Detector nonlinear measuring device based on double laser light sources

Abstract

The invention discloses a detector nonlinear measurement device and method based on double laser light sources. The detector nonlinear measurement device comprises a first laser, a second laser, a chopping disc, a chopping controller, a first light trap, a second light trap, a gold-plated integrating sphere, a photoelectric detector, a lock-in amplifier and a computer. According to the method, nonlinear characteristic measurement of the detector in a large-value range can be realized, single-time and multi-time accumulative measurement is considered, and a corresponding calculation method is provided. In addition, the luminous flux is adjusted directly through the on-off of the double laser light sources, moving parts are reduced, and the measurement stability is better. By adopting a double-laser measurement method, an optical measurement system is remarkably simplified, and the influence of non-ideal factors such as light blocking of an optical filter is reduced. Meanwhile, the projection laser is reflected for multiple times through the gold-plated integrating sphere and then is uniformly projected to the photoelectric detector to cover the whole photosensitive surface, so that the nonlinear measurement error caused by the difference of the light uniformity of the photosensitive surface is avoided.

Description

Technical Field

[0001] The invention relates to the field of infrared detection technology, and in particular to a detector nonlinear measurement device based on dual laser light sources. Background Art

[0002] In recent years, with the development of infrared technology, radiation temperature measurement, effective use of solar energy and material science, people have a stronger demand for a deep understanding of the performance of infrared detectors. The main function of infrared radiation detectors is to convert infrared radiation signals into electrical signals, and obtain effective information in infrared radiation light signals through the conversion, amplification and processing of electrical signals. Due to the large number of objects to be measured, the signal intensity received by the optical infrared detector has a large span. Therefore, in-depth research on the linear characteristics of the detector response is extremely important for the refined processing of signals and even the traceability of the value in the field of infrared detection.

[0003] For example, the spectral response rate of mercury cadmium telluride (MCT) detectors, which are widely used in the thermal infrared region, will drift slowly over time. The main reasons are the drift caused by the active ice film of the detector and the nonlinearity of the detector response. The drift caused by the active ice film of the detector can be eliminated by evacuating the detector dewar, but the influence of the nonlinearity of the detector on the drift of the spectral response rate belongs to the essential property of the detector and is difficult to eliminate, especially the nonlinear measurement of detectors in the mid-infrared range is relatively scarce. Therefore, the cross-order measurement and characterization of the nonlinear characteristics of the mid-infrared band detector is an important prerequisite for conducting high-precision infrared detection experiments.

[0004] CN217006983U discloses a target emissivity distribution characteristic measuring device with enhanced laser power stability, which aims to measure the emissivity of the target to be measured. In principle, it is assumed that the responsiveness within the output signal range of the detector involved is consistent and does not involve nonlinear measurement of the detector.

[0005] CN103245615A discloses a spectroscopy method N 2 O 4 The equivalent water content measuring device and measuring method in CN103245615A is a nonlinear correction of the transmittance measurement value of the sample to be measured. The light flux is adjusted by passing the light signal through two holes at the same time and through the light signal alone. The characteristics of the detector are not involved, and the single measurement is nonlinear, and the calculation formula of the nonlinear characteristics of the detector is not given. In addition, CN103245615A adopts the solution of light source + monochromator, and its light flux adjustment range is limited (even cannot cross orders of magnitude, which can be seen in its embodiment). Furthermore, CN103245615A does not constrain and explain the internal design results of the integrating sphere. Summary of the invention

[0006] In view of the deficiencies in the prior art, the present invention aims to provide a detector nonlinear measurement device based on dual laser light sources.

[0007] In order to achieve the above object, the present invention adopts the following technical solution:

[0008] A detector nonlinear measurement device based on a dual laser light source, comprising a first laser, a second laser, a chopper disk, a chopper controller, a first light trap, a second light trap, a gold-plated integrating sphere, a photodetector, a lock-in amplifier and a computer;

[0009] The chopper disk is arranged in front of the light output direction of the first laser and the second laser; the first light trap and the second light trap are arranged in front of the light output direction of the chopper disk and correspond to the first laser and the second laser respectively; the first light trap and the second light trap respectively control the on and off of the light paths of the first laser and the second laser through directional movement;

[0010] The gold-plated integrating sphere is arranged in front of the light output direction of the first light trap and the second light trap, and the photodetector is used to detect the light reflected from the inside of the gold-plated integrating sphere; the computer is respectively controlled and connected to the phase-locked amplifier and the chopper controller; the phase-locked amplifier is communicatively connected to the photodetector; and the chopper controller is control-connected to the chopper disk.

