An on-board calibration device

Abstract

This invention discloses an on-board calibration device, relating to the field of on-board calibration technology, comprising: a calibration source and a calibration lens; the calibration source includes a blackbody radiating surface, a temperature measuring unit, a support structure, conductive components, and a housing; wherein, the blackbody radiating surface is fabricated using MEMS technology and includes a metal heating layer and a specific coating for generating infrared radiation; the conductive components are used to power the blackbody radiating surface; the support structure is used to fix and support the blackbody radiating surface; the temperature measuring unit is used to monitor the temperature of the blackbody radiating surface; the housing is used to encapsulate the calibration source; the calibration lens is disposed in the light output path of the calibration source and is used to collect and compress the infrared radiation light emitted by the calibration source before introducing it into the lens of a remote sensing camera. This invention uses MEMS technology to fabricate the calibration source, which has excellent performance characteristics such as high emissivity, fast response, large dynamic range, and high temperature measurement accuracy, and is small in size and light in weight.

Description

Technical Field

[0001] This invention relates to the field of on-board calibration technology, and more specifically, to an on-board calibration device. Background Technology

[0002] With the development of space remote sensing technology, the demand for quantitative remote sensing is becoming increasingly urgent, requiring on-orbit radiometric calibration of remote sensing cameras.

[0003] Onboard calibration devices must meet requirements such as stability, repeatability, dynamic range, temperature measurement accuracy, irradiance uniformity, reliability, and redundancy, while also satisfying constraints related to stray light, space, weight, and power. The calibration source is a component of the onboard calibration system, used for radiometric correction throughout the remote sensor's lifespan. The calibration source needs to monitor changes in camera responsivity over time over extended periods, requiring high repeatability to accurately measure radiation changes caused by variations in camera temperature. Therefore, for use in a space environment, the calibration source must simultaneously meet multiple constraints, such as high repeatability and reliability, uniform illumination (while avoiding stray light), large dynamic range, fast response, high-precision temperature measurement, and small size and light weight.

[0004] SSG Corporation of the United States proposed a calibration source using a nickel-chromium alloy material. While nickel-chromium alloys can withstand high operating temperatures, ensuring high resistivity in the nickel-chromium alloy thin film requires fabrication of micron-level or even thinner films, a process that is difficult to achieve. Furthermore, nickel-chromium alloy thin films have low emissivity, requiring even higher temperatures to reach the desired radiation levels, thus necessitating higher power consumption. Large-area nickel-chromium alloy thin films are also prone to deformation under high temperatures, exhibiting significant thermal stress. Based on these issues, this invention proposes an on-board calibration device that is small in size, lightweight, has rapid heating and cooling rates, and a wide dynamic range. Summary of the Invention

[0005] The present invention provides an on-board calibration device to overcome at least one technical problem existing in the prior art.

[0006] This invention provides an on-board calibration device, comprising: a calibration source and a calibration lens; The calibration source includes a blackbody radiating surface, a temperature measuring unit, a support structure, conductive components, and a housing. The blackbody radiating surface is fabricated using MEMS technology and includes a metal heating layer and a specific coating to generate infrared radiation. The conductive components supply power to the blackbody radiating surface. The support structure fixes and supports the blackbody radiating surface. The temperature measuring unit monitors the temperature of the blackbody radiating surface. The housing encapsulates the calibration source. The calibration lens is disposed on the light output path of the calibration source and is used to collect and compress the infrared radiation light emitted by the calibration source before introducing it into the lens of the remote sensing camera.

[0007] Optionally, the blackbody radiating surface further includes: An insulating layer is located between the metal heating layer and the specific coating; The first insulating dielectric film is located on the side of the metal heating layer away from the insulating layer; A silicon substrate is located on the side of the first insulating dielectric film away from the metal heating layer; A second insulating dielectric film is located on the side of the silicon substrate away from the specific coating; A first coating is located on the side of the second insulating dielectric film away from the silicon substrate; the emissivity of the specific coating is higher than that of the first coating.

[0008] Optionally, the temperature measuring unit is mounted on the side of the silicon substrate near the first insulating dielectric film by adhesive bonding, and the temperature measuring unit is located at the edge of the silicon substrate.

[0009] Optionally, the temperature measuring unit is a platinum resistance temperature sensor.

[0010] Optionally, the material of the metal heating layer is platinum.

[0011] Optionally, the blackbody radiating surface has dimensions of 20mm × 20mm × 0.3mm, and multiple heating electrodes are provided at both ends of the blackbody radiating surface; the multiple heating electrodes are used to connect current and make the current uniformly distributed on the blackbody radiating surface.

