Image acquisition device and control method thereof

Abstract

To achieve the acquisition of various images with a relatively simple configuration.SOLUTION: An image acquisition device according to the present invention is an image acquisition device including a plurality of pixels, and each of the pixels includes a plurality of subpixels that can detect different lights, and the image acquisition device includes a plurality of signal holding portions each holding a plurality of signals output from the plurality of subpixels, and a signal processing portion that acquires and processes each of the plurality of signals from the plurality of signal holding portions, and the signal processing portion has a first mode in which the plurality of signals respectively held by the plurality of signal holding portions are amplified by a predetermined amplification factor and output individually, and a second mode in which the plurality of signals respectively held by the plurality of signal holding portions are amplified with an amplification factor that is at least partially different from the amplification factor in the first mode, and the sum is outputted.SELECTED DRAWING: Figure 5A

Description

[Technical Field]

[0001] The present invention relates generally to image acquisition devices. [Background technology]

[0002] Patent Document 1 describes the configuration of an image acquisition device that acquires color image data by individually detecting light of different frequencies in the visible light range, such as red light, green light, and blue light. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 6-204444 Summary of the Invention [Problem to be solved by the invention]

[0004] Some of the image acquisition devices described above are required to acquire images in two or more operation modes, and there is generally a demand for technology that can achieve this with a relatively simple configuration.

[0005] An exemplary object of the present invention is to realize a variety of image acquisitions with a relatively simple configuration. [Means for solving the problem]

[0006] One aspect of the present invention relates to an image acquisition device, the image acquisition device comprising: An image acquisition device comprising a plurality of pixels, Each pixel includes a plurality of sub-pixels capable of detecting different light, The image acquisition device a plurality of signal holding units that hold the plurality of signals output from the plurality of sub-pixels, respectively; a signal processing unit that acquires and processes the plurality of signals from the plurality of signal holding units; Equipped with The signal processing unit has the following operation modes: a first mode in which the plurality of signals held by the plurality of signal holding units are amplified by a predetermined amplification factor and individually output; a second mode in which the plurality of signals held by the plurality of signal holding units are amplified by an amplification factor at least partially different from the amplification factor of the first mode, and the amplified signals are summed and output; Contains It is characterized by: [Effects of the Invention]

[0007] According to the present invention, it is possible to obtain a variety of images with a relatively simple configuration. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram of an image acquisition device according to an embodiment. [Figure 2] FIG. 1 is a diagram showing an example of the configuration of an image sensor. [Figure 3] FIG. 2 is a diagram showing an example of the configuration of a sub-pixel. [Figure 4] FIG. 3 is a diagram showing an example of the configuration of a signal holding unit. [Figure 5A] FIG. 2 is a diagram showing an example of the configuration of a signal processing unit. [Figure 5B] FIG. 2 is a diagram showing an example of the configuration of a signal processing unit. [Figure 6A] FIG. 10 is a diagram showing an example of the state of a switching unit in a color mode. [Figure 6B] FIG. 10 is a diagram showing an example of the state of a switching unit in a color mode. [Figure 6C] FIG. 10 is a diagram showing an example of the state of a switching unit in a color mode. [Figure 7] FIG. 10 is a diagram showing an example of the state of a switching unit in a monochrome mode. [Figure 8A] 10 is a timing chart showing an example of a method for acquiring an image in color mode. [Figure 8B] 10 is a timing chart showing an example of a method for acquiring an image in monochrome mode. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the scope of the claimed invention. Although multiple features are described in the embodiments, not all of these multiple features are necessarily essential to the invention, and multiple features may be combined arbitrarily. Furthermore, in the accompanying drawings, the same reference numerals are used to designate the same or similar components, and redundant explanations will be omitted.

[0010] FIG. 1 is a schematic diagram of an image acquisition device 1 according to an embodiment. The image acquisition device 1 includes a document table 11, a document cover 12, and an operation panel 13. The document table 11 includes a light-transmitting plate such as a glass plate, and an image sensor 110 and a light source (e.g., an LED (Light Emitting Diode)) (not shown) disposed below the document table 11. The document cover 12 is disposed above the document table 11 and is openable and closable relative to the image acquisition device 1 body. The operation panel 13 is disposed on the front of the image acquisition device 1 body, and a touch panel display is typically used for the operation panel 13, but a switch-type operation input unit and a display unit such as a liquid crystal panel may also be provided separately.

