TW412708B - Method for reading signal and improving sensitivity of contact image sensor - Google Patents

Abstract

The invention relates to a method for reading signal and improving sensitivity of contact image sensor, in which the light signal of the photo-sensing component in the photo-sensing module is no longer stored in the photo sensing component, instead, the output is accumulated in the storage component external to the photo-sensing component. When the signal is to be read, the switch component is conducted and the storage component will send the stored the electric charge to the video line such that the working frequency can be increased and the sensitivity of the outputted signal can be improved with the amplification of current mirror.

Description

£ 4127〇 C7 D7 V. Creation Instructions (—) (Please read the weeping item on the back before filling in this card) Contact: Image sensor (contact image factory ns.r) _C is, it is a kind of The optical signal of the sensor is converted into a device that can determine the electrical signal, and this device accumulates the sensed light in a light-sensing element in the form of a charge. This pixel (P i X e 1) is to be output. Only the accumulated charge is rotated out. Due to the short reaction time and its own factors, the accumulated charge cannot be completely transmitted instantaneously. ^ The disadvantages of Im Age L ag and signal sensitivity are not enough. We don't accumulate the sensed signal in the sensing element 'but roll it out in another element. If you can avoid reading the sensing signal, the sensing element can't accumulate the internally accumulated charge signal due to insufficient response time. Completely transmitted, causing the defect of image retention-retention. In addition, it uses the current amplification principle to improve the sensitivity of the _out. Signal. Previous skills: 1. The current CIS device and its working principle are explained as follows: Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs, the current cIS is widely used in devices that need to read text 'graphic data with photoelectric elements, such as Figure 1 is a cross-section view of the c I s module. When the document is fed by the rotation axis, the light source illuminates the document, and the reflected light passes through the rod lens array. The reflected light will be reflected in an equal proportion. The image is projected on the CIS chip of the CIS module, and the CI S chip then transmits the optical signal sensed in this order as an electrical% signal. Standard size of this paper: China National Standard (CNS) A4 (210X297 mm)

41270S C7 D7 V. Creative Instructions (2) Printed by the Zhixian Property Bureau of the Ministry of Economic Affairs and Industrial Cooperatives, and the current CIS module is made up of several cIS chips connected in series. The main purpose is to apply to reading paper The size, that is, the larger the paper of the document, the more cIS chips used on the CIS module need to be connected to more CIS chips, and the length of the several c I s concatenations is greater than the width of the document paper; for example, 2 0 〇 The A4 CIS module with DPI resolution is taken as an example. '2 0 0 DPI has a resolution of 2000 dots per inch, which is 8 dots per mother a' and A4 paper size and width is 216 mm. A resolution of 20 ODPI requires a 4 size paper to be sensed, and the CI S module requires a total of 17 2 8 pixel sensing images to reach this specification. However, in view of the production yield, cost and applicability In consideration of the above, the c I s module is further subdivided into tens of chips with the same function under the above specifications, that is, the required length is formed by the several chips in a serial connection. The serial connection is applied to The total pixels of A4 (216 mm wide) are still 1γ 2 8 pixels, as shown in Figure 2. In Figure 2, c L0c κ is the working clock externally provided to the CI s module, the s I is the start signal of the externally activated c! S module, and E0ρ is the end signal of the chip, and also Is the start signal of the next chip, so C; [3 chipset is formed by serial connection of this signal. + In addition, the inside of the current C1 s chip is composed of an array of light-sensing elements and several bit buffers. For the inside of the c IS chip, please refer to Figure 3. The description of the array's several bit buffers is as follows: Light-sensing element array; consists of a row of light-sensing elements, such as photoelectric crystals (please read the precautions on the back before writing this page)