[0011] Furthermore, the first laser and the second laser are both equipped with a laser controller, the laser controller supports local and remote control, and the power range of the first laser and the second laser is not less than 10-450mW.

[0012] Furthermore, the first laser and the second laser both include an air-cooled laser head, the air-cooled laser head includes a laser chip and a collimating lens, and the laser chip is connected to a laser controller via a cable.

[0013] Furthermore, the first laser and the second laser both include a thermistor and a cooling plate, and the thermistor and the cooling plate are connected to the laser controller.

[0014] Furthermore, the first light trap and the second light trap have cavities with a diameter of 1-2 cm and a depth of 8-15 cm inside, and the inner surface of the cavity is coated with graphite.

[0015] Furthermore, the outer surface of the light trap has a heat dissipation groove.

[0016] Furthermore, the inner surface and the outer surface of the gold-plated integrating sphere are both plated with a gold coating with high reflectivity.

[0017] Furthermore, a gold-plated baffle is provided inside the gold-plated integrating sphere.

[0018] The present invention also provides a method for measuring the nonlinearity of a detector using the above-mentioned detector nonlinearity measuring device, and the specific process is as follows:

[0019] First, the required laser power is selected in the laser controller, and the first laser and the second laser are controlled by the laser controller to emit the first laser beam and the second laser beam with wavelength λ respectively, and the first laser beam and the second laser beam are kept stable for a period of time; the first laser beam and the second laser beam are modulated by the chopper disk and reach the first light trap and the second light trap;

[0020] Then, the first laser beam and the second laser beam are turned on and off by directional movement of the first light trap and the second light trap, so that the first laser beam enters the gold-plated integrating sphere alone, the second laser beam enters the gold-plated integrating sphere alone, and the first laser beam and the second laser beam enter the gold-plated integrating sphere at the same time:

[0021] 1) At time t A When the first laser beam is turned on;

[0022] 2) At time t 1 =t A +Δt, the computer collects the current reading of the photodetector through the phase-locked amplifier when the first laser beam passes through, and obtains the output signal I of the photodetector A ;

[0023] 3) At time t B =t 1 +Δt when the second laser beam is turned on;

[0024] 4) At time t 2 =t B During the +Δt time, the computer uses a phase-locked amplifier to collect the current readings of the photodetector when the first laser beam and the second laser beam pass through at the same time, and obtains the output signal I of the photodetector AB ;

[0025] 5) Close the second light path;

[0026] 6) At time t 3 =t 2 +Δt, the computer collects the current reading of the photodetector through the phase-locked amplifier when the second laser beam passes through, and obtains the output signal I of the photodetector B ;

[0027] 7) Turn off the second laser beam and the computer collects the dark current I of the photodetector through the lock-in amplifier 0 ;

[0028] Afterwards, the computer calculates the nonlinear value NL of the photodetector according to formula (1):

[0029]

[0030] Furthermore, the above method also includes: by changing the laser power of the first laser and the second laser, performing multiple nonlinear measurements to obtain multiple cumulative nonlinear measurement results, as shown in the following formula:

[0031]

[0032] Among them, INL i is the nonlinear value accumulated multiple times, NL j is the single nonlinear value of the detector.

[0033] The beneficial effects of the present invention are:

[0034] 1. The measurement target of the present invention is the detector. By adjusting the projected laser to different powers and combining the optical system and characterization method provided by the present invention, the nonlinear characteristics of the photodetector within a large current range can be characterized.

[0035] 2. The present invention directly adjusts the light flux by switching the dual laser light sources, which reduces moving parts and improves the measurement stability;

[0036] 3. The present invention takes into account both single and multiple cumulative measurements, and provides corresponding calculation methods;

[0037] 4. The present invention uses two monochromatic lasers with widely adjustable output power as light sources. By using them together, the measurement range can span more than two orders of magnitude, or even close to three orders of magnitude. Usually, the nonlinear characteristics of the photodetector are more obvious when the measurement signal spans multiple orders of magnitude. Therefore, the present invention has great practical value in realizing the measurement of nonlinear characteristics of detectors with a large value range.

