Infrared optical material refractive index temperature coefficient measuring device and measuring method

Abstract

The application belongs to the field of optical measurement technology, and discloses a kind of infrared optical material refractive index temperature coefficient measuring device, comprising: light source, monochromator, oscillation slit, off-axis parabolic mirror, precision temperature control system, precision angle measuring system, detector, signal processing unit and computer;Optical material sample is placed in precision temperature control system and heated, the outgoing light of light source is aimed at monochromator, oscillation slit, collimated by off-axis parabolic mirror, enters sample after being transmitted by half-transmission half-reflection mirror, the reflected light of sample back surface is sequentially reflected by half-transmission half-reflection mirror, reflected mirror, focuses after being reflected by axis parabolic mirror and enters detector, is converted into electric signal, is transmitted to computer by signal processing unit, obtains the corresponding autocollimation angle value of sample at the temperature, changes temperature and repeats the above steps, obtains the refractive index temperature coefficient of the optical material sample.The application has the advantages of high measurement precision, high temperature, wide wavelength coverage range and the like.

Description

Technical Field

[0001] This invention belongs to the field of optical metrology and measurement technology, and relates to a device for measuring the refractive index temperature coefficient of infrared optical materials, and more particularly to a device for measuring the refractive index temperature coefficient of near-infrared optical materials with a temperature up to 500°C. Background Technology

[0002] Infrared optical materials have wide applications in optoelectronic weaponry, such as in the fabrication of optical windows for infrared seekers and optical imaging lenses for infrared thermal imagers. Infrared optical windows typically withstand extremely high temperatures, which alter their refractive index and cause optical distortion. The temperature coefficient of refractive index describes the change in refractive index of an optical material under different temperature conditions. Accurate measurement of this parameter is a fundamental technical approach to compensate for the distortion of infrared optical windows and improve their imaging performance, and it is also an urgent requirement in the design of optoelectronic weaponry.

[0003] The National Institute of Standards and Technology (NIST) in the United States has conducted research on the measurement of the temperature coefficient of refractive index of infrared materials. The measurement wavelengths were 0.633 μm and 3.39 μm, with a temperature range of 25 °C to 500 °C, and a measurement uncertainty of 2% to 4%. The National Physical Laboratory in the United Kingdom used precision goniometric methods to measure the temperature coefficient of refractive index of infrared optical materials such as germanium, silicon, ZnS, and ZnSe, with wavelengths of 1 μm to 3 μm, 3 μm to 5 μm, and 8 μm to 12 μm, and a temperature range of 25 °C to 150 °C, with a measurement uncertainty of 4%. Shimadzu Corporation of Japan has achieved the measurement of the temperature coefficient of refractive index in the visible light band, with a temperature range of 25 °C to 80 °C and wavelengths from visible to near-infrared, with a measurement uncertainty of approximately 6%.

[0004] Major domestic institutions conducting research on the temperature coefficient of refractive index of optical materials have all established their own temperature coefficient measurement devices by purchasing and modifying foreign precision refractive index measurement equipment. Specifically, Hubei Xinhua Optoelectronic Materials Co., Ltd. purchased a visible-long-wave infrared refractive index meter from Trioptics of Germany and modified its device to measure the refractive index in the temperature range of 25℃ to 100℃; Chengdu Guangming Optoelectronics Co., Ltd. purchased a visible-near-infrared refractive index temperature coefficient meter from Shimadzu of Japan, enabling the measurement of the temperature coefficient of refractive index in the temperature range of 25℃ to 80℃.

[0005] Problems exist in the measurement of refractive index temperature coefficient of infrared optical materials in China: the temperature range is 25℃~100℃, and the measurement of refractive index temperature coefficient at 500℃ cannot be carried out; the wavelength range is 0.4μm~2.1μm, and the measurement of refractive index temperature coefficient in a wide wavelength range of 2μm~12μm cannot be carried out. The temperature range, wavelength range, and measurement accuracy are all lower than the international level. Summary of the Invention

[0006] (I) Purpose of the Invention

[0007] The purpose of this invention is to shorten the gap between my country and the international advanced level in measuring the performance parameters of optical materials under high temperature conditions. This invention provides a device for measuring the temperature coefficient of refractive index of infrared optical materials using a precision angle measurement method.

