CN101763175A - Image processing method for displacement detection device and displacement detection device using the same - Google Patents

Abstract

An image processing method of a displacement detection device, the method comprising the steps of: acquiring a first image and solving the average brightness of the first image; judging whether the average brightness is between a first threshold value and a second threshold value; when the average brightness is between the first threshold and a second threshold, judging whether the attenuation value of the first image is deducted; updating the attenuation value and gain when the attenuation value has not been subtracted from the first image; subtracting the updated attenuation value from the first image and amplifying the attenuated first image by the gain; and comparing the attenuated and amplified first image with a reference image to obtain a displacement. The invention also provides a displacement detection device.

Description

Image processing method of displacement detection device and displacement detection device using the method

technical field

The invention relates to a displacement detection device, in particular to an image processing method of the displacement detection device and a displacement detection device using the method.

Background technique

When the brightness of the image sensed by the image sensing device in the displacement detection device such as a mouse is not in the preset range, it is usually necessary to adjust the exposure time of the displacement detection device to make the image sensing device in the displacement detection device An image with appropriate brightness can be acquired. For example, U.S. Patent No. 6,297,513 "Exposure Servo for Optical Navigation over Micro-textured Surface", which controls the exposure parameters according to the average brightness of the image captured by the displacement detection device, The control method of said patent includes the following steps: (a) changing the setting of exposure control parameters until the average brightness is 50% of the maximum possible value; (b) maintaining the current Otherwise, further change the exposure control parameters until the relevant data meet the requirements; (c) store the current average brightness; (d) use the current exposure control parameters to navigate (navigation) to obtain the displacement, wherein The steps of navigating include storing the latest average brightness and related data; and (e) adjusting exposure control parameters.

However, the above exposure control method is limited to changing the exposure control parameters to adjust the brightness of surface images with different reflection intensities when the average brightness of the image is not within the preset range. When the average brightness of the image meets the requirement, the image acquired by the displacement detection device is not further processed, so the dynamic processing capability of the reflective surface image cannot be effectively improved.

Based on the above reasons, it is indeed still necessary to propose another image processing method for the displacement detection device to increase the resolution of surface images with different reflection intensities, thereby increasing the dynamic processing capability of reflection surface images.

Contents of the invention

The invention provides an image processing method of a displacement detection device and a displacement detection device using the method. The displacement detection device uses an analog/digital unit combined with an amplifier to process the image acquired by the image sensor to increase the surface with different reflection intensities Image resolution, which in turn increases dynamic handling of reflective surface images.

The invention provides an image processing method of a displacement detection device and a displacement detection device using the method. The displacement detection device uses a nonlinear analog/digital function to process images acquired by an image sensor to increase surfaces with different reflection intensities Image resolution, which in turn increases dynamic handling of reflective surface images.

The invention provides an image processing method of a displacement detection device. The displacement detection device obtains an image according to exposure parameters. The image processing method includes the following steps: obtaining a first image and calculating the average brightness of the first image; judging Whether the average brightness is between the first threshold and the second threshold; when the average brightness is not between the first threshold and the second threshold, change the exposure parameters of the displacement detection device, and compare the The first image and the reference image are used to obtain the displacement; when the average brightness is between the first threshold and the second threshold, it is judged whether the attenuation value has been deducted from the first image; when the first image When the attenuation value has been deducted, compare the first image with the reference image to obtain the displacement; when the first image has not deducted the attenuation value, update the attenuation value and gain; from the first image subtracting the updated attenuation value and amplifying the attenuated first image with the gain; comparing the attenuated and amplified first image with a reference image to obtain a displacement; and calculating the displacement transmitted to the image display device.

In the image processing method of the displacement detection device of the present invention, the gain may be a linear gain or a nonlinear gain; the digitalization method may be linear or nonlinear.

