JP3703712B2 - Image sensor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image sensor having a plurality of photoelectric conversion elements arranged on a straight line.
[0002]
[Prior art]
A contact image sensor used for facsimiles, copiers, hand scanners, and the like has a plurality of photoelectric conversion elements arranged on a straight line, and a switch in which an output signal from each photoelectric conversion element is connected to each element. Are sequentially taken out by closing them with a shift register, and the image information is converted into a time-series electrical signal.
FIG. 8 is a schematic diagram showing a configuration of a conventional image reading apparatus.
In FIG. 8, 1 is an image sensor unit, 2 is a photoelectric conversion element circuit IC of the image sensor unit 1, and there are, for example, eight conversion element rows per 1 mm, that is, for A4 size original paper as a whole. It is composed of 1728 photoelectric conversion elements. 3 is a document read by the image sensor unit 1, 4 is a selfoc lens array arranged between the image sensor unit 1 and the document 3 so that an image of the document is connected to a photoelectric conversion element, and 5 is a selfoc lens array. The light emitting diode rows arranged on both sides of the light emitting diode row 4 irradiate the original 3 with the light from the light emitting diode row 5. In the photoelectric conversion element circuit IC2, an IC shift register, an analog switch, and a signal amplifier circuit are arranged.
[0003]
A basic circuit and a timing chart for driving the image sensor unit 1 are shown in FIGS. 9 and 10, respectively.
FIG. 9 is a diagram showing a basic circuit for driving a conventional image sensor.
In FIG. 9, reference numeral 6 denotes 128 photoelectric conversion elements, which are sequentially numbered, and are constituted by thin-film photodiodes or photoconductive thin films. Although not shown in the drawing, each photoelectric conversion element 6 has a common electrode and is grounded or an appropriate bias voltage is applied. 7 is an analog switch, 8 is an SIG terminal which is an output signal line, 9 is a shift register, and 10 is an SI terminal to which a start signal of the shift register 9 is input. Reference numeral 11 denotes a CLK terminal to which a clock is input, and reference numeral 12 denotes an SO terminal to which an end signal of the shift register 9 is output.
The photoelectric conversion element 6 in FIG. 9 is electrically connected to the SIG terminal 8 that is an output signal line by applying a voltage to the gate of the analog switch 7 on a one-to-one basis. The gate of each analog switch 7 is connected to each stage of a shift register (128 stages in the figure) 9 and opens / closes the analog switch 7 by a signal from the shift register 9.
[0004]
FIG. 10 is a timing chart of the circuit of FIG.
Next, the operation will be described.
As shown in FIG. 10, when a start signal is input to the SI terminal 10 of the shift register 9, the shift register 9 starts to operate, and the first gate and the second gate are sequentially connected according to the clock pulse input to the CLK terminal 11. Close. At the same time as the 128th gate is closed, an end signal is output to the SO terminal 12. If the SO terminal 12 and the SI terminal 10 of the next photoelectric conversion element circuit IC2 are connected, the gate 7 of the photoelectric conversion element 6 can be opened and closed sequentially.
[0005]
[Problems to be solved by the invention]
FIG. 11 is a diagram showing a resolution switching circuit of a conventional image sensor.
11, 6 to 12 are the same as those in FIG. Reference numeral 13 denotes a resolution switching terminal to which a resolution switching signal is input. Reference numeral 14 denotes a selector arranged in the preceding stage of the shift register 9, and is connected to the SI terminal 10 and the resolution switching terminal 13. The shift register includes an 8-dot / mm shift register 9a and a 4-dot / mm shift register 9b.
For example, when converting the resolution of the image sensor from 8 dots / mm as shown in FIG. 9 to 4 dots / mm, a selector 14 is provided in front of the shift register as shown in FIG. 11, and a start signal is input to the SI terminal 10. Then, the SI signal is input to either the 8-dot / mm shift register 9a or the 4-dot / mm shift register 9b according to the logic of the resolution switching terminal 13 input to the selector 14, and the resolution is changed. Switching is possible.
