Method and device for protecting focal plane of uncooled infrared camera

Abstract

The invention discloses an uncooled infrared camera focal plane protection method. The method comprises the following steps: S1, defining a coordinate system; comprising a navigation coordinate system and a gyroscope body coordinate system; s2, positioning the axial angle of the camera; acquiring a vertical deviation angle and a horizontal deviation angle of the axial direction of the camera relative to the coordinates of the gyroscope; s3, self-inspection is carried out; s4, satellite signals are received through a satellite receiver, and time information and positioning information are obtained through a satellite signal resolving module in a satellite signal receiving module; s5, calculating an attitude angle; the gyroscope attitude measurement module takes the course angle of the magnetic sensor as a course initial value, calculates attitude angles including a roll angle, a pitch angle and a yaw angle, and outputs the attitude angles to the data processor; s6, integrating the data; s7, calculating a positive elevation angle and an azimuth angle; s8, judging and feeding back; judging whether the sunlight direction is in the field of view of the camera, and updating the aperture control semaphore; s9, sending out a control signal; transmitting an aperture control semaphore to an aperture control mechanism; the aperture varies. The objective of protecting the camera focal plane is achieved.

Description

Technical Field

[0001] This invention relates to the field of infrared camera protection technology, and in particular to a method and apparatus for protecting the focal plane of an uncooled infrared camera. Background Technology

[0002] Uncooled infrared focal plane array cameras are the core component of thermal imaging systems, crucial for detecting, identifying, and analyzing the infrared information of objects. They are commonly used for field surveys or fixed-point detection. Uncooled infrared focal plane array thermal imagers typically operate at wavelengths within the specified range. The intensity response of infrared thermal imagers to light energy in this band is at a certain level; light with energy exceeding this range can cause the focal plane to be burned due to strong electrostatic discharge, damaging the detector. This burning can be further divided into permanent, irreversible burns caused by continuous exposure to excessively strong infrared energy, and temporary, slowly recoverable burns caused by the detector not continuously receiving excessively strong infrared energy at the same point.

[0003] Chinese patent CN115597720A discloses a sunburn protection mechanism for an infrared thermal imager, comprising: a housing having an internal space and a light-receiving window; an infrared detector installed in the internal space and opposite to the light-receiving window; a linear module located on the side of the infrared detector; and a light-blocking strip connected to the linear module, wherein the width of the light-blocking strip is smaller than the width of the infrared detector.

[0004] The width of the light window is such that when sunlight appears in the detection scene of the infrared detector, the linear module is used to drive the light-blocking strip to move and block the sunlight in the detection scene. At the same time, the infrared rays in the detection scene that are not blocked by the light-blocking strip, other than sunlight, can be collected by the infrared detector.

[0005] The FLIR Lepton series detectors employ an electronic protection scheme: when the focal plane camera detects excessive infrared energy, it quickly closes the shutter aperture to prevent the infrared energy from continuing to illuminate the image.

[0006] The aforementioned patents or products mainly protect the optimized focal plane camera detector components, but the current equipment judgment is not accurate enough, lacks precision, has harsh operating conditions, and often requires manual intervention, resulting in a low overall level of automation and poor performance. Summary of the Invention

[0007] The purpose of this invention is to provide a method and apparatus for protecting the focal plane of an uncooled infrared camera. This method is implemented on an uncooled infrared focal plane thermal imager, which incorporates a satellite positioning system and a gyroscope attitude measurement system. By acquiring the imager's own attitude angle, solar altitude angle, and azimuth angle in real time, it determines whether the solar direction vector is within the safe threshold of the focal plane camera's field of view. The aperture is then quickly closed before sunlight directly hits the camera's focal plane, thus protecting the camera's focal plane. Specifically, the technical solution of this invention is as follows:

[0008] A method for protecting the focal plane of an uncooled infrared camera includes the following steps: S1, defining a coordinate system, including a navigation coordinate system (NED) and a gyroscope body coordinate system;

[0009] S2. Locate the camera axis angle; calibrate the uncooled infrared camera module and gyroscope attitude measurement module to obtain the vertical offset angle of the camera axis relative to the gyroscope coordinates. Horizontal offset angle ;

[0010] S3. Self-test; Perform self-test on the satellite signal receiving and positioning module, gyroscope attitude measurement module, solar altitude angle calculation module, camera module, and aperture control module.

[0011] S4. Receive satellite signals. The satellite receiver receives the signals and the satellite signal processing module within the satellite signal receiving module obtains the time and location information: Standard UTC time. latitude of the receiver ,longitude and height The data is output to the data processor.