According to another feature of the present invention, the present invention further provides a displacement detection device, which includes an image sensor, a digital/analog unit, an adding unit, an amplifier, an analog/digital unit, and a digital signal processor. An image sensor is used to acquire an image of the surface to form a simulated image, wherein the simulated image has an average brightness. A digital/analog unit is used to generate the attenuation value. The adding unit is coupled to the image sensor and the digital/analog unit, and is used for subtracting the attenuation value from the analog image. The amplifier amplifies the attenuated analog image. An analog/digital unit digitizes the attenuated and amplified analog image. The digital signal processor compares the digitized analog image with the reference image to form a displacement, and controls the digital/analog unit to generate the attenuation value.

According to another feature of the present invention, the present invention further provides a displacement detection device, which includes an image sensor, a digital/analog unit, an adding unit, a nonlinear analog/digital unit, and a digital signal processor. An image sensor is used to acquire an image of the surface to form a simulated image, wherein the simulated image has an average brightness. A digital/analog unit is used to generate the attenuation value. The adding unit is coupled to the image sensor and the digital/analog unit, and is used for subtracting the attenuation value from the analog image. The non-linear analog/digital unit digitizes the attenuated analog image. The digital signal processor compares the digitized analog image with the reference image to form a displacement, and controls the digital/analog unit to generate the attenuation value.

In the displacement detection device of the present invention, according to different applications, the analog/digital unit can be a linear or nonlinear analog/digital unit, and the amplifier can have linear and nonlinear gains to effectively increase the surface image resolution.

Description of drawings

FIG. 1 is a block diagram of a displacement detection device according to an embodiment of the present invention.

Fig. 2 is a block diagram of an image processing method according to an embodiment of the present invention, wherein (a) is a schematic diagram of a one-dimensional distribution of image brightness acquired by an image sensor in Fig. 2; (b) is a one-dimensional distribution of image brightness after attenuation in Fig. 2 Schematic diagram; and (c) is a schematic diagram of the one-dimensional distribution of image brightness after attenuation and amplification in FIG. 2 .

Fig. 3 is another block diagram of an image processing method according to an embodiment of the present invention, wherein (a) is a schematic diagram of a one-dimensional distribution of image brightness obtained by the image sensor in Fig. 3; (b) is a schematic diagram of the attenuated image brightness in Fig. 3 and (c) is a schematic diagram of the one-dimensional distribution of image brightness after passing through the nonlinear analog/digital unit in FIG. 3 .

4 is a graph showing a relationship between a digital value and an analog voltage, wherein (a) is a graph showing a linear relationship between a digital value and an analog voltage; and (b) is a graph showing a nonlinear relationship between a digital value and an analog voltage.

FIG. 5 is a flowchart of an image processing method of the displacement detection device according to an embodiment of the present invention.

Explanation of main component symbols

1: Displacement detection device 10: Light source

11: Image sensor 12: Image processing unit

121: Digital/Analog Unit 122: Amplifier

123: Analog/Digital Unit 124: Digital Signal Processor

125: Transmission interface unit ADD: Addition unit

D _x : Average luminance A _x : Luminance characteristic change value

DAC: attenuation value g: gain

110～170: steps

Detailed ways

In order to make the above and other objects, features, and advantages of the present invention more apparent, the embodiments of the present invention are listed below and described in detail in conjunction with the accompanying drawings.

Please refer to FIG. 1 . FIG. 1 shows a displacement detection device 1 according to an embodiment of the present invention. The displacement detection device 1 includes a light source 10 , an image sensor 11 and an image processing unit 12 . Examples of light sources 10 include light emitting diodes or laser diodes for illuminating a surface S, such as a table top or a mouse pad surface. Embodiments of the image sensor 11 include a charge-coupled device (CCD) image sensor or a complementary metal-oxide-semiconductor (CMOS) image sensor for sensing reflected light from the surface S to generate a two-dimensional analog image, the two-dimensional analog The image is an image composed of brightness values of each pixel of the image sensor 11 . The image processing unit 12 is coupled to the light source 10 and the image sensor 11 for processing the image captured by the image sensor 11 and controlling the light emitting mechanism of the light source 10 , such as light emitting frequency and brightness. In the present invention, the image resolution of the surface S is effectively increased by using the image processing unit 12 to further process the image captured by the image sensor 11 .