'IT X. Paper ruler and universal medium-sized national standard (CNS) 8 4 specifications (210X297 male; ϋ) 4127〇ε.' C7 _ D7 * — I. _ V. Creation instructions (3)., Guang Er Polar body, etc., each light sensing element also represents the aforementioned pixel (PIXEL). When the image through the lenticular lens shown in Figure 1 is projected onto the light sensing element array, its light sensing element will receive the light signal and form a charge accumulate with charge. Inside the light sensor. Therefore, the light sensing element array is an element group for sensing and accumulating optical signals in current applications. Light sensor element array switch: The light sensor switch corresponding to each light sensor element is used to control whether the signal accumulated by the light sensor element is output or not. Shift register array: Receive the start signal (SI 0UT) from the signal buffer of the chip and the clock signal (CLK) from the clock buffer. The element switch enables the signals in the light-sensing element to be transmitted in order according to the position of the pixel. Start signal buffer: receive external start signal (SI) or end-of-chip (EOP) signal. Printed by the Ministry of Economic Affairs. ¾ Printed by a property cooperative. Clock buffer: Receives an external clock signal (C L 0 C K) to provide the required working clock (CLK) and reset signal (R S T) in the chip. • ........ Chip selection controller: Receive the start signal buffer Xianghan and ^ Begin signal (si 〇ut), clock signal (c 1 and green meter) Turning out ............ --i, paper paper g 8; (CNS) A4 * US- (210X2974 ^ *) ~~ 41270ε C7 __ D7 V. Creation instructions (tough) The end-of-print signal (E0P) is printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs, and the chip selection signal (cs) is obtained through its logical operation, which is used as the external start signal of the next chip ( s I). End signal buffer. Receives the last register output signal of the shift register array to round out the end signal (EO) to end the chip selection signal (CS). The external start signal (s I) of a chip. Output controller: a signal line (V ide 〇1 ine) connected to each sensor element switch 'use chip select signal (cs) to control the signal output or not, and reset by Signal (r S ding) to reset the output signal to zero. The working mode of the above CIS chip can be shown by the current c ISPCB circuit block diagram and diagram in Figure 2. Explain the current c I s PCB circuit timing diagram. As shown in the figure: When the start signal SI (1) is transmitted to the first CIS chip (1), so that cs (i) becomes a high level, the first is started. A CIS chip (1) 'The signals in the light-sensing element are also transmitted in sequence' (such as 0 S () signals) 'Pending signal Ε Ο P (1) appears, CS (1) is turned to a low level, The first c IS chip (1) is also turned off. The signal of this first c IS chip (1) is no longer output, and the end signal (EOP) of the first c IS chip (1) is also transmitted to the first On the two cIS chips (2), and use them as the external start signal SI (2), then change the signal OS (2) output of the second CIS chip (2) so that each CIS can be started in sequence Chips, signals are also lost one by one C — __ This paper size is generally Chinese National Standard (CNS) A4 size (4x297 mm) f Please read the notes on the back of the results before filling out this page} 47-order. 41270 £ C7 D7 V. Creation Instructions (1) Printed by the Consumer Cooperative of the Intellectual Property Staff of the Ministry of Economic Affairs (such as 0 S signal), waiting for the transmission of the last CIS chip (L) signal in the c ISPCB circuit. 4 After the next start signal (SI) is transmitted to the first CI S chip (1), the signal is output again. 2. The reading method of the current CIS signal is explained as follows: The reading of the current CIS signal is Accumulate the induction light in the form of electric charge in the light-sensing element, and output the accumulated charge only when the pixel is output; therefore, the signal processing method of a single light-sensing element will be explained. Please refer to the current CIS chip signal reading in Figure 5. Block diagram and timing diagram of the current cIs chip in Figure 6. As shown in the figure: The light-sensing element (eg Sm, due to the limited current gain, generally CIS adopts a transistor as the light-sensing element). It is excited by the optical signal and generates a charge, which is accumulated on its P-N junction. Capacitance (CBC) 'Until the corresponding shift register array outputs the gm signal to turn on the component switch (SWM, which can be NMOS or transmission gate switch, etc.), the charge accumulated in the CBC will be current ( IV / Ling) Input + il to the signal line (Video- line), and output it to the large capacitor CL of the 0 S terminal of the PC B line part through the control of CS, and charge it to convert the signal into a voltage form. The output (0 S) is amplified by the operational amplifier. Therefore, when the shift register array receives the start signal (si 〇ut), "make the first register in the shift register array output G1 signal" to turn on the first light-sensing element switch SW1, so that the first The charge signal in a light-sensing element S1 can be output to the signal line (Vide 〇1 ine) and the wheel-out signal line 0s, after charging through the capacitor CL to the discharge --------} installed,-(Please Read the notes on the back of the fir first, save the lacquered book fr ding 4 ° This paper size is applicable to the central countries (CNS) M specifications (210X297) and 41270ε C7 D7

