WO2023103207A1

WO2023103207A1 - Imaging focusing system for specified monitoring area

Info

Publication number: WO2023103207A1
Application number: PCT/CN2022/081182
Authority: WO
Inventors: 李俊杰; 高超; 曹渊; 顾伟
Original assignee: 江苏航天大为科技股份有限公司
Priority date: 2021-12-06
Filing date: 2022-03-16
Publication date: 2023-06-15
Also published as: CN114422660A

Abstract

Disclosed in the present invention is an imaging focusing system for a specified monitoring area. The imaging focusing system comprises a focusing ring driving wheel, a lens focus-fixing ring, an electric motor system and a fixed support, wherein the electric motor system comprises an electric motor control system and an electric motor; the electric motor control system controls the rotation direction and the rotation time of the electric motor, a transmission structure in the electric motor then drives the focusing ring driving wheel to rotate, and the focusing ring driving wheel is connected to the lens focus-fixing ring, so as to control the lens focus-fixing ring to implement a focusing operation of a lens. In the present invention, the rotation of a focus-fixing ring is controlled by using an electric mechanism, without needing to perform manual focusing when a camera is mounted, and adjustment can also be performed in a timely manner after a specified area is modified. The definition of a focused image is calculated by using an assessment algorithm, and therefore, compared with a traditional subjective assessment method, focusing is more accurate. A focusing ring driver uses a gear set structure, and therefore, compared with other transmission methods, a control angle is more accurate, and thus there is no need to rotate a lens backwards.

Description

An imaging focusing system for designated monitoring area

technical field

The invention belongs to the technical field of video monitoring, in particular to an imaging focusing system for a designated monitoring area.

Background technique

Autofocus technology is one of the key technologies of computer vision and various imaging systems, and it is widely used in imaging systems such as digital cameras and digital video cameras. The traditional autofocus technology mostly uses the distance measurement method, that is, by measuring the object distance, the image distance or focal length of the system is obtained from the lens equation to adjust the system to make it in the state of accurate focus. With the development of modern computing technology and the increasing maturity of digital image processing theory, auto-focus technology has entered a new digital era. More and more auto-focus methods analyze and calculate image-related information based on image processing theory, and then according to control strategy Drive the motor and adjust the system to make it focus accurately.

Auto Focus (Auto Focus) is the use of the principle of object light reflection, the reflected light is received by the sensor on the camera, processed by a computer, and the way to drive the electric focus device to focus is called auto focus. It is divided into active and passive two categories. Active autofocus: use the infrared generator and ultrasonic generator on the camera to emit infrared light or ultrasonic waves to the subject. The receiver on the camera accepts the reflected infrared light or ultrasonic to focus, and its optical principle is similar to the triangular ranging focusing method. There is an energy method in the active type, which is used for the autofocus of low-end popular cameras, and is widely used in various head-up viewfinder cameras. Passive autofocus: It is a way to directly receive and analyze the reflection from the scene itself and perform autofocus. The advantage of this autofocus method is that it does not require a launch system, so it consumes less energy and is conducive to miniaturization. It can autofocus ideally for subjects with a certain brightness, and it can also focus well under backlighting. It can automatically focus on objects with high brightness in the distance, and can focus through glass.

In the road and traffic video monitoring system, due to the fixed position of the intersection or road section of the shooting scene, the shooting objects are traffic participants on the road, and most of them are a large number of moving targets. The movement of traffic objects or the change of light cannot guarantee the clear picture of the designated shooting area. Therefore, fixed-focus lenses with manual focus are commonly used in road and traffic video surveillance systems. However, due to the particularity of road and traffic video monitoring installations, special vehicles and personnel are needed to focus the camera. Therefore, the present invention designs an imaging focusing system for a designated monitoring area, and the lens of the user's video monitoring camera focuses.

