CN1234250C - Scanner RGB signal for color space conversion circuit - Google Patents

Abstract

A circuit for converting RGB signal of scanner into color space includes several sampling, amplifying and shifting devices, which can respectively sample, amplify and level compensate an R charge signal, a G charge signal and a B charge signal to obtain an R analog signal, a G analog signal and a B analog signal; a gain adder for multiplying the R, G and B analog signals by corresponding weighted gain values, respectively, and adding the results to obtain an added analog signal; a multiplexer for selecting one of the R analog signal, the G analog signal, the B analog signal and the addition analog signal for output.

Description

Scanner RGB signal for color space conversion circuit

technical field

The present invention relates to a RGB signal processing circuit of a scanner, in particular to a circuit for color space conversion of RGB signals of a scanner.

Background technique

The light sensing device used in a general color scanner is a color charge coupled device (Charge Couple Device, CCD) or a contact image sensor (Contact ImageSensor, CIS), which is composed of many sensing units (Sensor Cell) Composed, it can sense the light intensity of the three primary colors of R, G, and B (Red, Green, and Blue), and send the sensing results to the R charge signal, G charge signal, and B charge signal respectively. The obtained R charge signal, G charge signal, and B charge signal still need to be processed before they can be used as input signals of subsequent circuits. As shown in the partial circuit diagram of the signal processing of the known scanner shown in Fig. 1, the R charge signal, the G charge signal and the B charge signal are sent to the sampling amplification displacement device (Sampling-Amplified-Offset Device) 102, 104, 106 respectively, and the sampling The amplification and displacement devices 102 , 104 , and 106 respectively sample, amplify, and level-compensate the R charge signal, the G charge signal, and the B charge signal to generate R analog signals, G analog signals, and B analog signals. Next, the multiplexer 108 sends the R analog signal, the G analog signal, and the B analog signal to the analog-to-digital converter 110, and the analog-to-digital converter 110 converts the received analog signal into a digital signal, and converts the digital signal sent to the subsequent circuit.

When the color scanning result is to be scanned and output in grayscale, the general practice is to select one of the analog signals R, G, and B to output as a grayscale analog signal, as shown in Figure 1. When the multiplexer 108 selects the R analog signal as the grayscale analog signal to output to the ADC 110 , the G analog signal and the B analog signal are no longer output to the ADC 110 via the multiplexer 108 .

The above method is to use the brightness of the R analog signal to determine the degree of grayscale. When the brightness of the R analog signal of a pixel (Pixel) at a certain point is higher, the color of the pixel at this point is closer to white; The color of the pixel is closer to black. However, when the brightness of the R analog signal of the pixel is low, it does not mean that the brightness of the G analog signal and the B analog signal of the pixel is also low. If the brightness of one of the analog signals G and B is high, Then the grayscale displayed by the color of the pixel is incorrect.

The image under the RGB color model is composed of three independent images, and each primary color corresponds to a plane. When these three image planes are sent to the RGB display, the three images are combined to form a color image. So when the image itself is represented by three color planes, it makes sense to use the RGB model for image processing. On the other hand, most color cameras used to acquire digital images use the RGB method, so it is an important model in image processing.

Another important color model is the y, u, v model. The advantage of using the yuv model is that the brightness y and color-related u and v can be separated separately. Furthermore, the RGB color model can be converted to other models, such as the stimulus values X, Y, and Z of the theoretical three primary colors, the Adams chromaticity-brightness space, and the CMY (Cyan Magenta Yellow) color model, etc. Here, the conversion from the RGB color model to the yuv color model is taken as an example for the following description.

Applying the RGB color model to the conversion of the yuv color model generally converts the R analog signal, the G analog signal, and the B analog signal into digital signals, and then converts these digital signals into yuv colors by software (such as a conversion program) Each parameter value of the space. Using software to convert RGB color model signals and yuv color model signals has the disadvantage that it takes too long to convert using software.

Contents of the invention

The present invention provides a color space conversion circuit for the RGB signal of a scanner, which can reflect the response of each pixel to the gray scale more accurately when applied to grayscale scanning, and when applied to RGB color model signals for different The conversion of the color model uses hardware to perform the conversion work, which can shorten the time spent on converting the RGB color model signal to different color models.

