JPH11355516A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image reader with which there is no degradation in the information quantity and the sensitivity even when pixel density conversion is performed but the sensitivity is improved in the case of reduction in size (pixel density is made coarse) rather than the case of no density conversion. SOLUTION: This device is provided with an LED array 3 for illuminating an original, a rod lens array 5 for condensing reflected light or transmitted light from the original, a photoelectric converting element 6 for converting the condensed optical information to an electrical signal, and a pixel density converting circuit 101 for outputting a pixel density converted signal by adding the output values of arbitrary continuous plural pixels from the photoelectric conversion element 6 based on parameter data inputted from the outside. Thus, the pixel density is converted while suppressing the degradation in information quantity to a minimum, at the same time, output sensitivity is improved and an S/N can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus using a one-dimensional line sensor having a new pixel density conversion technique.

[0002]

2. Description of the Related Art A conventional image reading apparatus will be described with reference to the drawings. FIG. 10 is a diagram showing a configuration of a conventional image reading device (contact image sensor). FIG.
FIG. 1 is a diagram showing a cross-sectional structure of the conventional image reading apparatus of FIG.

[0003] In FIGS. 10 and 11, reference numeral 1 denotes a transparent plate for determining the position of a document 8, 2 denotes an LED chip (light emitting element) mounted on a substrate over a reading width and constituting an LED array (light source) 3 Is a housing for holding each component, 5
Is a rod lens array (optical system) for guiding the reflected light from the original 8 to the photoelectric conversion element 6 mounted on the substrate 7.
The photoelectric conversion element 6 includes 3456 sensors (chips), a shift register, and an analog switch.

In FIG. 1, reference numeral 9 denotes a photoelectric conversion element 6;
An analog-to-digital (A / D) converter for converting an analog output from a digital signal into a digital signal is a digital image processing IC. Further, 11 and 12 are power terminals (V _LED , G _LED ) of the LED array 3, 13 and 14 are power terminals (V _DD , GND) of the image reading device, and 15 and 16 are photoelectric conversion elements 6.
Are control terminals (SI, CLK), 19 is an output terminal (SIG) of the photoelectric conversion element 6, 17 is a clock (ADCK) of the A / D converter 9, and 18 is binary information of the output of the digital image processing IC 10.

Next, the operation of the above-described conventional image reading apparatus will be described with reference to the drawings. FIG. 12 is a timing chart showing the operation of the conventional image reading apparatus.

The reflected light information from the original 8 illuminated by the LED array (light source) 3 is collected on the photoelectric conversion element 6 by the rod lens array (optical system) 5. The photoelectric conversion element 6 outputs an analog output substantially proportional to the input light to the control signals (SI) and (C) from the control terminals 15 and 16.
LK) and output.

[0007] When it is necessary to reduce the size in the main scanning direction or when it becomes necessary to reduce the number of outputs of the photoelectric conversion elements included in the reading width, conventionally, a technique of simply thinning out pixels has been adopted.

In FIG. 12, a pixel density of 400 dpi-A4
An example of a case where the size of the image reading apparatus is reduced to 1/2 (or the pixel density may be converted to 200 dpi) will be described. That is, the frequency of the clock ADCK input to the A / D converter 9 is set to half of the pixel clock (CLK), thereby sampling pixel information of every other pixel (even pixel). When not reducing or thinning, the clock ADCK
Is the same as that of the pixel clock CLK. More generally, a method capable of arbitrarily setting the reduction ratio is proposed in Japanese Patent Laid-Open No. Hei 6-205200.

[0009]

In the conventional image reading apparatus as described above, there is a problem that pixel information which is not sampled is completely lost when thinning is performed.

For example, in the example of FIG. 12 (1/2 thinning-out), information of odd-numbered pixels is missing. As a result of thinning, 20
Although the pixel density is the same as that of the image reading apparatus of 0 dpi-A4, the fill-ratio (the ratio of the sum of the main scanning dimensions of the pixels to the reading line length (A4, 216 mm in this example)) becomes significantly smaller. For example, the original 40
Assuming that the pixels of 0 dpi are 50 μm square, the fill-ratio when used without thinning is (0.0
5 * 3456) / 216 = 80%, whereas 1 /
The fill-ratio in the case of using the thinning of (2) is (0.
05 * 1728) / 216 = 40%.