[0012] S5. Calculate attitude angles; the gyroscope attitude measurement module uses the heading angle from the magnetic sensor as the initial heading value to calculate the attitude angles: roll angle. Pitch angle Yaw angle The data is output to the data processor.

[0013] S6. Data integration; the data processor uses the received satellite signals to calculate the data standard UTC time. latitude of the receiver ,longitude and height The roll angle is calculated from the speed and gyroscope attitude measurement module. Pitch angle Yaw angle Perform integrated navigation to obtain the positioning and attitude data: latitude. ,longitude ,high Roll angle Pitch angle and yaw angle ;

[0014] S7. Calculate the solar altitude angle and azimuth angle;

[0015] S8. Judgment and feedback; Determine whether the direction of sunlight is within the camera's field of view and update the aperture control signal;

[0016] S9. Send control signals; send aperture control signals to the aperture control mechanism; aperture changes.

[0017] Furthermore, the calculation process in step S7 includes:

[0018] S7.1, Solar declination angle;

[0019]

[0020] Adjust the relationship between the time frame and the starting point at the beginning of the year;

[0021] It is the sun's horn;

[0022] It refers to the accumulated days, which are the days in the year (January 1st is the first day of the year). December 31st is );

[0023] S7.2, Solar Hour Angle ;

[0024]

[0025] The hour angle reflects the sun's time shift, with positive and negative values ​​indicating the sun's position relative to the meridian of the observation point: a positive value indicates the sun is west of the meridian of the observation point, and a negative value indicates the sun is east of the meridian of the observation point;

[0026] S7.3, Solar altitude angle;

[0027]

[0028] S7.4 solar azimuth angle;

[0029]

[0030] Sun azimuth and system azimuth in the Navigation Coordinate System (NED) The difference Sun altitude angle and system pitch angle The difference :

[0031] .

[0032] Furthermore, in step S1, the navigation coordinate system (NED) is X-axis: due north, Y-axis: due east, Z-axis: ground; the gyroscope body coordinate system is X-axis: forward, Y-axis: right, Z-axis: downward.

[0033] Furthermore, it also includes step S10, fault feedback; if aperture locking is triggered, the user is reminded to adjust the device's viewing angle to avoid sunlight; if aperture locking is not triggered, the device can work normally.

[0034] A focal plane protection device for an uncooled infrared camera includes: a satellite signal receiving module 1, a gyroscope attitude measurement module 2, a housing 3, an uncooled infrared camera module 4, a computing processor 5, an aperture control module 6, a lens 7, and display and control peripherals 8. The satellite signal receiving and positioning module is mounted above the uncooled infrared camera and includes a satellite receiver and a satellite calculation unit for receiving UTC time and latitude / longitude positioning information from the receiving system. The gyroscope attitude measurement module 2 is mounted above the uncooled infrared camera and includes a nine-axis inertial measurement unit comprising an accelerometer, a gyroscope, and a geomagnetic sensor; it is used to calculate the pitch angle, yaw angle, and roll angle of the entire device relative to the local horizontal plane. The computing processor 5 is mounted on the housing. Inside module 3, satellite positioning data and gyroscope attitude data are received for combined navigation to obtain precise positioning and attitude information. The solar altitude and azimuth angles are calculated and converted to the local geographic horizontal coordinate system along with the optical axis of the uncooled infrared camera. The converted solar azimuth and altitude angles are then determined to be within the field of view of the uncooled infrared camera, and the results are transmitted to the aperture control system. The uncooled infrared camera module 4 includes the uncooled infrared camera core, which is used to receive infrared radiation and form an image. The aperture control module 6 includes a control motor and an aperture, which receives control commands transmitted from the computing processor module 5 to control the aperture to lock or open to protect the focal plane of the uncooled infrared camera. The lens module 7 performs optical path focusing.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0036] 1. By simultaneously introducing a satellite positioning module and an attitude measurement module into a traditional uncooled thermal imager, the angle between the optical axis direction vector and the sunlight direction vector is calculated by combining time, positioning data, and attitude data to determine whether the aperture is locked or closed. This method is simple, practical, low-cost, and highly automated.

[0037] 2. The thermal imager integrates positioning and attitude information: during use, it can quickly locate the specific orientation of the observed target, integrate range measurement, and accurately locate the observed target, and has scalability. Attached Figure Description

[0038] Figure 1This is a schematic diagram of the device structure and connection of the present invention;

[0039] Figure 2 This is a diagram showing the results of solar altitude angle, azimuth angle, and aperture control signals during a fixed-point observation of an uncooled camera within a day, as described in this embodiment of the invention.

