TW202118275A - Residual image eliminating method for optical image and electronic device using the same pre-storing a residual image decay coefficient lambda or a decay curve comparison table in a memory unit - Google Patents

Abstract

Disclosed is a residual image eliminating method for an optical image, which includes: pre-storing a residual image decay coefficient lambda or a decay curve comparison table in a memory unit, wherein 0 < lambda < 1, and the decay curve comparison table includes a plurality of groups of data composed of average values of anterior-frame images and average values of posterior-frame images; performing continuous two image acquisition operation on an acquired image to obtain a first-frame image and a second-frame image; and performing a residual image elimination calculation on the first-frame image and the second-frame image according to the residual image decay coefficient lambda or the decay curve comparison table to generate an output image.

Description

Optical image residual image elimination method and electronic device using the same

The present invention relates to an optical image acquisition method, especially an optical image residual image elimination method.

Optical image collection is a kind of imaging that uses a light source (visible light, invisible light or X-ray) to irradiate the collection object to generate a reflected light signal or a transmitted light signal, which is then converted into an electrical signal by an image sensor (CMOS or CCD) Information collection method. For example, the under-screen optical fingerprint collection requires a screen (OLED or TFT-LCD) to provide a light source, and an image sensor is placed under the screen to receive the reflected light signal to obtain the fingerprint signal. In order to expand the image acquisition area or increase the image quality, it is generally necessary to continuously acquire multiple images.

However, due to the internal equivalent capacitance of the image sensor (CMOS or CCD), image afterimages may be generated when the driving circuit is continuously collecting images. Please refer to FIG. 1, which is a schematic diagram of the comparison between the images collected by the image sensor when there is no afterimage and when there is afterimage. As shown in Figure 1, the first frame of image 10a, the second frame of image 11a, and the third frame of image 12a show A, B, and C, respectively. In addition to displaying A, B, and C on the first frame image 10b, the second frame image 11b, and the third frame image 12b, the second frame image 11b also retains the afterimage A from the last acquisition, and The third frame of image 12b also retains the afterimage B collected last time and the afterimage A collected last time.

In order to solve the above-mentioned problems, a novel method for removing residual images of optical images is urgently needed in the art.

An object of the present invention is to provide a method for removing the residual image of an optical image, which can effectively remove the residual image of the image without adding additional circuit operations.

Another object of the present invention is to provide an electronic device, which can effectively eliminate the residual image of the image captured by the optical image capture device without adding additional circuit operations.

In order to achieve the aforementioned purpose, a method for removing the residual image of an optical image is proposed, which is implemented on an optical image acquisition device and includes the following steps:

An afterimage attenuation coefficient λ or an attenuation curve comparison table is pre-stored in a memory unit of the optical image acquisition device, where 0＜λ＜1, and the attenuation curve comparison table contains a complex array of images from previous frames Data composed of the average value and the average value of the subsequent frame images;

Perform two consecutive image capture operations on a captured object to obtain a first frame image and a second frame image; and

Perform an afterimage elimination calculation on the first frame image and the second frame image to generate an output image, where the afterimage elimination calculation is expressed as C = C ₂ -λ*C ₁ , and C represents the output The grayscale value of each pixel of the image, C ₂ represents the grayscale value of each pixel of the second frame of image, and C ₁ represents the grayscale value of each pixel of the first frame of image; or the residual image elimination calculation Expressed as C = C ₂ -Map(C ₁ ), C represents the grayscale value of each pixel of the output image, C ₂ represents the grayscale value of each pixel of the second frame of image, and Map(C ₁ ) represents by the attenuation curve table for pixel gray level value within one interpolation calculation to the generated each pixel grayscale value C ₁ of the first frame image.

In a possible embodiment, the optical image acquisition device has a CMOS image sensor or a CCD image sensor.

In an embodiment, the residual image attenuation coefficient λ or the attenuation curve comparison table is obtained through a pre-measurement program, and the pre-measurement program includes:

Place the optical image acquisition device in a dark box and be illuminated by a light source for a period of time;

Turn off the light source, and then enable the optical image acquisition device to continuously capture a plurality of frames of images; and

Generating at least two pixel gray scale average values according to at least one group of adjacent two frame images of the plurality of frame images, and calculating the residual image attenuation coefficient λ according to the at least two pixel gray scale average values; Or generate n-1 average values of the subsequent frame images according to the average value of the pixel gray scales of the second to nth frames in the plurality of frames of images, and according to the average value of the images in the plurality of frames The average value of the pixel gray scales of the first to n-1th frame images produces the average value of n-1 images of the previous frame, and the sum of the average values of n-1 images of the subsequent frame The average value of n-1 the previous frame images generates the attenuation curve comparison table, and n is an integer greater than 2.

In a possible embodiment, the collection object may be a fingerprint or a palm.