Assuming that the pixel of the image reading apparatus originally formed at 200 dpi is 85 μm, the fill-ratio in the case of A4 size is (0.085 * 172).
8) / 216 = 68%, and it is apparent that the fill-ratio is particularly reduced in the case of thinning use of 400 dpi. A smaller fill-ratio means a smaller amount of information and a correspondingly smaller sensitivity (S / N).

Further, the photoelectric conversion element 6 generally has a sensitivity variation for each pixel. As a result, for example, within the A4 width,
It has a certain output distribution (deviation). FIG. 12 above
In the case of (1), if one of the even-numbered pixels has a large sensitivity variation, the deviation of the one pixel remains even after thinning-out, resulting in deterioration of the reading performance.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems. Even when the pixel density conversion is performed, the information amount and the sensitivity do not deteriorate. It is an object of the present invention to obtain an image reading apparatus having higher sensitivity than the case where no density conversion is performed.

It is still another object of the present invention to provide an image reading apparatus in which the influence of sensitivity variation for each pixel is reduced so that the output deviation between adjacent pixels or the output deviation over the entire reading width is small.

[0015]

According to the present invention, there is provided an image reading apparatus comprising: a light source for illuminating a medium to be read; an optical system for collecting light reflected or transmitted from the medium to be read; A photoelectric conversion element that converts optical information into an electric signal, and based on parameter data input from the outside, add the output values of any continuous plurality of pixels from the photoelectric conversion element to obtain a signal that has been subjected to pixel density conversion. And a pixel density conversion circuit for outputting.

Further, in the image reading apparatus according to the present invention, the pixel density conversion circuit samples the output signal from the photoelectric conversion element using a first sample hold signal generated based on the parameter data. A sample-and-hold circuit, an integrator for transferring the charges charged by the first sample-and-hold circuit one pixel at a time by a charge transfer signal generated based on the parameter data, and adding the charge over a plurality of pixels; And a second sample-and-hold circuit for sampling the integrated voltage by the sampler using a second sample-and-hold signal generated based on the parameter data.

Further, in the image reading apparatus according to the present invention, the pixel density conversion circuit samples the output signal from the photoelectric conversion element using a first sample hold signal generated based on the parameter data. A sample-and-hold circuit, an integrator that transfers the charges charged by the first sample-and-hold circuit collectively to a plurality of pixels by a charge transfer signal generated based on the parameter data, and adds the charges over a plurality of pixels. A second sample-and-hold circuit for sampling an integrated voltage by the integrator with a second sample-and-hold signal generated based on the parameter data.

Further, in the image reading apparatus according to the present invention, the pixel density conversion circuit converts the output signal from the photoelectric conversion element into a first sample hold signal for each of a predetermined number of pixels generated based on the parameter data. A first sample-and-hold circuit that samples and charges each pixel by a signal, an adder that adds the charge that is charged for each pixel by the first sample-and-hold circuit, and an addition voltage by the adder, And a second sample-and-hold circuit for sampling with a second sample-and-hold signal generated based on the parameter data.

Further, in the image reading apparatus according to the present invention, the photoelectric conversion element has a plurality of photoelectric conversion element chips connected in series in the main scanning direction, and the pixel density conversion circuit is connected to an adjacent photoelectric conversion element. This is to add and output a plurality of pixel outputs over a chip.

Further, in the image reading apparatus according to the present invention, the optical system has a plurality of condensing lenses shorter than the reading width connected in series in the main scanning direction.

Further, the image reading apparatus according to the present invention is
The condensing lens is a rod lens array capable of forming an erect image at the same magnification.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 An image reading apparatus according to Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a configuration of an image reading apparatus according to Embodiment 1 of the present invention. FIG. 2 is a diagram showing a detailed configuration of a pixel density conversion circuit of the image reading device according to the first embodiment of the present invention. In the drawings, the same reference numerals indicate the same or corresponding parts. The mechanical and optical structure of the image reading apparatus is the same as that of the conventional apparatus shown in FIG.