[0011] A user can open the document cover 12 and place a document to be scanned on the document table 11. The document is typically made of paper, with an image (such as text, graphics, or a photograph) formed on its surface. After placing the document on the document table 11, the user can close the document cover 12 and perform an operation to acquire the image via the operation panel 13. In response to this operation, the image sensor 110 is scanned in a predetermined direction while detecting reflected light from the document illuminated by the light source, thereby acquiring an image signal representing the image of the document.

[0012] The image signal thus acquired can be processed as image data by a processor (not shown) and stored in a predetermined memory. The image acquisition device 1 may be called an image reading device, a scanner, or the like, but may also be equipped with an auxiliary image acquisition function. For example, the image acquisition device 1 may be a printer (a so-called multifunction printer) that has a recording function that can be realized by a recording head as its main function and an image acquisition function as an auxiliary function.

[0013] 2 shows an example of the configuration of the image sensor 110. The image sensor 110 includes a pixel PX, a signal holding unit 21, and a signal processing unit 22. A plurality of pixels PX are arranged, and in this embodiment, the plurality of pixels PX are arranged in one direction (here, a direction substantially perpendicular to the scanning direction of the image sensor 110). Each pixel PX includes a plurality of sub-pixels capable of detecting different light beams, and in this embodiment, the sub-pixels include a red pixel SPX R , green pixel SPX G and blue pixel SPX B Red pixel SPX R is capable of detecting red light, and the green pixel SPX G enables detection of green light, and the blue pixel SPX B enables detection of blue light.

[0014] In the following explanation, red pixel SPX R , green pixel SPX G and blue pixel SPX B When there is no need to distinguish between them, simply use the subpixel SPX (or subpixel SPX R , SPX G and SPX B ) Note that each pixel PX only needs to be configured to be able to individually detect light of different frequencies, that is, the number of types of sub-pixels SPX is not limited to this example, and may be four or more.

[0015] 3 shows an example of the configuration of a single subpixel SPX. The subpixel SPX includes a photoelectric conversion element 31, a reset transistor 32, an amplifying transistor 33, and a current source .

[0016] The photoelectric conversion element 31 typically uses a photodiode, and a color filter is provided above the photoelectric conversion element 31. R In the case of , a red filter is provided, and the green pixel SPX G In the case of , a green filter is provided, and in the case of blue pixel SPX B In this case, a blue filter is provided. The photoelectric conversion element 31 performs photoelectric conversion on the light corresponding to the color filter, that is, converts the light that has passed through the color filter into an electrical signal.

[0017] The reset transistor 32 is used to initialize the photoelectric conversion element 31. The amplification transistor 33 is connected to a current source 34 and performs a source follower operation, thereby amplifying the signal from the photoelectric conversion element 31 and outputting it as a pixel signal. Note that the reset transistor 32, the amplification transistor 33, and the current source 34 are typically MOS (Metal Oxide Semiconductor) transistors, but other elements may also be used.

[0018] Referring again to FIG. 2, the plurality of pixels PX are red pixels SPX in this embodiment. R , green pixel SPX G and blue pixel SPX B In another embodiment, the plurality of pixels PX are arranged in one direction to form a line sensor. R , green pixel SPX G and blue pixel SPX B In other words, the concept of the image sensor 110 can include a line sensor and an area sensor.

[0019] The power supply voltage V1 and the like shown in the figure may be set to an appropriate value, such as 5V (volts), depending on the circuit configuration.

[0020] 4 shows an example of the configuration of the signal holding unit 21. A plurality of signal holding units 21 are provided corresponding to a plurality of subpixels SPX (see FIG. 2), and each signal holding unit 21 includes a sampling circuit that samples the pixel signal output from the corresponding subpixel SPX. That is, each signal holding unit 21 includes a switch element 211 and a capacitance (capacitor) 212, and by controlling the switch element 211, the pixel signal output from the corresponding subpixel SPX is held in the capacitance 212.

[0021] The signal holding unit 21 may be configured as a part of the subpixel SPX, and it is preferable that the plurality of subpixels SPX are uniformly arranged in the same layout.

