CN118301437A - Image synchronization method for linear array panoramic thermal imager - Google Patents

Abstract

The invention discloses a method for synchronizing images of a linear array panoramic thermal imager, which belongs to the technical field of infrared imaging and comprises the following steps: acquiring a zero signal Z phase and an increment signal A phase B phase of an encoder, and outputting 1 path of differential synchronous signals by an FPGA after waveform setting and frequency division; after receiving the synchronous signal, the digital imaging board superimposes the frame synchronous number on the image and outputs the video; and when the images are acquired, the panoramic image stitching is carried out according to the frame numbers. The invention realizes the frame synchronization with simple structure, less signal lines, high stability and real-time performance.

Description

Image synchronization method for linear array panoramic thermal imager

Technical Field

The invention belongs to the technical field of infrared imaging, and particularly relates to a method for synchronizing the azimuth angle of a linear array circumferential scanning panoramic thermal imager image and a servo turntable.

Background

With the development of infrared imaging technology, thermal infrared imagers are widely used in various fields. The refrigeration type long-wave linear array thermal imager has the characteristics of high sensitivity to an empty target, difficult interference of cloud layers and the like and easy scanning panoramic imaging, and is widely applied to warning photoelectric systems of platforms such as carrier-borne, vehicle-mounted, roadbed and the like, such as 288×4, 576×6, 768×8, 1024×6 and the like linear array refrigeration type infrared thermal imagers.

The linear array refrigeration thermal infrared imager for searching and warning realizes the scanning panoramic imaging of the linear array detector through the azimuth rotation of the servo turntable, and realizes the detection, identification and positioning of the target through the target detection algorithm of the upper computer (or the image plate). However, in the process of rotationally scanning and outputting images, the linear array thermal infrared imager often has the phenomena of left and right shaking, moving and the like of the images, so that targets cannot be identified and accurately positioned, and image observation is affected. Therefore, the panoramic output image of the linear array thermal infrared imager is required to ensure that the initial position of the output image is consistent all the time, the image is consistent with azimuth position information, the stability of the output image can be ensured, and the calculation of the target position is accurate.

The image synchronization information commonly used by the linear array panoramic refrigeration thermal infrared imager is as follows: (1) a ring synchronization information and a frame synchronization signal; (2) Real-time angle information is transmitted through an RS485 serial port and a serial SSI/SPI interface.

Rate of real-time angular transmission: the RS485 interface is generally within 1Mbit/S, and the SSI/SPI interface is generally 2-10 Mbit/S; these signals are typically transmitted from the azimuth base of the optoelectronic system to the infrared digital panel of the optoelectronic load cell. As shown in fig. 1. The transmission process is required to pass through a slip ring, a connector and the like, and is often easy to be disturbed, a synchronous signal is lost, the angle is received inaccurately and the image shakes. The RS485 interface has low speed and low data update rate, so that the synchronism is not strong; the SSI/SPI interface generally needs clock signals, data signals, chip selection signals, and circle synchronous information, the number of data lines is 6-8, and the number of occupied slip ring signal lines is more. When data information is wrong due to rotation of the azimuth turntable, the debugging process is complex, and the reliability and maintainability are low.

Disclosure of Invention

Aiming at the defects or improvement demands of the prior art, the invention provides an image synchronization method of a linear array panoramic thermal imager, which adopts an FPGA to receive an incremental encoder output A, B, Z signal, outputs 1 path of differential synchronization signal after shaping and counting frequency division, and can realize the stable output of the image and the real-time synchronization of the azimuth angle of the linear array thermal imager.

In order to achieve the above object, the present invention provides a method for synchronizing images of a linear array panoramic thermal imager, comprising:

Acquiring a zero signal Z phase and an increment signal A phase B phase of an encoder, and outputting 1 path of differential synchronous signals by an FPGA after waveform setting and frequency division;

after receiving the synchronous signal, the digital imaging board superimposes the frame synchronous number on the image and outputs the video;

and when the images are acquired, the panoramic image stitching is carried out according to the frame numbers.

In some optional embodiments, the acquiring zero signal Z phase and increment signal a phase B phase of the encoder output 1-path differential synchronization signals after waveform setting and frequency division by the FPGA, including:

The encoder outputs A, B, Z coding signals in the rotation process of the azimuth motor, the coding signals are input to the FPGA after passing through the differential receiving chip, the FPGA outputs frame synchronization information after counting, shaping and frequency division through edge detection, wherein the ring synchronization signals come from Z phase signals of the encoder, namely 1 st frame synchronization signals of initial frames, the 2 nd to 100 th frame synchronization signals are output after frequency division after being counted through A, B phases, and the counter clears the Z phase zero signals and the frame synchronization positions.