The invention provides a circuit for color space conversion of RGB signals of a scanner, the circuit includes three sampling, amplification and displacement devices, which can respectively sample, amplify and align an R charge signal, a G charge signal and a B charge signal. Bit compensation to obtain an R analog signal, a G analog signal and a B analog signal; a gain adder, which can multiply the R analog signal, G analog signal and B analog signal by the corresponding weighted gain value to obtain All the results are added to obtain an additive analog signal; a multiplexer can select one of the R analog signal, G analog signal, B analog signal and the additive analog signal to output. Among them, the gain adder includes three gain amplifiers, which can multiply the R analog signal, G analog signal and B analog signal by corresponding weighted gain values to obtain three weighted analog signals; an adder can combine these weighted The analog signal is added to obtain the added analog signal. In this way, the scanner's response to the grayscale can be accurately reflected, which lies in the conversion of the RGB color model signal to different color models, and the use of hardware to perform the conversion work.

In order to make the above-mentioned purposes, features, and advantages of the present invention more comprehensible, the preferred embodiments are specifically cited below, together with the accompanying drawings, and are described in detail as follows:

Description of drawings

FIG. 1 shows a partial circuit diagram of signal processing of a known scanner;

Fig. 2A, Fig. 2B depict the circuit diagram of a preferred embodiment of the signal processing part of the scanner which converts RGB into grayscale and yuv color models of the present invention;

3A and 3B are circuit diagrams of another preferred embodiment of the signal processing part of the scanner for converting RGB into grayscale and yuv color models of the present invention.

Explanation of reference signs:

102, 104, 106, 202, 204, 206, 232～234, 302, 304, 306: Sampling-Amplified-Offset Device

108, 216, 316, 364: Mutliplexer

110, 218, 318, 366: Analog Digital Converter (Analog Digital Converter)

208, 248, 308: Correlated Double Sampler

209～211, 245, 310: Programmable Gain Amplifier (Programmable Gain Amplifier)

212, 241, 312: Shifter (Offset Device)

214, 314, 360～362: Adder (Adder)

320, 322, 324, 351～359: Gain Amplifier

Detailed ways

Please refer to FIG. 2A , which shows a circuit diagram of a preferred embodiment of the signal processing part of the scanner for converting RGB into grayscale and yuv color models of the present invention. In FIG. 2A, the R charge signal, G charge signal and B charge signal sensed by the sensor (not shown) are respectively sent to the sampling amplification displacement devices 202, 204, 206, and the sampling amplification displacement devices 202, 204, 206 can be Perform signal sampling, amplification and level compensation on the R charge signal, G charge signal and B charge signal respectively to obtain R analog signal, G analog signal and B analog signal.

Next, the adder 214 adds the R analog signal, the G analog signal, and the B analog signal to obtain an added analog signal. The multiplexer 216 can select one of the R analog signal, the G analog signal, the B analog signal and the added analog signal to output to the analog-to-digital converter 218, and the analog-to-digital converter 218 converts the analog signal into a digital signal.

In FIG. 2A , the sampling, amplification and displacement devices 202 , 204 , and 206 also include several devices. Taking the sampling, amplification and displacement device 202 as an example, it includes a correlated double sampler 208 , a programmable gain amplifier 210 and a shifter 212 . The correlated double sampler 208 samples the R charge signal twice, and subtracts the results of the two samples to obtain an R brightness value. The programmable gain amplifier 210 can adjust a gain value (the adjustment range of the gain value is determined by the bit length of the gain value), and amplify the R luminance value sent by the associated double sampler 208 according to the gain value to obtain an R Amplifies the brightness value. The shifter 212 performs level compensation on the R amplified luminance value to obtain an R analog signal. Likewise, the device description of the sampling amplification displacement device 204 , 206 is the same as the description of the sampling amplification displacement device 202 .

When the scanner is scanning in grayscale, the R analog signal, G analog signal and B analog signal are adjusted with different gain values through the programmable gain amplifiers 209, 210, 211, and the obtained R-weighted analog signal and G-weighted analog signal The B-weighted analog signal is added by the adder 214, and the added analog signal obtained is sent to the analog-to-digital converter 218 and the subsequent stage circuit through the multiplexer 216. In this way, the analog-to-digital converter 218 and the subsequent stage circuit are based on the gain The adjusted luminance value of the additive analog signal enables the scanner to more accurately reflect the gray scale response.