[0006]
In the circuit as shown in FIG. 11, a shift register 9b must be provided in addition to the shift register 9a, and the number of shift register circuits increases. For lower resolutions, for example, for a resolution of 2 dots / mm, another half of the shift register 9b of 4 dots / mm must be provided, and the attached circuit becomes more complicated. The scale of the photoelectric conversion element circuit IC2 becomes larger.
[0007]
Further, in the case of lowering the resolution by adding the shift register 9b as shown in FIG. 11, the operation of partially increasing the resolution or partially decreasing the resolution cannot be performed on the same photoelectric conversion element circuit IC2.
[0008]
The present invention has been made to solve the above-described problems, and an object of the present invention is to obtain an image sensor capable of freely switching the resolution without increasing the number of shift registers.
[0009]
[Means for Solving the Problems]
Image sensor according to claim 1 is placed in a straight line, a plurality of photoelectric conversion elements for converting an optical signal into an electric signal, arranged to correspond to the photoelectric conversion element so as to select the output of the photoelectric conversion element a plurality of analog switches which are, in synchronism with a clock operating at a predetermined order, a plurality of shift registers, each of which outputs a control signal to the gate of the analog switch, is arranged between adjacent contact shift register, the switching of the resolution Provided with a plurality of selectors for changing the connection between the shift registers according to the resolution switching signal to be instructed ,
The selector has a resolution switching terminal to which a resolution switching signal is input, and a plurality of output ports that are sequentially connected to the input of the subsequent shift register and are switched according to the resolution switching signal input to the resolution switching terminal. According to the logic of the switching signal, the output port is switched, the output of the photoelectric conversion element is thinned out, and the resolution is switched .
[0010]
The resolution switching signal is composed of 2 bits.
The resolution switching signal is composed of N bits.
[0011]
Furthermore, the logic of the resolution switching signal is changed in synchronization with the clock.
The logic of the resolution switching signal is changed so as to correspond to a part of the document read by the photoelectric conversion element.
Further, the logic of the resolution switching signal is changed at a constant cycle.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
The overall configuration of the image sensor unit according to the first embodiment is the same as FIG.
1 is a diagram showing a resolution switching circuit using a selector of an image sensor according to Embodiment 1 of the present invention.
In FIG. 1, reference numeral 6 denotes 128 photoelectric conversion elements, which are sequentially numbered, and are constituted by thin film photodiodes or photoconductive thin films. Although not shown in the drawing, each photoelectric conversion element 6 has a common electrode and is grounded or an appropriate bias voltage is applied. 7 is an analog switch for controlling the output of the photoelectric conversion element 6, 8 is an SIG terminal which is an output signal line, and 9 is a shift register which is arranged so as to correspond to the photoelectric conversion element 6 and outputs a signal to the gate of the analog switch 7. Reference numeral 10 denotes an SI terminal to which a start signal of the shift register 9 is input. Reference numeral 11 denotes a CLK terminal to which a clock is input, and reference numeral 12 denotes an SO terminal to which an end signal of the shift register 9 is output. Reference numeral 13 denotes a resolution switching terminal to which a 2-bit resolution switching signal is input. Reference numeral 14 denotes a selector disposed between the stages of the shift register 9, to which a resolution switching terminal 13 is connected.
[0013]
The basic operation of the circuit of FIG. 1 is the same as that described with reference to FIG. 9. The photoelectric conversion element 6 is selected by applying a voltage to the gate of the analog switch 7 on a one-to-one basis, and the output It conducts to the SIG terminal 8 which is a signal line. The gate of each analog switch 7 is connected to each stage of a shift register (128 stages in the figure) 9 and opens / closes the analog switch 7 by a signal given from the shift register 9 in a predetermined order.
FIG. 2 is a diagram showing the logic of the selector of the image sensor according to Embodiment 1 of the present invention.
In FIG. 2, 14 is a selector.
FIG. 3 is a timing chart of the image sensor according to the first embodiment of the present invention.
[0014]
Next, the operation will be described.