In some alternative embodiments, the encoder outputs three differential pulse signals of: a+, A-, B+, B-, Z+, Z-.

In some alternative embodiments, the frame synchronization signal is transmitted to an infrared imaging digital board of the linear array panoramic thermal imager, the digital board receives the frame synchronization signal, the frame number is superimposed into the image, and the linear array detector continuously outputs in columns.

In some alternative embodiments, the infrared digital board completes the infrared image signal processing and the superposition of frame numbers and column numbers, and then outputs the signal to the upper computer acquisition card or the image processing board through an interface.

In some alternative embodiments, after the upper computer acquisition card or the image processing board receives the digital video signal, the upper computer display control software displays the digital video signal at a fixed position on the display screen according to the frame number of the video.

In some alternative embodiments, the host acquisition card or the image processing board calculates the target azimuth angle according to the frame number, the column number and the pixel angle after receiving the digital video signal.

In some alternative embodiments, the target azimuth angle = frame number x azimuth field angle + column number x pixel angle.

In general, the above technical solutions conceived by the present invention, compared with the prior art, enable the following beneficial effects to be obtained:

The invention provides a frame synchronization method with simple realization, less signal lines, high stability and real-time performance for 576×6 linear array panoramic thermal imagers. The method is used in the existing equipment, the image is stable, the target angle is accurately calculated, and the effect is good.

Drawings

FIG. 1 is a schematic diagram of an infrared array alert optoelectronic system according to an embodiment of the present invention;

FIG. 2 is a frame synchronization pulse waveform provided by an embodiment of the present invention;

fig. 3 is a flowchart of a synchronization signal implementation according to an embodiment of the present invention.

Detailed Description

The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention. In addition, the technical features of the embodiments of the present invention described below may be combined with each other as long as they do not collide with each other.

The invention provides a real-time synchronization method for stable image output and azimuth angle of a linear array panoramic thermal infrared imager. The invention fully utilizes the characteristics of signal output of the high-precision incremental encoder, and outputs 1 path of differential synchronous signals after the zero signal Z phase and the incremental signal A phase B phase of the encoder are collected, waveform setting and frequency division, as shown in figure 2. And the stable output of the linear array panoramic infrared thermal imager image and the real-time synchronization of the image and the azimuth angle are realized.

More specifically, the incremental encoder adopts a high-precision high-resolution encoder, and the encoder outputs A, B, Z encoded signals in the rotation process along with the azimuth motor; the signals are input to the FPGA after passing through the differential receiving chip, the FPGA outputs 100Hz frame synchronization information after counting, shaping and frequency division through edge detection, wherein the ring synchronization signal is from the Z phase signal of the encoder, and is also the 1 st frame synchronization signal of the initial frame, and the 2 nd to 100 th frame synchronization signals are output after counting through A, B phases. The counter is cleared at the Z-phase zero signal and frame synchronization position. To distinguish the 1 st frame signal, the 1 st frame synchronization signal pulse is set to 20us, and the other frame synchronization signals are 10us. After the digital imaging board receives the synchronous signal, the frame synchronous number is superimposed on the image, then the video is output, and the image acquisition system performs panoramic image stitching according to the frame number when the image is acquired. The image stability depends on the encoder Z-phase stability. Because the incremental encoder has high resolution and high real-time performance, the actual measurement can ensure the image stability and the target azimuth error to be within 1 pixel.

As shown in fig. 3, in step S1, the present invention employs a high-precision incremental encoder with a resolution of 1536000; the encoder outputs three paths of differential pulse signals respectively as follows: a+, A-, B+, B-, Z+, Z-.

In step S2, the differential signal output by the encoder is output to the FPGA through the differential receiving chip and the single-ended signal is detected by the FPGA through the edge level detection algorithm logic, and the rising edge of the pulse is counted by A, B. Every 1536 times of counting, the counter is cleared, and the frame synchronization pulse is output with the pulse width of 10us. When the Z pulse signal is detected, the pulse is extended to 20us and then outputted, and the pulse is also a start frame (first frame) synchronization signal as a ring synchronization signal. The frame synchronization signal is output with a differential signal 422 level, and the waveform is shown in fig. 2.