In FIG. 1, reference numeral 2 denotes an LE mounted on a substrate over a reading width to constitute an LED array (light source) 3.
D chip 5 and rod lens array (optical system) 5 for guiding the reflected light from the document to photoelectric conversion element 6 mounted on substrate 7, and 4 a housing for holding each component.

In the same figure, reference numerals 11 and 12 denote LEs.
D array (light source) 3 power supply terminals (V _LED , G _LED ), 13
And 14 are power terminals (V _DD , GND) of the image reading device,
111 is an input terminal of a line synchronization signal (SII), 112
Is an input terminal of a system clock (S-CLK), 113
Is an input terminal for parameter data, 19 is an image (SIG)
Is an output terminal of the data clock (D-CLK).

Further, in the figure, 101 is a pixel density conversion circuit, 102 is a data selector, 103 is a frequency division block counter, 104 is a sample and hold signal generator,
Reference numeral 105 denotes an image clock generator, 106 denotes a clock counter, 107 denotes a synchronization circuit, and 108 denotes a synchronization signal generator.

In FIG. 2, 201, 202, 203 and 204 are operational amplifiers, 205, 206 and 207 are capacitors, 208, 209, 210 and 211 are analog switches, and 212 and 213 are resistors.

Next, the operation of the image reading apparatus according to the first embodiment will be described with reference to the drawings.
FIG. 3 is a timing chart showing the operation of the image reading apparatus according to Embodiment 1 of the present invention.

The reflected light information from the document 8 illuminated by the LED array (light source) 3 is collected on the photoelectric conversion element 6 by the rod lens array (optical system) 5. The photoelectric conversion element 6 converts an analog sensor output 71 shown in FIG. 3 (2) which is almost proportional to the input light into a control signal (image clock) 72 and a (line start signal) shown in FIG. 3 (1).
Output in synchronization with 73.

When it is necessary to reduce the size in the main scanning direction or when it is necessary to reduce the number of photoelectric conversion element outputs included in the reading width, the pixel density conversion circuit 101 operates as follows.

A synchronizing signal generator 108 receives a line synchronizing signal (SII) from an input terminal 111, and further has a line start signal 73 synchronized with the image clock 72 generated by the image clock generator 105 in the synchronizing circuit 107.
Occurs.

On the other hand, in the clock counter 106, the system clock signal (S-
CLK), the image clock generator 105 is controlled, and the sample and hold signal groups 74a to 74d,
And a data clock (D-C) synchronized with the image data 19
LK) to control the sample and hold signal generator 104.

On the other hand, the data selector 102 receives the parameter data from the input terminal 113, and receives a clock counter 106 and a sample-and-hold signal generator 104.
Control.

Next, the pixel density conversion circuit 101 of FIG. 2 and the timing chart of FIG. 3 will be described.

From the photoelectric conversion element 6 to the pixel density conversion circuit 10
The analog signal (sensor output) 71 (FIG. 3)
(2)) The operational amplifier 201 and the analog switch 20
8 and the capacitor 205, the sample hold signal 74a
(FIG. 3 (3)), the signal is sampled and held and the signal V
a (FIG. 3 (4)).

Next, an integrator composed of the analog switch 209, the operational amplifier 202, and the capacitor 206 outputs a charge transfer (sample / hold) signal 74b (FIG. 3).
(5)), the operational amplifier 203 and the resistor 21
Signal Vb through an inverting amplifier consisting of
(FIG. 3 (6)) is obtained.

Further, a sample-and-hold circuit composed of the analog switch 211, the operational amplifier 204 and the capacitor 207 forms a sample-and-hold signal 74d (FIG. 3 (7)).
To obtain a signal (SIG) Vc (FIG. 3 (9)).

Incidentally, 74c inputted to the analog switch 210 is a reset signal. Also, the reset signal 7
4c or the sample hold signal 74d is a data clock (D-CL) synchronized with the image signal Vc (SIG).
K).