[0012] Optionally, the support structure includes four gold-plated solid pillars located at the four corners of the blackbody radiating surface. Each solid pillar has a slot on the side closest to the blackbody radiating surface. The blackbody radiating surface is fixed to the solid pillar through the slot and encapsulated with heat-resistant inorganic adhesive.

[0013] Optionally, the conductive component is a gold-plated copper electrode, and the copper electrode has a hollow structure; The conductive component is connected to multiple heating electrodes on the blackbody radiating surface via gold wire bonding.

[0014] Optionally, the overall dimensions of the calibration source are Φ80mm×40mm, and the weight is less than or equal to 200g.

[0015] Optionally, the upper limit of the dynamic range of the operating temperature of the calibration source is 750K, and the time to heat up to 750K is less than or equal to 60 seconds at the maximum heating power of 12W. After the temperature stabilizes, the temperature field uniformity of the radiant surface is 1.5K.

[0016] The innovative aspects of this invention include: (1) In this embodiment, the lens and the camera lens itself are used to generate uniformly distributed light covering the entire focal plane. The uniformity is better than 2K, and stray light can be avoided. This is one of the innovative points of this embodiment.

[0017] (2) In this embodiment, the calibration source based on metal is prepared by MEMS process, which has excellent performance of high emissivity, fast response, large dynamic range and high temperature measurement accuracy, and is small in size and light in weight, which is one of the innovations of this embodiment. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of a satellite calibration device provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of a blackbody radiating surface provided in an embodiment of the present invention; Figure 3 For along Figure 2 A cross-sectional view of AA'; Figure 4 A physical image of a calibration source provided in an embodiment of the present invention; Figure 5 This is a schematic diagram of another structure of the calibration source provided in an embodiment of the present invention; Figure 6 The graph shows the relationship between temperature and time obtained from the simulation. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] It should be noted that the terms "comprising" and "having," and any variations thereof, in the embodiments and drawings of this invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the steps or units listed, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or devices.

[0022] This invention discloses an on-board calibration device and method. These will be described in detail below.

[0023] Figure 1 This is a schematic diagram of a satellite calibration device provided in an embodiment of the present invention. Please refer to... Figure 1 The on-board calibration device 100 provided in this embodiment of the invention includes: a calibration source 1 and a calibration lens 2; The calibration source 1 includes at least a blackbody radiating surface 11, a temperature measuring unit 14, a support structure 12, a conductive component 13, and a housing 15. The blackbody radiating surface 11 is fabricated using MEMS technology and includes a metal heating layer 112 and a specific coating 114 for generating infrared radiation. The conductive component 13 supplies power to the blackbody radiating surface 11. The support structure 12 fixes and supports the blackbody radiating surface 11. The temperature measuring unit 14 monitors the temperature of the blackbody radiating surface 11. The housing 15 encapsulates the calibration source 1. The calibration lens 2 is placed in the light output path of the calibration source 1 to collect and compress the infrared radiation light emitted by the calibration source 1 before introducing it into the lens of the remote sensing camera.

[0024] For details, please refer to Figure 1 The on-board calibration device 100 provided in this application embodiment includes a calibration source 1 and a calibration lens 2. The calibration lens 2 is placed in the light output path of the calibration source 1. After the infrared radiation light emitted by the calibration source 1 is collected and compressed by the calibration lens 2, it is introduced into the lens of the remote sensing camera and projected onto the focal plane of the detector. The calibration lens 2 and the camera lens work together to generate uniform radiation on the camera plane through the method of projection radiation calibration, thereby achieving radiation correction with a large dynamic range.

[0025] Furthermore, the present invention places the aperture stop of the optical system formed by cascading the calibration lens 2 and the camera at the detector, which can not only effectively suppress stray radiation, but also improve the uniformity of the image plane.

[0026] The key technical indicators of calibration source 1 are emissivity, temperature range, heating and stabilization time, cooling time, temperature field uniformity, and illuminance distribution uniformity of the image plane. In this invention, calibration source 1 is fabricated using MEMS (Microelectromechanical systems) technology. Calibration source 1 includes a blackbody radiating surface 11, which serves as a radiation emitting device. During operation, its temperature is controlled by a power supply to increase or decrease, thereby generating infrared radiation that meets the requirements within the load's operating wavelength band, serving as a standard radiation source for radiation calibration.

