CN108900734B - A wide-angle lens distortion automatic correction device and method - Google Patents

Abstract

The invention discloses a wide-angle lens distortion automatic correction device and method. The device comprises: an image acquisition control circuit, a controllable diaphragm, a CCD imaging camera, an FPGA distortion correction circuit, a split-field image restoration and fusion circuit; a host computer image display with parameter control software. The device automatically corrects the distortion of the wide-angle lens by dividing the field of view through the combination of software and hardware, overcomes the problem of large distortion and poor correction accuracy in the imaging process of the traditional wide-angle lens, greatly improves the imaging quality and improves the correction rate.

Description

A wide-angle lens distortion automatic correction device and method

technical field

The invention relates to the fields of computer, electronics and optics, and in particular, relates to a wide-angle lens distortion automatic correction device and method.

Background technique

Today, wide-angle lenses play an increasingly important role in cameras in military, surveillance, medical, transportation, photography, and other fields. In the above fields, wide-angle lenses are widely used because they can acquire image information with a larger field of view. However, due to the structural characteristics of the wide-angle lens itself, the captured image usually produces a certain degree of nonlinear distortion, which affects the geometrical position accuracy of the objects in the image, making it more demanding in image measurement, image recognition and other geometrical accuracy requirements. High fields lose application value. There is no doubt that the distortion correction of the image can effectively solve the problem of wide-angle lens imaging.

At present, the nonlinear distortion in wide-angle lenses is mainly radial distortion, and a set of widely accepted mathematical models have been researched and proposed. The model is based on the following specific mathematical models:

δ _x , δ _y represent the offset of the pixel in the x and y directions, respectively, and k ₁ , k ₂ , k ₃ , r ² =x ² +y ² are the distortion coefficients.

Based on the above model, it is very important to study the distortion correction of wide-angle lenses. For wide-angle imaging systems, the main problems that need to be solved are as follows: (1) Distortion correction is usually implemented on a computer, which is inconvenient for real-time processing and observation; ( 2) The distortion of different fields of view is different, and the current calibration methods are basically treated the same, resulting in poor calibration accuracy.

SUMMARY OF THE INVENTION

Aiming at the shortcomings of the prior art, the present invention proposes an automatic correction device and method for wide-angle lens distortion, which can effectively shorten the correction time and improve the correction accuracy. Its technical solutions are as follows:

An automatic correction device for wide-angle lens distortion, comprising a wide-angle lens parameter acquisition module, an image display and parameter control module, a wide-angle image correction module, an FPGA control processing module, an image acquisition module, a split-field image fusion module, and a controllable aperture control module,

The signal output terminals of the wide-angle lens acquisition parameter module and the image acquisition module are connected to the input terminal of the FPGA control processing module, and the output terminal of the FPGA control processing module is respectively connected to the image display and parameter control module and the input terminal of the controllable aperture control module. The output end is connected with the input end of the sub-field image fusion module.

Further, a controllable diaphragm is inserted between the wide-angle lens of the image acquisition module and the CCD to control the size and lateral position.

Further, the wide-angle image correction module and the sub-field-of-view image fusion module use FPGA hardware circuits.

An automatic correction method for wide-angle lens distortion, comprising the following steps:

Step 1: The wide-angle lens parameter acquisition module pre-collects the lens parameters and stores them in the FPGA;

Step 2: The controllable diaphragm control module controls the left and right movement and size of the field diaphragm, so that the image information is presented on the CCD in sub-fields, which are synchronized with the CCD exposure time. Divide and collect sub-field images for each additional 10° field of view;

Step 3: Use the CCD sensor array in the image acquisition module to first store the video stream in RAM through the I2C bus, and then transfer the distorted image data in the RAM to the image of each frame frame by frame through the I/O control port FPGA;

Step 4: In the wide-angle image correction module, it includes a lookup table module, an image data buffer module, a geometric correction module, and a grayscale correction module; the correction algorithm based on bilinear interpolation is used to correct each frame under different fields of view through FPGA. image;

Step 5: fuse the corrected field-of-view images through the field-of-view image fusion module, and perform operations such as filtering;

Step 6: The image display module displays the corrected image and related parameters.

Further, in step 5, median filtering and mean filtering are performed on the image obtained after fusion to remove noise therein.

Further, it also includes a manual control mode, in which parameters are transmitted to the FPGA to control the hardware device.

The advantages of the present invention are:

Different degrees of correction are performed for images in different fields of view of the wide-angle lens to obtain more accurate images. The FPGA is used as the control circuit to control the diaphragm to directly obtain the images of the divided fields of view, respectively correct the images of each field of view, fuse the corrected images of each field of view according to the division of the field of view, and reconstruct the fused image. is very high, and the real-time performance is better.