A selector 14 is provided between the shift registers 9. If the operation logic of the selector 14 is as shown in FIG. 2, for example, the photoelectric conversion element 6 has a resolution of 8 dots / mm (output from Y0). When it is desired to obtain an output of half of 4 dots / mm, if the input of the resolution switching terminal 13 of the selector 14 is A [0: 1] = 1, the output of the photoelectric conversion element 6 is shown in FIG. As shown in the timing chart, the first, third, fifth,... And 1 dot can be thinned out and output (output from Y1).
If the resolution is to be 2.67 dots / mm, which is 1/3 of 8 dots / mm, the input of the resolution switching terminal 13 of the selector 14 may be set to A [0: 1] = 2 (Y2 If you want to set the resolution to 2 dots / mm, which is 1/4 of 8 dots / mm, change the image resolution by setting A [0: 1] = 3 (output from Y3). It becomes possible.
[0015]
According to the first embodiment, the resolution can be switched freely without increasing the number of shift registers.
[0016]
Embodiment 2. FIG.
FIG. 4 is a timing chart of the image sensor according to the second embodiment of the present invention.
FIG. 5 is a diagram showing a high resolution portion in the document of the image sensor according to the second embodiment of the present invention.
In FIG. 5, 3 is a document, 15 is a high resolution area, and 16 is a low resolution area.
[0017]
In the circuit as shown in FIG. 1, not only the usage method as in the first embodiment but also the resolution can be partially changed.
In the timing chart in this case, as shown in FIG. 4, by changing the logic by synchronizing the input signal A1 of the selector 14 with the clock, the decimation number (number of skipped registers) at that time is changed. It becomes possible.
Accordingly, for example, as shown in FIG. 5, the high-resolution area 15 that requires high-resolution reading is partially included in the read document 3, and the low-resolution area 16 that is a low-resolution area may be used. Only in the portion of the image area 15, the resolution switching terminal 13 of the selector 14 is set to the input signal A [0: 1] = 0 to obtain a high resolution, and in other cases, the resolution switching terminal 13 of the selector 14 is set to the input signal. By setting A [0: 1] = 3, a partially high resolution image can be obtained.
[0018]
According to the second embodiment, by partially reading a high-resolution image, it is possible to read the entire original faster than when reading the entire image at a high resolution.
[0019]
Embodiment 3 FIG.
FIG. 6 is a timing chart of the image sensor according to the third embodiment of the present invention.
In the circuit configuration as shown in FIG. 1, the selector 14 is first supplied with a signal from the SI terminal 10 (SI2) at the timing shown in FIG. 6, and the resolution switching terminal 13 receives the input signal as A [0: 1. ] = 1 and A [0: 1] = 2, and if the number of thinnings is changed by switching every clock, the output bits are also shifted to the third, fifth, eighth, tenth and thirteenth (2 bits skipped, 1 bit skipped, 2 An irregular output bit can be obtained as shown in FIG. As a result, if the photoelectric conversion element 6 is 8 dots / mm, for example, a pseudo resolution of 3.2 dots / mm (8 ÷ 5 × 2 dots / mm) can be obtained, and more resolutions can be handled. become able to.
In the above description, the case where the logic of the resolution switching signal is switched for each clock has been described. However, if the resolution switching signal is switched at a constant period, a pseudo resolution can be formed.
[0020]
According to the third embodiment, it is possible to obtain a pseudo resolution by switching the resolution at regular intervals, and it is possible to deal with more resolutions.
[0021]
Embodiment 4 FIG.
In the first to third embodiments, the case where the input to the resolution switching terminal 13 of the selector 14 is 2 bits has been described. However, there is no problem even if the number of bits is more than that.
If 3 bits are used as shown in FIG. 7, seven bits can be thinned out. For example, if the photoelectric conversion element 6 is 8 dots / mm, the resolution can be further reduced to a minimum of 1 dot / mm, and more resolutions can be handled.
[0022]
According to the fourth embodiment, it is possible to deal with more resolutions by increasing the number of input bits to the resolution switching terminal.