The conversion relationship between the RGB color model and the yuv color model can be described by the following matrix type:

$\left[\begin{array}{c}\mathrm{<span\; class="notranslate">\; the\; y</span>}\\ \mathrm{<span\; class="notranslate">\; u</span>}\\ \mathrm{<span\; class="notranslate">\; v</span>}\end{array}\right]<span\; class="notranslate">\; =</span>\left[\begin{array}{ccc}\mathrm{<span\; class="notranslate">\; 0.299</span>}& \mathrm{<span\; class="notranslate">\; 0.587</span>}& \mathrm{<span\; class="notranslate">\; 0.114</span>}\\ \mathrm{<span\; class="notranslate">\; 0.596</span>}& <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 0.275</span>}& <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 0.321</span>}\\ \mathrm{<span\; class="notranslate">\; 0.212</span>}& <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 0.523</span>}& \mathrm{<span\; class="notranslate">\; 0.311</span>}\end{array}\right]\left[\begin{array}{c}\mathrm{<span\; class="notranslate">\; R</span>}\\ \mathrm{<span\; class="notranslate">\; G</span>}\\ \mathrm{<span\; class="notranslate">\; B</span>}\end{array}\right]$

Among them, y represents the brightness (Luminance), u represents the hue (Hue), and v represents the saturation (Saturation). If only the brightness y in the yuv color model is used, the circuit shown in FIG. 2A can also fulfill its requirements. According to the above matrix type, it can be known that the relationship between brightness y and RGB signal is as follows:

y=0.299R+0.587G+0.114B

Therefore, the adjustable gain value of the programmable gain amplifier 210 in FIG. 2A is 0.299, the adjustable gain value of the programmable gain amplifier 209 is 0.587, and the adjustable gain value of the programmable gain amplifier 211 is 0.114.

In FIG. 2A , the front and back positions of the programmable gain amplifiers and shifters (such as the programmable gain amplifier 210 and the shifter 212 ) in the sampling amplification shifting devices 202 , 204 , and 206 can be interchanged. As shown in FIG. 2B , the associated double sampler 248 in the sampling, amplification and shifting device 232 samples the R charge signal twice, and subtracts the results of the two samplings to obtain an R brightness value. The shifter 241 performs level compensation on the R luminance value to obtain an R-compensated luminance value. The programmable gain amplifier 245 can adjust a gain value, and amplify the R-compensated luminance value sent by the shifter 241 according to the gain value, so as to obtain an R analog signal. Likewise, the description of the sampling amplification displacement device 233 , 234 is the same as the description of the sampling amplification displacement device 232 . In the sampling amplifier shifting device mentioned below, the front and rear positions of the shifter and the programmable gain amplifier are interchangeable.

Please refer to FIG. 3A , which shows a circuit diagram of another preferred embodiment of the signal processing part of the scanner for converting RGB to grayscale and yuv color models of the present invention. In FIG. 3A, the R charge signal, G charge signal and B charge signal sensed by the sensor (not shown) are respectively sent to the sampling amplification displacement devices 302, 304, 306, and the sampling amplification displacement devices 302, 304, 306 can be Perform signal sampling, amplification and level compensation on the R charge signal, G charge signal and B charge signal respectively to obtain R analog signal, G analog signal and B analog signal.

At this time, the gain amplifier 320 multiplies the R analog signal by a first weighted value to obtain and output the R-weighted analog signal to the adder 314 . The gain amplifier 322 multiplies the G analog signal by a second weighted value to obtain and output the G weighted analog signal to the adder 314 . The gain amplifier 324 multiplies the B analog signal by a third weighted value to obtain and output the B weighted analog signal to the adder 314 .

Next, the adder 314 adds the R-weighted analog signal, the G-weighted analog signal and the B-weighted analog signal output by the gain amplifiers 320 , 322 , and 324 to obtain an added analog signal. The multiplexer 316 can select one of the R analog signal, the G analog signal, the B analog signal and the added analog signal to output to the ADC 318, and the ADC 318 converts the analog signal into a digital signal.

