JPH10327293A - Picture reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize efficient picture read work corresponding to read width by controlling charge discharge in the plural picture element parts in a light reception means where the plural picture element parts accumulating the prescribed charges are arranged in accordance with the division. SOLUTION: Shift gates 11, 21 and 31 control the reading of the charges accumulated in the respective picture element parts of linear image sensors 10, 20 and 30, which correspond to respective colors, in a vertical direction. Horizontal transfer registers 12, 22 and 32 transfer the charges in a horizontal direction. Control signals DS1-DS3 from a vertical transfer pulse generation circuit 101 are applied to the respective control areas of shutter drains 13, 23 and 33 divided into the plural control areas. The discharge of the charges of the picture element parts corresponding to the respective control areas is controlled in accordance with the application of the control signals DS1-DS3. Thus, the charges can be discharged for the respective control areas by controlling the signal levels of the control signals DS1-DS3 in accordance with the division.

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 for reading image information by a pixel section of a light receiving means and transferring a predetermined charge to an output circuit.

[0002]

2. Description of the Related Art An image reading apparatus such as a copying machine or a scanner is provided with a linear image sensor having a number of pixels corresponding to the size of a document to be read and the data sampling density.

For example, a device for reading a document of maximum A3 (JIS) size at a sampling density of 400 spi requires a linear image sensor of about 5000 pixels, and a device for reading a document of A2 (JIS) size at a sampling density of 600 spi. Then, a linear image sensor of about 10,000 pixels is required.

For this reason, the image reading apparatus prepares a linear image sensor corresponding to the maximum size of a document to be read at a predetermined sampling density, and reads a document having a size smaller than that size using the same linear image sensor. .

[0005]

However, as the number of pixels of the linear image sensor increases, the number of read lines per unit time decreases, so that the linear image sensor cannot be read along the pixel arrangement direction (main scanning direction). This causes a reduction in the scanning speed in a direction perpendicular to the scanning direction (sub-scanning direction).

Further, when reading a document of a smaller size using a linear image sensor adapted to the maximum size of the document (for example, a linear image sensor corresponding to A2 (JIS) size (length in the main scanning direction) 420
mm) for reading an A4 (JIS) size original (length 210 mm corresponding to the main scanning direction).
Since reading is performed at a scanning speed that matches the maximum size, there is a problem that a long reading time is required even for a small document.

Japanese Patent Application Laid-Open No. 5-75929 discloses a solid-state imaging device that prevents signal charges from being swept out of a plurality of pixel cells outside the effective display screen. A pixel cell that does not sweep out signal charges is used for light amount detection, and does not shorten the reading time.

[0008]

SUMMARY OF THE INVENTION The present invention is an image reading apparatus made to solve such a problem. That is, the present invention provides a light receiving means in which a plurality of pixel units for receiving image information and accumulating predetermined charges are arranged, and the electric charges accumulated in each pixel unit of the light receiving means are arranged along the light receiving means and sequentially output. There are provided transfer means for transferring in the circuit direction, and charge discharging means which is divided into a plurality of control areas along the light receiving means and controls discharge of charges in a plurality of pixel portions of the light receiving means in accordance with the division.

Further, a light receiving means in which a plurality of pixel portions for receiving image information and accumulating predetermined charges are arranged, and arranged along the light receiving means to obtain the electric charges accumulated in each pixel portion of the light receiving means and to sequentially output the signals. Transfer means for transferring in the direction, and disposed between the light receiving means and the transfer means, and divided into a plurality of control areas along the light receiving means, and a charge transfer from a plurality of pixel portions of the light receiving means to the transfer means. There is also provided a reading means for controlling according to the classification.

[0010] Further, a light receiving means in which a plurality of pixel portions for receiving image information and accumulating a predetermined electric charge are arranged, and the electric charges accumulated in each pixel portion of the light receiving means are respectively arranged along the light receiving means on both sides thereof. Two transfer means for obtaining and sequentially transferring the charges in the direction of the output circuit, and discharging the electric charges transferred from the plurality of pixel portions of the light receiving means to the two transfer means arranged along each of the two transfer means at a predetermined timing And a charge discharging means for controlling the charge discharging in accordance with the condition.