In FIG. 3, the finally obtained signal V
The pixel density of c is shown as an example that is ４ of that of the original image signal 71. The signal level of each pixel of the obtained signal Vc is the sum (integral) value of four pixels of the original image signal 71, and at the same time as the 1/4 density conversion,
A four-fold improvement in sensitivity is obtained.

Of course, this conversion ratio depends on the sample and hold signal generator 104 and the clock counter 106.
It is needless to say that 1 / n (n: any positive integer) can be obtained by changing the configuration of

Further, in order to keep the final output (Vc) substantially constant even when n changes, the ratio between the capacitance C ₂₀₅ of the capacitor ₂₀₅ and the capacitance C _{206 of the} capacitor 206 must satisfy the following relationship. It is convenient if either of the capacities is made variable. C ₂₀₆ / C ₂₀₅ = n

Also, by selecting the resistance ratio between the resistor 212 and the resistor 213, the same effect can be obtained by varying the gain of the operational amplifier 203. Furthermore, when the polarity of the final output (Vc) may be inverted from that of the input 71,
Needless to say, the above-mentioned inverting amplifier is unnecessary.

Embodiment 2 Embodiment 2 An image reading apparatus according to Embodiment 2 of the present invention will be described with reference to the drawings. FIG. 4 is a diagram showing a detailed configuration of a pixel density conversion circuit of an image reading apparatus according to Embodiment 2 of the present invention. FIG. 5 is a timing chart showing the operation of the image reading apparatus according to Embodiment 2 of the present invention. Other configurations are the same as those in the first embodiment.

In the first embodiment, the electric charge stored in the capacitor 205 of the first stage sample and hold circuit is
Although the pixels are transferred to the next integrator one by one by the transfer signal 74b, the second embodiment is characterized in that the signals of a plurality of pixels are transferred collectively (in each case, four pixels).

The analog switch 209 of the integrator is shown in FIG.
As shown in (3) and (5), since the sample and hold signal 74b is closed by a plurality of pixels, the sample and hold signal 74a of the first stage sample and hold circuit is closed.
In this case, the operational amplifier 214 that is unnecessary in FIG. 2 of the first embodiment is inserted.

As described above, in the second embodiment, the signal Va
Is also transferred to the integrator in the sampling period (the high-level period of the sample-and-hold signal 74b).
Although there is a disadvantage that the accuracy is reduced, the sample and hold signal 74
There is an advantage that b can be obtained as an inverted signal of the reset signal 74c and can be easily obtained as a divided clock of the sample and hold signal 74a.

Further, even when n changes, the final output V
To keep c substantially constant, the capacitance C of the capacitor 205
_As described in the first embodiment, it is possible to select the ratio between ₂₀₅ and the capacitance C _{206 of the} capacitor 206 or the resistance ratio between the resistor 212 and the resistor 213.
Further, when the polarity of the final output Vc is inverted from that of the input 71, the inverting amplifier is not required.

Embodiment 3 Embodiment 3 An image reading apparatus according to Embodiment 3 of the present invention will be described with reference to the drawings. FIG. 6 is a diagram showing a detailed configuration of a pixel density conversion circuit of an image reading device according to Embodiment 3 of the present invention. FIG. 7 is a timing chart showing the operation of the image reading apparatus according to Embodiment 3 of the present invention. Other configurations are the same as those in the first embodiment.

In the first and second embodiments, an example has been described in which the charge sampled and held by the first-stage sample-hold circuit is transferred to the integrator by another transfer signal. In the third embodiment, the transfer is performed. The integrator and the integrator are abolished and replaced by an adder described later.

That is, the first-stage buffer operational amplifier 20
Subsequent to 1, analog switches 208-1 to 208-2 of four systems
08-4, operational amplifiers 215-1 to 215-4, and capacitors 205-1 to 205-4, a four-series sample-hold circuit 74
a-1 to 74a-4, the signals Va to V
Obtain d.

Further, an operational amplifier 217, a resistor 216 and
Through an adder consisting of 1-216-4 and a resistor 218,
The signal Ve (minimal inversion) is obtained.

