13 are integrating sphere detectors. The detector one 16 is used to record the light intensity signal of the reference light, the amplifier circuit one 17 is used to convert the light intensity signal of the reference light into a voltage signal, the detector two 13 is used to record the light intensity signal of the measurement light, the amplifier circuit two 19 is used to convert the light intensity signal of the measurement light into a voltage signal, and the synchronous acquisition card 18 is used to collect the voltage signals of the amplifier circuit one 17 and the amplifier circuit two 19 to the industrial control computer 20 and is used for subsequent data processing.

[0040] The spot position positioning system includes a small aperture diaphragm 10, a mirror 11, a CCD camera 12, a detector horizontal translation stage 14, and a detector rotation stage 15. The CCD camera 12 is in the conjugate position of the detector two 13, and the incident light passes through the center of the small aperture diaphragm 10 and then enters the center position of the CCD camera 12; during the two-dimensional scanning of the element, first, the CCD camera 12 records the initial position of the spot. When the spot position changes during the scanning process, the movement of the small aperture diaphragm 10, the mirror 11, the CCD camera 12, and the detector two 13 can be realized through the detector horizontal translation stage 14, so that the spot position returns to the initial position, thereby realizing that when the zero calibration measurement and the actual measurement are carried out, the position where the spot enters the detector two 13 does not change greatly.

[0041] The component attitude leveling system includes a reference high-reflection lens translation stage 7, a sample two-dimensional translation stage 8, and a sample rotation stage 9. The reference high-reflection lens translation stage 7 is used to adjust the position of the reference high-reflection mirror 6. The sample two-dimensional translation stage 8 is used to adjust the position of the component to be measured. The sample rotation stage 9 is used to rotate the sample two-dimensional translation stage 8 and the component to be measured. When the component to be measured is translated two-dimensionally, when there is an angle between the component to be measured and the two-dimensional scanning plane, the position of the light spot reflected onto the detector two 13 will change. The angle between the component and the two-dimensional scanning plane is reduced by the sample two-dimensional translation stage 8 and the sample rotation stage 9. When the angle is zero, the adjustment stops. The sample two-dimensional translation stage 8 and the sample rotation stage 9 can ensure that when the component to be measured is scanned two-dimensionally, its reflecting surface is parallel to the guide rail running plane, reducing the measurement error introduced by the change in the position of the light spot during the scanning process.

[0042] The detector rotation stage 15 rotates coaxially, at the same angle, and in the same direction as the sample rotation stage 9. The sample rotation stage 9 is used to control the rotation of the component to be measured to achieve the measurement of the residual reflectivity or residual transmittance of the component to be measured at different angles. The detector rotation stage 15 is used to rotate the position of the detector two 13 so that when measuring the residual reflectivity, the position of the detector two 13 follows.

[0043] In addition, it also includes a beam splitter 5 and a reference high-reflection mirror 6. The reference high-reflection mirror 6 is placed on the reference high-reflection lens translation stage 7. The sample two-dimensional translation stage 8 is placed on the sample rotation stage 9. The small hole aperture 10, the mirror 11, the CCD camera 12, the detector two 13, and the detector horizontal translation stage 14 are all placed on the detector rotation stage 15 and rotate together with the detector rotation stage 15. The synchronous acquisition card 18 is connected to the industrial control computer 20.

[0044] The laser generated by the laser 1 is incident on the beam splitter 5 successively through the constant power meter 2, the collimating lens 3, and the polarizer 4. The laser is reflected and transmitted on the beam splitter 5, so that the laser is divided into two beams of light, the reference light I1 and the measurement light I2, after passing through the beam splitter 5. Among them, the reference light I1 generated by the reflection of the beam splitter 5 enters the detector one 16, is converted into a voltage signal by the amplifier circuit one 17, and then is collected by the synchronous acquisition card 18 to the industrial control computer 20 and used for subsequent data analysis. The measurement light I2 generated by the transmission of the beam splitter 5 can enter the center position of the detector two 13 after passing through the reference high-reflection mirror 6 or the component to be measured, is converted into a voltage signal by the amplifier circuit two 19, and then is collected by the synchronous acquisition card 18 to the industrial control computer 20 and used for subsequent data analysis.

[0045] When using this measuring device for measurement, the specific steps are as follows:

[0046] Step S1, measurement of the residual transmittance of the reference high-reflection mirror 6

[0047] Place the reference highly reflective mirror 6 on the reference highly reflective lens translation stage 7, and measure the remaining transmittance T before and after the reference highly reflective mirror 6 is moved into the optical path respectively:

[0048]

[0049] wherein, F1 represents the light intensity before the reference highly reflective mirror 6 is moved in, and F2 represents the light intensity after the reference highly reflective mirror 6 is moved in;

[0050] Step S2, zero calibration

[0051] Adjust the detector two 13 to make the light spot incident on the center position of the detector two 13. Keep the position of the reference highly reflective mirror 6 in the optical path unchanged, perform zero calibration, and collect the converted voltage signals V1 and V2 of the amplifier circuit one 17 and the amplifier circuit two 19 respectively at this time to obtain the zero calibration parameter K:

[0052]