[0022] 5A and 5B show an example of the configuration of the signal processing unit 22. A plurality of signal processing units 22 are provided for a plurality of pixels PX (see FIG. 2), and each signal processing unit 22 includes an amplifier 221 and an output holding unit 222.

[0023] 5A shows an example of the configuration of the amplifier unit 221. Details will be described later, but the amplifier unit 221 includes a plurality of input capacitors 51a to 51d, a signal amplifier unit 52, a feedback capacitor 53, and a switching unit 54, thereby enabling the image signal received from the signal holding unit 21 to be amplified at a variable amplification factor.

[0024] 5B shows an example of the configuration of the output holding unit 222. The output holding unit 222 includes a sampling circuit that samples the image signal received from the amplifier 221. In this embodiment, the output holding unit 222 includes a switching element 55 S , switch element 55 N , capacity 56 S and capacity 56 N Includes:

[0025] Switch element 55 S and capacity 56 S The switch element 55 samples the pixel signal output from the sub-pixel SPX by photoelectric conversion of the photoelectric conversion element 31 as an optical signal (or S signal). N and capacity 56 NThe pixel signal of the sub-pixel SPX when the photoelectric conversion element 31 is initialized by the reset transistor 32 is sampled as a dark signal (or N signal). The light signal and the dark signal are respectively output from the output switch element 57 S and 57 N and the difference between them is output by the differential amplifier 23 in the subsequent stage, and thus correlated double sampling can be performed.

[0026] Although the signal holding unit 21 and the output holding unit 222 are given names that allow them to be distinguished from each other, they may also be expressed as the first holding unit 21 and the second holding unit 222, respectively.

[0027] 5A again, the amplifier unit 221 includes a plurality of input capacitors 51a to 51d, a signal amplifier unit 52, a feedback capacitor 53, and a switching unit 54. The input capacitors 51a to 51d are connected to the subpixels SPX R , SPX G and SPX B The input capacitors 51a to 51d are arranged between the three signal holding units 21 corresponding to the respective input capacitors 51a to 51d and the signal amplifying unit 52. Here, in the electrical path between any one of the signal holding units 21 and the signal amplifying unit 52, at least two of the input capacitors 51a to 51d are arranged in parallel connection.

[0028] Feedback capacitor 53 is arranged to connect the output terminal and input terminal of signal amplifier 52, and as will be described in detail later, this allows the image signal to be amplified at an amplification factor according to input capacitors 51a to 51d and feedback capacitor 53. Signal amplifier 52 can be initialized by reset transistor 58, which connects its output terminal and input terminal.

[0029] The switching unit 54 includes a plurality of switch elements 541 to 548, each of which can be individually controlled to be in a conductive state or a non-conductive state.

[0030] Red Pixel SPX R The pixel signal held by the signal holding unit 21 can be input to the input capacitor 51b via the switch element 541.G The pixel signal held by the signal holding unit 21 can be input to the input capacitor 51b via the switch element 542, and can also be input to the input capacitor 51c via the switch element 543. B The pixel signal held by the signal holding unit 21 can be input to the input capacitor 51c via the switch element 544.

[0031] Furthermore, red pixel SPX R The pixel signal held by the signal holding unit 21 is input to the input capacitor 51a and can be input to the signal amplifier 52 via the switch element 545. R and / or green pixel SPX G The pixel signal held by the signal holding unit 21 is input to the input capacitor 51b and can be input to the signal amplifier 52 via the switch element 546. G and / or blue pixel SPX B The pixel signal held by the signal holding unit 21 is input to the input capacitor 51c and can be input to the signal amplifier 52 via the switch element 547. B The pixel signal held by the signal holding unit 21 is input to the input capacitor 51 d and can be input to the signal amplifier 52 via the switch element 548 .

[0032] With this configuration, the switching unit 54 controls the subpixel SPX R , SPX G and SPX B The connection between each of the three signal holding units 21 corresponding to the above and the signal amplifier unit 52 can be switched.

[0033] In summary, with the above configuration, each signal processing unit 22 R , green pixel SPX G and blue pixel SPX B The image signals can be received from the corresponding signal storage units 21 individually or in combination and processed.