Further, a sample and hold circuit comprising the analog switch 211, the operational amplifier 204 and the capacitor 207 operates according to the sample and hold signal 74d,
The signal Vf is obtained through an inverting amplifier including an operational amplifier 203, a resistor 212, and a resistor 213.

The signal level of each pixel of the obtained signal Vf is the total (integral) value of the four pixels of the original image signal 71, and the sensitivity is increased four times at the same time as the 1/4 density conversion. An improvement is obtained.

Of course, this conversion ratio can be made 1 / n (n: any positive integer) by changing the configuration of the sample hold generator 104 and the clock counter 106.

Furthermore, even when n changes, the final output V
To keep f substantially constant, the resistance R
₂₁₆ (the combined resistance of the resistors 216-1 to 216-4) and the resistance R ₂₁₈ of the resistor 218, so that either one of the resistances can be varied so that R ₂₁₆ / R ₂₁₈ = n. It would be convenient.

Also, by selecting the resistance ratio between the resistor 212 and the resistor 213, the same effect can be obtained by varying the gain of the operational amplifier 203. Furthermore, the final output V
If the polarity of f can be inverted from that of the input 71, the inverting amplifier is not required.

Embodiment 4 Embodiment 4 An image reading apparatus according to Embodiment 4 of the present invention will be described with reference to the drawings. FIG. 8 is a timing chart showing the operation of the image reading apparatus according to Embodiment 4 of the present invention. The configuration is the same as in each embodiment.

The pixel density conversion circuit according to the fourth embodiment will be described with reference to FIG. In general, an image reading device (contact image sensor) corresponds to a required reading width by mounting a plurality of photoelectric conversion element chips having several tens to several hundreds of pixels on a straight line. Generally varies.

FIG. 8 shows a boundary portion between the nth and (n + 1) th chips having 128 pixels of photoelectric conversion elements per chip as an input signal 71 to the pixel density conversion circuit 101.

Then, assuming a case where the sensitivities of the adjacent chips are largely different, a case where the sensitivity of the n-th chip is higher than that of the (n + 1) -th chip will be described.

The density conversion rate is set to 1/2, and the integration interval is set so as to extend between adjacent chips. By setting the integration (addition) section in this way,
The change in the output Vc after the density conversion at the boundary between adjacent chips is more gradual than the change in the original input waveform (71). That is, it is possible to reduce the output deviation of adjacent pixels generated at the boundary.

Further, the output sensitivity can be almost doubled by adding the output values of two pixels. It goes without saying that substantially the same effect can be obtained in any of FIGS. 4 and 6 as the pixel density conversion circuit in addition to FIG.

Embodiment 5 Embodiment 5 An image reading apparatus according to Embodiment 5 of the present invention will be described with reference to the drawings. FIG. 9 is a diagram showing a configuration of an image reading apparatus according to Embodiment 5 of the present invention.

The image reading apparatus according to the fifth embodiment has
Although the reading width is equal to or larger than the A3 size (for example, A0 size), a plurality of short (for example, about A4 size) rod lens arrays (four in the example of FIG.
1 to 5-4) are connected in a line.

Now, the rod lens arrays 5-1 to 5-4
Are used in series, it is difficult to ensure that the connection position accuracy of the rod lens array at the connection boundary is at the same level as at the boundary, and as a result, the output deviation of the portion corresponding to the boundary is reduced. Getting worse. However, FIG.
By using such a pixel density conversion circuit, the output deviation can be reduced according to the principle described in the fourth embodiment, and the output sensitivity can be improved. 2, 4 and 6 as the pixel density conversion circuit.
It goes without saying that almost the same effect can be obtained by any of the above.

In each of the above embodiments, an example in which an LED array is used as a light source has been described. However, other equivalent means, for example, a lamp light source such as a fluorescent lamp may be used instead.

The image reading apparatus according to each of the embodiments of the present invention is provided with a switched capacitor filter circuit, an adding circuit, or an integrating circuit as a means for converting pixel density after outputting a photoelectric conversion element. A total (integral) value of the output of the pixel can be output. Further, the number of pixels to be integrated can be changed by parameter data input from the outside, and as a result, the reduction ratio (density conversion coefficient) can be changed. Similarly, the address of the pixel to be integrated can be designated by parameter data input from the outside.