[0008] (II) Technical Solution

[0009] To address the aforementioned technical problems, this invention provides an infrared optical material refractive index temperature coefficient measuring device, comprising: a light source 1-1; an infrared monochromator 1-2, an oscillating slit 2, a reflector 3, an off-axis parabolic mirror 5-1, and a semi-transparent mirror 5-2 arranged sequentially along the light path of the emitted beam from the light source 1-1; a precision temperature-controlled furnace 7-2 arranged on the light-transmitting side of the semi-transparent mirror 5-2; and a high-precision angle measuring system 9-2, an off-axis parabolic mirror 5-3, and an infrared detector 10-1 arranged sequentially along the light path on the reflective side of the semi-transparent mirror 5-2; an optical material sample 6 is placed on the sample stage 7-1 in the precision temperature-controlled furnace 7-2; the infrared detector 10-1 is connected to a computer 11 via a preamplifier circuit 10-2 and a lock-in amplifier 10-3; the high-precision angle measuring system 9-2 is connected to the computer 11 via an air-bearing turntable control circuit 9-3; and the precision temperature-controlled furnace 7-2 is connected to the computer 11 via a temperature control furnace control circuit 7-3.

[0010] The light emitted by the light source 1-1 passes through the monochromator 1-2, is aimed through the oscillating slit 2, collimated by the off-axis parabolic mirror 5-1, and then enters the sample block 6 after passing through the semi-transparent mirror 5-2. It is reflected by the rear surface of the sample block and returns to the semi-transparent mirror 5-2, where it is reflected into the reflector 9-1 in the high-precision angle measurement system 9-2. The reflected light reaches the off-axis parabolic mirror 5-3, is focused, and then enters the detector 10-1. The detector 10-1 receives the light signal and converts it into an electrical signal. The electrical signal is transmitted to the computer 11 after passing through the preamplifier circuit 10-2 and the lock-in amplifier 10-3. The computer simultaneously records the autocollimation angle of the sample block at the current temperature. By changing the temperature value and repeating the above steps, the refractive index temperature coefficient of the sample block is calculated based on the autocollimation angle at different temperatures.

[0011] The wavelength range of the light source 1 covers 0.8μm to 12μm.

[0012] The precision temperature-controlled furnace 7-2 has a temperature range of 25℃ to 500℃. Optical material samples are placed in the furnace, contacting only the rear surface of the worktable 7-1. The furnace utilizes high-power electric heating to achieve heating and temperature rise, and uses precision platinum resistance thermometers and differential thermocouple sensors to accurately and in real-time collect the temperatures of the bottom and sides of the sample holder. Signals from each temperature sensor are sequentially entered into the temperature measurement channel via a multiplexer, and after precision amplification and 24-bit analog-to-digital conversion, are sent to the computer 11.

[0013] The detector 10-1, the preamplifier circuit 10-2, the lock-in amplifier 10-3, and the data acquisition and processing system constitute a weak signal processing and detection system.

[0014] The high-precision angle measurement system 9-2 includes an air bearing, a marble base, and an angle reading meter with a grating ruler.

[0015] Among them, the oscillating slit 2 is made of a tuning fork oscillator, and the oscillating slit driving circuit is mainly composed of a CPLD and a 10MHz crystal oscillator.