Contents of the invention

Video surveillance cameras with fixed-focus lenses are widely used in road and traffic monitoring. Due to the different scenes and objects of video surveillance, it is necessary to focus on the lens every time the camera is installed or replaced. Due to the particularity of road and traffic video surveillance installations, the focus debugging requires the cooperation of professionals, and the process is complicated. At the same time, the common auto-focus lens will be automatically calculated according to the focus algorithm, which will cause the focus point or area to change with the movement of the object and the change of light, which is not conducive to the requirement of a fixed shooting area in road and traffic video surveillance. In view of this, the present invention proposes an imaging focusing system in a specified environment. By setting the shooting area, collecting images multiple times, using the image definition value algorithm and focusing ring driver control, the automatic focusing of the specified area is realized, which greatly reduces the It eliminates the difficulty of focusing work of fixed-focus lens monitoring cameras in road and traffic monitoring.

An imaging focusing system for a designated monitoring area disclosed in the present invention includes a focusing ring driving wheel, a lens focusing ring, a motor system and a fixed bracket, and the motor system includes a motor control system and a motor; the motor control system controls the rotation of the motor direction and rotation time, and then the transmission structure in the motor drives the focus ring drive wheel to rotate, and the focus ring drive wheel is connected with the lens fixed focus ring to control the lens focus ring to realize the focusing operation of the lens.

Further, the gear ratio of the drive wheel of the focus ring enables the focus ring of the lens to rotate and focus in units of 1°.

Further, the motor control system reads the configuration of the detection area in the camera, sets the start point and end point, and then reads the gray value of the current frame detection area image, calculates the sharpness value of the image, and controls the The focus ring of the lens is rotated to adjust the focus.

Further, the controlling the rotation and focusing of the lens fixed focus ring according to the sharpness value of the image includes:

Rotate the fixed focus ring of the lens at a speed of 1°/time, and calculate the image sharpness, and compare the values of the two image sharpness before and after;

If the image sharpness increases gradually, continue to rotate the fixed focus ring of the lens;

When the image sharpness calculated by rotating the fixed focus ring of the lens starts to be smaller than the previous image sharpness, the drive wheel of the focus ring stops rotating, and the focus is completed.

Further, the image sharpness is calculated using the gray variance product method, and the formula is as follows:

Among them (m _s , n _s ) represents the starting point of the image detection area, which is the coordinate point of the upper left corner of the area; (m _e , n _e ) represents the end point of the image detection area, which is the coordinate point of the lower right corner of the area; x _ij represents The gray value of the image pixels in the detection area.

The beneficial effects of the present invention are as follows:

The electric mechanism is used to control the rotation of the fixed focus ring, so there is no need to manually focus when installing the camera, and at the same time, it can be adjusted in time after the specified area is modified.

The evaluation algorithm is used to calculate the sharpness of the image after focusing. Compared with the traditional subjective evaluation method, the focus is more accurate.

The focus ring driver adopts a gear set structure, which can control the angle more precisely than other transmission methods, so there is no need to rotate the lens.

Description of drawings

Fig. 1 is a structural connection diagram of the imaging focusing system of the present invention;

Fig. 2 is a flow chart of the calculation of the definition of the detection area of the present invention;

FIG. 3 is a flow chart of the imaging focus control algorithm of the present invention.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings, but the present invention is not limited in any way. Any transformation or replacement based on the teaching of the present invention belongs to the protection scope of the present invention.

The present invention is mainly aimed at installing video surveillance cameras on the road. In this type of camera configuration, the detection area is a common configuration, which is mainly used to calibrate the area where the camera needs to detect and shoot. Therefore, the clarity of the image in the detection area directly affects the function of the camera. . When the camera is installed, it will also focus manually according to the detection area, and judge whether the focus is successful through subjective evaluation. The present invention utilizes the gray scale variance product (SMD2) algorithm to calculate the definition value of the detection area, so as to reduce the error caused by the subjective evaluation.

In image processing, compared with images in unfocused areas, the image in the focused area has a clearer segmentation of the scene content, so the difference between pixels is greater, and in a more complex scene, the clearer the image, the greater the change in adjacent pixels; The more blurred, the more uniform the gray level distribution of the entire image, and the smaller the variation of adjacent pixels. The SMD2 algorithm takes advantage of this feature and uses the gray variance product index to measure the sharpness of the image. The calculation formula of the gray variance product is as follows:

Among them (m _s , n _s ) represents the starting point of the image detection area, which is the coordinate point of the upper left corner of the area; (m _e , n _e ) represents the end point of the image detection area, which is the coordinate point of the lower right corner of the area; x _ij represents The gray value of the image pixels in the detection area. The larger the value of the gray variance product in the detection area (m, n), the clearer the image and the better the quality of the image; otherwise, the blurrier the image, the worse the quality.

