JP2001257836A - Device and method for reading image and storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an image with better S/N by sufficiently displaying the capability that a photoelectric converting element has. SOLUTION: The capability of a picture-quality increased photoelectric converting means can sufficiently be displayed by smoothly matching the photoelectric converting means whose picture quality is made high by performing analog processing by adjusting the DC level of the output of the photoelectric converting means to a specific level after the output is converted to a specific signal level using an attenuator 200 with an analog-processing IC which lowers the driving voltage as much as possible so as to suppress heat generation and reduce noise as much as possible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an image reading device,
The image reading method and the storage medium are particularly suitable for use in an image reading apparatus for reading a reflection optical image or a transmission optical image of a document placed on a document table.

[0002]

2. Description of the Related Art Conventionally, an image scanner using a linear image sensor (hereinafter referred to as CCD) has been known as an image reading apparatus. FIGS. 6A and 6B schematically show a general hardware configuration of an apparatus called a flatbed scanner. FIG. 6A is a top view and FIG. ) Is a side view.

In FIG. 6A and FIG. 6B, reference numeral D denotes a read original placed on an original platen glass 100.
Folded by 3,104, C by lens 105
An image is formed on the CD 106.

A light source 101 and mirrors 102, 103, 1
The reading unit 107 on which the lens 104, the lens 105, and the CCD 106 are fixedly mounted is moved in parallel to the platen glass 100, and, for example, is scanned from left to right in FIG. 1
得 る Obtain an image signal for one page. The CCD 106 board 113 on which the CCD 106 is mounted and the main board 112 fixed on the image reading apparatus main body side are connected to a cable 11.
1 connected.

As shown in FIG. 6A, the direction from top to bottom is the main scanning direction, and the direction from right to left is the sub-scanning direction. The interior is shielded from light by the exterior cover 1 and the document holder 110 in order to avoid the influence of external light.

FIG. 7 shows a general configuration example of a circuit block constituting output level adjusting means. Of the light emitted from the light source 101 capable of dimming control, the reflected light from the original or the optical signal transmitted through the original is imaged on the CCD 106 via the lens 105.

The optical signal formed on the CCD 106 is C
After being subjected to signal processing by an analog control circuit 30 that can be controlled by a PU 31, the signal is digitized by an A / D converter 32. Then, it is sequentially supplied to the shading correction circuit 3 and the image processing circuit 4. The analog control circuit 30 and the A / D converter 32 will be described together as an analog processing circuit 31.

The output of the A / D converter 32 is supplied to the peak detector 5 for light, and the peak detector 5 detects the peak output in the area designated by the CPU 36 and stores it. Further, a control signal from the CPU 36 is supplied to the output level control circuit 6, and the output level control circuit 6 performs dimming control so that the luminous intensity of the light emitted from the light source 101 is optimized.

In FIG. 7, an output level control circuit 6 of the light source 101 is used as means for controlling the output level.
Is described as an example, but the accumulation time control of the CCD 106, the electronic shutter level control means, the analog control circuit 3
0, a gain adjustment unit by ref control of an A / D converter (not shown), and a level control unit such as a level adjustment unit in the image processing circuit 4 can be considered. However, in order to obtain an image with a better S / N, it is most effective to use the dimming control as shown in FIG.

[0010] The CCD 10 is controlled by a light signal by dimming control.
As an example of controlling the output level of No. 6,
FIG. 8 shows a flowchart relating to dimming control. In FIG. 8, step S101 is an example in which processing is performed from the time when the power of the image reading apparatus is turned on.
Is described starting from the lamp ON in the sense of starting lighting.

Normally, the light source 101 includes a cold cathode lamp, a halogen lamp, etc., and the dimming control is generally performed by PWM control in an output level control circuit 6 in which voltage control, current control, intermittent lighting control, and the like are performed. It is.

In the first step S101, the lamp PWM is set to 100% because the normal lamp is ON. Next, in step S102, a wait time of 10 seconds is provided,
Wait until the light amount of the light source 101 is stably turned on.
The it time is not constant because it depends on the performance of the lamp and the configuration of the image reading device.

In step S103, the bright peak detection circuit 5 detects the bright output level Pn in order to measure the stability of the light source 101. Next, in step S104,
Light control is performed until the target output level Pt is reached. Next, in step S105,
It is determined whether or not the light output level Pn has reached the target output level Pt. If the result of this determination is that the light output level Pn has not reached the target output level Pt, needless to say, the PWM of the lamp is maintained at 100%.