[0016] This invention also provides a method for measuring the temperature coefficient of refractive index of infrared optical materials, comprising the following steps:

[0017] Step 1: Place the infrared optical material sample in the precision temperature control furnace 7-2, heat the precision temperature control furnace 7-2 to the set value, and transmit the temperature value to the computer 11;

[0018] Step 2: The light emitted by the light source 1-1 passes through the monochromator 1-2, is aimed through the oscillating slit 2, collimated by the off-axis parabolic mirror 5-1, and then enters the sample block 6 after passing through the semi-transparent and semi-reflective mirror 5-2. It is reflected back to the semi-transparent and semi-reflective mirror 5-2 by the rear surface of the sample block, and after being reflected by the mirror 9-1, it reaches the off-axis parabolic mirror 5-3. After being focused, it enters the detector 10-1.

[0019] Step 3: After receiving the optical signal, the detector 10-1 converts it into an electrical signal. The electrical signal is transmitted to the computer 11 after passing through the preamplifier circuit 10-2 and the lock-in amplifier 10-3. After processing, the computer obtains the angle reading corresponding to the maximum value of the signal, which is the autocollimation right angle of the sample block at the current temperature.

[0020] Step 4: Gradually increase the temperature of the precision temperature control furnace 7-2 and repeat the above steps. Calculate the refractive index temperature coefficient of the sample based on the corresponding autocollimation angle at different temperatures.

[0021] In step 4, the computer 11 calculates the refractive index temperature coefficient of the sample at various temperatures. The formulas used for calculating the refractive index temperature coefficient are as follows:

[0022]

[0023] β k —The temperature coefficient of refractive index of the sample at the k-th temperature, in °C. -1 ;

[0024] n—the refractive index of the sample being tested;

[0025] T k —The temperature value measured at the kth temperature, in °C;

[0026] P k —The angular position of the peak signal measured at the k-th temperature, in degrees;

[0027] θ — prism apex angle of the sample being tested, unit: °.

[0028] The aforementioned measuring device employs a silicon carbide rod and a monochromator to generate monochromatic light with continuously adjustable wavelengths. Silicon carbide is used as the infrared light source, powered by a precision voltage and current regulated source. The light emitted from the silicon carbide rod enters the entrance slit of the monochromator through a focusing optical system, and after being dispersed by the monochromator, forms monochromatic light with a wavelength range covering 0.8 μm to 12 μm.

[0029] The precision temperature-controlled furnace 7-2 is used to place the optical materials being tested. It is a self-designed furnace, constructed with stainless steel exterior and an internal insulation layer. Heating and temperature rise are achieved using high-power electric heating. The temperature range is 25℃~500℃, with a temperature control accuracy of ±0.1℃, temperature stability of ±0.2℃ / 10min, and temperature uniformity better than ±0.2℃. The precision temperature control system also includes a worktable, optical window, and adjustment mechanism. The basic principle of the temperature controller circuit is as follows... Figure 2 As shown, the temperature controller uses precision platinum resistance thermometers and differential thermocouples embedded in the sample block worktable to collect the temperature of the bottom and sides of the sample block holder in real time and accurately. It then calculates the PID values ​​to control the heating power of the multiple heating devices in real time, achieving precise temperature control and positioning. The reference resistor provides accurate temperature compensation for the differential thermocouples, and the reference constant current source provides stable current for the standard platinum resistance thermometer and feedback platinum resistance thermometer. The signals from each temperature sensor are sequentially entered into the temperature measurement channel via a multiplexer, and after precision amplification and 24-bit analog-to-digital conversion, they are sent to the computer. The computer processes and controls the signal according to the PID control model.

[0030] The right-angled face of the standard sample block of the right-angle prism is attached to the rear surface of the worktable. The rear surface has an opening in the middle to observe the deformation of the sample block during the heating process. Heating resistance wires are wrapped around the upper, lower and rear surfaces of the worktable to ensure uniform heating of the standard sample block.

[0031] To prevent oxidation during sample heating, the temperature control system was evacuated and a sealed optical window was installed. The optical window was made of ZnS material and had high transmittance.