V. Creation instructions (manufactured by the Consumers ’Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs, the printed device (OP amp.) Is enlarged and output to the vp terminal, followed by the second register to output the G 2 signal to turn on the second light. The sensor element switch swg outputs the signal in the second light sensor element S 2, but before the G 2 signal is output, there will be a reset signal RS D, and the switch (swo1) will be turned on to reset the signal. The signal on the cable (Vide 〇iine) at this time is also the signal resetting the first light sensor element S1. After the first signal (0 S1) is reset, the second signal is output ( 〇 $ 2) .The third and fourth signals are output in this order until the signal (◦ SL) of the last light-sensing element (SL) of the chip is output. At this time, the control signal is output to the chip selection of the module's end. The signal (c S) turns off the switch S W 0 2. The above is a cycle of the signal output of the chip, and then the signal reading of the next chip is followed, the reading method is the same as above. 3. The current CIS signal Lack of reading method · The above CIS signal reader There are many problems in the design. 'This problem often causes the accumulated charge to not be completely transmitted instantly, resulting in shadowing and affecting the accuracy of the output signal. In the traditional design, the light sensed by the light sensing element of CI s will The charge is accumulated on the light-sensing element, and the digital control buffer does not turn on the switch of the light-sensing element until the sensing pixel data is read, so that the accumulated charge is output to the capacitor (c L) outside the chip as a current. Instead, the signal is output in the form of voltage. However, the reading time of the light-sensing element is short. Taking the operating frequency of 500KHZ as an example, the reading time is about 2 us. However, the light-sensing element uses a photoelectric crystal as an example. '' If it accumulates more charges or increases the operating frequency, the stored charges (Q) cannot be fully transmitted within the reading time (t), because mathematically (please read the precautions on the back before filling out this肓 r

As paper-like, the country ’s national rubbing rate (CNS) from the secret (2 like 297 public directors) 4i2⑽5. Creation instructions (especially j C7 D7 to analyze Q = IE. Tz ·, τ p & current, tr is The emitter generated by the base-charged crystal is identified by the time * # If the read time (t) is less than the charge-out time (t τ) of the first sensing element, Q-Qt is called Ε · tr —ΙΕ ·, ^ IE-(t τ-t) = 厶 Q so-this will cause part of the surface charge to remain in this light sensation (within UQ), and then accumulate to the next photoexcitation The charge will be read as +, and the value of the signal output next time will have a relative error. The printed solution of the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs: The main purpose of the present invention is to To avoid the limitation that the current CI s. Light sensing element (can be a photodiode or a photoelectric crystal), the charge cannot be completely transmitted within the signal reading time, a light sensing module is designed to prevent the light sensing element from Output the sensed optical signal to another element outside the light sensing element to store another object of the present invention ' Amplify the current value of the photocell by the current mirror circuit, and then charge the storage element with its value. In this way, the amplification of the signal current value can increase the signal sensitivity (sensitjity), which is the same as the current CI S The signal output value of the light sensing element and illumination will increase.

V (Please read the notes on the back before filling in 4 pages.)

