CN116405784A - Multiple exposure method, device and scanning equipment for line scanning camera - Google Patents
Multiple exposure method, device and scanning equipment for line scanning camera Download PDFInfo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
- H04N23/70—Circuitry for compensating brightness variation in the scene
- H04N23/741—Circuitry for compensating brightness variation in the scene by increasing the dynamic range of the image compared to the dynamic range of the electronic image sensors
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- G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
- G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
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Abstract
The invention discloses a multiple exposure method, a device and a scanning device of a line scanning camera, which realize the multiple exposure effect of the line scanning camera by periodically adjusting the brightness of light rays emitted by an object and then sending the light rays into the line scanning camera; wherein the brightness value set corresponding to each line of images scanned by the line scan camera is adjusted periodically corresponding to the scanning line frequency of the camera. The periodic brightness adjustment can be carried out on the light rays emitted by the object according to the periodic change of the reflectivity; or periodically adjusting the brightness of the light emitted by the object according to the periodic change of the transmissivity; or the light is subjected to periodic brightness adjustment according to the periodic variation of the included angle between the transmission direction of the polaroid and the polarization direction of the polarized light. The line scanning camera does not need to change the exposure time of each time when scanning, and the subsequent data transmission process continues to transmit according to the common mode, so that the complexity of algorithm operation is reduced, and the design difficulty of the line scanning camera is simplified.
Description
Technical Field
The present invention relates to the field of line scanning camera applications, and in particular, to a multiple exposure method, apparatus and scanning device for a line scanning camera.
Background
In the defect detection field, a scene with severe brightness change exists, and a general low dynamic range photosensitive sensor can be represented as overexposure or underexposure, which represents loss of detail information of certain areas and is not beneficial to defect detection of products such as photovoltaic panels. It is therefore necessary to achieve a wide dynamic range to obtain important details in environments with sharp contrast. In order to increase the dynamic range of the final image, there are basically two methods:
1. hardware is improved to increase the dynamic range of the photosensitive assembly. This puts higher demands on the sensor, increasing the cost of development.
2. Improved by software algorithms. Image data is acquired by using different exposure times. And after the image data is obtained, fusing by using an exposure fusion algorithm to generate a wide dynamic range image.
The existing multiple exposure or long-short exposure technology mainly modifies the exposure time of each time of a sensor through a program, and a classical line scanning camera long-short exposure scheme such as odd line short exposure and even line long exposure finally obtains 2 images, and an HDR image is obtained by combining the 2 images into one by an algorithm.
The exposure fusion algorithm is used to synthesize a plurality of differently exposed low dynamic range images into an HDR image, the main idea being that for a sequence of multi-exposure images, the most valuable part of each image is taken for synthesis. For example, dark areas in images with long exposure times are valuable parts because of their rich detail and low noise levels. The pixel value is generally evaluated from three dimensions of contrast, saturation and brightness, then the value index of each pixel in each graph is calculated as a corresponding weight, and finally the HDR image is obtained through a weighted fusion mode.
The existing multiple exposure implementation technology of the line scanning camera comprises the following steps:
an automatic exposure device and a method thereof are disclosed in Chinese patent publication CN 102143325A;
chinese patent publication CN 102369539A is for exposure control of multiple imaging scanners;
chinese patent publication CN 103379287A light receiving apparatus, light receiving method, and transmission system;
chinese patent publication CN 111263080A is a progressive exposure method based on a line scan camera.
The Chinese patent publication CN 111263080A discloses a gradual change exposure method based on a line scanning camera, which comprises the following steps: s1: setting an exposure range value through an empirical value through a plurality of exposure surrounding experiments, calculating the required exposure time line by line/column according to the set value during progressive scanning, and transmitting the exposure range value to an FPGA chip in the form of an exposure range parameter by using upper computer software with an increment of 0.1 ms as a minimum step length when calculating the exposure time line by line/column, wherein the transmitted parameter comprises the scanning line number, the initial value and the final value of exposure, and the variation of exposure increases/decreases the value; s2: the FPGA dynamically forms CCD control waveforms according to parameters transmitted by the upper computer.