[0040] Figure label:

[0041] 1—Satellite signal receiving module; 2—Gyroscope attitude measurement module; 3—Housing; 4—Uncooled infrared camera module; 5—Computation processor; 6—Aperture control module; 7—Lens; 8—Display control peripherals. Detailed Implementation

[0042] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings.

[0043] A focal plane protection device for an uncooled infrared camera includes: a satellite signal receiving module 1, a gyroscope attitude measuring module 2, a housing 3, an uncooled infrared camera module 4, a computing processor 5, an aperture control module 6, a lens 7, and a display and control peripheral device 8.

[0044] The satellite signal receiving and positioning module is installed above the uncooled infrared camera and includes a satellite receiver and a satellite calculation unit. It is used to receive UTC time and latitude, longitude, and altitude positioning information from the receiving system. The gyroscope attitude measurement module 2 is installed above the uncooled infrared camera and includes a nine-axis inertial measurement unit, comprising an accelerometer, a gyroscope, and a geomagnetic sensor. It is used to calculate the pitch, yaw, and roll angles of the entire device relative to the local horizontal plane. The computing processor 5 module is installed inside the housing 3 and is used to receive satellite positioning data and gyroscope attitude data for combined navigation, further obtaining accurate positioning and attitude information. The solar elevation angle and azimuth angle are further calculated and converted to the local geographic horizontal coordinate system along with the optical axis direction of the uncooled infrared camera. It is then determined whether the converted solar azimuth angle and elevation angle are within the field of view of the uncooled infrared camera, and the determination result is transmitted to the aperture control system. The uncooled infrared camera module 4 includes the uncooled infrared camera core, which is used to receive infrared radiation and form an image. The aperture control module 6 consists of a control motor and an aperture, which is used to receive control commands transmitted from the computing processor module 5 and control whether the aperture is locked or opened to protect the focal plane of the uncooled infrared camera or to ensure normal operation. The lens module 7 focuses the optical path.

[0045] The aperture control process of the invention is as follows: Satellite signal receiving module 1 receives satellite signals and calculates the standard UTC time. latitude of the receiver ,longitude and height The three axial velocities are output to the data processor; the gyroscope attitude measurement module 2 calculates the initial attitude angle information and roll angle. Pitch angle Yaw angle The data is output to the data processor. The uncooled infrared camera module 4, computing processor 5, aperture control module 6, and lens 7 are installed inside the housing 3. The uncooled infrared camera module 4 acquires infrared radiation, generates infrared image data, and outputs it to the data processor. The data processor receives data transmitted from the satellite signal receiving module 1 and the gyroscope attitude measurement module 2, as well as the image data transmitted from the uncooled infrared camera. The data from the satellite signal receiving module 1 and the gyroscope attitude measurement module 2 are used for satellite / inertial navigation integrated calculations to obtain more accurate positioning data and attitude angle data (latitude). ,longitude ,high Roll angle Pitch angle and yaw angle Next, calculate the solar altitude angle. and azimuth The system determines whether the converted solar azimuth and elevation angles are within the field of view of the uncooled infrared camera. If so, it outputs a locking signal to the aperture control module 6 to lock the aperture and protect the camera. Otherwise, it opens the aperture. The aperture control module 6 receives a control signal from the computing processor 5 and controls the aperture to close or open. The display control module receives the video signal output from the data processor to display basic software information and controls the software through peripherals such as keyboard and mouse.

[0046] The following is the data from a fixed-point experiment on a certain day, camera The angles were 12° and 10° respectively. The camera and gyroscope were calibrated beforehand. The azimuth angle of the camera assembly was adjusted to 70°, the pitch angle to 10°, and the roll angle to 0°. The solar azimuth angle, altitude angle, and aperture control signal were calculated and recorded every 4 seconds. The data record for one day is as follows: Figure 2 As shown.

[0047] The azimuth, elevation, and field of view of the sun at 7:00 AM and 10:00 AM are determined as follows:

[0048]

[0049] Therefore, at 7 o'clock sharp, an aperture locking signal is sent to aperture control module 6, and the aperture is locked;

[0050] At 10:00, the aperture was already open, so there was no need to send an aperture opening signal to the aperture control module 6; the aperture remained open.