[0034] Referring again to FIG. 2, the image sensor 110 further comprises a shift register 24, which allows for synchronous control of the above-mentioned elements.

[0035] Figure 6A shows the red pixel SPX R 6B shows the state of the switching unit 54 when processing the pixel signal of the green pixel SPX. G 6C shows the state of the switching unit 54 when processing the pixel signal of the blue pixel SPX. B 1 shows the state of the switching unit 54 when processing pixel signals of 1. In the figure, dashed lines among the plurality of switch elements 541 etc. indicate that they are in a non-conducting state.

[0036] In the example of FIG. 6A, the input capacitors 51a and 51b are active, and therefore the red pixel SPX R In the example of FIG. 6B, the input capacitor 51c is activated, and the pixel signal of the green pixel SPX is amplified with an amplification factor according to the ratio of the capacitance value of the input capacitor 51c to the capacitance value of the feedback capacitor 53. G 6C, the input capacitor 51d is activated, and the pixel signal of the blue pixel SPX is amplified with an amplification factor according to the ratio of the capacitance value of the input capacitor 51d to the capacitance value of the feedback capacitor 53. B The pixel signal is amplified.

[0037] 6A to 6C in this manner, it is possible to acquire image data in color. This operation mode is called the color mode (or color scan mode).

[0038] Figure 7 shows the subpixel SPX R , SPX G and SPX B 6A to 6C, the state of the switching unit 54 when processing the pixel signal of the red pixel SPX is shown. In this case, all of the input capacitors 51a to 51d are active. RThe pixel signal of the green pixel SPX is amplified by an amplification factor according to the ratio of the capacitance value of the input capacitor 51a to the capacitance value of the feedback capacitor 53, via the path indicated by the dashed arrow. G The pixel signal of the blue pixel SPX is amplified by an amplification factor according to the ratio of the capacitance value of the input capacitor 51b to the capacitance value of the feedback capacitor 53 through the path indicated by the dashed arrow. B The pixel signal is amplified through the path indicated by the dashed two-dot arrow at an amplification factor according to the ratio between the combined capacitance value of the input capacitors 51c and 51d and the capacitance value of the feedback capacitor 53. Since the switch elements 545 to 548 are in a conductive state, the amplified pixel signal of the subpixel SPX R , SPX G and SPX B The pixel signals are summed.

[0039] According to the embodiment of Fig. 7, image data can be acquired in monochrome, and this operation mode is called monochrome mode (or monochrome scan mode).

[0040] For example, if the capacitance value of the feedback capacitor 53 is C FB The capacitance value of the input capacitor 51a is set to 2×C FB The capacitance value of the input capacitor 51b is set to 1×C FB The capacitance value of the input capacitance 51c is 3 × C FB The capacitance value of the input capacitance 51d is set to 3 × C FB In this case, in color mode, the subpixel SPX R , SPX G and SPX B On the other hand, in monochrome mode, the red pixel SPX R The pixel signal of green pixel SPX is amplified by 2 times. G The pixel signal of the blue pixel SPX is amplified by 1x. B The pixel signals are amplified by a factor of 6 and then summed (see FIG. 7).

[0041] In summary, red pixel SPX R The amplification factor of the pixel signal is G Rand green pixel SPX G The amplification factor of the pixel signal is G G and blue pixel SPX B The amplification factor of the pixel signal is G B In color mode, R :G G :G B =(2+1):3:3=1:1:1. Also, in monochrome mode, G R :G G :G B =2:1:(3+3)=2:1:6 holds true.

[0042] In this way, the switching unit 54 switches the connection state of the multiple input capacitors 51a to 51d between the multiple signal holding units 21 and the signal amplifier 52 depending on the operation mode. In this embodiment, at least two of the input capacitors 51a to 51d are arranged so as to be connected in parallel in the electrical path between any one of the signal holding units 21 and the signal amplifier 52, and these are switched to selectively form the electrical path. Therefore, the amplification factor of the pixel signal can be changed depending on the operation mode without unnecessarily increasing the circuit size of the amplifier 221. From this perspective, the multiple input capacitors 51a to 51d and the switching unit 54 can be said to form an amplification factor variable unit.