When the present invention calculates the image sharpness value, it first reads the detection area configuration in the camera, sets the starting point (m _e , n _e ), the end point (m _s , n _s ), and then reads the detection area of the current frame ( m, n) the gray value of the image, and finally use the SMD2 algorithm to output the sharpness value of the image. The process is shown in Figure 1 below.

The present invention can evaluate the adjustment of the focus system on the basis of the sharpness value, and control the focus system based on this, so as to achieve the purpose of clearly focusing the detection area.

There are generally two adjustment mechanisms in the fixed-focus lens used in common video surveillance cameras: one is the aperture adjustment ring, which is used to adjust the size of the aperture and control the amount of light entering; That is to say, adjusting the focus ring can keep the subject clear. The focus ring driver of the present invention is a structure composed of a focus ring drive wheel, a motor system and a fixed bracket, and the physical connection structure is shown in FIG. 2 .

The main working principle of the focus ring driver in the present invention is that the control system controls the rotation direction and rotation time of the motor, and then the transmission structure in the motor system drives the focus ring drive wheel to rotate, and the focus ring drive wheel is connected with the lens fixed focus ring to directly control the lens The focus ring realizes the focus operation of the lens.

In the present invention, the motor system needs to calibrate the system before working. It is necessary to calibrate the working time of the motor system when the focus ring rotates 1° according to the gear ratio of the transmission system in the system, so as to control the focus ring with 1° as The unit rotates to adjust the focus.

The present invention designs a set of focus ring driver control algorithms based on the SMD2 algorithm and the focus ring driver. The algorithm first initializes the parameters of the focus ring driver and the SMD2 algorithm. The initialization parameters include the time required to power on the motor when the focus ring rotates 1° and the designated area in the camera monitoring screen. Then calculate SMD2(m,n) while rotating the fixed focus ring at a speed of 1°/time, and compare the values of SMD2(m,n) twice before and after. Since the image of the specified area is in a blurred state at the beginning, the value of SMD2(m,n) is small. After rotating the fixed focus ring, the image gradually becomes clear. At this time, SMD2(m,n) gradually increases, and when the SMD2 When (m,n) is smaller than the previous SMD2(m,n), it means that the previous SMD2(m,n) reaches the apex, and the image is the clearest image. At this time, the focus ring driver stops rotating and the focus is completed. The algorithm flow is shown in Figure 3 below.

In the algorithm flow chart, SMD2(m,n)' is the sharpness value of the image in the specified area after the previous rotation, and the initial value of SMD2(m,n)' is the maximum value of the current calculation accuracy, which is initialized to 65535 in this algorithm , so as to ensure that the algorithm can enter the judgment process. And because the lens has a certain latitude, once the SMD2(m,n) exceeds the maximum value point, the focus ring driver will not make the next rotation, and will not retreat 1° to correct the focus result.

Take a CCTV_LENS_3MP·HD_12MM_IR manual fixed-focus lens as an example. When the lens is facing us, we turn the lens clockwise and cannot rotate, and the focus of the lens is at the closest point. Install the lens to the camera, install the focus ring driver, and rotate the lens counterclockwise at this time, the focus of the lens will be from forward to far, mark the designated area, and calibrate the focus ring driver according to the gear ratio of the motor system. The optional speed is 2 seconds/degree, and then focus It takes 2 seconds for every 1° of the ring driver to be installed, and the comparison between SMD2(m,n) and SMD2(m,n)' is completed in these 2 seconds. If the comparison result is SMD2(m,n)<=SMD2(m,n)', the focus ring driver rotates 1° and captures the image, and updates SMD2(m,n), if SMD2(m,n)>SMD2( m, n)' then stop the rotation to complete the focus.