[0032] The high-precision angle measurement system includes an air bearing, a marble base, and a linear encoder angle reading meter. The air bearing provides a worktable, allowing the plane mirror to rotate smoothly on its surface. Compressed air is introduced into the bearing, causing it to float and rotate freely. Two worm gears are mounted at the bottom of the air bearing, driven by stepper motors. These worm gears rotate the inner or outer shaft of the air bearing, respectively, thus rotating the worktable and turntable. The basic structure of the air-bearing goniometer is as follows: Figure 4 As shown. The turntable diameter is 300mm, with horizontal runout better than 2μm and axial runout better than 1μm. To prevent mechanical deformation of the air bearing due to temperature changes and the influence of high-frequency vibration on the angle measurement accuracy, the air bearing is fixed on a marble platform. The marble platform is 100mm thick, with a surface grinding precision of 4μm and a linear expansion coefficient of 4.6×10⁻⁶ / ℃. A circular grating is mounted on the working surface of the air bearing and rotates with the turntable. The reading head is fixed on the base of the air bearing and records the number of pulses during the rotation of the circular grating, converting them into an angle quantity. A reading head is placed 180° apart on the outer side of the circular grating. The data obtained from the two reading heads are added together and the average value is taken as the final measurement result to eliminate the angle measurement error caused by system eccentricity. The maximum transmission distance of the reading head data is 10mm.

[0033] The electronic processing and detection system for weak signals includes a detector, a precision amplification circuit, a lock-in amplifier circuit, and a data acquisition and processing system. The infrared light signal emitted from the monochromatic optical system is extremely weak. After passing through the optical window of the temperature-controlled furnace twice, it is reflected and absorbed, further reducing its strength. The infrared light signal reaching the detector is even weaker. The temperature-controlled furnace where the sample is placed is also an infrared radiation source, generating infrared radiation. Being closer to the detector, the background radiation signal is much stronger than the infrared radiation signal from the light source, resulting in a low signal-to-noise ratio (SNR) for the system's detection signal. Since the background infrared radiation signal appears as a DC component, optical modulation technology is used to modulate the signal light, and lock-in amplification technology is used to amplify the signal, isolating the DC component to eliminate stray radiation. Furthermore, the background radiation generated by the temperature-controlled furnace and other infrared radiation sources has poor directionality. By adding a water-cooled aperture to the measurement optical path, background radiation can be effectively reduced, improving the SNR.

[0034] To achieve precise angle measurement, this invention employs an oscillating slit for accurate aiming of the optical signal. Near the aiming point, the voltage changes linearly with the angle, simultaneously changing from negative to positive, making the determination very easy. The oscillating slit modulates and aligns the infrared light signal. The basic principle is to scan the slit image at the exit of the grating monochromator using the oscillating slit. To obtain optimal measurement results, the oscillating slit amplitude, oscillating slit width, and monochromator slit width are chosen to be equal. This invention uses a tuning fork oscillator to create the oscillating slit, and the oscillating slit driving circuit mainly consists of a CPLD and a 10MHz crystal oscillator. Its functional block diagram is shown below. Figure 5 As shown, when the oscillating slit drive circuit is working, it divides the input clock of the 10MHz crystal oscillator using a programmed algorithm, and sends the resulting clock at a TTL level to the input of the micro-displacement platform. The slit that moves with the micro-displacement platform then oscillates at this frequency. The selected crystal oscillator has a frequency accuracy and frequency temperature stability of 30ppm. The micro-displacement platform is driven by a voice coil motor, and upon receiving the clock signal from the CPLD, the micro-displacement platform oscillates according to the clock frequency.

[0035] (III) Beneficial Effects

[0036] The infrared optical material refractive index temperature coefficient measuring device provided by the above technical solution raises the temperature to 500℃ and extends the wavelength to 12μm to measure the refractive index temperature coefficient of infrared optical materials. It has the characteristics of good stability and can provide high-accuracy refractive index temperature coefficient parameter values, so as to meet the measurement of refractive index temperature coefficient of different infrared optical materials and different wavelength ranges. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of a device for measuring the temperature coefficient of refractive index of optical materials.

[0038] Figure 2 This is a schematic diagram of the temperature control principle of a precision temperature control furnace.