According to each embodiment of the present invention, the pixel density conversion is performed while minimizing the deterioration of the information amount.
The output sensitivity is increased, the S / N ratio is improved, and the output deviation generated in pixel units or chip units is averaged, whereby the output deviation can be reduced, and an image reading apparatus with good reproducibility can be obtained. it can. By improving the output sensitivity, when the reading speed is constant, the light source light amount can be reduced, and the cost can be reduced.
When the light source light amount is constant, the reading speed can be increased at the same cost.

[0068]

As described above, the image reading apparatus according to the present invention comprises: a light source for illuminating a medium to be read; an optical system for collecting light reflected or transmitted from the medium to be read; A photoelectric conversion element for converting the converted optical information into an electric signal, and a pixel density converted signal obtained by adding output values of arbitrary continuous pixels from the photoelectric conversion element based on parameter data input from the outside. Is provided, the pixel density conversion is performed while minimizing the deterioration of the information amount, and at the same time, the output sensitivity is increased and the S / N can be improved.

As described above, in the image reading apparatus according to the present invention, the pixel density conversion circuit converts the output signal from the photoelectric conversion element into the first sample hold signal generated based on the parameter data. A first sample and hold circuit for sampling by
The charge charged by the sample and hold circuit of
An integrator that transfers one pixel at a time by a charge transfer signal generated based on the parameter data and adds over a plurality of pixels; and a second sample and hold signal generated based on the parameter data by integrating the integrator. And the second sample-and-hold circuit, which performs sampling by the method described above, has an effect that the pixel density conversion can be performed while minimizing the deterioration of the information amount, the output sensitivity can be increased, and the S / N can be improved.

Further, as described above, in the image reading apparatus according to the present invention, the pixel density conversion circuit converts the output signal from the photoelectric conversion element into the first sample hold signal generated based on the parameter data. A first sample and hold circuit for sampling by
The charge charged by the sample and hold circuit of
An integrator that collectively transfers a plurality of pixels based on the charge transfer signal generated based on the parameter data and adds over a plurality of pixels; and a second sample hold generated based on the parameter data by an integrated voltage generated by the integrator. Since the second sample-and-hold circuit for sampling with a signal is provided, it is possible to convert the pixel density while minimizing the deterioration of the information amount, and at the same time, to increase the output sensitivity and improve the S / N.

Further, in the image reading apparatus according to the present invention, as described above, the pixel density conversion circuit converts the output signal from the photoelectric conversion element for each of a predetermined number of pixels generated based on the parameter data. A first sample-and-hold circuit that samples and charges for each pixel by a first sample-and-hold signal, an adder that adds the charge charged for each pixel by the first sample-and-hold circuit, A second sample-and-hold circuit for sampling the added voltage with a second sample-and-hold signal generated based on the parameter data. And the S / N can be improved.

As described above, in the image reading apparatus according to the present invention, the photoelectric conversion element has a plurality of photoelectric conversion element chips connected in series in the main scanning direction, and the pixel density conversion circuit has Since the outputs of a plurality of pixels extending over adjacent photoelectric conversion element chips are added and output, the output deviation can be reduced by averaging the output deviation generated in pixel units or chip units.

Further, in the image reading apparatus according to the present invention, as described above, since the optical system has a plurality of condensing lenses shorter than the reading width connected in series in the main scanning direction, the pixel unit or the By averaging the output deviation generated for each chip, the output deviation can be reduced and the output sensitivity can be improved.

Further, the image reading apparatus according to the present invention
As described above, since the condensing lens is a rod lens array capable of erecting an equal-magnification image, it is possible to reduce the output deviation by averaging the output deviation generated in pixel units or chip units. As a result, there is an effect that the output sensitivity can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an image reading device according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a detailed configuration of a pixel density conversion circuit of the image reading device according to the first embodiment of the present invention;

FIG. 3 is a timing chart illustrating an operation of the image reading apparatus according to the first embodiment of the present invention.

FIG. 4 is a diagram showing a detailed configuration of a pixel density conversion circuit of an image reading device according to a second embodiment of the present invention.