In the present invention, since the charge discharging means divided into a plurality of control areas is provided, the discharge of the charge accumulated in the pixel portion can be controlled according to the division, and the charge to the transfer means can be controlled. The number of pixel units to be transferred can be selected according to the division.

Further, in an image reading apparatus provided with a reading means divided into a plurality of control areas, the transfer of the electric charge accumulated in the pixel portion can be controlled according to the division, and the electric charge is transferred. The number of pixel units can be selected according to the classification.

In the image reading apparatus having two transfer means on both sides of the light receiving means, the charge accumulated in the pixel portion is discharged at a predetermined timing, that is, at a stage when a predetermined amount of charge is transferred by the transfer means. By discharging the remaining charge, the number of pixel units that transfer charge to two transfer units can be selected.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the image reading apparatus of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram illustrating the first embodiment, and FIG. 2 is a timing chart illustrating the first embodiment.

As shown in FIG. 1, the image reading apparatus according to the first embodiment is a three-line sensor corresponding to reading of three colors of R (red), G (green), and B (blue).
Linear image sensors 10, 20, 30 corresponding to each color
And shift gates 11, 21, and 31 for controlling readout of charges accumulated in the respective pixel units of the linear image sensors 10, 20, and 30 in the vertical direction in the figure, and a horizontal transfer register for transferring charges in the horizontal direction in the figure. 12, 22, 32 and a plurality of control areas (for example, 13a to 13c, 23a to 23
c, 33a to 33c).

The image reading apparatus also includes a shift pulse SH for controlling the shift gates 11, 21, and 31 and a control region 1 for each of the shutter drains 13, 23, and 33.
Vertical transfer pulse generation circuit 101 for generating control signals DS1, DS2, DS3 corresponding to 3a to 13c, 23a to 23c, 33a to 33c, horizontal transfer registers 13, 2
A horizontal transfer pulse generating circuit 102 for generating transfer pulses φ1 and φ2 for driving the transfer circuits 3 and 33; charge-voltage converters 14, 24 and 34 for converting transferred charges into voltages such as a floating diffusion configuration;
5, 35, A / that converts analog signals to digital signals
It includes D converters 16, 26 and 36 and a signal processing circuit 103 for processing digital signals.

Each of the linear image sensors 10, 20, 30
In this case, a plurality of pixel units corresponding to the sampling density of image reading are arranged in a length corresponding to the size of the read document.

The shift gates 11, 21, 31 are
It is controlled by a shift pulse SH applied from the vertical transfer pulse generation circuit 101, and charges the pixel portion with the horizontal transfer registers 12, 22, 3 based on the application of the shift pulse SH.
Read to 2.

The horizontal transfer registers 12, 22, and 32 transfer the charge of each pixel read out via the shift gates 11, 21, 31 to transfer pulses φ 1 having different phases applied from the horizontal transfer pulse generating circuit 102. , Φ2, and sequentially transferred in the horizontal direction in FIG.
4 and 34.

Further, in the image reading apparatus according to the first embodiment, each of the control areas 13a to 13 of the shutter drains 13, 23, 33 divided into a plurality of control areas.
c, 23a to 23c, 33a to 33c, control signals DS1, DS2, DS3 from the vertical transfer pulse generation circuit 101.
Are applied, and in response to the application of the control signals DS1, DS2, DS3, the respective control areas 13a to 13c, 23a to 23
c, discharge of charges of the pixel portion corresponding to 33a to 33c is controlled.

That is, the control signals DS1, DS2, DS
When 3 goes high, charges are discharged through the corresponding control areas 13a to 13c, 23a to 23c, and 33a to 33c, and when the 3 goes low, the corresponding control areas 13a to 13a to 13c are discharged. 13c, 23a-23
c, discharge of electric charges via 33a to 33c is not performed.

By controlling the signal levels of the control signals DS1, DS2 and DS3 in accordance with the division, the control area 1 is controlled.
Electric discharge can be performed for each of 3a to 13c, 23a to 23c, and 33a to 33c.

For example, all control signals DS1, DS2,
When DS3 is at the Low level, the charge is not discharged from the shutter drains 13, 23, and 33, and the charges are read from all the pixel units to the horizontal transfer registers 12, 22, and 32 by the subsequent shift pulse SH. In the following description, the read width at this time is A, and the number of read stages is H0.