The image processing unit 12 includes a digital/analog unit (DAC) 121, an amplifier 122, an analog/digital unit (ADC) 123, a digital signal processor (Digital Signal Processor, DSP) 124 and a transmission interface unit 125. The digital/analog unit 121 receives the digital signal from the digital signal processor 124 to generate a DC attenuation value (referred to as DAC in this specification), and the attenuation value is used to attenuate the brightness of the two-dimensional analog image acquired by the image sensor 11 value, so as to prevent the brightness of the pixel from exceeding a preset range (for example, 0-255 grayscale values) in subsequent amplification and digitization steps. The amplifier 122 is used to amplify the two-dimensional analog image after the attenuation value has been deducted (after attenuation). omitted. The analog/digital unit 123 can be a linear or non-linear analog/digital unit for converting the two-dimensional analog image (with or without subtracting the attenuation value and amplifying) acquired by the image sensor 11 into a digital value , such as a grayscale value within the range of 0 to 255; the digital signal processor 124 receives the grayscale value of each pixel from the analog/digital unit 123 to form a two-dimensional digital image and obtain the displacement, for example, according to The correlation between digital images at different times is used to obtain the displacement. In addition, the digital signal processor 124 controls the digital/analog unit 121 to generate an attenuation value, which is determined according to the image processed by the digital signal processor 124 . The transmission interface unit 125 wirelessly or wiredly transmits the displacement obtained by the digital signal processor 124 to an image display device (not shown) for relative control.

Please refer to (a) to (c) in FIG. 2 , which show a block diagram of an image processing method according to an embodiment of the present invention. (a) to (c) in FIG. 2 show a schematic diagram of one-dimensional distribution of image brightness in different processing stages of an embodiment. First, the image sensor 11 acquires a two-dimensional analog image of the surface S, wherein (a) in FIG. 2 indicates that the brightness value (D _x +A _x ) of a column of pixels in the two-dimensional analog image varies with The variation of the lateral distance of the sensing array (not shown) of the sensor 11, _Dx represents the average luminance and _Ax represents the luminance characteristic change value. The luminance value (D _x +A _x ) is subtracted from the attenuation value by the addition unit ADD (which can also be realized by a subtractor) to become (D _x -DAC)+A _x and is shown in (b) in FIG. 2 , The size of the DAC is determined by the digital signal processor 124 . The amplifier 122 has a gain g, and then amplifies the brightness value (D _x −DAC)+A _x of a column of pixels of the attenuated two-dimensional analog image with the gain g to become g×(D _x −DAC)+g× A _x is shown in (c) in Fig. 2, where g×A _x is the wavelet signal of brightness change. Finally, the analog/digital unit 123 converts the brightness distribution of a column of pixels of the attenuated and enlarged two-dimensional analog image into digital values (digitized) in a linear or non-linear manner and transmits it to the digital signal processor 124. It must be understood that the purpose of subtracting the DAC from the luminance value (D _x +A _x ) is to avoid the situation that the luminance value is too large in the subsequent amplification and digitization steps; comparing (b) and (c) in Figure 2, we can see that, After the luminance value of a column of pixels in the two-dimensional analog image is amplified, the peak-and-peak value of the luminance characteristic change value A _x increases significantly, which helps to increase the resolution of the digitized image. In addition, the gain of the amplifier 122 can be linear or non-linear. It can be understood that although the brightness of a column of pixels of the two-dimensional analog image is used for illustration, in fact all pixels of the two-dimensional analog image are further processed by the image processing method.

Please refer to (a) and (b) shown in Figure 4, (a) in Figure 4 shows when the amplifier 122 or the analog/digital unit 123 is linear, the relationship between the digital value and the analog voltage in the digitization stage; Figure 4 (b) in (b) shows the relationship between the digital value and the analog voltage in the digitization stage when the amplifier 122 or the analog/digital unit 123 is non-linear. Comparing (a) and (b) in Figure 4 shows that in the steps of nonlinear amplification and digitization, a higher resolution can be obtained for the same analog voltage change relative to a larger digital value change.