FIG. 5 is a timing chart showing an operation of the image reading apparatus according to Embodiment 2 of the present invention.

FIG. 6 is a diagram showing a detailed configuration of a pixel density conversion circuit of an image reading device according to a third embodiment of the present invention.

FIG. 7 is a timing chart showing an operation of the image reading apparatus according to Embodiment 3 of the present invention.

FIG. 8 is a timing chart showing an operation of the image reading apparatus according to Embodiment 4 of the present invention.

FIG. 9 is a diagram showing a configuration of an image reading apparatus according to Embodiment 5 of the present invention.

FIG. 10 is a diagram illustrating a configuration of a conventional image reading apparatus.

FIG. 11 is a diagram illustrating a cross-sectional structure of a conventional image reading apparatus.

FIG. 12 is a timing chart showing the operation of a conventional image reading apparatus.

[Explanation of symbols]

1 Transparent plate, 2 LED chip (light emitting element), 3 LE
D array (light source), 4 housings, 5 rod lens array (optical system), 6 photoelectric conversion elements, 7 substrates, 8 originals, 1
1, 12 light source power terminal, 13, 14 power terminal, 71
Sensor output, 72 image clock, 73 line start signal, 74a, 74b, 74c, 74d sample and hold signal, 101 pixel density conversion circuit, 102 data selector, 103 dividing block counter, 104
Sample and hold signal generator, 105 image clock generator, 106 clock counter, 107 synchronization circuit, 108 synchronization signal generator, 201, 202, 20
3, 204, 214, 215, 217 operational amplifier, 2
05, 206, 207 capacitors, 208, 209,
210, 211 analog switches, 212, 213,
216, 218 resistance.

Claims (7)

[Claims] 1. A light source for illuminating a medium to be read, an optical system for condensing reflected light or transmitted light from the medium to be read, a photoelectric conversion element for converting collected light information into an electric signal, A pixel density conversion circuit for adding a pixel density converted signal by adding output values of arbitrary continuous pixels from the photoelectric conversion element based on parameter data input from the outside; Image reading device. 2. The pixel density conversion circuit, comprising: a first sample-and-hold circuit that samples an output signal from the photoelectric conversion element using a first sample-and-hold signal generated based on the parameter data; An integrator that transfers the electric charge charged by the sample and hold circuit by one pixel by a charge transfer signal generated based on the parameter data and adds over a plurality of pixels; 2. The image reading apparatus according to claim 1, further comprising: a second sample-and-hold circuit that performs sampling using a second sample-and-hold signal generated based on the second sample-and-hold signal. 3. The pixel density conversion circuit, comprising: a first sample-and-hold circuit that samples an output signal from the photoelectric conversion element using a first sample-and-hold signal generated based on the parameter data; An integrator that collectively transfers a plurality of pixels by a charge transfer signal generated based on the parameter data and adds the charges charged by the sample-and-hold circuit to the plurality of pixels; 2. The image reading apparatus according to claim 1, further comprising: a second sample-and-hold circuit that performs sampling using a second sample-and-hold signal generated based on the data. 4. The pixel density conversion circuit samples and charges an output signal from the photoelectric conversion element for each pixel by a first sample and hold signal for each of a predetermined number of pixels generated based on the parameter data. A first sample and hold circuit, an adder for adding the charge charged for each pixel by the first sample and hold circuit, and a second voltage generated by the adder based on the parameter data. 2. The image reading apparatus according to claim 1, further comprising: a second sample-and-hold circuit that performs sampling by the sample-and-hold signal. 5. The photoelectric conversion element has a plurality of photoelectric conversion element chips connected in series in a main scanning direction, and the pixel density conversion circuit adds a plurality of pixel outputs over adjacent photoelectric conversion element chips. The image reading device according to claim 2, 3 or 4, wherein the image reading device outputs the image. 6. The optical system according to claim 1, wherein the optical system includes a plurality of condensing lenses shorter than a reading width connected in series in the main scanning direction. Image reading device. 7. The image reading apparatus according to claim 6, wherein the condenser lens is a rod lens array capable of forming an erect image at an equal magnification.