In the existing line scan camera multiple exposure technology, different exposure times are used for scanning, so that the whole gray value response of the line is different from that of other lines. However, changing the exposure time of different rows requires complex design of the graph acquisition flow on the algorithm, the calculated amount is large, and the requirements of large data flow, high efficiency and real-time data processing in the field of appearance defect detection cannot be met under partial conditions.
Disclosure of Invention
The invention provides a multiple exposure method, a multiple exposure device and a multiple exposure scanning device for a line scanning camera, which can at least solve one of the technical problems.
In order to achieve the above purpose, the present invention proposes the following technical solutions:
a line scan camera multiple exposure method comprising:
the light emitted by the object is sent to the line scanning camera after periodic brightness adjustment;
the periodic brightness adjustment corresponds to the scanning line frequency of the line scanning camera so that each line of images scanned by the line scanning camera corresponds to a set brightness value.
Further, the periodic brightness adjustment for the light emitted by the object includes:
adjusting the intensity of light rays emitted by an object once every a period of time T;
the periodic brightness adjustment corresponds to a scan line frequency of a line scan camera, comprising:
the scanning line frequency of the line scanning camera is f, and the interval time between two exposures is 1/f; t=1/f is satisfied between T and 1/f.
Further, the periodic brightness adjustment of the light emitted by the object is then sent to the line scanning camera, which includes:
the light emitted by the object is reflected and then sent to the line scanning camera, and the light emitted by the object is subjected to periodic brightness adjustment according to the periodic change of the reflectivity; or (b)
Light of the object enters the line scanning camera after being transmitted, and the light emitted by the object is subjected to periodic brightness adjustment according to the periodic change of the transmissivity; or (b)
Light emitted by the object is converted into polarized light, and the light emitted by the object is periodically adjusted in brightness according to the periodic change of the included angle between the vibration transmission direction of the polaroid and the polarization direction of the polarized light.
On the other hand, the invention also provides a multiple exposure device of the line scanning camera, which comprises the line scanning camera and further comprises:
the brightness adjusting device is used for periodically adjusting the brightness of the light rays emitted by the object and then sending the light rays to the line scanning camera; the period corresponds to a scanning line frequency of the line scanning camera, so that each line of images scanned by the line scanning camera corresponds to a set brightness value.
Further, the brightness adjusting device includes:
the regular polygon prism light reflecting device has a set reflectivity on each side surface; the position of the regular polygon prism light reflecting device is adapted to the position of the line scanning camera, so that when each side surface of the regular polygon prism light reflecting device rotates to a specific position, light rays emitted by an object can be reflected into the line scanning camera;
the power device is used for driving the regular polygon prism light reflecting device to rotate by taking the central line as an axis, and the rotating angular speed corresponds to the scanning line frequency of the line scanning camera so that each line of images scanned by the line scanning camera corresponds to a set brightness value.
Further, if the line scanning camera performs N-time exposure, where N is a positive integer greater than 2, the regular polygon prism light reflecting device is a regular N prism, and each side surface of the regular N prism has different reflectivity; at this time, the angular speed N of the power device driving the positive N prism to rotate is:
n=2πf/N
wherein f is the scanning line frequency of the line scanning camera.
Further, if the line scanning camera performs N re-exposure, where N and a are positive integers greater than 1, the regular polygon prism light reflecting device is a regular a×n prism, each a of the sides of the regular a×n prism is a group, the reflectivities of the sides of different groups are different, and the reflectivities of a sides in the same group are the same; at this time, the angular speed N of the power device driving the positive a×n prism to rotate is:
n=2πf/N
wherein f is the scanning line frequency of the line scanning camera.
Further, if the line scanning camera performs N re-exposure, where N and a are positive integers greater than 1, the regular polygon prism light reflecting device is a regular a×n prism, each N sides of the regular a×n prism are a group, and the reflectivity of each side in each group is R1, R2. At this time, the angular speed N of the power device driving the positive a×n prism to rotate is:
n=2πf/(a×N)
wherein f is the scanning line frequency of the line scanning camera.
