CN108900734B

CN108900734B - Wide-angle lens distortion automatic correction device and method

Info

Publication number: CN108900734B
Application number: CN201810780492.9A
Authority: CN
Inventors: 赵巨峰; 吴超; 叶晓杰; 崔光茫; 华玮平
Original assignee: Hangzhou Dianzi University
Current assignee: Hangzhou Dianzi University
Priority date: 2018-07-16
Filing date: 2018-07-16
Publication date: 2020-12-08
Anticipated expiration: 2038-07-16
Also published as: CN108900734A

Abstract

The invention discloses a wide-angle lens distortion automatic correction device and a method, wherein the device comprises: the system comprises an image acquisition control circuit, a controllable diaphragm, a CCD imaging camera, an FPGA distortion correction circuit and a sub-field image restoration fusion circuit; and the upper computer image display and parameter control software. The device carries out distortion sub-field automatic correction on the wide-angle lens through the combination of software and hardware, overcomes the problem of poor distortion large correction precision in the imaging process of the traditional wide-angle lens, greatly improves the imaging quality and improves the correction rate.

Description

Wide-angle lens distortion automatic correction device and method

Technical Field

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

Background

Nowadays, wide-angle lenses play an increasingly important role in the fields of military affairs, monitoring, medical treatment, traffic, photography and the like. In the above-mentioned fields, wide-angle lenses are widely used because they can acquire image information of a larger field of view. However, due to the structural characteristics of the wide-angle lens, a captured image usually generates a certain degree of nonlinear distortion, so that the geometric position accuracy of an object in the image is affected, and the wide-angle lens loses application value in the fields with higher geometric accuracy requirements such as image measurement and image recognition. Distortion correction of the image can effectively solve the imaging problem of the wide-angle lens.

At present, the nonlinear distortion appearing in the wide-angle lens is mainly radial distortion, and a set of widely accepted mathematical models based on the following specific mathematical models have been studied and proposed:

_x，_yrespectively representing the offset, k, of a pixel point in the x and y directions₁,k₂,k₃,r²＝x²+y²Is the distortion coefficient.

Based on the model, the study on the distortion correction of the wide-angle lens is very important, and for a wide-angle imaging system, the problems are mainly solved as follows, (1) the distortion correction is usually realized on a computer and is not convenient for real-time processing and observation; (2) the distortion of different fields is different, and the current correction method is basically treated in the same way, so that the correction precision is poor.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a wide-angle lens distortion automatic correction device and method, which can effectively shorten the correction time and improve the correction precision. The technical scheme is as follows:

an automatic correction device for wide-angle lens distortion comprises 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 sub-field image fusion module and a controllable diaphragm control 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.

Furthermore, a controllable diaphragm is inserted between the wide-angle lens of the image acquisition module and the CCD, and the size and the transverse position are controlled.

Furthermore, the wide-angle image correction module and the sub-field image fusion module adopt FPGA hardware circuits.

A wide-angle lens distortion automatic correction method comprises 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 carrying out operations such as filtering;

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

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

Furthermore, 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.

The invention has the advantages that:

the images in different field angles of the wide-angle lens are corrected to different degrees, so that a more accurate image is obtained. The FPGA is used as a control circuit to control the diaphragm to directly acquire the images of the sub-fields, the images of the sub-fields are respectively corrected, the corrected images of the sub-fields are fused according to the field division, the fused images are obtained through reconstruction, and the obtained corrected images are very high in precision and good in real-time performance.

Drawings

FIG. 1 is a block diagram of an apparatus and method for automatically correcting wide-angle lens distortion

FIG. 2 is a schematic diagram of an apparatus and a method for automatically correcting wide-angle lens distortion

Detailed Description

In order to reduce the distortion of the wide-angle lens and realize real-time processing, an optical method is used for matching with FPGA (field programmable gate array) correction.

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

As shown in fig. 1, it comprises the following steps:

the method comprises the following steps: assembling the wide-angle lens, inserting a controllable field diaphragm between the CCD and the wide-angle lens as shown in FIG. 2, and performing operations such as image input and image acquisition in different fields. The whole wide-angle device system comprises an image input object plane, a wide-angle lens, a controllable diaphragm, a CCD imaging camera and an FPGA. The image of the input object plane is presented on the CCD through the wide angle lens and the field stop.

Step two: the left and right movement and the size of the field diaphragm are controlled in real time through the FPGA, the field diaphragm is synchronous with the CCD exposure time, and the field images are divided and collected according to the field angle increased by 10 degrees.

Step three: the CCD collects video stream information and transmits the frame images into the FPGA frame by frame. The FPGA comprises a control module and a distortion correction module, and the control module and the distortion correction module are respectively stored in a block RAM in the FPGA according to the field angle division.

Step four: and correcting distortion in an image distortion correction module by a correction method based on a bilinear interpolation method, and transmitting the distortion into an image fusion module.

Step five: and fusing the view-divided images corrected by the distortion correction module in the image fusion module, fusing the restored images of each view field according to view field division for each view field, and reconstructing to obtain a fused image.

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

Step six: and the image display and parameter control module is in communication with the FPGA through a serial port by using upper computer programming software and is responsible for displaying the original image and the restored image.

Claims

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:

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

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.