In a possible embodiment, the optical image acquisition device may use visible light or invisible light to perform the image acquisition operation.

In order to achieve the foregoing objective, the present invention further provides an electronic device, which includes a central processing unit and a touch screen, wherein the touch screen has the aforementioned optical image acquisition device to realize the optical image Afterimage elimination method, and the central processing unit is used to communicate with the touch screen.

In possible embodiments, the touch screen may be an optical touch screen or a capacitive touch screen.

In possible embodiments, the touch screen may include a liquid crystal display array, an organic light emitting diode display array, a micro light emitting diode display array, or a quantum dot light emitting diode display array.

In possible embodiments, the electronic device can be a smart phone or a portable computer.

The principle of the present invention is that the internal equivalent capacitance C and equivalent resistance R of the image sensor (CMOS or CCD) form an RC equivalent circuit. When an optical image acquisition device performs continuous image acquisition operations on the acquisition object, provided captured image n-th frame is a _n, fingerprint signal of the n-th frame is S _n, the equivalent capacitance C due to the voltage can not change suddenly, resulting in the n-1 a captured image frame _n-1 is not completely empty In particular, when the equivalent circuit is a first-order RC circuit, the voltage decays exponentially, that is, the attenuation ratio is constant at a certain value. In general formula is expressed _{as: s n = a n - f} (a n-1), wherein, f is an attenuation function.

That is to say, after obtaining the attenuation function f, the present invention can calculate the residual image value f(a _n-1 ) of the n-1th frame image on the nth frame image, and then according to the nth frame image The difference between the image (a _n ) and the residual image value f (an _-1 ) is the signal (s _n ) of the nth frame.

In an embodiment, the residual image value f(a _n-1 )=λa _n-1 , λ is the residual image attenuation coefficient, 0<λ<1.

In another embodiment, the residual image value f(a _n-1 ) = Map(a _n-1 ), which means that it is based on an attenuation curve comparison table on the n-1th frame of the acquired image a _n-1 Generated by an interpolation calculation.

The attenuation function f can be pre-stored in a memory unit, and it can be obtained according to a pre-measurement program. The pre-measurement program (please refer to Figure 2a and Figure 2b together) includes:

(1) Place an optical image acquisition device 22 in a dark box 20 and be illuminated by a light source 21 for a period of time;

(2) Turn off the light source 21, and then enable the optical image capture device 22 to capture multiple frames of images; and

(3) Generate at least two pixel grayscale average values according to at least one group of adjacent two frame images of the plurality of frame images, and calculate the residual image attenuation based on the at least two pixel grayscale average values Coefficient λ; or according to the average value of the pixel gray scales of the second to nth frames in the plurality of frames of images, n-1 average values of the subsequent frame images are generated, according to the plurality of frames of images The pixel gray scale average value of the first to n-1th frame images produces the average value of n-1 previous frame images, and the average value of n-1 subsequent frame images and n -1 The average value of the previous frame images generates the attenuation curve comparison table, and n is an integer greater than 2.

Please refer to Fig. 3a and Fig. 3b together, in which Fig. 3a shows the change of the average pixel gray scale of 15 frames of image; and Fig. 3b shows the pixel gray of the previous 8 frames of image shown in Fig. 3a The change graph of the residual image attenuation coefficient λ produced by the ratio of any two adjacent average values of the order average value. It can be seen from Figure 3b that λ is approximately equal to 0.6.

In addition, please refer to FIGS. 4a and 4b together. Among them, FIG. 4a shows an embodiment of the attenuation curve, which has 19 two-dimensional data points, and each of the two-dimensional data points corresponds to a previous The average value of the frame image and the average value of the subsequent frame image, that is, the 19 two-dimensional data points are composed of the pixels of the second to the twentieth frame of the 20 frames of images The gray scale average value and the pixel gray scale average value of the first to 19th frames of the 20 frames of images; and FIG. 4b is the average value of an input image as the previous frame image The average value of the image, and the attenuation curve shown in FIG. 4a corresponds to a schematic diagram of the average value of the subsequent frame image.