The beneficial effects of the present invention are as follows:

As used herein, the word "preferred" means serving as an example, instance or illustration. Any aspect or design described herein as "preferred" is not necessarily to be construed as advantageous over other aspects or designs. Rather, use of the word "preferred" is intended to present concepts in a concrete manner. As used in this application, the term "or" is intended to mean an inclusive "or" rather than an exclusive "or". That is, unless otherwise specified or clear from context, "X employs A or B" is meant to naturally include either of the permutations. That is, if X employs A; X employs B; or X employs both A and B, then "X employs A or B" is satisfied in any of the foregoing instances.

Moreover, although the disclosure has been shown and described with respect to one or an implementation, equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. The present disclosure includes all such modifications and variations and is limited only by the scope of the appended claims. With particular regard to various functions performed by the above-mentioned components (eg, elements, etc.), terms used to describe such components are intended to correspond to any component that performs the specified function of the component (eg, it is functionally equivalent) Even if there are no structural equivalents to the disclosed structures that perform the functions in the exemplary implementations of the present disclosure shown herein (unless otherwise indicated). Furthermore, although a particular feature of the present disclosure has been disclosed with respect to only one of several implementations, such feature may be combined with one or other features of other implementations as may be desirable and advantageous for a given or particular application. combination. Moreover, to the extent the terms "comprises", "has", "comprising" or variations thereof are used in the detailed description or the claims, such terms are intended to be encompassed in a manner similar to the term "comprising".

Each functional unit in the embodiment of the present invention may be integrated into one processing module, or each unit may physically exist separately, or multiple or more of the above units may be integrated into one module. The above-mentioned integrated modules can be implemented in the form of hardware or in the form of software function modules. If the integrated modules are implemented in the form of software function modules and sold or used as independent products, they can also be stored in a computer-readable storage medium. The storage medium mentioned above may be a read-only memory, a magnetic disk or an optical disk, and the like. Each of the above devices or systems may execute the storage method in the corresponding method embodiment.

In summary, the above-mentioned embodiment is an embodiment of the present invention, but the embodiment of the present invention is not limited by the embodiment, any other changes that deviate from the spirit and principle of the present invention, Modifications, substitutions, combinations, and simplifications should all be equivalent replacement methods, and are all included within the protection scope of the present invention.

Claims

An imaging focusing system for a designated monitoring area is characterized in that it includes a focus ring drive wheel, a lens fixed focus ring, a motor system and a fixed bracket, and the motor system includes a motor control system and a motor; the motor control system controls the rotation of the motor direction and rotation time, and then the transmission structure in the motor drives the focus ring drive wheel to rotate, and the focus ring drive wheel is connected with the lens fixed focus ring to control the lens focus ring to realize the focusing operation of the lens.
The imaging focusing system for a designated monitoring area according to claim 1, wherein the gear ratio of the driving wheel of the focusing ring enables the focusing ring of the lens to rotate and focus in units of 1°.
The imaging focusing system for a specified monitoring area according to claim 1, wherein the motor control system reads the configuration of the detection area in the camera, sets the starting point and the end point, and then reads the gray value of the current frame detection area image , calculate the sharpness value of the image, and control the rotation and focus of the fixed focus ring of the lens according to the sharpness value of the image.
The imaging focusing system for a designated monitoring area according to claim 1, wherein the controlling the rotation and focusing of the lens fixed focus ring according to the sharpness value of the image comprises:

Rotate the fixed focus ring of the lens at a speed of 1°/time, and calculate the image sharpness, and compare the values of the two image sharpness before and after;

If the image sharpness increases gradually, continue to rotate the fixed focus ring of the lens;

When the image sharpness calculated by rotating the fixed focus ring of the lens starts to be smaller than the previous image sharpness, the drive wheel of the focus ring stops rotating, and the focus is completed.
The imaging focusing system for a designated monitoring area according to claim 3, wherein the image sharpness is calculated using a gray scale variance product method, and the formula is as follows:

Among them (m s , n s ) represents the starting point of the image detection area, which is the coordinate point of the upper left corner of the area; (m e , n e ) represents the end point of the image detection area, which is the coordinate point of the lower right corner of the area; x ij represents The gray value of the image pixels in the detection area.