[0038] 5. The present invention significantly simplifies the optical measurement system by adopting a dual laser measurement method, reducing the influence of non-ideal factors such as light blocking by filters. At the same time, the projected laser is evenly projected to the photodetector and covers the entire photosensitive surface after multiple reflections through a gold-plated integrating sphere, thereby avoiding nonlinear measurement errors caused by differences in light uniformity on the photosensitive surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a connection principle diagram of the device in Example 1 of the present invention. DETAILED DESCRIPTION

[0040] The present invention will be further described below in conjunction with the accompanying drawings. It should be noted that this embodiment is based on the technical solution and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to this embodiment.

[0041] Example 1

[0042] This embodiment provides a detector nonlinear measurement device based on dual laser light sources, such as Figure 1 As shown, it includes a first laser 1, a second laser 2, a chopper disk 3, a chopper controller 4, a first light trap 5, a second light trap 6, a gold-plated integrating sphere 7, a photodetector 8, a phase-locked amplifier 9 and a computer 10.

[0043] The chopper disk 3 is arranged in front of the light output direction of the first laser 1 and the second laser 2; the first light trap 5 and the second light trap 6 are arranged in front of the light output direction of the chopper disk 3 and correspond to the first laser 1 and the second laser 2 respectively; the first light trap 5 and the second light trap 6 respectively control the on and off of the light paths of the first laser 1 and the second laser 2 through directional movement.

[0044] The gold-plated integrating sphere 7 is arranged in front of the light output direction of the first light trap 5 and the second light trap 6. The photodetector 8 is used to detect the light reflected from the inside of the gold-plated integrating sphere 7; the computer 10 is respectively controlled and connected to the phase-locked amplifier 9 and the chopper controller 4; the phase-locked amplifier 9 is communicatively connected to the photodetector 8; and the chopper controller 4 is controllably connected to the chopper disk 3.

[0045] The first laser 1, the second laser 2, and the chopper disk 3 together constitute the laser light source subsystem, which is used to expand the nonlinear measurement range and modulate the output signal. The first light trap 5, the second light trap 6, and the gold-plated integrating sphere 7 together constitute the optical path subsystem, which is used to transmit optical signals and control the on-off of the optical path. The photodetector 8, the phase-locked amplifier 9, and the computer 10 together constitute the signal acquisition subsystem. The signal acquisition subsystem characterizes the nonlinear data of the representative photodetector under the corresponding radiation illumination by obtaining the detector electrical signal under different on-off conditions.

[0046] After being emitted from the first light trap 5 or the second light trap 6, the laser beam of the first laser 1 or the second laser 2 enters the gold-plated integrating sphere 7 at different positions. Due to the diffusion characteristics of the inner surface of the gold-plated integrating sphere 7, the light will be diffusely reflected after entering the gold-plated integrating sphere 7. Therefore, when the photodetector 8 measures, the radiant illumination is independent of the position where the light enters.

[0047] In this embodiment, the first laser 1 and the second laser 2 are both equipped with a laser controller, which supports local and remote control, and the power range of the first laser and the second laser is not less than 10-450mW. The laser controller provides a variety of interfaces, including SMA connectors for modulation and tuning and other connection options, such as synchronization output, interlocking and grounding ports.

[0048] The first laser 1 and the second laser 2 both include an air-cooled laser head, which includes a laser chip and a collimating lens and can generate collimated continuous 4 μm mid-infrared light. The laser chip is connected to a laser controller via a cable.

[0049] More specifically, the first laser and the second laser both include a thermistor and a cooling plate (TEC), which are connected to the laser controller to achieve a temperature regulation function and maintain the temperature of the laser chip. When the laser chip is overheated, the laser controller automatically shuts down the laser chip.

[0050] In this embodiment, the first light trap 5 and the second light trap 6 have cavities with a diameter of 1-2 cm and a depth of 8-15 cm. The inner surface of the cavity is coated with graphite as a high absorption material, which can absorb laser light in the wavelength range of 1-12 μm and effectively avoid multiple reflections of the laser light. Furthermore, the outer surface of the light trap has a heat dissipation groove design, so as to have an excellent heat dissipation effect, and the surface temperature is lower during operation, which is safer.