In step S3, the frame synchronization signal is transmitted to the infrared imaging digital board of the linear array panoramic thermal imager through the slip ring, the connector, etc., the digital board receives the frame synchronization signal, the frame number is superimposed into the image, the linear array detector continuously outputs according to the column, and the number of pixels in each column of the detector is 576. When the digital board outputs video, each column outputs according to 640 pixel formats, wherein the 1 st to 64 th columns are filled with other data/state information, the 65 th to 640 th columns are image information of 576 pixels of the detector, and each column of data bit is 16 bits. As shown in table 1, wherein column 1 fills in frame numbers: 1 to 100; the second column fills the current frame column number: 1 to 625; the number of columns per frame is calculated from the pixel angle and the column period.

Table 1 list of image data information tables

Column number	Data
		1	Frame number
2	Column number
		3～64	Data/status information
65～640	576-Column image information

The calculation process is as follows:

The rotating speed of the linear array panoramic hotline instrument is as follows: 1 turn/second;

the equivalent pixel size of the detector is as follows: 14.3um;

The focal length of the infrared lens is 142mm;

the frame synchronization signal is output at 100 hz;

azimuth field angle corresponding to each frame:

360°/100＝3.6°

A frame period of 10ms and a column period of 16us;

Column number per frame:

10ms/16us＝625

pixel angle:

3.6°/625＝0.00576°

In step S4, after the infrared digital board finishes the infrared image signal processing and the superposition of the frame number and the column number, the infrared image signal is output to the upper computer acquisition card or the image processing board through the camera link interface.

In step S5, after the upper computer acquisition card (or the image processing board) receives the camera link digital video signal, the upper computer display control software displays the video at a fixed position on the display screen according to the frame number of the video. And calculating the target azimuth angle according to the frame number, the column number and the pixel angle, and realizing stable display of the image and accurate calculation of the target angle.

Target azimuth angle=frame number×3.6++column number×pixel angle (0.00576 °)

The invention provides a frame synchronization method with simple realization, less signal lines, high stability and real-time performance for 576×6 linear array panoramic thermal imagers. The method is used in the existing equipment, the image is stable, the target angle is accurately calculated, and the effect is good.

It should be noted that each step/component described in the present application may be split into more steps/components, or two or more steps/components or part of operations of the steps/components may be combined into new steps/components, according to the implementation needs, to achieve the object of the present application.

It will be readily appreciated by those skilled in the art that the foregoing description is merely a preferred embodiment of the invention and is not intended to limit the invention, but any modifications, equivalents, improvements or alternatives falling within the spirit and principles of the invention are intended to be included within the scope of the invention.

Claims (8)

1. The image synchronization method of the linear array panoramic thermal imager is characterized by comprising the following steps of:

Acquiring a zero signal Z phase and an increment signal A phase B phase of an encoder, and outputting 1 path of differential synchronous signals by an FPGA after waveform setting and frequency division;

after receiving the synchronous signal, the digital imaging board superimposes the frame synchronous number on the image and outputs the video;

and when the images are acquired, the panoramic image stitching is carried out according to the frame numbers.

2. The method of claim 1, wherein the acquiring zero signal Z phase and delta signal a phase B phase of the encoder, after waveform setting and frequency division, outputs 1 path of differential synchronization signal by the FPGA, comprises:

The encoder outputs A, B, Z coding signals in the rotation process of the azimuth motor, the coding signals are input to the FPGA after passing through the differential receiving chip, the FPGA outputs frame synchronization information after counting, shaping and frequency division through edge detection, wherein the ring synchronization signals come from Z phase signals of the encoder, namely 1 st frame synchronization signals of initial frames, the 2 nd to 100 th frame synchronization signals are output after frequency division after being counted through A, B phases, and the counter clears the Z phase zero signals and the frame synchronization positions.

3. The method of claim 2, wherein the encoder outputs three differential pulse signals of: a+, A-, B+, B-, Z+, Z-.

4. The method of claim 1, wherein the frame synchronization signal is transmitted to an infrared imaging digital board of the linear array panoramic thermal imager, the digital board receives the frame synchronization signal, and the frame number is superimposed into the image, and the linear array detector continuously outputs in columns.

5. The method of claim 1, wherein the infrared digital board performs infrared image signal processing and frame number and column number superposition, and outputs the signal to the upper computer acquisition card or the image processing board through the interface.

6. The method of claim 1, wherein the host computer display control software displays the digital video signal on the display screen at a fixed position according to the frame number of the video after the host computer acquisition card or the image processing board receives the digital video signal.

7. The method of claim 6, wherein the host acquisition card or the image processing board receives the digital video signal and calculates the target azimuth angle according to the frame number, the column number and the pixel angle.

8. The method of claim 7, wherein target azimuth angle = frame number x azimuth field angle + column number x pixel angle.