[0039] Figure 3 This is a schematic diagram of the standard sample workbench structure.

[0040] Figure 4 This is a 3D view of an air bearing.

[0041] Figure 5 This is a functional block diagram of the oscillating slit drive circuit.

[0042] Figure 6 This is a flowchart of the measurement method. Detailed Implementation

[0043] 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.

[0044] The infrared optical material refractive index temperature coefficient measuring device in this embodiment includes an infrared monochromatic light source system 1, a collimation and focusing optical system, a temperature control system, a precision angle measurement system, a photoelectric detection system, and a computer with built-in measurement software package.

[0045] like Figure 1 As shown, the infrared monochromatic light source system 1 consists of an infrared light source 1-1 and an infrared monochromator 1-2. The infrared light source 1-1 uses a silicon carbide rod from Zolihan Optoelectronics Co., Ltd., with a spectral range of 0.5μm to 16μm and a light source stability better than 0.1%. The light emitted from the light source enters the entrance slit of the monochromator 1-2 through a focusing optical system. After being dispersed by the monochromator 1-2, monochromatic light with a wavelength range covering 0.8μm to 12μm is formed.

[0046] The oscillating slit 2 modulates the optical path and aligns the signal. A tuning fork oscillator is used to fabricate the oscillating slit. The oscillating slit driving circuit mainly consists of a CPLD and a 10MHz crystal oscillator. The crystal oscillator selected is Wuhan Haichuang's ZA50-DB-3.3-10M, with a frequency accuracy and frequency temperature stability of 30ppm. The oscillating slit has a frequency range of 15Hz-3000Hz, an amplitude >±1mm, a frequency accuracy of 20ppm (25℃), and a frequency stability of 30ppm / ℃.

[0047] The plane mirror 3 reflects the signal light to the off-axis parabolic mirror 5-1.

[0048] The alignment laser 4 uses lasers with wavelengths of 0.632μm and 10.6μm to provide a reference for the system and realize optical path adjustment.

[0049] The long-focal-length parabolic mirror 5-1 and the semi-transparent mirror 5-2 constitute a collimating optical system; the off-axis parabolic mirror 5-1 has a focal length of 600mm. The collimating and focusing optical system provides the optical path for testing and employs a reflective optical system with small aberrations and no chromatic aberration.

[0050] The long focal distance axis parabolic mirror 5-1 converts the signal light into parallel light, which then passes through the semi-transparent and semi-reflective mirror 5-2 and illuminates the standard sample block 6.

[0051] The standard sample 6 is machined into a right-angle prism with a vertex angle of θ. The right-angled face of the standard sample 6 is placed on the rear surface of the workbench 7-1. A hole is opened in the middle of the rear surface of the workbench 7-1 to observe the deformation of the standard sample during the heating process. Heating resistance wires are wound on the upper surface, lower surface and rear surface of the workbench 7-1 to ensure uniform heating of the standard sample 6.

[0052] The standard sample 6, along with the workbench 7-1, is placed inside the precision temperature-controlled furnace 7-2. The precision temperature-controlled furnace 7-2 is custom-designed, with an exterior made of stainless steel and an internal insulation layer. It utilizes high-power electric heating for heating and temperature rise. The temperature range is 25℃~500℃, with a temperature control accuracy of ±0.1℃, temperature stability of ±0.2℃ / 10min, and temperature uniformity better than ±0.2℃. To prevent oxidation of the sample during heating, the temperature control system is evacuated and fitted with a sealed optical window made of ZnS material, which has high transmittance. The temperature setting of the precision temperature-controlled furnace 7-2 can be manually controlled by the temperature control circuit 7-3. The temperature measurement signal from the temperature control circuit 7-3 is simultaneously amplified and converted to a 24-bit analog-to-digital converter before being sent to the computer 11. The computer 11 can also control the temperature of the precision temperature-controlled furnace 7-2 based on the PID control model of the temperature control circuit 7-3.