Based on the above description, the present invention proposes a method for removing the residual image of an optical image. Please refer to FIG. 5, which shows a flow chart of an embodiment of the method for removing the residual image of an optical image of the present invention. As shown in FIG. 5, the method for eliminating the residual image of an optical image of the present invention is implemented on an optical image acquisition device, wherein the optical image acquisition device has a CMOS (complementary metal-oxide-semiconductor; complementary metal-oxide-semiconductor; Oxygen half) image sensor or a CCD (charge coupled device; charge coupled device) image sensor, and the method includes the following steps: prestore a residual image attenuation coefficient in a memory unit of the optical image device λ or an attenuation curve comparison table, where 0＜λ＜1, and the attenuation curve comparison table contains a complex array of data consisting of the average value of the previous frame image and the average value of the subsequent frame image (step a1 ); Perform two consecutive image capture operations on a captured object to obtain a first frame image and a second frame image (step b1); and perform a second frame image on the first frame image and the second frame image Afterimage elimination calculation to generate an output image, where the afterimage elimination calculation is expressed as C = C ₂ -λ*C ₁ , C represents the grayscale value of each pixel of the output image, and C ₂ represents the second The grayscale value of each pixel of the frame image, C ₁ represents the grayscale value of each pixel of the first frame image; or the residual image elimination calculation is expressed as C = C ₂ -Map(C ₁ ), and C represents the The grayscale value of each pixel of the output image, C ₂ represents the grayscale value of each pixel of the second frame of image, and Map(C ₁ ) represents each painting of the first frame of image according to the attenuation curve comparison table. C ₁ pixel gray level value for the gray scale pixel value (step c1) interpolation calculation within a generated. In addition, in the above method, the collection object can be a fingerprint or a palm print, and the optical image collection device can use visible light or invisible light to perform the image collection operation.

Based on the above description, the present invention further provides an electronic device. Please refer to FIG. 6, which is a block diagram of an embodiment of the electronic device of the present invention. As shown in FIG. 6, an electronic device 100 includes a central processing unit 110 and a touch screen 120. The touch screen 120 may have a liquid crystal display array, an organic light emitting diode display array, and a micro light emitting diode. Volume display array or a quantum dot light emitting diode display array, and it has an optical image acquisition device 120a.

The central processing unit 110 is used to communicate with the touch screen 120 to provide a touch display function.

The optical image acquisition device 120a has a CMOS image sensor or a CCD image sensor, and is used to perform the aforementioned optical image afterimage elimination method.

In addition, in possible embodiments, the electronic device 100 may be a smart phone or a portable computer.

According to the above description, the present invention can provide the following advantages:

1. The optical image afterimage elimination method of the present invention can effectively eliminate image afterimage without adding additional circuit operations.

2. The electronic device of the present invention can effectively eliminate the residual image of the image collected by the optical image collecting device without adding additional circuit operations.

The disclosure of the present invention is one of the preferred embodiments. Any partial change or modification that is derived from the technical idea of the present invention and can be easily deduced by those skilled in the art does not deviate from the scope of the patent right of the present invention.

In summary, regardless of the purpose, means and effects of this case, it is shown that it is very different from the conventional technology, and its first invention is suitable for practicality, and it does meet the patent requirements of the invention. I implore the examiner to observe it and grant the patent as soon as possible. Society is for the best prayer.

10a: the first frame without residual image 11a: the second frame without residual image 12a: the third frame without residual image 10b: the first frame image 11b: the second frame image 12b: the third frame image Image 20: Dark box 21: Light source 22: Optical image capture device 100: Electronic device 110: Central processing unit 120: Touch screen 120a: Optical image capture device Step a1: In one of the memory unit of the optical image capture device Prestore a residual image attenuation coefficient λ or an attenuation curve comparison table, where 0＜λ＜1, and the attenuation curve comparison table contains a complex array consisting of the average value of the previous frame image and the average value of the subsequent frame image. Composition data Step b1: Perform two consecutive image acquisition operations on a collection object to obtain a first frame image and a second frame image Step c1: Perform the first frame image and the second frame image An afterimage elimination calculation to generate an output image, where the afterimage elimination calculation is expressed as C = C ₂ -λ*C ₁ , C represents the grayscale value of each pixel of the output image, and C ₂ represents the first The grayscale value of each pixel of the two frames of image, C ₁ represents the grayscale value of each pixel of the first frame of image; or the residual image elimination calculation is expressed as C = C ₂ -Map(C ₁ ), C represents The grayscale value of each pixel of the output image, C ₂ represents the grayscale value of each pixel of the second frame of image, and Map(C ₁ ) represents each of the first frame of image according to the attenuation curve comparison table. Pixel gray level value C ₁ Pixel gray level value generated by an interpolation calculation

Figure 1 is a schematic diagram of the comparison between the images collected by the image sensor when there is no afterimage and when there is afterimage. Figure 2a is a schematic diagram of placing an optical image capture device in a dark box and subjecting it to a light source for a period of time. Fig. 2b is a schematic diagram of turning off the light source shown in Fig. 2a, and then allowing the optical image acquisition device to capture multiple frames of images to calculate an afterimage attenuation coefficient or an attenuation curve. FIG. 3a shows the change of the average value of the pixel gray scale of 15 frames of images. FIG. 3b shows the change diagram of the residual image attenuation coefficient produced by the ratio of any two adjacent average values of the pixel grayscale average values of the previous 8 frames of the image shown in FIG. 3a. Fig. 4a is a schematic diagram of an embodiment of the attenuation curve adopted in the present invention. FIG. 4b is a schematic diagram of taking the average value of an input image as the average value of a previous frame image, and the attenuation curve shown in FIG. 4a corresponds to the average value of a subsequent frame image. FIG. 5 shows a flowchart of an embodiment of the method for removing residual image of an optical image according to the present invention. FIG. 6 is a block diagram of an embodiment of the electronic device of the present invention.