Further, the brightness adjusting device includes:
the reflectivity of the side surface of the cylindrical reflecting device changes periodically when the cylindrical reflecting device rotates along the central line; the position of the cylindrical reflecting device is adapted to the position of the line scanning camera, so that the side surface of the cylindrical reflecting device can reflect light rays emitted by an object into the line scanning camera in the rotating process of the cylindrical reflecting device;
the power device is used for driving the cylindrical reflecting device to rotate by taking the central line as an axis, and the rotating angular speed corresponds to the scanning line frequency of the line scanning camera so that each line of images scanned by the line scanning camera corresponds to a set brightness value.
Further, before the line scan camera starts to collect image data, the following steps are further performed:
using a strip light source with set stripes or colors to be incident to the line scanning camera multiple exposure device;
the regular polygon prism light reflecting device rotates according to a set angular speed, a line scanning camera is started, and scanning is performed according to a set scanning line frequency f;
if the line scanning camera does not scan the image of the strip light source, the line scanning camera pauses scanning, and the line scanning camera is started again after an interval time t;
the interval time T is increased from T to T+1/f until the line scanning camera scans the image of the strip-shaped light source;
wherein T is any time.
In yet another aspect, the present invention also proposes a scanning apparatus including:
the platform is used for carrying the shot object and driving the shot object to move relative to the platform at a set speed;
the line scanning camera multiple exposure device is arranged on the platform and is used for acquiring an image of a shot object.
The beneficial effects of the invention are as follows:
(1) Aiming at the defects of the prior art, the line scanning camera does not need to change the exposure time of each time when scanning, and the follow-up data transmission process continues to transmit according to the common mode, so that the high-efficiency and real-time data processing requirements of the line scanning camera are not affected. And the acquired image data is the same as the data acquired by adopting a multiple exposure algorithm in the prior art, and the same exposure fusion algorithm can be performed to obtain an HDR image.
(2) The invention starts from the intensity of the light projected from the object, can realize the functions realized by the algorithm in the past through the mechanical design, reduces the complexity of the algorithm operation and simplifies the design difficulty of the line scanning camera.
Drawings
FIG. 1 is a schematic diagram of a multiple exposure apparatus of a line scan camera according to an embodiment 1 of the present invention;
FIG. 2 is a schematic view of a regular polygon prism light reflecting device in embodiment 1 of the present invention;
FIG. 3 is a schematic diagram of the stitching of scan data from a line scan camera in accordance with embodiment 1 of the present invention;
FIG. 4 is a graph showing the surface reflectance distribution of a regular polygon prism light-reflecting device according to example 1 of the present invention;
FIG. 5 is a scanning process light path diagram of embodiment 1 of the present invention;
FIG. 6 is a graph showing the reflectance distribution of the surface of a regular polygon prism light-reflecting device according to embodiment 2 of the present invention;
fig. 7 is a schematic diagram of a multiple exposure apparatus of a line scanning camera according to embodiment 3 of the present invention.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention.
Example 1
The multiple exposure device of the line scanning camera of the embodiment comprises a line scanning camera and a brightness adjusting device, wherein light emitted by an object is sent to the line scanning camera through the brightness adjusting device, the brightness adjusting device can periodically change the brightness of the light emitted by the object, and the periodic change corresponds to the line frequency of the line scanning camera, so that each line of images scanned by the line scanning camera corresponds to a set brightness value.