[0053] The autocollimating light tube 8 monitors the deformation of the standard sample 6 in real time through the optical window of the precision temperature control furnace 7-2 and the circular hole on the rear surface of the worktable 7-1.

[0054] The front surface of standard sample 6 is coated with an anti-reflection film, and the rear surface is coated with an internal reflection film. The signal is reflected by the rear surface of standard sample 6 and returns to the semi-transparent and semi-reflective mirror 5-2, and after reflection, it reaches the plane mirror 9-1.

[0055] The high-precision angle measurement system 9-2 includes an air bearing, a marble base, and an angle reading meter. The air bearing turntable controller 9-3 is connected to the computer 11 via an RS422 interface. The computer 11 can drive the air bearing in the high-precision angle measurement system 9-2 to rotate through the air bearing turntable controller 9-3, while simultaneously recording the angle change of the plane reflector 9-1, thereby obtaining the change in autocollimation angle after temperature change.

[0056] The light reflected by the plane mirror 9-1 is converged by the short focal length off-axis parabolic mirror 5-3. The off-axis parabolic mirror 5-3 constitutes a focusing optical system with a focal length of 300mm.

[0057] The photoelectric detection and receiving system 10 includes an infrared detector 10-1, a preamplifier circuit 10-2, and a lock-in amplifier 10-3. Detector 10-1 receives the light signal focused by the off-axis parabolic mirror 5-3. Detector 10-1 uses a cooled HgCdTe detector and an InGaAs detector manufactured by Judson Instruments, USA, known for their fast response and high sensitivity, and outputs an electrical signal. By switching between the two detectors, accurate measurement of infrared signals in the 0.8μm–12μm band is achieved. The amplifier circuit 10-2 amplifies the signal; it is custom-designed and operates at tens to hundreds of megahertz frequencies, with a stability of less than 0.1%. The lock-in amplifier 10-3 uses an SR830 digital lock-in amplifier from [Company Name] to further amplify and process the signal, thereby detecting the weak infrared light signal.

[0058] Computer 11 is connected to the temperature control circuit 7-3 of the temperature control furnace, the air flotation turntable control circuit 9-3, and the lock-in amplifier 10-3 via three USB interfaces. Computer 11 has a built-in data acquisition card and memory, which can perform functions such as data acquisition, hardware control, data processing, and result output, and ultimately realize the automatic measurement of the refractive index temperature coefficient.

[0059] The software functions to control the air-floating turntable controller 9-3 to set relevant operating parameters, including motor speed and stroke; to acquire the signal voltage output of the lock-in amplifier 10-3 through a series of optical path conversions and process controls; to control the temperature control circuit 7-3 of the temperature control furnace and read the temperature change value; to perform a series of processing and analysis on the acquired data; and finally to obtain an objective evaluation result of the temperature coefficient of refractive index of the infrared optical material under test.

[0060] The method for measuring the temperature coefficient of refractive index of infrared optical materials in this embodiment includes the following steps.

[0061] Step 1: Place the infrared optical material sample on 7-1 of the precision temperature control furnace 7-2. The precision temperature control furnace 7-2 heats up to the first set temperature value and transmits the temperature value to the computer 11.

[0062] Step 2: The light emitted by the light source 1-1 passes through the monochromator 1-2, is aimed through the oscillating slit 2, collimated by the off-axis parabolic mirror 5-1, and then enters the sample block 6 after passing through the semi-transparent and semi-reflective mirror 5-2. It is reflected back to the semi-transparent and semi-reflective mirror 5-2 by the rear surface of the sample block, and after being reflected by the mirror 9-1, it reaches the off-axis parabolic mirror 5-3. After being focused, it enters the detector 10-1.

[0063] Step 3: After receiving the optical signal, the detector 10-1 converts it into an electrical signal. The electrical signal is then transmitted to the computer 11 after passing through the preamplifier circuit 10-2 and the lock-in amplifier 10-3.