In FIG. 3A , the sampling, amplification and shifting devices 302 , 304 , and 306 also include several devices. Taking the sampling, amplification and shifting device 302 as an example, it includes a correlated double sampler 308 , a programmable gain amplifier 310 and a shifter 312 . The associated double sampler 308 samples the R charge signal twice, and subtracts the results of the two samples to obtain an R brightness value. The programmable gain amplifier 310 can adjust a gain value (the adjustment range of the gain value is determined by the bit length of the gain value), and amplify the R luminance value sent by the associated double sampler 308 according to the gain value to obtain a R Amplifies the brightness value. The shifter 312 performs level compensation on the R amplified luminance value to obtain an R analog signal. Likewise, the device description of the sampling amplification displacement device 304 , 306 is the same as the description of the sampling amplification displacement device 302 .

When the scanner is scanning in gray scale, the R analog signal, G analog signal and B analog signal are adjusted with different weighted values through the gain amplifiers 320, 322, 324, and the obtained R weighted analog signal, G weighted analog signal and B The weighted analog signal is added by the adder 314, and the added analog signal obtained is sent to the analog-to-digital converter 318 and the subsequent stage circuit through the multiplexer 316, so that the analog-to-digital converter 318 and the subsequent stage circuit are adjusted according to the weighted The luminance value of the added analog signal can make the scanner's response to the gray scale more accurately reflected.

The conversion relationship between the RGB color model and the yuv color model The circuit shown in Fig. 3A can also fulfill its requirements. According to the above matrix type, it can be known that the relationship between brightness y and RGB signal is as follows:

y=0.299R+0.587G+0.114B

Therefore, the first weighted value of the gain amplifier 320 in FIG. 3A is 0.299, the second weighted value of the gain amplifier 322 is 0.587, and the third weighted value of the gain amplifier 324 is 0.114.

As mentioned above, the RGB color model is converted to the yuv color model, and the brightness y, hue u and saturation v in the yuv color model need to be used, the circuit shown in Figure 3A needs to be corrected, and the corrected circuit is shown in Figure 3B shown.

In FIG. 3B , the gain amplifier 351 multiplies the R analog signal by a first weighted value to obtain and output the first R-weighted analog signal to the adder 360 . The gain amplifier 352 multiplies the G analog signal by a second weighted value to obtain and output the first G-weighted analog signal to the adder 360 . The gain amplifier 353 multiplies the B analog signal by a third weighted value to obtain and output the first B-weighted analog signal to the adder 360 . The gain amplifier 354 multiplies the R analog signal by a fourth weighted value to obtain and output a second R-weighted analog signal to the adder 361 . The gain amplifier 355 multiplies the G analog signal by a fifth weighted value to obtain and output a second G-weighted analog signal to the adder 361 . The gain amplifier 356 multiplies the B analog signal by a sixth weighted value to obtain and output a second B-weighted analog signal to the adder 361 . The gain amplifier 357 multiplies the R analog signal by a seventh weighted value to obtain and output a third R-weighted analog signal to the adder 362 . The gain amplifier 358 multiplies the G analog signal by an eighth weighted value to obtain and output a third G-weighted analog signal to the adder 362 . The gain amplifier 359 multiplies the B analog signal by a ninth weighted value to obtain and output a third B-weighted analog signal to the adder 362 .

Next, the adder 360 adds the first R-weighted analog signal, the first G-weighted analog signal, and the first B-weighted analog signal output by the gain amplifiers 351 , 352 , and 353 to obtain brightness y. The adder 361 adds the second R-weighted analog signal, the second G-weighted analog signal and the second B-weighted analog signal output by the gain amplifiers 354 , 355 , and 356 to obtain the hue u. The adder 362 adds the third R-weighted analog signal, the third G-weighted analog signal and the third B-weighted analog signal output by the gain amplifiers 357 , 358 , and 359 to obtain the saturation v. The multiplexer 364 can select one of the analog signals R, G, B, brightness y, hue u and saturation v to output to the analog-to-digital converter 366, and the analog-to-digital converter 366 converts the analog signal converted to a digital signal.