As shown in fig. 2, the brightness adjusting device comprises a regular polygon reflecting device, and the cross section of the regular polygon reflecting device is from the direction vertical to any one of the edges, and the obtained cross section is regular polygon, including triangle, square, regular pentagon, etc., wherein the line passing through the center points of the upper and lower surfaces of the regular polygon reflecting device is the center line of the regular polygon reflecting device. Each side of the regular polygon prism light reflecting device can reflect light rays and has different reflectivity. The reflectivity of the different sides is different and in a preferred embodiment can be increased in a clockwise/counter-clockwise direction with equal value from a set minimum to a set maximum. Specifically, each side of the regular polygon prism light reflecting device is light reflecting plane glass with different reflectivity. The brightness adjusting device also comprises a controlled power device which can be a controlled motor and is used for driving the regular polygon prism light reflecting device to rotate along the central line.
The overall structure of the multiple exposure device is shown in fig. 1, and the center line of the regular polygon prism light reflecting device is parallel to the line scanning sensor of the line scanning camera. The light emitted from the object reaches one side surface of the regular polygon prism reflecting device, and the side surface reflects the light and then just projects the light onto the line scanning sensor. Because the side reflectivity of the regular polygon prism reflecting device takes a value between 0 and 1, the brightness of the light emitted from the object changes after reflection. If the original light intensity is L, the reflected light intensity is L1, and the reflectance is R, l1=rχl2.
The working procedure of the multiple exposure apparatus of this embodiment is as follows:
according to the requirement of multiple exposure, if N times of different exposure time are needed, N is larger than 2, namely the exposure time of the line scanning camera is different for N times continuously in the scanning process. At this time, the regular polygon prism light reflecting device in the brightness adjusting device is a regular N prism, and the reflectivities of N sides of the regular N prism are R1, R2, R3, and R.
The shot object and the multiple exposure device perform relative movement, the movement speed is v, and specifically, the shot object can move relative to the multiple exposure device at the speed v along the direction perpendicular to the scanning line of the line scanning camera; or, the multiple exposure device moves at a speed v along a direction perpendicular to a scanning line of the line scanning camera with respect to the object to be photographed.
The line scanning camera scans according to the set line frequency f, and in a certain exposure time, a part of light rays emitted by an object reach a sensor of the line scanning camera through reflection of a certain side surface on the regular polygon prism light reflecting device, and the reflectivity of the side surface to the light rays is R1. When the line scanning camera reaches the next exposure time, the regular polygon prism light reflecting device rotates, and the light reflecting surface becomes the side surface of the regular polygon prism light reflecting device with the reflectivity of R2. I.e. the light emitted by another part of the object reaches the sensor of the line scanning camera by reflection from the side of the regular polygon mirror, which side has a reflectivity R2. The operation makes the whole brightness of the image data obtained by the line scanning camera by two continuous scans different, and achieves the same effect as changing the exposure time of the line scanning camera.
According to the same steps, the sensors of the line scanning camera sequentially receive light rays emitted by different parts of the photographed object after being reflected by the reflective surfaces of the RN, wherein the reflectivity of the light rays is R1, R2, R3, and the reflective surfaces of the RN, and sequentially and circularly scan the light rays until a complete scanned image of the photographed object is obtained.
In the above process, the angular speed of the regular polygon prism light reflecting device rotating along the central line is N, and the relationship among the different exposure time numbers N of the multiple exposure, the scanning line frequency f of the line scanning camera, and the angular speed of the regular polygon prism light reflecting device rotating along the central line is N is:
in order to meet the requirement of N-time exposure, the line scanning camera should just complete N-line scanning every time the regular polygon prism light reflecting device rotates. The known regular polygon prism light reflecting device adjusts the light intensity of the light beam emitted by the object at intervals of a period of time T, and the scanning line frequency of the line scanning camera is f, so that the exposure period of the line scanning camera is 1/f, i.e. the time interval between two exposures is 1/f. The regular polygon prism light reflecting device should run through 1/N circle in 1/f time, the angle is 2 pi/N, the rotating angular velocity of the regular polygon prism light reflecting device is:
n=(2π/N)/T=(2π/N)/(1/f)=2πf/N
through the steps, the scanning picture of the shot object can be obtained, the pixel points of the scanning picture change once every N rows, and the overall brightness of the pixel points of each row increases or decreases in the N rows. The image stitching method of the present embodiment is described below with n=4, wherein the scanned image has M rows of pixels in total, and the image stitching process of the multiple exposure device of the present embodiment is:
the line scanning camera acquires a line trigger signal, sequentially acquires each line of data according to the steps, and packages the data and sends the data to the upper computer;
the upper computer driver analyzes the received data packet, converts the packet id (packet identifier) into a line number to be filled, sequentially increases the line number from 0 to M, and fills the data packet into the line. As shown in fig. 3; a storage space of four segments of image data lines is set, in which the data packet starts from the first (packetid=1), every four padding into image data of different segments. The camera circularly outputs all lines of the image, and the upper computer drives the circularly converting PacketId to the line number and filling, so that four image data lines are filled in sequence. Each section is a single scanned image of the shot object, 4 complete images of the shot object with different exposure time are obtained, and the 4 images can be fused into one image through an exposure fusion algorithm.