[0064] Step 4: Computer 11 drives the air-floating turntable in the high-precision angle measurement system 9-2 to rotate through the air-floating turntable control circuit 9-3. The signal reflected by the reflector 9-1 and focused by the off-axis parabolic mirror 5-3 enters the detector 10-1, and the signal will show changes in strength. When the computer collects the maximum value of the signal, it stops rotating. At this time, the angle reading of the high-precision angle measurement system 9-2 is the autocollimation right angle of the sample block at the current temperature.

[0065] Step 5: Increase the temperature of the precision temperature control furnace 7-2 and transmit the temperature value to the computer 11; at this time, the refractive index of the sample changes accordingly, and the direction of the signal reflected from the back surface will change. The detector 10-1 will not collect the maximum signal value. The above steps need to be repeated to re-collect the signal and determine the autocollimation angle.

[0066] Step 6: Repeat the above steps multiple times to obtain angle and temperature measurements at multiple temperatures. The computer software, based on model formula (1), processes multiple sets of temperature values ​​T... k and angle value P k By performing fitting, the measured sample at temperature T can be obtained. k The refractive index temperature coefficient β is as follows k .

[0067]

[0068] β k —Temperature coefficient of refractive index of the sample at the k-th temperature, in °C -1 ;

[0069] n—the refractive index of the sample being tested;

[0070] T k —The temperature value measured at the kth temperature, in °C;

[0071] P k —The angular position of the peak signal measured at the k-th temperature, in degrees;

[0072] θ — prism apex angle of the sample being tested, unit: °.

[0073] 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 device for measuring the temperature coefficient of refractive index of infrared optical materials, characterized in that, include: Light source (1-1), along the light path of the emitted beam from light source (1-1), an infrared monochromator (1-2), an oscillating slit (2), a reflector (3), an off-axis parabolic mirror (5-1), and a semi-transparent mirror (5-2) are arranged in sequence; a precision temperature-controlled furnace (7-2) is arranged on the light-transmitting side of the semi-transparent mirror (5-2), and a high-precision angle measurement system (9-2), an off-axis parabolic mirror (5-3), and an infrared detector (10-) are arranged in sequence along the light path on the reflective side of the semi-transparent mirror (5-2). 1) An optical material sample (6) is placed on a sample stage (7-1) in a precision temperature-controlled furnace (7-2). An infrared detector (10-1) is connected to a computer (11) via a preamplifier circuit (10-2) and a lock-in amplifier (10-3). The high-precision angle measurement system (9-2) is connected to the computer (11) via an air-floating turntable control circuit (9-3). The precision temperature-controlled furnace (7-2) is connected to the computer (11) via a temperature control circuit (7-3). The high-precision angle measurement system (9-2) includes an air bearing, a marble base, and a grating ruler angle reading meter. The air bearing is fixed on the marble base and provides a worktable, allowing the reflector (9-1) to rotate smoothly on its worktable surface. By inputting compressed air into the air bearing, the air bearing floats up and rotates freely. Two worm gears are installed at the bottom of the air bearing, which are driven by stepper motors to rotate the inner or outer shaft of the air bearing, respectively, thereby driving the turntable and the worktable mounted on the turntable to rotate. The grating ruler angle reading meter uses a circular grating and is installed on the working surface of the air bearing turntable, rotating with the turntable. The reading head is fixed on the base of the air bearing, recording the number of pulses during the rotation of the circular grating and converting them into an angle quantity. A reading head is placed at 180° intervals on the outer side of the circular grating, and the data obtained from the two reading heads are added together and the average value is taken as the final measurement result.