This paper size is printed in China (CNS) A4 Washing (210X297 mm > £ 41270 C7 D7) The Consumers' Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs printed the re-invention of the present invention-the switch for the gas of the age component The element mpg is used to reset the two ends of the storage element === 〇 Another purpose of the present invention is to respond to the signal size at the end of the miscellaneous element. The other end is biased at Vdd, and the tone == line, you can Schematic description of the signal transmission i to the output stage: In order to achieve the above-mentioned method and device, the solution used in the present invention is almost a paragraph. Here is a drawing of this redesigned c I sBM, and the method virtual device is explained in detail as follows: ' Figure 1 is a schematic cross-sectional view of the current cIS module. Figure = is a block diagram of the current c I s P CB circuit. Figure 2 is a block diagram of a current cIS chip. Figure 4 is a schematic diagram of the current cI s P CB line timing. Figure 5 is a block diagram of the current CIs chip signal reading. Figure 6 is a timing diagram of the current ClS chip. FIG. 7 is a schematic diagram of a single light sensing module of the present invention. FIG. 8 is a schematic diagram of a signal reading block of a CIS chip according to the present invention. Figure 9 is a timing diagram of the CIS chip of the present invention. V Please refer to Figure 7 for details. In order to avoid being limited by the current c I s light sensor, the paper is used in the Zhongguanjia kneading rate (coffee). > < 297 public broadcasting) (Please read the notes on the back before filling out this page. r Binding · 412706 C7 D7 Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs 5. Creative Instructions (/ i >)

The shortcoming that the 'charge in the element cannot be completely transmitted within the signal reading time, and a light-sensing module has been redesigned, so that the light-sensing element outputs the sensed optical signal to the storage element outside the light-sensing element from time to time. The photo-sensing module of this design continuously flows from the photo-sensing element to the first switching element M1 at the photo current I ce 0, and uses the third, fourth, fifth, and sixth switching elements M3, M4, M5, and M6. (M3M4M5M6 can be a MO SFET) composed of a current mirror (CURRENT M IRR 0 R), which magnifies the I ceo current value to I 1 (I 1 = M. I ceo) 'and then uses the value to the storage element c 1 Charging, so that the method of amplifying the signal current value can improve the sensitivity of the signal (sensit 1 vity), that is, under the same light sensing element and illuminance as the current cI S, its signal output value will increase. '' When the signal is read, the shift register array outputs the G1 signal, and the second switching element switch is turned on, so that the voltage signal at the common contact point (A 1) of the storage element C1 can be immediately output to the signal line (V ide ο 1 i η e) on the 'eliminates the time factor of the charge transfer of the light-sensing element, thereby increasing the operating frequency' and there is no concern about waiting for electricity. In addition, a seventh switching element mpg with a reset signal is placed next to the storage element C1, and is turned on only at the reset time when the second switching element M2 is turned on to reset the potential across the storage element C1 to the external power supply (V dd ). In addition, the common contact point A of the storage element C1 responds to the signal size, and the other end is biased to an external power supply (Vdd). Its purpose is to provide a stable signal transmission wheel to the output without increasing the 'dust line'. Stage bias. The size of this paper is suitable for China National Standards (CNS) M specifications (210X297 mm) --------- i Pack 7 --------.-- Order ------ (please first Read the precautions on the back and fill in this page) \ 412708 C7 D7 V. Creation Instructions (So the currentmirror circuit and signal reading method mentioned above can make the accuracy and sensitivity of the output signal (sens 1 tiv 1 ty) increase. At the same time, reduce the phenomenon of image retention (J mage L ag). Please refer to Figures 8 and 9 to output signals G1G2_ .., GL · through the shift register array sequence. The voltage signal in the storage element c 1 of each light-sensing module is read out, but because the signal is biased at Vdd, when the amplified light f flows I 1, the storage element c 丄 is charged so that the common contact (A 1 The voltage at the) terminal drops, so the size of this output signal (vide 〇) is a decrease rather than an increase from the reset point (vdd). Therefore, 'If you want to output the same signal mode (VP) as the current CIS' Another signal reference level can be added to make it 'output parameter under the load effect of the same signal output Examination level signal. So the output switch and chip selection signal (CS) are used to control the switch (swo1 / SWO 2) to get the signal V (〇S) and the reference level signal ^ (D 0 s). You can use the line to handle the bias point that is the same as the current cIS signal Vp, where VP = V (DOS)-V (〇s). Please-read the note on the back and write this page to order the consumption of employees of the Intellectual Property Bureau of the Ministry of Economic Affairs Printed by a cooperative