[0053] Step S3, measurement of remaining transmittance

[0054] Remove the reference highly reflective mirror 6, place the element to be measured (i.e., the large-aperture flat optical element) on the sample two-dimensional translation stage 8, and move it into the optical path. Adjust the attitude of the element to be measured through the sample two-dimensional translation stage 8 to make the surface of the element to be measured parallel to the sample two-dimensional translation stage 8;

[0055] Rotate the angle of the element to be measured through the sample rotary table 9 to make the incident angle on the element to be measured meet the measurement requirements (this measurement requirement is prior art and existing measurement parameters and requirements can be directly applied). At this time, collect the converted voltage signals V`1 and V`2 of the amplifier circuit one 17 and the amplifier circuit two (19). The remaining transmittance P of the element to be measured is expressed as:

[0056]

[0057] Step S4, measurement of remaining reflectance

[0058] Adjust the position of the detector two 13 through the detector horizontal translation stage 14 and the detector rotary table 15 to make the light spot incident on the center position of the detector two 13; At this time, collect the converted voltage signals V``1 and V``2 of the amplifier circuit one 17 and the amplifier circuit two 19. The remaining transmittance M of the element to be measured is expressed as:

[0059]

[0060] Step S5, measurement of non-uniformity

[0061] The remaining reflectivity and / or remaining transmittance of the element to be measured are obtained by moving the element to be measured along the horizontal and vertical directions by the sample two-dimensional translation stage 8, so as to calculate the non-uniformity of the element to be measured.

[0062] When calculating the non-uniformity based on the remaining reflectivity and / or remaining transmittance, the existing calculation methods can be directly applied.

Claims

1. A measuring device for the remaining transmittance and non-uniformity of a large-aperture flat element, characterized in that: It includes a laser (1), a stable power meter (2), a collimating lens (3), a polarizer (4), a beam splitter (5), a reference high reflector (6), a reference high reflector lens translation stage (7), a sample two-dimensional translation stage (8), a sample rotation stage (9), a small aperture diaphragm (10), a reflector (11), a CCD camera (12), a detector two (13), a detector horizontal translation stage (14), a detector rotation stage (15), a detector one (16), an amplifier circuit one (17), a synchronous acquisition card (18), an amplifier circuit two (19), and an industrial control computer (20); the reference high reflector (6) is placed on the reference high reflector lens translation stage (7), the sample two-dimensional translation stage (8) is placed on the sample rotation stage (9), and the small aperture diaphragm (10), the reflector (11), the CCD camera (12), the detector two (13), and the detector horizontal translation stage (14) are all placed on the detector rotation stage (15) and rotate together with the detector rotation stage (15); the synchronous acquisition card (18) is connected to the industrial control computer (20); The laser (1) generates laser light that sequentially passes through the stable power meter (2), the collimating lens (3), and the polarizer (4) and then enters the beam splitter (5), and is divided by the beam splitter (5) into reference light I1 and measurement light I2; among them, the reference light I1 enters the detector one (16), and after being converted into a voltage signal by the amplifier circuit one (17), it is collected by the synchronous acquisition card (18) and recorded by the industrial control computer; the measurement light I2 enters the center position of the detector two (13), and after being converted into a voltage signal by the amplifier circuit two (19), it is collected by the synchronous acquisition card (18) and recorded by the industrial control computer; When using this measuring device for measurement, the specific steps are as follows: Step S1, measurement of the remaining transmittance of the reference high reflector (6) Place the reference high reflector (6) on the reference high reflector lens translation stage (7), and measure the remaining transmittance T before and after the reference high reflector (6) is moved into the optical path respectively: Among them, F1 represents the light intensity before the reference high reflector (6) is moved in, and F2 represents the light intensity after the reference high reflector (6) is moved in; Step S2, zero calibration Adjust the detector two (13) so that the light spot enters the center position of the detector two (13), keep the reference high reflector (6) in the optical path, perform zero calibration, and collect the voltage signals V1 and V2 converted by the amplifier circuit one (17) and the amplifier circuit two (19) respectively at this time to obtain the zero calibration parameter K: Step S3, measurement of the remaining transmittance Remove the reference high reflector (6), place the element to be measured on the sample two-dimensional translation stage (8), and move it into the optical path. Adjust the posture of the element to be measured through the sample two-dimensional translation stage (8) so that the surface of the element to be measured is parallel to the sample two-dimensional translation stage (8); Rotate the angle of the element to be measured through the sample rotation stage (9) so that the incident angle on the element to be measured meets the measurement requirements; at this time, collect the voltage signals V`1 and V`2 converted by the amplifier circuit one (17) and the amplifier circuit two (19), and the remaining transmittance P of the element to be measured is expressed as: Step S4, Residual Reflectance Measurement Adjust the position of the second detector (13) through the detector horizontal translation stage (14) and the detector rotation stage (15) so that the light spot is incident on the center position of the second detector (13); at this time, collect the voltage signals V``1 and V``2 converted by the first amplification circuit (17) and the second amplification circuit (19), and the residual transmittance M of the element to be measured is expressed as: Step S5, Inhomogeneity Measurement Move the element to be measured horizontally and vertically through the sample two-dimensional translation stage (8) to obtain the residual reflectance and / or residual transmittance at different positions of the element to be measured, thereby calculating the inhomogeneity of the element to be measured.

2. The measuring device for the remaining transmittance, reflectance and non-uniformity of the large-aperture flat element according to claim 1, wherein: The CCD camera (12) is located at the conjugate position of the second detector (13).

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