[0023]
【The invention's effect】
Since this invention is comprised as mentioned above, there exists an effect as shown below.
Are placed in a straight line, a plurality of photoelectric conversion elements for converting an optical signal into an electric signal, the plurality of analog switches disposed to correspond to the photoelectric conversion element to select the output of the photoelectric conversion element, the clock synchronously operated in a predetermined sequence, each respectively disposed a plurality of shift register for outputting a control signal to the gate of the analog switch, between adjacent contact shift register, shifting in accordance with the resolution switching signal for instructing the switching of the resolution It has multiple selectors that change the connection between registers ,
The selector has a resolution switching terminal to which a resolution switching signal is input, and a plurality of output ports that are sequentially connected to the input of the subsequent shift register and are switched according to the resolution switching signal input to the resolution switching terminal. According to the logic of the switching signal, the output port is switched, the output of the photoelectric conversion element is thinned out, and the resolution is switched. Therefore, the resolution can be switched freely without newly providing a shift register.
[0024]
Also, since the resolution switching signal is composed of 2 bits, it is possible to switch between four types of resolutions.
Further, since the resolution switching signal is composed of N bits, it is possible to switch between various types of resolutions.
[0025]
Furthermore, since the logic of the resolution switching signal is changed in synchronization with the clock, the resolution can be switched in synchronization with the clock.
Further, since the logic of the resolution switching signal is changed so as to correspond to a part of the document read by the photoelectric conversion element, it can partially correspond to the high-resolution document.
[0026]
Further, since the logic of the resolution switching signal is changed at a constant cycle, the resolution can be formed in a pseudo manner.
[Brief description of the drawings]
FIG. 1 is a diagram showing a resolution switching circuit using a selector of an image sensor according to Embodiment 1 of the present invention.
FIG. 2 is a diagram showing logic of a selector of an image sensor according to Embodiment 1 of the present invention.
FIG. 3 is a timing chart of the image sensor according to the first embodiment of the present invention.
FIG. 4 is a timing chart of an image sensor according to Embodiment 2 of the present invention.
FIG. 5 is a diagram showing a high resolution portion in an original of an image sensor according to Embodiment 2 of the present invention.
FIG. 6 is a timing chart of the image sensor according to the third embodiment of the present invention.
FIG. 7 is a diagram showing the logic of a selector of an image sensor according to a fourth embodiment of the present invention.
FIG. 8 is a schematic diagram illustrating a configuration of a conventional image reading apparatus.
FIG. 9 is a diagram showing a basic circuit for driving a conventional image sensor.
FIG. 10 is a timing chart of the circuit of FIG.
FIG. 11 is a diagram illustrating a resolution switching circuit of a conventional image sensor.
[Explanation of symbols]
1 sensor unit, 2 photoelectric conversion element circuit IC, 3 manuscript,
4 Selfoc lens array, 5 LED array,
6 photoelectric conversion elements, 7 analog switches, 8 SIG terminals,
9 Shift register, 10 SI terminal, 11 CLK terminal,
12 SO terminal, 13 resolution switching terminal, 14 selector,
15 High resolution area, 16 Low resolution area.

Claims (1)

Are placed in a straight line, a plurality of photoelectric conversion elements for converting an optical signal into an electric signal, the plurality of analog switches disposed to correspond to the photoelectric conversion element so as to select the output of the photoelectric conversion element, the clock in synchronization with the work in a predetermined order, each respectively disposed between a plurality of shift registers, adjacent contact shift register for outputting a control signal to the gate of the analog switch, depending on the resolution switching signal for instructing the switching of the resolution With multiple selectors to change the connection between shift registers ,
The selector has a resolution switching terminal to which the resolution switching signal is input and a plurality of output ports that are sequentially connected to the input of the subsequent shift register and switched according to the resolution switching signal input to the resolution switching terminal. An image sensor , wherein the output port is switched according to the logic of a resolution switching signal, the output of the photoelectric conversion element is thinned out, and the resolution is switched .

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