According to the image data splicing method, the pcketId sent by the camera is still gradually increased from 1, the pcketId does not need to be changed according to the line number, the image transmission speed is increased, and the algorithm operation amount is saved. And in the multiple exposure mode, the retransmission mechanism still works normally.
Further, the number of bytes contained in each line of the image must be a positive integer multiple of the number of bytes of the valid image contained in a data packet. This is to prevent that a line of pixels is too long, and the data packet in one data packet cannot completely contain one line of data, and at this time, one line of data can be divided into an integer number of data packets for transmission. When the splicing is carried out, the data packets belonging to the same row of pixel data are filled into the storage space of the same row, and the rest methods are unchanged.
In this embodiment, if n=2, the requirement cannot be satisfied because there is no regular biprism. In this case, the N-prism may be changed to a×n-prism, and a is a positive integer greater than 1, for example, when n=2, a regular square prism, a regular hexagonal prism, a regular eight prism, or the like may be selected. The sides a of the regular a×n prism are grouped, and each group of sides has the same reflectivity, for example, when n=2, a=3, a regular hexagonal prism is selected, and the side refractive index of the regular hexagonal prism is shown in fig. 4, where the first 3 are R1, and the second three are R2. At this time, the relationship among the number N of different exposure times of the multiple exposure, the scanning line frequency f of the line scanning camera, and the angular velocity of the regular polygon prism reflective device rotating along the center line is N, also n= (2pi/N)/(1/f) =2pi/N.
The more stable the number of sides of the regular polygon mirror body is when rotated along the center line, the less the effect on the entire multiple exposure apparatus is when rotated.
Further, in this embodiment, if the rotation speed of the regular polygon mirror is limited, as shown in fig. 5, the position relationship between the reflective surface on the regular polygon mirror and the light entrance of the line scan camera and the object to be photographed at the moment when the line scan camera starts exposure may cause that the line scan camera scans the part of the object not facing the whole multiple exposure device, as shown in the optical path 1, in this case, although the relationship between the rotation speed of the regular polygon mirror and the line frequency of the line scan camera is kept unchanged, the whole image of the object to be photographed may be obtained, but the image is distorted due to the angle problem. It is also necessary to solve the problem of the scanning angle between the line scan camera and the brightness adjusting means.
In order to solve the problem, the embodiment designs a scanning angle correction step before the multiple exposure device starts to pick up the image, so that the image scanned by the line scanning camera during each exposure is the image of the part of the object under the multiple exposure device. The directly-below image is shown in the optical path in fig. 1, and in fig. 5, refers to the object image propagated by the optical path 2, that is, the included angle between the emitted light and the reflected light of the object is pi/2 radian.
The regular polygon prism light reflecting device rotates at a set angular speed n, a strip light source with a set color is used for irradiating the multiple exposure device, the line frequency of the line scanning camera is set to be the set line frequency f, the line scanning camera is started to observe whether the acquired picture is the picture with the set color, if not, the line scanning camera is stopped, and the camera is started again after a set interval time t until the picture acquired by the line scanning camera is the picture with the set color. Wherein the set time interval T is incremented between T and t+1/f, where T is any time.