Next, the detection of the light output level Pn is repeated every 0.75 seconds in step S106, and the light output level Pn is detected.
When n reaches within ± 1% of the level target output level Pt, the process proceeds to the stabilization control in step S107 and thereafter.

In the stability check in step S108,
If the fluctuation of the output level is maintained at a fluctuation of one level or less for a certain period of time (1.5 seconds in this case), it is determined that the output level is stable, and the dimming control is ended.

FIG. 9 shows a configuration example in which the board 113 of the CCD 106 and the main board 112 are connected by a cable 111. The output Vo of the CCD 106 is once input to the input Vin of the analog processing circuit 31 through the cable 111 via a current amplifier circuit (emitter follower) composed of the NPN transistor 8, the emitter resistor 7 and Vcc.

The power supply voltage of the CCD 106 is Vcc (usually 12 VDC), and the analog processing circuit 31 has a Vd (usually 5) lower than the above-mentioned Vcc for the sake of convenience of the digital circuit at the subsequent stage.
VDC).

FIG. 10 shows an output example of the CCD 106. FIG. 10A shows an example of the output Vo of the CCD 106. Assuming that the light level or the DC component of the output of the CCD 106 is Vd in a time corresponding to one line of the CCD 106 (abbreviated as lHSYNC). , FIG.
Indicates that a bright signal of 2 [V] is obtained near the center. At this time, the signal output in FIG.
[V] A low waveform, that is, (Vd-0.6) [V] is obtained.

[0019]

However, the maximum signal input range Vanmax of the analog processing circuit is, for example, 2.1 [V], and the maximum output level Vsat of the CCD 106 is, for example, 3 [V]. In the case where the output capacity is sufficiently larger than Vanmax, in the conventional example,
There was a problem that the ability of the CCD 106 could not be fully utilized.

FIG. 11 shows a configuration example of the analog processing circuit 31. As shown in FIG. 11, the analog processing circuit 31
In recent years, low power consumption and cost reduction technologies have been developed, and an analog processing IC 209 including an A / D converter has been developed.
The one-chip configuration as described above becomes mainstream and is used in combination with the AC coupling capacitor 201.

The analog processing IC 209 includes a DC clamp circuit 202 serving as a current supply circuit for maintaining the DC level of the AC coupling capacitor 201, a CDS circuit 203 for performing correlated double sampling, and a gain control for performing output level gain adjustment. Circuit 204, DC correction circuit 205 for finely adjusting the DC level, and A / D converter 2
06, an internal reference voltage generation circuit 208 for generating a reference voltage for these circuits, and a control register 207 for controlling these circuits. Note that, for color reading, an RGB 3-input type analog processing IC is also mainstream, but is not shown for simplification of description.

In FIG. 11, the output of the CCD 106 is
Digital signal input from Analog Signal Input shown in Fig. 9
From the Output, for example, it is digitized with an 8-bit output. Then, the Control Signal sent from the CPU 36
By controlling the control register 207, analog control is performed.

As described above, in recent years, cost reduction technology and low power consumption have become the mainstream for analog processing ICs, and it is possible to achieve high speed / high bandwidth and low noise at low cost. There is a situation in which heat generation must be suppressed as much as possible and the drive voltage level must be reduced.

At present, the drive voltage Vd of the analog processing IC 209 is currently 5 VDC to 3.3 VDC. In addition, as the power supply voltage Vd decreases, the dynamic range of analog signal input is decreasing.
On the contrary, as for the CCD 106, a differentiating technique of higher image quality is progressing, and the maximum output range Vsat of the CCD 106 is expanding.

An example of control in the related art using the CCD 106 and the analog processing circuit will be described with reference to FIG. 12 in accordance with the flowchart of FIG. In the image reading apparatus as shown in FIG.
When the converter 32 has an output level of 8 bits, the CCD 106 is affected by the target level Pt (240 level in FIG. 12) near the full range (255 level).
Is Vt (2 [V] in FIG. 12). Therefore, the dynamic range is limited to the dynamic range D1, and there is a problem that the performance of the CCD 106 cannot be sufficiently utilized for the dynamic range Dmax up to Vsat.