Claims

1. A method for protecting the focal plane of an uncooled infrared camera, characterized in that, Includes the following steps: S1. Define the coordinate system, including the navigation coordinate system (NED) and the gyroscope body coordinate system; S2. Locate the camera axis angle; calibrate the uncooled infrared camera module and gyroscope attitude measurement module to obtain the vertical offset angle of the camera axis relative to the gyroscope coordinates. Horizontal offset angle ; S3. Self-test; Perform self-test on the satellite signal receiving and positioning module, gyroscope attitude measurement module, solar altitude angle calculation module, camera module, and aperture control module. S4. Receive satellite signals. The satellite receiver receives the signals and obtains the time and location information from the satellite signal processing module in the satellite signal receiving module (1): Standard UTC time. latitude of the receiver ,longitude and height The data is output to the data processor. S5. Calculate the attitude angles; The gyroscope attitude measurement module uses the heading angle from the magnetic sensor as the initial heading value to calculate the attitude angles: roll angle. Pitch angle Yaw angle The data is output to the data processor. S6. Data integration; the data processor uses the received satellite signals to calculate the data standard UTC time. latitude of the receiver ,longitude and height The roll angle is calculated from the speed and gyroscope attitude measurement module. Pitch angle Yaw angle Perform integrated navigation to obtain the positioning and attitude data: latitude. ,longitude ,high Roll angle Pitch angle and yaw angle ; S7. Calculate the solar altitude angle and azimuth angle; S8. Judgment and feedback; Determine whether the direction of sunlight is within the camera's field of view and update the aperture control signal; S9. Send control signals; send aperture control signals to the aperture control mechanism; aperture changes.

2. The method for protecting the focal plane of an uncooled infrared camera as described in claim 1, characterized in that, The calculation process in step S7 includes: S7.1, Solar declination angle; ； ； ； Adjust the relationship between the time frame and the starting point at the beginning of the year; It is the sun's horn; It refers to the accumulated days, which are the days in the year (January 1st is the first day of the year). December 31st is ); S7.2, Solar Hour Angle ; ； ； ； ； The hour angle reflects the sun's time shift, with positive and negative values ​​indicating the sun's position relative to the meridian of the observation point: a positive value indicates the sun is west of the meridian of the observation point, and a negative value indicates the sun is east of the meridian of the observation point; S7.3, Solar altitude angle; ； S7.4 solar azimuth angle; ； Sun azimuth and system azimuth in the Navigation Coordinate System (NED) The difference Sun altitude angle and system pitch angle The difference : 。 3. The method for protecting the focal plane of an uncooled infrared camera as described in claim 1, characterized in that: In step S1, the navigation coordinate system (NED) is: X-axis: due north, Y-axis: due east, Z-axis: ground; the gyroscope body coordinate system is: X-axis: forward, Y-axis: right, Z-axis: downward.

4. The method for protecting the focal plane of an uncooled infrared camera as described in claim 1, characterized in that: It also includes step S10 and fault feedback; if aperture locking is triggered, the user is reminded to adjust the device's viewing angle to avoid sunlight; if aperture locking is not triggered, the device can work normally.

5. A focal plane protection device for an uncooled infrared camera, characterized in that, include: The satellite signal receiving module (1), gyroscope attitude measurement module (2), housing (3), uncooled infrared camera module (4), computing processor (5), aperture control module (6), lens (7) and display control peripherals (8); the satellite signal receiving and positioning module is installed above the uncooled infrared camera and includes a satellite receiver and a satellite calculation unit, used to receive UTC time and latitude and longitude positioning information of the receiving system; The gyroscope attitude measurement module (2) is installed above the uncooled infrared camera and includes a nine-axis inertial measurement unit, including an accelerometer, a gyroscope and a geomagnetic sensor; it is used to calculate the pitch angle, heading angle and roll angle of the entire device relative to the local horizontal plane; the calculation processor (5) module is installed inside the housing (3) and is used to receive satellite positioning data and gyroscope attitude data for combined navigation, further obtain accurate positioning information and attitude information, calculate the solar altitude angle and azimuth angle, and convert them together with the optical axis direction of the uncooled infrared camera to the local geographic horizontal coordinate system, determine whether the solar azimuth angle and altitude angle after conversion are within the field of view of the uncooled infrared camera, and transmit the judgment result to the aperture control system; the uncooled infrared camera module (4) includes the uncooled infrared camera core and is used to receive infrared radiation and image; the aperture control module (6) includes a control motor and an aperture and is used to receive control commands transmitted by the calculation processor (5) module and control the aperture to lock or open in order to protect the focal plane of the uncooled infrared camera; the lens (7) module performs optical path focusing.

Images