For a black-and-white line scanning camera, the set color bar light source is changed into a discontinuous light source, and the discontinuous light source is preferably a bar light source which emits light again at intervals. And judging whether the pictures acquired by the line scanning camera can display the pictures of the interval luminous information or not, if not, stopping the line scanning camera, and starting the camera again after a set time interval t until the pictures acquired by the line scanning camera can display the interval luminous information. Wherein the set time interval T is incremented between T and t+1/f.
Example 2
In example 1, N-fold exposure scanning was completed with one revolution of the regular polygon mirror. However, since the line frequency of the line scanning camera is generally high, for example, when f=10khz and n=4, the rotation speed of the regular polygon prism light reflecting device is required to be f/n=2500 rpm, and the rotation speed has high requirements on the design of the corresponding power device. In this embodiment, the number of sides of the regular polygon prism light reflecting device is increased based on embodiment 1.
In this example, if N-fold different exposure times are required, a positive a×n prism is used as in one embodiment of example 1, a and N are positive integers greater than 1, for example, when n=2, a positive quadrangular prism, a positive hexagonal prism, a positive octagonal prism, or the like is selected. The sides of the positive a x N prism are N groups of a total, each group having a side with a reflectivity of R1, R2, R3. For example, when n=2 and a=4, a regular eight prism is selected as the luminance adjusting device, and the side surface of the regular eight prism has the reflectances of R1, R2, R1, R2 in this order, as shown in fig. 6.
At this time, the relationship among the different exposure time numbers N of the multiple exposure, the scanning line frequency f of the line scanning camera, and the angular speed N of the regular polygon prism light reflecting device rotating along the central line is:
to meet the N-fold exposure requirement, the line scanning camera should complete a×n line scanning every revolution of the regular polygon prism light reflecting device. Given that the scan line frequency of the line scan camera is f, the exposure period of the line scan camera is 1/f, i.e., the time interval between two exposures is 1/f. The adjusting period T of the regular polygon prism light reflecting device to the light intensity is equal to 1/f, so the regular polygon prism light reflecting device should run through 1/(a multiplied by N) circle in 1/f time, the angle size is 2 pi/(a multiplied by N), and the rotating angular speed of the regular polygon prism light reflecting device is: n= [ 2pi/(a×n) ]/(1/f) =2pi f/(a×n).
From the above equation, n is smaller as a is larger, that is, the rotation speed of the regular polygon prism light reflecting device is smaller, and the design requirement of the related power device is reduced. The more the sides of the regular polygon prism reflecting device are, the better the rotation stability of the regular polygon prism reflecting device is.
Example 3
The regular polygon prism light reflecting device in embodiment 1 is a regular N prism, when in use, the type of the regular N prism needs to be selected according to the requirement of multiple exposure, if the requirement of multiple exposure changes in the scanning process, the regular N prism needs to be replaced, and each replacement needs to be subjected to precision adjustment, which is inconvenient. In the embodiment 3 of the invention, on the basis of the embodiment 1, the regular polygon prism light reflecting device is replaced by a cylinder light reflecting device with smooth side surfaces and capable of reflecting light, and the cylinder light reflecting device is stable in rotation and low in noise. And if the multiple exposure requirement changes, the brightness adjusting device does not need to be replaced, and only the rotating speed of the cylindrical reflecting device needs to be changed.
The reflectivity of the side surface of the cylindrical light reflecting device along the central line direction is the same, when the cylindrical light reflecting device rotates along the central line, the reflectivity of the surface of the cylindrical light reflecting device changes, and preferably, when the cylindrical light reflecting device rotates clockwise by taking the central line direction as a normal vector, the reflectivity of the surface of the cylindrical light reflecting device increases or decreases.
As shown in fig. 7, the light emitted from the surface of the photographed object reaches the sensor of the line scanning camera through the reflection of the surface of the cylindrical light reflecting device, and when the cylindrical light reflecting device rotates, the reflectivity changes, and the overall brightness of the image data collected by the sensor changes, as well as the effect generated by changing the exposure time of the line scanning camera.