[0051] In this embodiment, the outer diameter of the gold-plated integrating sphere 7 is 500 mm, and its inner and outer surfaces are coated with a high-reflectivity gold coating. The gold-plated integrating sphere has high stability and repeatable spectral reflectivity characteristics, good thermal stability under most temperature conditions, and can ensure the stability of the reflected signal. The gold-plated integrating spheres include a laser input port with a diameter of 200 mm, a laser output port with a diameter of 200 mm, and several detection ports (such as 2). The laser input port is used to input laser, and the laser output port can be used to realize the nonlinear study of the overall gold-plated integrating sphere reflectivity measurement device, and the nonlinear study of different detection directions can be realized through each detection port.

[0052] Furthermore, in this embodiment, a gold-plated baffle is provided inside the gold-plated integrating sphere to prevent the laser beam from directly entering the photodetector without reflection. Preferably, two gold-plated baffles are respectively arranged near the two detection ports of the photodetector 8, with a diameter of about 5 cm, so that the laser is diffusely reflected in the gold-plated integrating sphere, and the detection surface of the detector can be fully covered.

[0053] In this embodiment, a chopper disk 4 is arranged in front of the first laser 1 and the second laser 2 to modulate the laser signal so that the signal received by the detector can be accurately input and output in the phase-locked amplifier 9.

[0054] In this embodiment, the computer 10 is pre-installed with a Labview program, which controls the lock-in amplifier 9 and the chopper controller 4 to achieve automatic measurement of collected data, and obtain the nonlinearity of the photodetector through data calculation.

[0055] Example 2

[0056] This embodiment provides a method for measuring the nonlinearity of a detector using the detector nonlinearity measuring device described in Embodiment 1. The specific process is as follows:

[0057] First, the required laser power is selected in the laser controller, and the first laser 1 and the second laser 2 are controlled by the laser controller to emit the first laser beam and the second laser beam with a wavelength of λ (4μm) respectively, and the first laser beam and the second laser beam are kept for a period of time so that the first laser beam and the second laser beam have good stability. After being modulated by the chopper disk 3, the first laser beam and the second laser beam reach the first light trap 5 and the second light trap 6.

[0058] The first laser beam and the second laser beam are turned on and off by directional movement of the first light trap 5 and the second light trap 6, so that the first laser beam enters the gold-plated integrating sphere alone, the second laser beam enters the gold-plated integrating sphere alone, and the first laser beam and the second laser beam enter the gold-plated integrating sphere at the same time:

[0059] 1) At time t A When the first laser beam is turned on;

[0060] 2) At time t 1 =t A +Δt, the computer collects the current reading of the photodetector through the phase-locked amplifier when the first laser beam passes through, and obtains the output signal I of the photodetector A ;

[0061] 3) At time t B =t 1 +Δt when the second laser beam is turned on;

[0062] 4) At time t 2 =t B During the +Δt time, the computer uses a phase-locked amplifier to collect the current readings of the photodetector when the first laser beam and the second laser beam pass through at the same time, and obtains the output signal I of the photodetector AB ;

[0063] 5) Close the second light path;

[0064] 6) At time t 3 =t 2 +Δt, the computer collects the current reading of the photodetector through the phase-locked amplifier when the second laser beam passes through, and obtains the output signal I of the photodetector B ;

[0065] 7) Turn off the second laser beam and the computer collects the dark current I of the photodetector through the lock-in amplifier 0 .

[0066] When using flux multiplication to describe the nonlinearity of a photodetector, the beams of the two optical paths are the first laser beam and the second laser beam. The nonlinearity can be expressed as the difference between the ratio of the electrical signal generated when the first laser beam and the second laser beam are simultaneously projected onto the gold-plated integrating sphere and the sum of the electrical signals generated when the first laser beam and the second laser beam are respectively projected onto the gold-plated integrating sphere and 1. After calculating the nonlinearity value of the photodetector under this radiation illumination, continue to change the laser power of the first laser and the second laser to obtain the nonlinearity value NL of the photodetector under different radiation illuminations. The calculation formula is as follows:

[0067]

[0068] Based on the above process, by changing the laser power of the first laser and the second laser (the laser power of the first laser and the second laser can be adjusted from 10mW to more than 450mW), multiple nonlinear measurements are carried out, and multiple cumulative nonlinear measurement results can be obtained. The measurement value range can span more than 2 orders of magnitude, thereby describing the nonlinear characteristics of the photodetector from different dimensions, which is difficult to achieve with traditional nonlinear measurement schemes, as shown in the following formula:

[0069]

[0070] Where: INL i is the nonlinear value accumulated multiple times, NL j is the single nonlinear value of the detector.