Also, depending on the environmental temperature and the variation of the solid,
Vd which is a DC component of the output of the CCD 106 is, for example, 3
Even in the case of [V], the NPN emitter follower is subject to the same restrictions as described above, and the CCD 10
6 cannot be fully utilized.

In view of the above problems, an object of the present invention is to make it possible to sufficiently exhibit the capability of the photoelectric conversion means and to obtain an image with a better S / N.

[0028]

In order to solve the above problems, an image reading apparatus according to the present invention converts an output from a photoelectric conversion means into a predetermined signal level by an attenuator, and then converts the DC level to a predetermined level. And perform analog processing. Another feature of the present invention is that a light source for obtaining a reflection optical image or a transmission optical image of a document placed on a platen glass,
An optical unit for forming an image of a document placed on the platen glass in a line at a predetermined position, and a photoelectric conversion of a reflection optical image or a transmission optical image formed in a line at a predetermined position by the optical unit. A photoelectric conversion unit that accumulates as signal charges and outputs a line-sequential first image signal at regular intervals, and a second image signal of a predetermined level based on the first image signal output from the photoelectric conversion unit , A third image signal generating means for generating a third image signal by raising the DC level of the second image signal generated by the attenuator to a predetermined level, and the third image signal A fourth image signal generating means for current-amplifying the third image signal obtained by the generating means to generate a fourth image signal; and a fourth image signal generated by the fourth image signal generating means. It is characterized by comprising an analog signal processing means for processing analog signals. Also,
Another feature of the present invention is that a resistor partial pressure is used as the attenuator. Another feature of the present invention is that a light source for obtaining a reflection optical image or a transmission optical image of a document placed on a document table and a document placed on the platen glass An optical unit for forming a line at a position, and a plurality of photoelectric conversion elements arranged in a line at the predetermined position, and a reflection optical image or a transmission optical image formed in a line by the optical unit. Photoelectric conversion means for accumulating signal charges in the photoelectric conversion element and outputting it as a line-sequential first image signal at regular intervals, and an attenuator for attenuating the output of the photoelectric conversion means to generate a second image signal Current amplification means for increasing the DC level of the second image signal generated by the attenuator and amplifying the current, and analyzing the third image signal current-amplified by the current amplification means. It is characterized by comprising an analog signal processing means for signal processing. Another feature of the present invention is that a resistance partial pressure is used as the photoelectric conversion unit. Another feature of the present invention is that a PNP transistor is used as the current amplifying means.

The image reading method according to the present invention is characterized in that the output from the photoelectric conversion means is converted to a predetermined signal level by attenuating processing, and then the DC level is adjusted to a predetermined level to perform analog processing. . According to another feature of the present invention, an optical process for forming an image of a document placed on the platen glass in a line at a predetermined position, and an image formed in a line at a predetermined position by the optical process. Photoelectric conversion of the reflected optical image or transmitted optical image,
The charge is accumulated as signal charges, and the first
Photoelectric conversion processing, an attenuating processing for generating a second image signal of a predetermined level from the first image signal output from the photoelectric converting processing, and a second attenuating processing generated by the attenuating processing. D of image signal
A third image signal generating process for generating a third image signal by raising the C level to a predetermined level, and a fourth image signal obtained by current-amplifying the third image signal obtained by the third image signal generating process. A fourth image signal generation process of generating an image signal of
An analog signal process for performing an analog signal process on the fourth image signal generated by the fourth image signal generation process is performed. Another feature of the present invention is that a resistance partial pressure is used as the attenuation process. Another feature of the present invention is that it comprises an optical process for forming an image of a document at a predetermined position, and a plurality of photoelectric conversion elements arranged in a line at the predetermined position. A photoelectric conversion process for accumulating a reflected optical image or a transmitted optical image to be formed as signal charges in the photoelectric conversion element, and outputting the image signal as a first image signal line-sequentially at regular intervals; Attenuating process for generating a second image signal by performing the above process, increasing the DC level of the second image signal generated by the attenuating process, amplifying the current, and amplifying the current amplified third image. And performing analog signal processing for performing analog signal processing on the signal. Another feature of the present invention is that a resistance partial pressure is used as the photoelectric conversion process.

A storage medium according to the present invention is characterized in that a program constituting each means described above is stored so as to be readable from a computer. Another feature of the present invention is that a program for executing the above-described method is stored in a computer-readable manner.