At this time, the relationship among the number N of different exposure times of the multiple exposure, the scanning line frequency f of the line scanning camera, and the angular velocity of rotation of the cylindrical light reflecting device along the center line is N, also n= (2pi/N)/(1/f) =2pi f/N.
In another embodiment, the surface of the cylindrical reflector is equally divided into a identical areas in a direction parallel to the center line, and the reflectivity of each area increases or decreases when the surface rotates clockwise by taking the center line direction as a normal vector. In one embodiment, the a identical regions are equally divided into N identical regions according to the same method, and each region has a reflectivity of R1, R2, R3, and R.
The brightness adjusting device for the cylindrical light reflecting device in the embodiment is not suitable for use scenes with higher requirements on precision and resolution, because the side surface of the cylindrical light reflecting device is not a plane, the obtained image has inherent distortion, but simultaneously, because the relative position between the cylindrical light reflecting device and the line scanning camera and the curvature of the side surface of the cylindrical light reflecting device are known, a corresponding distortion removing algorithm can be designed to carry out distortion removing operation, and the scanning precision is improved.
The above-mentioned embodiments are preferred embodiments of the present invention, and according to the present invention, the purpose of the brightness adjustment device is to adjust the brightness of the light emitted from the object and then send the light to the line scanning camera, so that multiple exposure can be achieved without the need for the line scanning camera to adjust the exposure time. For the purpose of brightness adjustment, the following technical scheme may be used:
the light brightness can be adjusted by using the reflection device with adjustable reflectivity in the prior art, the light transmission device with adjustable transmissivity in the prior art, and the light intensity transmitted on the polaroid by utilizing different incident angles of polarized light. The above-mentioned scheme can be understood by those skilled in the art and can be directly implemented without inventive thought, without departing from the spirit and scope of the technical scheme of the embodiments of the present invention.
The embodiment also comprises a scanning device which comprises a platform and the various multiple exposure devices, wherein the platform carries a shot object and drives the shot object to move relative to the platform at a set speed; the multiple exposure device is mounted on the stage for acquiring an image of the subject in accordance with the multiple exposure steps described above.
It will be appreciated that the term multiple exposure is used herein to describe the device of the present invention and is in fact defined from the standpoint of the technical effect of the device of the present invention. The device provided by the invention can achieve the technical effect that pixels of different rows of the line scanning camera have different overall brightness values by adjusting the exposure time of each scanning in the prior art. The line scan camera of the present invention has the same exposure time each time, and is essentially different from the existing multiple exposure technology, so the term multiple exposure should not be construed as limiting the present invention.
The technical features of the above embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims (11)
1. A line scan camera multiple exposure method, comprising:
the light emitted by the object is sent to the line scanning camera after periodic brightness adjustment;
the periodic brightness adjustment corresponds to the scanning line frequency of the line scanning camera so that each line of images scanned by the line scanning camera corresponds to a set brightness value.
2. The multiple exposure method of claim 1, wherein the periodic brightness adjustment of the light emitted from the object comprises:
adjusting the intensity of light rays emitted by an object once every a period of time T;
the periodic brightness adjustment corresponds to a scan line frequency of a line scan camera, comprising:
the scanning line frequency of the line scanning camera is f, and the interval time between two exposures is 1/f; t=1/f is satisfied between T and 1/f.
3. The multiple exposure method of claim 2, wherein the periodically brightness-adjusted light emitted from the object is sent to the line-scan camera, and the method comprises:
the light emitted by the object is reflected and then sent to the line scanning camera, and the light emitted by the object is subjected to periodic brightness adjustment according to the periodic change of the reflectivity; or (b)
Light of the object enters the line scanning camera after being transmitted, and the light emitted by the object is subjected to periodic brightness adjustment according to the periodic change of the transmissivity; or (b)
Light emitted by the object is converted into polarized light, and the light emitted by the object is periodically adjusted in brightness according to the periodic change of the included angle between the vibration transmission direction of the polaroid and the polarization direction of the polarized light.