According to the matrix type of converting the RGB color model to the yuv color model above, it can be known that the relationship between brightness y, hue u, saturation v and RGB signals is as follows:

y=0.299R+0.587G+0.114B

u=0.596R-0.275G-0.321B

v=0.212R-0.523G+0.311B

Therefore, the first weighted value of the gain amplifier 351 in Figure 3B is 0.299, the second weighted value of the gain amplifier 352 is 0.587, the third weighted value of the gain amplifier 353 is 0.114, and the fourth weighted value of the gain amplifier 354 is 0.596, the fifth weighted value of gain amplifier 355 is (-0.275), the sixth weighted value of gain amplifier 356 is (-0.321), the seventh weighted value of gain amplifier 357 is 0.212, and the eighth weighted value of gain amplifier 358 is (-0.523), the ninth weighted value of the gain amplifier 359 is 0.311.

Converting the RGB color model to the yuv color model is to use the hardware circuit of the circuit (such as a gain amplifier and an adder) to complete the color space conversion. Compared with using software to complete the color space conversion, the hardware circuit does the conversion. The time spent is very less, thus, the scanner can operate at a higher scanning speed.

Therefore, the advantage of the present invention is that when the scanner is used in grayscale scanning, the response of each pixel to the grayscale can be reflected more accurately.

Another advantage of the present invention is that the scanner is used to convert RGB color model signals to different color models, and uses hardware to perform the conversion work, which can shorten the time spent on converting RGB color model signals to different color models.

However, the above descriptions are only preferred embodiments of the present invention, and are not used to limit the present invention. Any person familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. The protection scope of the invention shall be determined by the claims.

Claims (14)