Please refer to (a) to (c) in FIG. 3 , which show another block diagram of the image processing method according to the embodiment of the present invention. The difference between FIG. 3 and FIG. 2 is that only one nonlinear analog/digital unit 123 is used instead of the amplifier 122 in FIG. 3 . Likewise, the image sensor 11 first acquires a two-dimensional simulated image of the surface S, as shown in (a) in FIG. 3 . Then the luminance value (D _x +A _x ) of a column of pixels in the two-dimensional analog image is subtracted by the addition unit ADD and the attenuation value DAC to become (D _x -DAC)+A _x and is shown in (b in FIG. 3 ). Finally, the nonlinear analog/digital unit 123 digitizes the two-dimensional analog image captured by the image sensor 11 in a nonlinear manner, as shown in (c) in FIG. 3 , and sends it to the digital signal processing device 124. The digital signal processor 124 determines the attenuation value and gain to be deducted by the image sensor 11 when acquiring the next image according to the currently processed image, and notifies the digital/analog unit 121 to generate the attenuation value.

Please refer to FIG. 5 , which shows a flow chart of an image processing method of the displacement detection device according to an embodiment of the present invention. The image processing method comprises the following steps: utilizing an image sensor to acquire a first image, the first image has an average brightness (step 110); judging whether the average brightness converges between a first threshold and a second threshold (step 120 ); if not, change the exposure parameters (step 130) and compare the first image with the reference image to output the displacement (step 170), then reacquire the next image; if the average brightness converges to the first Between one and the second threshold, it is judged whether the attenuation value (step 140) has been deducted from the first image, if so, step 170 is performed, if not, the attenuation value and gain are updated (step 150); value and amplify the attenuated first image with the gain (step 160); and compare the attenuated and amplified first image with a reference image to output a displacement (step 170), and finally reacquire the image to Repeat the above steps.

Referring again to FIGS. 1 , 2 , 3 and 5 , the detailed implementation of the image processing method of the displacement detection device according to the embodiment of the present invention will be described below. First, use the image sensor 11 to acquire a first image of the surface S, the first image has an average brightness (for example, D _x ), wherein the brightness distribution sensed by a row of pixels of the sensing array of the image sensor 11 It may be shown in (a) in FIG. 2 (step 110). Then the image processing unit 12 judges whether the average brightness is between two thresholds (for example, in the 256 gray scale range, the first threshold can be 64, and the second threshold can be 128, but not limited thereto) (step 120 ). When the average brightness is not between the two preset thresholds, the image processing unit 12 changes the exposure parameters, such as changing the luminous intensity and/or frequency of the light source 10, so that the image captured by the image sensor 11 The average brightness of the next image can be between two preset thresholds (step 130); then the image processing unit 12 compares the first image and the reference image to obtain the amount of displacement (step 170), and and transmitted to the transmission interface unit 125 for transmission, wherein the reference image may be, for example, a previous image of the first image captured by the image sensor 11 . When the average brightness is between two preset thresholds, the image processing unit 12 judges whether the attenuation value has been deducted from the first image (as shown in FIGS. 2 and 3 ) (step 140), if the attenuation has been deducted value, then the image processing unit 12 directly converts the first image into a digital image and compares the digitized first image with the reference image to obtain the displacement (step 170), and the displacement will be obtained by the The transmission interface unit 125 transmits; if the first image has not deducted the attenuation value, the image processing unit 12 judges the current attenuation value and gain according to the first image, and updates the obtained value based on the previous image. The attenuation value and gain of (step 150), wherein the gain can be a linear gain or a nonlinear gain. Then subtract the attenuation value and amplify the attenuated first image with the gain (as shown in Figure 2 and Figure 3) (step 160), and use the analog/digital unit to digitize the image, wherein the digitization method can be be linear or non-linear; when the analog/digital unit is a non-linear analog/digital unit, the step of updating the gain in step 150 and step 160 can be omitted. Finally, the image processing unit 12 compares the digitized first image with the reference image to obtain the displacement (step 170), and transmits it through the transmission interface unit 125, wherein the displacement can be obtained, for example, through Comparing the correlation between the first image and the reference image to obtain. Finally, the image sensor 11 reacquires a new image and repeats steps 110-170.