[0071] For those skilled in the art, various corresponding changes and modifications can be made according to the above technical solutions and concepts, and all of these changes and modifications should be included in the protection scope of the claims of the present invention.

Claims

1. A detector nonlinear measurement device based on dual laser light sources, characterized in that: It includes a first laser, a second laser, a chopper disk, a chopper controller, a first light trap, a second light trap, a gold-plated integrating sphere, a photodetector, a phase-locked amplifier and a computer; The chopper disk is arranged in front of the light output direction of the first laser and the second laser; the first light trap and the second light trap are arranged in front of the light output direction of the chopper disk and correspond to the first laser and the second laser respectively; the first light trap and the second light trap respectively control the on and off of the light paths of the first laser and the second laser through directional movement; The gold-plated integrating sphere is arranged in front of the light output direction of the first light trap and the second light trap, and the photodetector is used to detect the light reflected from the inside of the gold-plated integrating sphere; the computer is respectively controlled and connected to the lock-in amplifier and the chopper controller; the lock-in amplifier is communicatively connected to the photodetector; A chopper controller is control-connected to the chopper disk.

2. The device according to claim 1, characterized in that The first laser and the second laser are both equipped with a laser controller, and the laser controller supports local and remote control. The power range of the first laser and the second laser is not less than 10-450mW.

3. The device according to claim 2, characterized in that The first laser and the second laser both include an air-cooled laser head, the air-cooled laser head includes a laser chip and a collimating lens, and the laser chip is connected to a laser controller via a cable.

4. The device according to claim 2, characterized in that The first laser and the second laser both include a thermistor and a cooling plate, and the thermistor and the cooling plate are connected to the laser controller.

5. The device according to claim 1, characterized in that The first light trap and the second light trap have cavities with a diameter of 1-2 cm and a depth of 8-15 cm inside, and the inner surface of the cavity is coated with graphite.

6. The device according to claim 5, characterized in that The outer surface of the light trap has a heat dissipation groove.

7. The device according to claim 1, characterized in that The inner surface and the outer surface of the gold-plated integrating sphere are both plated with a gold coating with high reflectivity.

8. The device according to claim 1, characterized in that A gold-plated baffle is arranged inside the gold-plated integrating sphere.

9. A method for measuring detector nonlinearity using the detector nonlinearity measuring device according to any one of claims 1 to 8, characterized in that: The specific process is: First, the required laser power is selected in the laser controller, and the first laser and the second laser are controlled by the laser controller to emit the first laser beam and the second laser beam with wavelength λ respectively, and the first laser beam and the second laser beam are kept stable for a period of time; the first laser beam and the second laser beam are modulated by the chopper disk and reach the first light trap and the second light trap; Then, the first laser beam and the second laser beam are turned on and off by directional movement of the first light trap and the second light trap, so that the first laser beam enters the gold-plated integrating sphere alone, the second laser beam enters the gold-plated integrating sphere alone, and the first laser beam and the second laser beam enter the gold-plated integrating sphere at the same time: 1) At time t A When the first laser beam is turned on; 2) At time t1 = t A +Δt, the computer collects the current reading of the photodetector through the phase-locked amplifier when the first laser beam passes through, and obtains the output signal I of the photodetector A ; 3) At time t B =t1+Δt when the second laser beam is turned on; 4) At time t2 = t B During the +Δt time, the computer uses a phase-locked amplifier to collect the current readings of the photodetector when the first laser beam and the second laser beam pass through at the same time, and obtains the output signal I of the photodetector AB ; 5) Close the second light path; 6) At time t3 = t2 + Δt, the computer collects the current reading of the photodetector when the second laser beam passes through the phase-locked amplifier to obtain the output signal I of the photodetector. B ; 7) Turn off the second laser beam and the computer collects the dark current I0 of the photodetector through a lock-in amplifier; Afterwards, the computer calculates the nonlinear value NL of the photodetector according to formula (1):

10. The method according to claim 9, characterized in that Also includes: By changing the laser power of the first laser and the second laser, multiple nonlinear measurements are carried out to obtain multiple cumulative nonlinear measurement results, as shown in the following formula: Among them, INL i is the nonlinear value accumulated multiple times, NL j is the single nonlinear value of the detector.

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