[0043] 8A is a timing chart showing an example of a method for controlling the switch elements 541 and the like when acquiring an image in color mode. The horizontal axis represents time. The vertical axis represents the clock signal CLK, the horizontal synchronization signal SH, the states of the switch elements 541 and the like, the state of the light source LED, and the output Vout of the differential amplifier 23. The switch elements 541 and the like are in a conductive state when at H level (high level) and in a non-conductive state when at L level (low level).

[0044] The clock signal CLK is used to synchronize and control the individual elements, for example, the shift register 24 is used to generate the horizontal synchronization signal SH. The horizontal synchronization signal SH corresponds to one signal readout (one line of signal readout) from the multiple pixels PX, that is, one line of signal readout is performed in the period from an H level pulse of one signal SH to an H level pulse of the next signal SH. The light source status LED indicates that the light source is in an emitting state and the document is illuminated during the H level. The output Vout indicates that the result of the above signal readout is being output by the differential amplifier 23 over the period indicated by the diagonal lines.

[0045] In color mode, red pixel SPX R The period for reading out the pixel signals is defined as period T R and green pixel SPX G The period for reading out the pixel signals is defined as period T G And also, blue pixel SPX B The period for reading out the pixel signals is defined as period T B Let's say.

[0046] In color mode, red pixel SPX R Input capacitors 51a and 51b are used to amplify the pixel signals of the green pixel SPX (see FIG. 6A). G An input capacitor 51c is used to amplify the pixel signal of the blue pixel SPX (see FIG. 6B). B The input capacitor 51d is used to amplify the pixel signal (see FIG. 6C). R , T G and T B Throughout this period, the switch elements 541 and 543 are maintained in a conductive state, and the switch elements 542 and 544 are maintained in a non-conductive state.

[0047] In color mode, the subpixel SPX R , SPX G and SPX BThat is, the switch elements 545 and 546 are controlled to be in a conductive state or a non-conductive state substantially simultaneously, the switch element 547 is controlled at a different timing, and the switch element 548 is controlled at a further different timing.

[0048] In color mode, the subpixel SPX R , SPX G and SPX B It is sufficient that each pixel signal is read out individually, and the order in which the signals are read out is not limited to this example.

[0049] 8B is a timing chart showing an example of a method for controlling the switch element 541 and the like when acquiring an image in monochrome mode, similar to FIG. 8A. In monochrome mode, the subpixels SPX R , SPX G and SPX B The period for adding up and reading out the pixel signals is defined as period T1.

[0050] In monochrome mode, red pixel SPX R The input capacitor 51a is used to amplify the pixel signal of the green pixel SPX G The input capacitor 51b is used to amplify the pixel signal of the blue pixel SPX B Input capacitors 51c and 51d are used to amplify the pixel signals (see FIG. 7). Therefore, during period T1 (over multiple periods T1 when signals for multiple lines are read out), switch elements 542 and 544 are maintained in a conductive state, and switch elements 541 and 543 are maintained in a non-conductive state.

[0051] In monochrome mode, the subpixel SPX R , SPX G and SPX B Therefore, the switch elements 545 to 548 are controlled to be in a conductive state or a non-conductive state substantially simultaneously.

[0052] Here, as can be seen from FIGS. 8A and 8B, the period T R , TG and T B The lengths of the respective periods are substantially equal to the length of period T1. Therefore, the time required to acquire an image in monochrome mode is approximately one-third of the time required to acquire an image in color mode. Therefore, this embodiment is also advantageous in increasing the speed of image acquisition in monochrome mode.

[0053] As described above, according to this embodiment, the signal processing unit 22 has two operating modes: a color mode (first mode) in which image data can be acquired in color, and a monochrome mode (second mode) in which image data can be acquired in monochrome. In the color mode, the pixel signals held by the signal holding units 21 are amplified at a predetermined amplification factor and output individually. In the monochrome mode, the pixel signals held by the signal holding units 21 are amplified at an amplification factor that is at least partially different from the amplification factor of the color mode, and then summed and output. The amplification factor is changed by switching the connection state of the input capacitors 51a to 51d using the switching unit 54, so the circuit size of the amplifier unit 221 does not increase unnecessarily. Therefore, according to this embodiment, it is possible to acquire a variety of images with a relatively simple configuration.