[0031]

Since the present invention has the above technical means, the output from the photoelectric conversion means is converted to a predetermined signal level by an attenuator, and the DC level is adjusted to a predetermined level and analogly processed. Smooth matching between high-quality photoelectric conversion means and analog processing ICs whose drive voltage level is reduced as much as possible to minimize heat generation and reduce noise can be performed smoothly. This makes it possible to make full use of the ability of the high-quality photoelectric conversion means.

[0032]

(First Embodiment) FIG. 1 shows a first embodiment of an image reading apparatus, an image reading method and a storage medium according to the present invention. In the following description,
The configuration of the image reading apparatus according to the present embodiment will be described with reference to the block diagram of FIG. 7 used for describing a conventional technique.

The CCD board 113 and the main board 112 are connected by a cable 111. C
The output Vo of the CD 106 is supplied to the first resistor 11 (R1) and the second resistor 12 (R
The voltage is divided by 2), and is input to the analog processing circuit 31 described in FIG. 9 through the cable 111 via the PNP transistor 10, the emitter resistor 9, and the current amplifying circuit (emitter follower) composed of Vcc. Vi
n. The emitter follower constitutes a third image signal generation unit and a fourth image signal generation unit of the present embodiment.

FIGS. 2C, 2D, and 2E show the CCD 1
06 shows an output example. FIG. 2C shows an example of the output Vo of the CCD 106. Assuming that the light level or the DC component of the output of the CCD 106 is Vd in a time corresponding to one line of the CCD 106 (abbreviated as 1HSYNC). 2 indicates that a bright signal of 3 [V] is obtained near the center.

At this time, the signal output in FIG. 2D is output by an attenuator 200 composed of a resistor 11 (R1) and a resistor 12 (R2) and an emitter follower composed of a PNP transistor 10. CC
D106 output signal 3 [V] is 3 × R2 / (R1 + R
2) It is divided into [V].

The signal output in FIG.
The current amplifier circuit composed of the NP-type transistor 10, the emitter resistor 9 and the VCC provides a waveform higher by about 0.6 [V]. At this time, the DC level Vd of the output of the CCD 106 is Vd × R2 / (R1 + R2) +0.6 [V].

The effect of the image reading apparatus of the present embodiment configured as described above will be described with reference to FIG.
FIG. 3 is a characteristic diagram showing a case where the attenuator 200 satisfies R1 / (R1 + R2) = 70 [%]. In the case of this example, when Vsat of the CCD 106 is set to 3 [V], the maximum input level Vam of the analog processing circuit 31 is set.
ax = 2.1 [V].

Therefore, the maximum output Vs of the CCD 106
At the output of the CCD 106 which becomes Vt very close to at (at this time, the target Pt of the output level by the lamp dimming is 240 when the A / D converter 32 is 8 bits).
Level) and image reading can be performed.

Also, depending on the environmental temperature and the variation in the solid,
Vd which is a DC component of the output of the CCD 106 is, for example, 3
Even in the case of [V], the PNP-type emitter follower is not subject to the restrictions as in the conventional NPN-type emitter follower, so that the capability of the CCD 106 can be fully exhibited. Therefore, according to the present embodiment, the capability of the CCD 106 can be sufficiently exhibited, and an image with a better S / N can be obtained.

(Second Embodiment) FIG. 4 shows a second embodiment of the present invention.
An embodiment will be described. The CCD 106 board 113 and the main board 112 are connected by a cable 111. The output Vo of the CCD 106 is supplied to the first resistor 11 (R 1), the second resistor 11 on the main board 112 via the cable 111 via a current amplifying circuit composed of the NPN transistor 8, the emitter resistor 7 and Vcc. The voltage is divided by the resistor 12 (R2), and the analog processing circuit 3 described with reference to FIG. 9 is passed through the PNP transistor 10, the emitter resistor 9, and the current amplifying circuit composed of Vcc.
1 is input. With such a configuration, the circuit according to the present embodiment also performs substantially the same operation as the first embodiment.