Step a1: Prestore a residual image attenuation coefficient λ or an attenuation curve comparison table in a memory unit of the optical image acquisition device, where 0<λ<1, and the attenuation curve comparison table contains a complex array of data from previous frames Data composed of the average value of the image and the average value of the subsequent frame image

Step b1: Perform two consecutive image capture operations on a captured object to obtain a first frame image and a second frame image

Step c1: Perform an afterimage elimination calculation on the first frame image and the second frame image to generate an output image, where the afterimage elimination calculation is expressed as C=C ₂ -λ *C ₁ , C Represents the grayscale value of each pixel of the output image, C ₂ represents the grayscale value of each pixel of the second frame of image, and C ₁ represents the grayscale value of each pixel of the first frame of image; or the residual The shadow elimination calculation is expressed as C=C ₂ -Map(C ₁ ), C represents the grayscale value of each pixel of the output image, C ₂ represents the grayscale value of each pixel of the second frame of image, Map(C ₁ ) Represents the pixel gray scale value generated by performing an interpolation calculation _{on each pixel gray scale value C 1 of the} first frame of image according to the attenuation curve comparison table

Claims (9)

An optical image residual image elimination method is implemented on an optical image acquisition device, which includes the following steps: Prestore a residual image attenuation coefficient λ or an attenuation curve comparison in a memory unit of the optical image acquisition device Table, where 0＜λ＜1, and the attenuation curve comparison table contains a complex array of data consisting of the average value of the previous frame image and the average value of the subsequent frame image; two consecutive operations on a collection object Image acquisition operation to obtain a first frame image and a second frame image; and performing an afterimage elimination calculation on the first frame image and the second frame image to generate an output image, wherein the The afterimage elimination calculation is expressed as C = C ₂ -λ*C ₁ , C represents the grayscale value of each pixel of the output image, C ₂ represents the grayscale value of each pixel of the second frame image, and C ₁ represents The grayscale value of each pixel of the first frame of image; or the afterimage elimination calculation is expressed as C = C ₂ -Map(C ₁ ), C represents the grayscale value of each pixel of the output image, and C ₂ represents The grayscale value of each pixel of the second frame of image, Map(C ₁ ) represents the result of an interpolation calculation _{for each pixel grayscale value C 1 of the} first frame of image according to the attenuation curve comparison table Pixel grayscale value. According to the method for removing the residual image of an optical image as described in item 1 of the scope of patent application, the optical image acquisition device has a CMOS image sensor or a CCD image sensor. As described in the first item of the scope of patent application, the residual image elimination method of an optical image, wherein the residual image attenuation coefficient λ or the attenuation curve comparison table is obtained through a pre-measurement program, and the pre-measurement program includes: Place the optical image acquisition device in a dark box and be illuminated by a light source for a period of time; Turn off the light source, and then enable the optical image capture device to capture a plurality of frames of images; and Generating at least two pixel gray scale average values according to at least one group of adjacent two frame images of the plurality of frame images, and calculating the residual image attenuation coefficient λ according to the at least two pixel gray scale average values; Or generate n-1 average values of the subsequent frame images according to the average value of the pixel gray scales of the second to nth frames in the plurality of frames of images, and according to the average value of the images in the plurality of frames The average value of the pixel gray scales of the first to n-1th frame images produces the average value of n-1 images of the previous frame, and the sum of the average values of n-1 images of the subsequent frame The average value of n-1 the previous frame images generates the attenuation curve comparison table, and n is an integer greater than 2. According to the method for removing the residual image of an optical image as described in item 1 of the scope of patent application, the collection object is a fingerprint or a palm print. According to the method for removing the residual image of an optical image as described in item 1 of the scope of patent application, the optical image acquisition device uses visible light or invisible light to perform the image acquisition operation. An electronic device, comprising a central processing unit and a touch screen, wherein the touch screen has the optical image acquisition device as described in any one of the 1 to 5 scope of the patent application to realize the optical image Image afterimage elimination method, and the central processing unit is used to communicate with the touch screen. For the electronic device described in item 6 of the scope of patent application, the touch screen is an optical touch screen or a capacitive touch screen. The electronic device described in item 6 of the scope of patent application, wherein the touch screen includes a liquid crystal display array, an organic light emitting diode display array, a micro light emitting diode display array, and a quantum dot light emitting diode A display array selected by the group consisting of display arrays. For example, the electronic device described in item 6 of the scope of patent application is a smart phone or a portable computer.

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