To sum up, the exposure control method of the commonly used displacement detection device only adjusts the exposure control parameters when the average brightness of the image is not in the preset range, and cannot effectively improve the dynamic processing capability of the reflective surface image. The present invention further processes the images acquired by the image sensor (as shown in Fig. 2 and Fig. 3 ) in a linear or non-linear manner to increase the peak-to-peak value of the image brightness feature change, which has the ability to increase the surface image resolution of different reflection intensities and increase the reflection The effect of dynamic processing capabilities of surface images.

Although the present invention has been disclosed with the aforementioned preferred embodiments, it is not intended to limit the present invention, and any person of ordinary skill in the technical field to which the present invention belongs can make various corrections and modifications without departing from the spirit and scope of the present invention. Revise. Therefore, the protection scope of the present invention should be determined by the scope defined by the appended claims.

Claims (16)

1. An image processing method of a displacement detection device, the displacement detection device obtains an image according to exposure parameters, and the image processing method comprises the following steps: Acquiring a first image and calculating the average brightness of the first image; judging whether the average brightness is between a first threshold and a second threshold; When the average brightness is between the first threshold and the second threshold, judging whether the attenuation value has been deducted from the first image; When the attenuation value has not been deducted from the first image, updating the attenuation value and the gain; subtracting the updated attenuation value from the first image and amplifying the attenuated first image by the gain; and Comparing the attenuated and amplified first image with the reference image to obtain the displacement. 2. The image processing method according to claim 1, the image processing method further comprising the following steps: changing the exposure parameter of the displacement detection device when the average brightness is not between the first threshold and a second threshold; and Comparing the first image with the reference image to obtain a displacement. 3. The image processing method according to claim 1, further comprising the step of: when the attenuation value has been deducted from the first image, comparing the first image with the reference image to find get displacement. 4. The image processing method according to claim 1, wherein the reference image is a previous image of the first image acquired by the displacement detection device. 5. The image processing method according to claim 1, wherein in the range of 256 gray scales, the first threshold is 64 and the second threshold is 128. 6. The image processing method according to claim 1, further comprising the step of: transmitting the displacement to an image display device. 7. The image processing method according to claim 1, wherein in the step of amplifying the attenuated first image with the gain, the gain is a linear gain or a nonlinear gain. 8. The image processing method according to claim 1, wherein before comparing the attenuated and enlarged first image with the reference image, the following step is further included: the attenuated and enlarged first image Digitizing. 9. The image processing method according to claim 8, wherein the digitalization method can be linear or non-linear. 10. A displacement detection device, the displacement detection device comprising: an image sensor for acquiring an image of the surface to form a simulated image, wherein the simulated image has an average brightness; Digital/analog unit for generating attenuation values; an addition unit, coupled to the image sensor and the digital/analog unit, for subtracting the attenuation value from the analog image; Amplifier to amplify the attenuated analog image; an analog/digital unit digitizing the attenuated and amplified analog image; and The digital signal processor compares the digitized analog image with a reference image to form a displacement, and controls the digital/analog unit to generate the attenuation value. 11. The displacement detection device according to claim 10, further comprising a transmission interface unit for transmitting the displacement amount to an image display device. 12. The displacement detection device according to claim 10, wherein the amplifier is a linear amplifier or a nonlinear amplifier. 13. The displacement detection device according to claim 10, wherein the analog/digital unit is a linear or non-linear analog/digital unit. 14. The displacement detection device according to claim 10, further comprising a light source for illuminating the surface. 15. A displacement detection device, the displacement detection device comprising: an image sensor for acquiring an image of the surface to form a simulated image, wherein the simulated image has an average brightness; Digital/analog unit for generating attenuation values; an addition unit, coupled to the image sensor and the digital/analog unit, for subtracting the attenuation value from the analog image; a non-linear analog/digital unit to digitize the attenuated analog image; and A digital signal processor compares the digitized analog image with a reference image to form a displacement, and controls the digital/analog unit to generate the attenuation value. 16. The displacement detection device according to claim 15, further comprising a transmission interface unit for transmitting the displacement to an image display device.

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