(Third Embodiment) FIG. 5 shows a third embodiment of the present invention.
An embodiment will be described. The CCD 106 board 113 and the main board 112 are connected via a cable 111. The output Vo of the CCD 106 is supplied to the first resistor 11 (R
1) The voltage is divided by the second resistor 12 (R2), and P
An NPN transistor 8 on a main boat 112 through a cable 111 through a current amplifier circuit composed of an NP transistor 10, an emitter resistor 9 and Vcc.
The current is input to the analog processing circuit 31 described with reference to FIG. With such a configuration, the circuit of the present embodiment also operates in substantially the same manner as the first embodiment.

(Other Embodiments of the Present Invention) The present invention can be applied to a system composed of a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.) and can be applied to a device composed of one device. May be applied.

Also, the functions of the above-described embodiment are implemented in an apparatus connected to the above-described various devices or a computer in a system so that various devices are operated so as to realize the functions of the above-described embodiment. Supplies the software program code for performing the
The invention implemented by operating the various devices according to the program stored in U) is also included in the scope of the present invention.

In this case, the program code itself of the software realizes the functions of the above-described embodiment, and the program code itself and means for supplying the program code to a computer, for example, the program The storage medium storing the code constitutes the present invention. As a storage medium for storing such a program code, for example, a floppy (registered trademark) disk, hard disk, optical disk, magneto-optical disk, CD-ROM, magnetic tape, nonvolatile memory card, ROM, or the like can be used.

When the computer executes the supplied program code, not only the functions described in the above embodiments are realized, but also the OS (operating system) in which the program code runs on the computer. Alternatively, even when the functions described in the above-described embodiments are implemented in cooperation with other application software or the like, it goes without saying that such program codes are included in the embodiments of the present invention.

Further, after the supplied program code is stored in the memory provided in the function expansion board of the computer or the function expansion unit connected to the computer, the function expansion board or the function expansion unit is specified based on the instruction of the program code. The present invention also includes a case where a CPU or the like provided in the apparatus performs part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.

[0047]

According to the present invention, as described above, according to the present invention, the output from the photoelectric conversion means is converted into a predetermined signal level by an attenuator, and then the DC level is adjusted to a predetermined level to obtain an analog signal. Processing.
Smooth matching between photoelectric conversion means with advanced image quality technology and analog processing ICs that lower the drive voltage level as much as possible to minimize heat generation and reduce noise can be performed smoothly. This makes it possible to make full use of the capability of the photoelectric conversion unit with high image quality.

According to another feature of the present invention, since a PNP transistor is used for the third image signal generating means for converting the output from the photoelectric conversion means to a predetermined signal level, the environment is improved. Even if the DC component of the output of the photoelectric conversion unit fluctuates due to variations in temperature and solids, the capability of the photoelectric conversion unit can be fully exhibited without being limited as in the conventional example, and It is possible to obtain an image with better S / N by fully utilizing the ability.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a circuit block for explaining a first embodiment of the present invention.

FIG. 2 is a diagram showing an example of an operation waveform for explaining the first embodiment of the present invention.

FIG. 3 is a diagram illustrating an example of an operation output explaining the first embodiment of the present invention.

FIG. 4 is a diagram illustrating an example of a circuit block illustrating a second embodiment of the present invention.

FIG. 5 is a diagram illustrating an example of a circuit block illustrating a third embodiment of the present invention.

FIG. 6 is a diagram illustrating an example of the appearance of an image reading apparatus.

FIG. 7 is a block diagram illustrating a general main configuration of an image reading apparatus.

FIG. 8 is a flowchart illustrating a procedure of dimming control of a conventional image reading apparatus.

FIG. 9 is a circuit configuration diagram for explaining a conventional example.

FIG. 10 is a diagram showing an example of an operation waveform for explaining a conventional example.

FIG. 11 is a diagram illustrating an example of an analog processing circuit illustrating a conventional example.

FIG. 12 is a diagram showing an example of an operation output for explaining a conventional example.