[0027] Figure 2 This is a schematic diagram of a blackbody radiating surface provided in an embodiment of the present invention. Figure 3For along Figure 2 A cross-sectional view of AA'. Figure 4 Please refer to the physical diagram of a calibration source provided in an embodiment of the present invention. Figure 2 and Figure 3 The blackbody radiating surface 11 uses single-crystal silicon as a substrate. To improve the chemical properties of the blackbody radiating surface 11, a heating layer is prepared using a metallic material. Since platinum metal has very stable chemical properties, excellent oxidation resistance, and a maximum operating temperature of 800°C when used directly in air, platinum metal is used to prepare the heating layer in this embodiment. To achieve a higher emissivity for the blackbody radiating surface 11, a specific coating 114 is applied to its surface. This specific coating 114 needs to have a high emissivity, such as a high-emissivity carbon black coating.

[0028] To achieve insulation between the wear-off layers, a first insulating dielectric film 111 is provided between the silicon substrate 110 and the metal heating layer 112, and an insulating layer 113 is provided between the metal heating layer 112 and the specific coating 114. Furthermore, to reduce the emissivity of the back side of the blackbody radiating surface 11, a second insulating dielectric film 115 is prepared on the back side of the silicon substrate 110, and a first coating 116, such as a platinum film, with an emissivity lower than that of the specific coating 114 is prepared on the second insulating dielectric film 115. This not only reduces the back side emissivity but also improves the efficiency of power utilization.

[0029] Please refer to Figure 2 In this embodiment, the blackbody radiating surface 11 is set to a size of 20mm × 20mm × 0.3mm. This effectively reduces the volume and weight of the calibration source 1, thereby reducing manufacturing costs. Heating electrodes 16 are provided at both ends of the blackbody radiating surface 11, and the surfaces of the heating electrodes 16 are gold-plated. This allows them to be connected to external terminals via gold wires, enabling circuit connection with an external control circuit. Furthermore, multiple heating electrodes 16 are provided at each end; for example, 25 heating electrodes 16 are provided at each of the opposite ends. This ensures uniform current distribution on the blackbody radiating surface 11.

[0030] Please refer to Figure 4 After the blackbody radiating surface 11 is fabricated, it needs to be installed and supported. Therefore, a support structure 12 is provided. In this embodiment, the support structure 12 is fabricated using high-temperature resistant all-zirconia ceramic material. The support structure 12 includes four solid pillars 121, and the surface of the solid pillars 121 is gold-plated to reduce the surface emissivity, ensure minimal heat leakage between the blackbody radiating surface 11 and the support structure 12, improve the input power utilization rate, and thus ensure the heating rate.

[0031] Four solid pillars 121 are located at the four corners of the blackbody radiating surface 11, and slots 122 are provided on the side of the solid pillars 121 close to the blackbody radiating surface 11. The height of the slots 122 must be sufficient to accommodate the blackbody radiating surface 11. For example, when the thickness of the blackbody radiating surface 11 is 0.3mm, the height of the slots 122 can be 0.35mm. In this way, the blackbody radiating surface 11 can be fixed to the four solid pillars 121 through the slots 122 and then potted with heat-resistant inorganic glue.

[0032] The calibration source 1 is a thermally excited infrared radiation source. Under a certain input power, the temperature of the blackbody radiating surface 11 rises until it reaches thermal equilibrium and stabilizes at a certain temperature point, generating stable infrared radiation. Therefore, the present invention includes a conductive component 13, which supplies power to the blackbody radiating surface 11, thereby providing heating power.

[0033] Please refer to Figure 4 In this embodiment, a copper electrode is used as the conductive component 13. In order to reduce heat loss, the copper electrode is set as a hollow structure and gold-plated on the surface to ensure the solderability of the gold wire and to form a gold wire bonding connection with the heating electrode 16 on the blackbody radiating surface 11.

[0034] Please refer to Figure 2 and Figure 3 During the operation of calibration source 1, the temperature of the blackbody radiating surface 11 needs to be monitored in real time. Therefore, a temperature measuring unit 14 is also provided. In this embodiment, a contact temperature measurement scheme is adopted, in which the temperature measuring unit 14 is placed on the silicon substrate 110 to measure the temperature. The temperature measuring unit 14 transmits the data to the temperature processing module to obtain the temperature data. To ensure that the temperature measuring unit 14 does not damage the radiating surface, the temperature measuring unit 14 is installed on the edge of the silicon substrate 110 by adhesive bonding, and is positioned on the side close to the radiating surface, thereby obtaining a temperature value that is closer to the radiating surface.