Description of drawings

FIG. 1 is a schematic diagram of a module flow diagram of a wide-angle lens distortion automatic correction device and method.

Fig. 2 is a schematic diagram of a wide-angle lens distortion automatic correction device and method mechanism

Detailed ways

In order to reduce the distortion of the wide-angle lens and realize real-time processing, the optical method is used with FPGA correction.

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

As shown in Figure 1, it includes the following steps:

Step 1: Assemble the wide-angle lens, insert a controllable field diaphragm between the CCD and the wide-angle lens, as shown in Figure 2, and perform operations such as image input, and image acquisition in different fields of view. The whole wide-angle device system includes the image of the input object plane, the wide-angle lens, the controllable diaphragm, the CCD imaging camera, and the FPGA. The image of the input object surface is presented on the CCD through the wide-angle lens and the field diaphragm.

Step 2: Control the left and right movement and size of the field diaphragm in real time through the FPGA, synchronize with the CCD exposure time, and divide and collect sub-field images according to the field angle of every 10° increase.

Step 3: The CCD collects the video stream information, and transfers the framed images to the FPGA frame by frame. The FPGA includes a control module and a distortion correction module, which are separately stored in the block RAM inside the FPGA according to the angle of view.

Step 4: In the image distortion correction module, the distortion is corrected by the correction method based on the bilinear interpolation method, and passed to the image fusion module.

Step 5: In the image fusion module, the images of different fields of view corrected by the distortion correction module are fused, and for each field of view, the restored images of each field of view are fused according to the division of the field of view, and reconstructed to obtain a fused image.

For the image obtained after fusion, perform median filtering and mean filtering to remove noise.

Step 6: In the image display and parameter control module, use the host computer to write software to communicate with the FPGA through the serial port, and be responsible for the display of the original image and the restored image.

Claims (5)

1. The utility model provides a wide-angle lens distortion automatic correction device, includes wide-angle lens parameter acquisition module, image display and parameter control module, wide-angle image correction module, FPGA control processing module, image acquisition module, divides visual field image fusion module, controllable diaphragm control module, its characterized in that:

the output end of the wide-angle lens acquisition parameter module and the signal output end of the image acquisition module are connected with the input end of the FPGA control processing module, the output end of the FPGA control processing module is respectively connected with the input ends of the image display and parameter control module and the controllable diaphragm control module, and the output end of the wide-angle image correction module is connected with the input end of the sub-field image fusion module; the input end of the wide-angle image correction module is connected with the output end of the FPGA control processing module;

a controllable diaphragm is inserted between the wide-angle lens and the CCD of the image acquisition module to control the size and the transverse position; the controllable diaphragm control module controls the left and right movement and the size of the field diaphragm, so that image information is displayed on the CCD in a sub-field manner, the sub-field acquisition is carried out from the field angle of 60 degrees in synchronization with the exposure time of the CCD, and the sub-field image is acquired in a divided manner according to the field angle increased by 10 degrees.

2. The device of claim 1, wherein the wide-angle image correction module and the sub-field image fusion module are implemented by using FPGA hardware circuits.

3. A wide-angle lens distortion automatic correction method is characterized by comprising the following steps:

the method comprises the following steps: the wide-angle lens parameter acquisition module acquires lens parameters in advance and stores the lens parameters in the FPGA;

step two: the controllable diaphragm control module controls the left and right movement and the size of the field diaphragm, so that image information is displayed on the CCD in a sub-field manner, the exposure time of the CCD is synchronous, sub-field acquisition is carried out from the field angle of 60 degrees, and sub-field images are acquired in a divided manner according to the field angle increased by 10 degrees;

step three: in the image acquisition module, a CCD sensor array is used for firstly storing a video stream in an RAM through an I2C bus, and then distorted image data in the RAM is transmitted into an FPGA frame by frame through an I/O control port;

step four: the wide-angle image correction module comprises a lookup table module, an image data buffer module, a geometric correction module and a gray correction module; respectively correcting each frame of image under different fields of view through the FPGA by using a correction algorithm based on a bilinear interpolation method;

step five: fusing the corrected sub-field images through a sub-field image fusion module, and performing filtering operation;

step six: the image display module displays the corrected image and the related parameters.

4. The wide-angle lens distortion automatic correction method according to claim 3, characterized in that:

and fifthly, performing median filtering and mean filtering on the image obtained after fusion to remove noise in the image.

5. The wide-angle lens distortion automatic correction method according to claim 3, characterized in that: the system also comprises a manual control mode, and parameters are transmitted to the FPGA in the manual control mode to control the hardware equipment.

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