[Explanation of symbols]

 Reference Signs List 9 emitter resistor 10 PNP transistor 11 first resistor 12 second resistor 31 analog processing circuit 106 CCD 112 main board 111 cable 113 board 200 attenuator

Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (reference) H04N 5/335 H04N 1/40 101B F-term (reference) 5B047 AA01 AB02 AB04 BB02 BC04 BC11 DA01 DA10 5C024 BX00 CX00 EX01 GY01 HX44 5C051 AA01 BA03 DB01 DB15 DB21 DB28 DE17 5C072 AA01 BA11 DA01 EA05 FB15 LA02 UA05 UA13 5C077 LL19 MM03 PQ03 PQ12 PQ22 RR01

Claims (15)

[Claims] 1. An image reading apparatus, comprising: converting an output from a photoelectric conversion unit into a predetermined signal level by an attenuator; adjusting the DC level to a predetermined level; and performing analog processing. A light source for obtaining a reflection optical image or a transmission optical image of the document placed on the platen glass; and a line-shaped image of the document placed on the platen glass at a predetermined position. An optical unit for causing the optical unit to photoelectrically convert a reflection optical image or a transmission optical image formed in a line at a predetermined position by the optical unit, accumulate as signal charges, and perform line-sequential first image signals at regular intervals. And an attenuator for generating a second image signal of a predetermined level from the first image signal output from the photoelectric conversion unit, and a DC level of a second image signal generated by the attenuator. To a predetermined level to generate a third image signal, and a fourth image obtained by current-amplifying the third image signal obtained by the third image signal generating means. A fourth image signal generating means for generating a signal, and an analog signal processing means for performing an analog signal processing on the fourth image signal generated by the fourth image signal generating means. apparatus. 3. The image reading apparatus according to claim 2, wherein a resistance partial pressure is used as the attenuator. 4. The method according to claim 3, wherein:
The image reading device according to claim 3, wherein a PNP transistor is used. 5. A PN signal generator as the fourth image signal generating means.
The image reading device according to claim 3, wherein a P-type transistor is used. 6. A light source for obtaining a reflection optical image or a transmission optical image of a document placed on a platen, and a line-shaped image of the document placed on the platen glass. An optical means, and a plurality of photoelectric conversion elements arranged in a line at the predetermined position, and a reflection optical image or a transmission optical image formed in a line by the optical means is stored as signal charges in the photoelectric conversion element. A photoelectric conversion unit that outputs a line-sequential first image signal at regular intervals, an attenuator that attenuates the output of the photoelectric conversion unit to generate a second image signal, and a second attenuator generated by the attenuator. Current amplifying means for increasing the DC level of the second image signal and amplifying the current; and an analog signal for subjecting the third image signal, which has been current amplified by the current amplifying means, to analog signal processing Image reading apparatus characterized by comprising a management unit. 7. The image reading apparatus according to claim 6, wherein a resistance partial pressure is used as said photoelectric conversion means. 8. The image reading apparatus according to claim 6, wherein a PNP transistor is used as said current amplifying means. 9. An output from the photoelectric conversion means is converted to a predetermined signal level by an attenuating process.
An image reading method, wherein a C level is adjusted to a predetermined level and analog processing is performed. 10. An optical process for forming an image of a document placed on a platen glass in a line at a predetermined position, and a reflection optical image or a transmission optical image formed in a line at a predetermined position by said optical process. Photoelectric conversion, accumulates as a signal charge, and outputs a line-sequential first image signal at regular intervals, and a predetermined level of the first image signal output from the photoelectric conversion processing. An attenuating process for generating the second image signal; a third image signal generating process for generating a third image signal by raising a DC level of the second image signal generated by the attenuating process to a predetermined level; A fourth image signal generating process of current-amplifying the third image signal obtained by the third image signal generating process to generate a fourth image signal; and a fourth image signal generating process. Image reading method characterized by the fourth image signal made performs analog signal processing that processes analog signals. 11. The image reading method according to claim 10, wherein a resistance partial pressure is used as the attenuation process. 12. An optical process for forming an image on a document at a predetermined position, and a plurality of photoelectric conversion elements arranged in a line at the predetermined position. A photoelectric conversion process of accumulating a transmission optical image as signal charges in the photoelectric conversion element and outputting the signal as a first image signal line-sequentially at regular intervals; and a second image obtained by attenuating the output of the photoelectric conversion process. Attenuating processing for generating a signal, current amplifying processing for increasing the DC level of the second image signal generated by the attenuating processing and amplifying the current, and analog signal processing for the third image signal subjected to the current amplifying processing. Image reading method. 13. The image reading method according to claim 12, wherein a resistance partial pressure is used as the photoelectric conversion processing. 14. A storage medium storing a program constituting each means according to claim 1 so as to be readable from a computer. 15. A storage medium storing a program for executing the method according to any one of claims 9 to 13 so as to be readable from a computer.