[0035] Because platinum resistance temperature sensors have good temperature measurement performance and stability, small size, light weight, and high temperature measurement accuracy, and can adapt to space working environments, platinum resistance temperature sensors are selected as temperature measurement units 14 in this embodiment.

[0036] Figure 5 For another structural schematic diagram of the calibration source provided in this embodiment of the invention, please refer to... Figure 5 In order to provide a packaging structure and mechanical support for the entire calibration source 1, the present invention provides a housing 15 for the calibration source 1 and provides certain mechanical interfaces on the housing 15, so as to realize mechanical connection and install it on the required mounting surface.

[0037] Since the calibration source 1 is installed inside the load, it is required to be small in size and light in weight. Therefore, in this embodiment, in order to achieve lightweight, the outer shell 15 is made of aluminum alloy and its dimensions are set to Φ80mm×40mm, so that the overall weight of the calibration source 1 is less than or equal to 200g.

[0038] The key technical indicators of calibration source 1 are effective radiating area, emissivity, temperature range, heating time and stabilization time, cooling time, temperature field uniformity, and illuminance distribution uniformity of the image plane. Among these, the effective radiating area is guaranteed by design, while the emissivity is determined by the material's inherent properties, surface treatment process, and coating characteristics. To verify the performance of this invention, simulation analysis was performed on the temperature range, heating time and stability, cooling time, and temperature field uniformity.

[0039] Figure 6 For the simulation-generated temperature versus time curve, please refer to... Figure 6 Simulation analysis shows that at a power of 12W, the maximum temperature can reach 750K, with a heating time of 60 seconds. After 60 seconds, the temperature basically reaches equilibrium and stabilizes, with a temperature field uniformity of 1.5K. It can reach room temperature after cooling for 180 seconds. Because the blackbody radiating surface exchanges heat with the environment, changes in ambient temperature affect the temperature stability of the radiating surface. Analysis shows that with an input power of 12W and an ambient temperature fluctuation of 20K, the temperature fluctuation of the blackbody radiating surface is approximately 0.18K; with an input power of 5W, the temperature drift is approximately 0.6K; and with an input power of 1W, the temperature drift is approximately 2.5K.

[0040] In this invention, since the temperature-sensing resistor is not directly mounted on the radiating surface, a temperature difference exists between the temperature-sensing resistor and the radiating surface. To obtain an accurate brightness temperature of the radiating surface using the temperature-sensing resistor, a model is established for the calibration source, and the relationship between the two is obtained through data fitting. , among which, T B For blackbody brightness temperature, T Pt T is the temperature of the platinum resistance thermometer. a Let T be the ambient temperature. The least squares method is used for fitting to obtain coefficients A0, A1, A2, A3, and A4. Then, based on T... Pt and T a The value of T is obtained by solving the problem. B .

[0041] Due to changes in ambient temperature, fluctuations in the radiant surface temperature, and the temperature difference between the temperature measuring resistor and the radiant surface, it is necessary to conduct high-precision calibration of the calibration source on the ground. This involves comparing the brightness temperature of the calibration source measured by high-precision ground testing equipment with the brightness temperature calculated from the temperature measured by the temperature measuring resistor, thereby evaluating the accuracy of the radiant surface brightness temperature calculated by the temperature measuring resistor.

[0042] The calibration source needs to be calibrated with high precision under simulated on-orbit vacuum and cryogenic conditions. The calibration equipment hardware includes a temperature-controlled vacuum chamber, a narrowband imaging radiometer, a turntable, and a high-precision programmable power supply. The narrowband imaging radiometer, as the standard transfer device, is composed of a wide-band high-precision temperature-measuring thermal imager manufactured by INFRATEC GmbH in Germany, combined with a narrowband filter, and has stable and reliable performance.

[0043] During calibration, the calibration source is mounted on a turntable. Different calibration sources are switched by rotating the turntable, aligning the calibration blackbody with the infrared window. A calibrated narrowband imaging radiometer is then used to measure the radiation temperature and radiation magnitude of the calibration blackbody in a specified wavelength band through the infrared window, thus completing the calibration. The calibration source is powered by a high-precision programmable power supply, which can provide different power levels to achieve multi-point calibration.

[0044] To avoid the influence of water vapor and CO2 in the air on the calibration accuracy, a transparent protective cover is used to cover the narrowband imaging radiometer and the entire measurement optical path during the calibration process. High-purity nitrogen is filled into the protective cover using a nitrogen cylinder to maintain a certain positive pressure and ensure a nitrogen environment inside the protective cover.