2. The infrared optical material refractive index temperature coefficient measuring device as described in claim 1, characterized in that, The light emitted by the light source (1-1) passes through a monochromator (1-2), is aimed by an oscillating slit (2), collimated by an off-axis parabolic mirror (5-1), and then enters the sample block (6) after passing through a semi-transparent mirror (5-2). The light is reflected by the rear surface of the sample block and returns to the semi-transparent mirror (5-2), where it is reflected into the mirror (9-1) of the high-precision angle measurement system (9-2). The reflected light reaches the off-axis parabolic mirror (5-3), is focused, and then enters the detector (10-1). The detector (10-1) receives the light signal and converts it into an electrical signal. The electrical signal is transmitted to the computer (11) after passing through the preamplifier circuit (10-2) and the lock-in amplifier (10-3). The computer simultaneously records the autocollimation angle of the sample block at the current temperature, changes the temperature value, and repeats the above steps. Based on the autocollimation angle at different temperatures, the refractive index temperature coefficient of the sample block is calculated.

3. The infrared optical material refractive index temperature coefficient measuring device as described in claim 2, characterized in that, The light source (1-1) uses silicon carbide as the infrared light source, and after being dispersed by a monochromator, it forms a wavelength range covering... Monochromatic light.

4. The infrared optical material refractive index temperature coefficient measuring device as described in claim 3, characterized in that, The precision temperature control furnace (7-2) is made of stainless steel on the outside and has an internal insulation layer. The sample stage (7-1) is equipped with platinum resistance and differential thermocouple sensors to collect the temperature of the bottom and side of the sample block (6) in real time. The collected signals are sequentially entered into the temperature measurement channel through a multiplexer, and after precision amplification and 24-bit analog-to-digital conversion, they are entered into the computer (11).

5. The infrared optical material refractive index temperature coefficient measuring device as described in claim 4, characterized in that, The sample block (6) is a standard sample block of a right-angle prism; the precision temperature control furnace (7-2) is evacuated and equipped with a sealed optical window, which is made of ZnS material.

6. The infrared optical material refractive index temperature coefficient measuring device as described in claim 5, characterized in that, The oscillating slit (2) is made using a tuning fork oscillator.

7. A method for measuring the refractive index temperature coefficient of infrared optical materials based on the refractive index temperature coefficient measuring device according to any one of claims 1-6, characterized in that, Includes the following steps: Step 1: Place the infrared optical material sample in a precision temperature control furnace (7-2), heat the precision temperature control furnace (7-2) to the set value, and transmit the temperature value to the computer (11). Step 2: The light emitted by the light source (1-1) passes through the monochromator (1-2), is aimed through the oscillating slit (2), collimated by the off-axis parabolic mirror (5-1), and then enters the sample block (6) after passing through the semi-transparent mirror (5-2). It is reflected back to the semi-transparent mirror (5-2) by the rear surface of the sample block, and after being reflected by the mirror (9-1), it reaches the off-axis parabolic mirror (5-3), and after being focused, it enters the detector (10-1). Step 3: After receiving the optical signal, the detector (10-1) converts it into an electrical signal. The electrical signal is transmitted to the computer (11) after passing through the preamplifier circuit (10-2) and the lock-in amplifier (10-3). After processing, the computer obtains the angle reading corresponding to the maximum value of the signal, which is the autocollimation right angle of the sample block at the current temperature. Step 4: Gradually increase the temperature of the precision temperature control furnace (7-2) and repeat the above steps. Calculate the temperature coefficient of the refractive index of the sample based on the corresponding autocollimation angle at different temperatures.

8. The method for measuring the refractive index temperature coefficient of infrared optical materials according to claim 7, characterized in that, In step 4, the computer (11) calculates the refractive index temperature coefficient of the sample at various temperatures. The formulas used to calculate the refractive index temperature coefficient are as follows: (k=1,2,3,4,5,6…) β k —The temperature coefficient of refractive index of the sample at the k-th temperature, in °C. -1 ; n—the refractive index of the sample being tested; T k —The temperature value measured at the kth temperature, in °C; P k —The angular position of the peak signal measured at the k-th temperature, in degrees; θ — The apex angle of the prism of the sample being tested, in °.

9. An application of a device for measuring the refractive index temperature coefficient of infrared optical materials based on any one of claims 1-6 in the field of optical metrology and measurement technology.

Images