4. A multiple exposure apparatus for a line scan camera, comprising a line scan camera, further comprising:
the brightness adjusting device is used for periodically adjusting the brightness of the light rays emitted by the object and then sending the light rays to the line scanning camera; the period corresponds to a scanning line frequency of the line scanning camera, so that each line of images scanned by the line scanning camera corresponds to a set brightness value.
5. The line scan camera multiple exposure apparatus according to claim 4, wherein the brightness adjustment means comprises:
the regular polygon prism light reflecting device has a set reflectivity on each side surface; the position of the regular polygon prism light reflecting device is adapted to the position of the line scanning camera, so that when each side surface of the regular polygon prism light reflecting device rotates to a specific position, light rays emitted by an object can be reflected into the line scanning camera;
the power device is used for driving the regular polygon prism light reflecting device to rotate by taking the central line as an axis, and the rotating angular speed corresponds to the scanning line frequency of the line scanning camera so that each line of images scanned by the line scanning camera corresponds to a set brightness value.
6. The multiple exposure apparatus of claim 5, wherein if the line scanning camera performs N-shot, N is a positive integer greater than 2, the regular polygon mirror is a regular N-prism, and each side of the regular N-prism has a different reflectivity; at this time, the angular speed N of the power device driving the positive N prism to rotate is:
n=2πf/N
wherein f is the scanning line frequency of the line scanning camera.
7. The multiple exposure apparatus of claim 5, wherein if the line scanning camera performs N-shot, N and a are positive integers greater than 1, the positive polygon reflecting device is a positive a x N prism, each a of the sides of the positive a x N prism is a group, the reflectivities of the sides of different groups are different, and the reflectivities of a sides in the same group are the same; at this time, the angular speed N of the power device driving the positive a×n prism to rotate is:
n=2πf/N
wherein f is the scanning line frequency of the line scanning camera.
8. The line scan camera multiple exposure apparatus according to claim 5, wherein if the line scan camera performs N-shot, N and a are positive integers greater than 1, the positive polygon prism light reflection device is a positive a×n prism, each N of the sides of the positive a×n prism is a group, and the reflectivity of the sides in each group is R1, R2, and..rn; at this time, the angular speed N of the power device driving the positive a×n prism to rotate is:
n=2πf/(a×N)
wherein f is the scanning line frequency of the line scanning camera.
9. The line scan camera multiple exposure apparatus according to claim 4, wherein the brightness adjustment means comprises:
the reflectivity of the side surface of the cylindrical reflecting device changes periodically when the cylindrical reflecting device rotates along the central line; the position of the cylindrical reflecting device is adapted to the position of the line scanning camera, so that the side surface of the cylindrical reflecting device can reflect light rays emitted by an object into the line scanning camera in the rotating process of the cylindrical reflecting device;
the power device is used for driving the cylindrical reflecting device to rotate by taking the central line as an axis, and the rotating angular speed corresponds to the scanning line frequency of the line scanning camera so that each line of images scanned by the line scanning camera corresponds to a set brightness value.
10. The multiple exposure apparatus of claim 5, wherein before the line scan camera starts to collect image data, the following steps are further performed:
using a strip light source with set stripes or colors to be incident to the line scanning camera multiple exposure device;
the regular polygon prism light reflecting device rotates according to a set angular speed, a line scanning camera is started, and scanning is performed according to a set scanning line frequency f;
if the line scanning camera does not scan the image of the strip light source, the line scanning camera pauses scanning, and the line scanning camera is started again after an interval time t;
the interval time T is increased from T to T+1/f until the line scanning camera scans the image of the strip-shaped light source;
wherein T is any time.
11. A scanning device, comprising:
the platform is used for carrying the shot object and driving the shot object to move relative to the platform at a set speed;
the line scanning camera multiple exposure apparatus according to any one of claims 4 to 10, mounted on a stage for acquiring an image of a photographed object.
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