'Cent f male Ji 7

Claims (1)

6. Scope of patent application Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs 1 _ A contact image sensor signal reading method and sensitivity improvement method 'It is mainly the light signal of the light sensor module and the light sensor elements in the group, not Then accumulate in the light-sensing element, but turn it out and accumulate on the storage element outside the light-sensing element. When the signal is to be read, the switching element is turned on, and the storage element can output the accumulated charge to the signal line. Can increase the working frequency 'and use the current mirror to increase the sensitivity of the wheel-out signal. 2 * —A method for reading a signal from a contact image sensor and a method for improving sensitivity, wherein the device includes: a light sensor element output is connected to the first switching element, and then the first switching element is connected to the current mirror amplification circuit ; And, the second switching element, the seventh switching element, and the current mirror amplification circuit are connected by the common contact point of the storage element; from the above, a brand-new light sensing module is formed so that the light sensing charge is no longer accumulated in the light sensing element And accumulated on the storage element of the sensor module, when the signal is read, the charge on the storage element can be completely transmitted out of the video line. 3. A contact image sensor signal reading method and sensitivity improvement method as described in the second item of the application scope, wherein the light sensing element is a diode or a photoelectric crystal or an equivalent element thereof.口 4. A contact image sensor signal reading method and sensitivity improvement method as described in the second item of the application scope, wherein the storage element companion may be a capacitor or an approximately equivalent < element. 5. A contact image sensor signal reading method and sensitivity improvement method as described in the second item of the application scope, wherein the first, second, third, fourth >, + paper dare standard universal nail trap Standard rate (CNS > A4 specification (210X297 ^ *): ---- ^ ---- :: '装 ^ ------ Order ----- ιπ) τ ------- ------- ^ ----- (Please read the precautions on the back before filling out this page) '41270S ABCD VI. Application for patent scope 6 · A contact image sensor as described in the second application scope The signal reading method and the sensitivity improvement method of the device, in which a current mirror amplifies the circuit, amplifies the photocurrent of the light-sensing element by an equal number, and then charges its storage element can increase the signal sensitivity and increase the signal output value. 7. A method for reading a contact image sensor signal and a method for improving sensitivity as described in the second item of the application scope, wherein the seventh switching element of the storage element 'resets the potential across the storage element to an external power supply (Vdd) on. 8. As described in the second item of the application scope, a contact image sensor signal reading method and sensitivity improvement method, wherein the communication contact of the storage element reflects the signal size, and the other end is biased to an external power supply (Vdd) In the case of not increasing the bias line, it can stably provide the bias voltage for the signal transmission to the output stage. 0 · A contact image sensor signal reading method and sensitivity improvement method as described in the second item of the application scope, where The voltage signal from the optical sensor module to the signal line (Video line) and the signal output from the DC bias reference line. The output stage chip selects the signal control switch (SWO1 / SW0 2) to obtain the signal V (os). And the reference level signal V (DOS) can be processed through the off-chip application circuit to obtain a bias point that is the same as the current CIS signal Vp. K --------- '^ Ί, -I (Please read the notes on the back before filling out this page}' 1Τ. Printed on paper scales by the Nitrogen Industry Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs, China Standard rate (CNS) A4 wash grid (210X297 mm)