[0054] In this embodiment, color mode and monochrome mode are exemplified as operating modes, but by changing the number of input capacitors 51a, etc. and the number of switch elements 541, etc., it may be possible to realize even more diverse operating modes, such as a high-speed color scan mode.

[0055] In the above description, for ease of understanding, each element is indicated by a name related to its function. However, each element is not limited to having the content described in the embodiment as its main function, but may have that function as an auxiliary function. Therefore, each element is not strictly limited to the expression, and the expression can be replaced with a similar expression. In the same spirit, the expressions "device" and "unit" can be interchangeable, or can be replaced with "circuit," "structure," "assembly," etc., or omitted.

[0056] The invention is not limited to the above-described embodiments, and various changes and modifications can be made without departing from the spirit and scope of the invention. Accordingly, the following claims are appended to apprise the public of the scope of the invention. [Explanation of symbols]

[0057] 1: Image acquisition device, PX: pixel, SPX: sub-pixel, 21: signal holding unit, 22: signal processing unit.

Claims

1. An image capture device comprising a plurality of pixels, Each pixel includes a plurality of sub-pixels capable of detecting different light, The image acquisition device includes: a plurality of signal holding units each holding a plurality of signals output from the plurality of sub-pixels; a signal processing unit that acquires and processes the plurality of signals from the plurality of signal holding units; Equipped with The signal processing unit has the following operation modes: a first mode which is a color mode, in which the plurality of signals held by the plurality of signal holding units are amplified at a predetermined amplification factor and individually output; a second mode being a monochrome mode, in which the plurality of signals respectively held by the plurality of signal holding units are amplified by an amplification factor at least partially different from an amplification factor in the first mode, and the amplified signals are summed and output; Includes 1. An image acquisition device comprising:

2. The signal processing unit includes: A signal amplifier unit; a switching unit that switches a connection state between the signal amplifier unit and each of the plurality of signal holding units in accordance with an operation mode; Includes 2. The image acquisition device according to claim 1.

3. The signal processing unit includes: A feedback capacitor connected to the signal amplifier; a plurality of input capacitances disposed between the plurality of signal holding units and the signal amplifying unit; Further comprising: The switching unit switches a connection state of the plurality of input capacitances between the plurality of signal holding units and the signal amplifying unit according to the operation mode.

3. The image acquisition device according to claim 2.

4. The switching unit includes a plurality of switch elements.

4. The image acquisition device according to claim 3.

5. At least two of the plurality of input capacitances are arranged to be connected in parallel in an electrical path between any one of the plurality of signal holding units and the signal amplifying unit.

5. The image acquisition device according to claim 4.

6. The plurality of switch elements are controlled so that the at least two input capacitances connected in parallel selectively form an electrical path between any one of the plurality of signal holding units and the signal amplifying unit.

6. The image acquisition device according to claim 5.

7. Each pixel has the following sub-pixels: A red pixel capable of detecting red light; a green pixel capable of detecting green light; A blue pixel capable of detecting blue light; Includes 2. The image acquisition device according to claim 1.

8. The plurality of pixels form a line sensor by arranging the red pixel, the green pixel, and the blue pixel in this order.

8. The image acquisition device according to claim 7.

9. The amplification factor of the red pixel signal is G Ｒ year, The amplification factor of the green pixel signal is G Ｇ year, The amplification factor of the signal from the blue pixel is G Ｂ When In the color mode, G Ｒ : G Ｇ : G Ｂ = 1:1:1 is established, In the monochrome mode, G Ｒ : G Ｇ : G Ｂ = 2:1:6 is established 8. The image acquisition device according to claim 7.

10. The image acquisition device according to any one of claims 1 to 9, A recording head is provided. A printer characterized by:

11. 1. A method for controlling an image capture device having a plurality of pixels, comprising: Each pixel includes a plurality of sub-pixels capable of detecting different light, The control method includes: a holding step of holding a plurality of signals output from the plurality of sub-pixels; and a processing step of acquiring and processing each of the plurality of held signals, The processing step comprises: amplifying the held signals at a predetermined amplification factor in a color mode and outputting the amplified signals individually; amplifying the held multiple signals at an amplification factor at least partially different from the predetermined amplification factor in a monochrome mode, summing the signals, and outputting the sum. A control method comprising:

Images