[0045] Brightness temperature calibration was performed on the calibration source. Within the temperature fluctuation range of the remote sensor camera, five ambient temperatures (254K, 256K, 258K, 260K, and 261K) were selected for calibration. Based on the calibration test data, the brightness temperature T was fitted. 亮温 Platinum resistance temperature t 铂 Ambient temperature t 环 The relationship between the two is shown in Table 1. Ten sets of power supply voltages were used for testing at each ambient temperature, and the temperature measurement accuracy was obtained. The tests show that the calibration source has a temperature measurement accuracy better than 2K, meeting the usage requirements.

[0046] ; The on-board calibration device provided by this invention utilizes lenses and the camera's own lens to generate uniformly distributed light covering the entire focal plane, achieving uniformity superior to 2K while avoiding stray light. The calibration source, fabricated using MEMS technology based on a metal heating layer and a special coating, exhibits high emissivity and can achieve a large dynamic range coverage of 750K with low electrical control requirements. It is also small in size and lightweight, weighing only 200g. After ground calibration, the temperature measurement accuracy is better than 2K, meeting the application requirements.

[0047] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of one embodiment, and the modules or processes shown in the drawings are not necessarily essential for implementing the present invention.

[0048] Those skilled in the art will understand that the modules in the apparatus of the embodiments can be distributed in the apparatus of the embodiments as described in the embodiments, or they can be located in one or more devices different from this embodiment with corresponding changes. The modules of the above embodiments can be combined into one module, or they can be further divided into multiple sub-modules.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An on-board calibration device, characterized in that include: Calibration source and calibration lens; The calibration source includes a blackbody radiating surface, a temperature measuring unit, a support structure, conductive components, and a housing. The blackbody radiating surface is fabricated using MEMS technology and includes a metal heating layer and a specific coating to generate infrared radiation. The conductive components supply power to the blackbody radiating surface. The support structure fixes and supports the blackbody radiating surface. The temperature measuring unit monitors the temperature of the blackbody radiating surface. The housing encapsulates the calibration source. The calibration lens is disposed on the light output path of the calibration source and is used to collect and compress the infrared radiation light emitted by the calibration source before introducing it into the lens of the remote sensing camera.

2. The on-board calibration device according to claim 1, characterized in that The blackbody radiating surface also includes: An insulating layer is located between the metal heating layer and the specific coating; The first insulating dielectric film is located on the side of the metal heating layer away from the insulating layer; A silicon substrate is located on the side of the first insulating dielectric film away from the metal heating layer; A second insulating dielectric film is located on the side of the silicon substrate away from the specific coating; A first coating is located on the side of the second insulating dielectric film away from the silicon substrate; the emissivity of the specific coating is higher than that of the first coating.

3. The on-board calibration device according to claim 2, characterized in that, The temperature measuring unit is mounted on the side of the silicon substrate near the first insulating dielectric film by adhesive bonding, and the temperature measuring unit is located at the edge of the silicon substrate.

4. The on-board calibration device according to claim 1, characterized in that, The temperature measuring unit is a platinum resistance temperature sensor.

5. The on-board calibration device according to claim 1, characterized in that, The material of the metal heating layer is platinum.

6. The on-board calibration device according to claim 1, characterized in that, The blackbody radiating surface has dimensions of 20mm × 20mm × 0.3mm, and multiple heating electrodes are provided at both ends of the blackbody radiating surface; the multiple heating electrodes are used to connect current and make the current evenly distributed on the blackbody radiating surface.

7. The on-board calibration device according to claim 6, characterized in that, The support structure includes four gold-plated solid pillars located at the four corners of the blackbody radiating surface. Each solid pillar has a slot on the side closest to the blackbody radiating surface. The blackbody radiating surface is fixed to the solid pillar through the slot and encapsulated with heat-resistant inorganic adhesive.

8. The on-board calibration device according to claim 6, characterized in that, The conductive component is a gold-plated copper electrode, and the copper electrode has a hollow structure; The conductive component is connected to multiple heating electrodes on the blackbody radiating surface via gold wire bonding.

9. The on-board calibration device according to claim 1, characterized in that, The calibration source has overall dimensions of Φ80mm×40mm and a weight of less than or equal to 200g.

10. The on-board calibration device according to claim 1, characterized in that, The upper limit of the dynamic range of the operating temperature of the calibration source is 750K. Under the maximum heating power of 12W, the time to heat up to 750K is less than or equal to 60 seconds. After the temperature stabilizes, the temperature field uniformity of the radiation surface is 1.5K.

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