1. a kind of RGB signal of scanner is done the circuit of color space conversion, it is characterized in that: comprise: Three sampling, amplification and displacement devices can respectively sample, amplify and level-compensate an R charge signal, a G charge signal and a B charge signal, so as to obtain an R analog signal, a G analog signal and a B analog signal; An adder, which can add the R analog signal, the G analog signal and the B analog signal to obtain an additive analog signal; A multiplexer can select one output of the R analog signal, the G analog signal, the B analog signal and the added analog signal. 2. the RGB signal of scanner as claimed in claim 1 is done the circuit of color space conversion, it is characterized in that: each sampling enlargement displacement device in the described three sampling enlargement displacement devices also comprises: A correlated double sampler, which can perform secondary sampling on the charge signal input to the sampling amplification displacement device, and subtract the result of the secondary sampling to obtain a brightness value; A programmable gain amplifier, which can adjust a gain value to amplify the brightness value, and obtain an amplified brightness value according to the gain value; A shifter can perform level compensation on the amplified luminance value, so as to obtain an analog signal corresponding to the charge signal of the sampling, amplifying and shifting device. 3. the RGB signal of scanner as claimed in claim 1 is done the circuit of color space conversion, it is characterized in that: each sampling amplification displacement device in the described three sampling enlargement displacement devices also comprises: A correlated double sampler, which can perform subsampling on the charge signal input to the sampling amplification displacement device, and perform subtraction operation on the result of the subsampling to obtain a brightness value; a shifter, which can perform level compensation on the luminance value to obtain a compensated luminance value; A programmable gain amplifier can adjust a gain value to amplify the compensation brightness value, and obtain an analog signal corresponding to the charge signal of the sampling amplification displacement device according to the gain value. 4. the RGB signal of scanner as claimed in claim 1 is done the circuit of color space conversion, it is characterized in that: this multiplexer selects with this R analog signal, this G analog signal, this B analog signal and this addition analog signal One of them is output to an analog-to-digital converter, and then converted into a digital signal by the analog-to-digital converter. 5. a kind of RGB signal of scanner is done the circuit of color space conversion, it is characterized in that: comprise: Three sampling, amplification and displacement devices can respectively sample, amplify and level-compensate an R charge signal, a G charge signal and a B charge signal to obtain an R analog signal, a G analog signal and a B analog signal; A gain adder, which can multiply the R analog signal, the G analog signal and the B analog signal by a corresponding weighted gain value, and add all the results obtained separately to obtain an additive analog signal; A multiplexer can select one output of the R analog signal, the G analog signal, the B analog signal and the added analog signal. 6. The RGB signal of scanner as claimed in claim 5 is done the circuit of color space conversion, it is characterized in that: each sampling enlargement displacement device in the described three sampling enlargement displacement devices also comprises: A correlated double sampler, which can perform subsampling on the charge signal input to the sampling amplification displacement device, and perform subtraction operation on the result of the subsampling to obtain a brightness value; A programmable gain amplifier, which can adjust a gain value to amplify the brightness value, and obtain an amplified brightness value according to the gain value; A shifter can perform level compensation on the amplified luminance value, so as to obtain an analog signal corresponding to the charge signal of the sampling, amplifying and shifting device. 7. the RGB signal of scanner as claimed in claim 5 is done the circuit of color space conversion, it is characterized in that: each sampling enlargement displacement device in the described three sampling enlargement displacement devices also comprises: A correlated double sampler, which can perform subsampling on the charge signal input to the sampling amplification displacement device, and perform subtraction operation on the result of the subsampling to obtain a brightness value; a shifter, which can perform level compensation on the luminance value to obtain a compensated luminance value; A programmable gain amplifier can adjust a gain value to amplify the compensation brightness value, and an analog signal corresponding to the charge signal of the sampling amplification displacement device can be obtained according to the gain value. 8. the RGB signal of scanner as claimed in claim 5 is done the circuit of color space conversion, it is characterized in that: this gain adder comprises: Three gain amplifiers, which can respectively multiply the R analog signal, the G analog signal and the B analog signal by the corresponding weighted gain value to obtain three weighted analog signals; An adder can add the three weighted analog signals to obtain the added analog signal. 9. The RGB signal of scanner as claimed in claim 5 is done the circuit of color space conversion, it is characterized in that: this multiplexer selects by this R analog signal, this G analog signal, this B analog signal and this addition analog signal One of them is output to an analog-to-digital converter, and then converted into a digital signal by the analog-to-digital converter. 10. The RGB signal of a kind of scanner is done the circuit of color space conversion, it is characterized in that: comprise: Three sampling, amplification and displacement devices can respectively sample, amplify and level-compensate an R charge signal, a G charge signal and a B charge signal, so as to obtain an R analog signal, a G analog signal and a B analog signal; Three gain adders, wherein, each gain adder multiplies the R analog signal, the G analog signal, and the B analog signal corresponding to the gain adder by a corresponding weighted gain value respectively and adds them together to obtain a Adding analog signals, the weighted gain values corresponding to the same analog signals among the three gain adders are different; A multiplexer can select one output among the R analog signal, the G analog signal, the B analog signal and the three added analog signals respectively generated by the three gain adders. 11. the RGB signal of scanner as claimed in claim 10 is done the circuit of color space conversion, it is characterized in that: each sampling enlargement displacement device in the described three sampling enlargement displacement devices also comprises: A correlated double sampler, which can perform subsampling on the charge signal input to the sampling amplification displacement device, and perform subtraction operation on the result of the subsampling to obtain a brightness value; A programmable gain amplifier, which can adjust a gain value to amplify the brightness value, and an amplified brightness value can be obtained according to the gain value; A shifter can perform level compensation on the amplified luminance value, so as to obtain an analog signal corresponding to the charge signal of the sampling, amplifying and shifting device. 12. the RGB signal of scanner as claimed in claim 10 is done the circuit of color space conversion, it is characterized in that: each sampling amplification displacement device in the described three sampling enlargement displacement devices also comprises: A correlated double sampler, which can perform subsampling on the charge signal input to the sampling amplification displacement device, and perform subtraction operation on the result of the subsampling to obtain a brightness value; a shifter, which can perform level compensation on the luminance value to obtain a compensated luminance value; A programmable gain amplifier can adjust a gain value to amplify the compensation luminance value, and an analog signal corresponding to the charge signal of the sampling amplification displacement device can be obtained according to the gain value. 13. the RGB signal of scanner as claimed in claim 10 is done the circuit of color space conversion, it is characterized in that: any one gain adder of described three gain adders comprises: Three gain amplifiers, which can respectively multiply the R analog signal, the G analog signal and the B analog signal by the corresponding weighted gain value to obtain three weighted analog signals; An adder can add the three weighted analog signals to obtain the added analog signal. 14. the RGB signal of scanner as claimed in claim 10 is done the circuit of color space conversion, it is characterized in that: this multiplexer is this R analog signal, this G analog signal, this B analog signal and described three additions One of the analog signals is selected to be output to an analog-to-digital converter, and then converted into a digital signal by the analog-to-digital converter.

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