When only the control signal DS1 is at a high level and the other control signals DS2 and DS3 are at a low level, electric charges are discharged from the control regions 13a, 23a and 33a in the shutter drains 13, 23 and 33,
The control regions 13b, 1
Charges are read out to the horizontal transfer registers 12, 22, 32 only from the pixel portions corresponding to 3c, 23b, 23c, 33b, 33c. In the following description, the read width at this time is B, and the number of read stages is H1.

The control signals DS1 and DS2 are High.
When the control signal DS3 is at the low level, the control region 1 in the shutter drains 13, 23, 33 is controlled.
Charges are discharged from 3a, 13b, 23a, 23b, 33a, 33b, and charges are transferred to the horizontal transfer registers 12, 22, 32 only from the pixel portions corresponding to the control regions 13c, 23c, 33c by the subsequent shift pulse SH. Is read. In the following description, the read width at this time is C, and the number of read stages is H2.

Next, a specific timing in image reading will be described with reference to FIG. In the timing chart shown in the upper diagram of FIG. 2, the interval between the shift pulses SH corresponds to the exposure cycle length T, and the number of transfer clocks is from the fall of the shift pulse SH to the fall of the last transfer pulse φ2 within the exposure cycle length T. N.

At such a timing, the shift pulse SH becomes High level, so that charges are horizontally transferred from the pixel portions of the linear image sensors 10, 20, and 30 shown in FIG. The transfer pulses φ1 and φ2 which are read out to the registers 12, 22, and 32 and have different phases are repeatedly
The electric charges are sequentially transferred in the horizontal transfer direction by applying the charges to 2, 22, and 32.

In the first embodiment, during such a timing, the control signals DS1, DS2, and DS3 are set before the shift pulse SH is set to the high level and the charge is read out (see the two-dot chain line in the figure). By appropriately controlling, the read widths A, B, and C of the charges are controlled.

As shown in the lower diagram of FIG. 2, the control signal DS
The reading widths A, B, and C can be controlled by a combination of High level (H) and Low level (L) of 1, DS2, and DS3.

When reading charges with the read width A, the control signals DS1, DS2, and DS3 are all set to the low level (L). As a result, charges are not discharged from the shutter drains 13, 23, and 33 shown in FIG. 1, and charges are read from all the pixel units to the horizontal transfer registers 12, 22, and 32 by the shift pulse SH. It is possible to perform charge readout at H0.

When reading charges with the read width B, the control signal DS1 is set to a high level (H), and the control signals DS2 and DS3 are set to a low level (L). Thereby, the shutter drains 13, 23, 3 shown in FIG.
3, the charge in the corresponding pixel portion can be discharged from the control regions 13a, 23a, and 33a, and the shift pulse S
H, the control areas 13b, 13c, 23b, 23c,
Charges are read out from the pixel portions corresponding to 33b and 33c to the horizontal transfer registers 12, 22, and 32. That is, it is possible to perform charge readout with the number of readout stages H1.

When reading charges with the read width C, the control signals DS1 and DS2 are set to a high level (H), and the control signal DS3 is set to a low level (L).
Thereby, the shutter drains 13 and 2 shown in FIG.
Control areas 13a, 13b, 23a, 2 in 3, 33
3b, 33a, and 33b can discharge the charge of the corresponding pixel portion, and the control region 1 is controlled by the shift pulse SH.
Charges are read from the pixel portions corresponding to 3c, 23c, and 33c to the horizontal transfer registers 12, 22, and 32. That is, it is possible to perform charge reading with the number of reading stages H2.

By such reading, horizontal transfer of electric charges according to the number of reading stages can be performed.
That is, since the transfer clock number N can be reduced as the read width becomes shorter, the read speed can be increased.

Next, a second embodiment of the image reading apparatus of the present invention will be described. FIG. 3 is a configuration diagram illustrating the second embodiment, and FIG. 4 is a timing chart illustrating the second embodiment.

As shown in FIG. 3, the image reading apparatus according to the second embodiment is a three-line sensor corresponding to reading of three colors of R (red), G (green), and B (blue).
Linear image sensors 10, 20, 30 corresponding to each color
And a plurality of control areas (for example, 11a to 11c, 21a
, 21a, and 31a to 31c), and horizontal transfer registers 12, 22, and 32 that transfer charges in the horizontal direction in the figure.
Shutter drains 13, 23 for discharging electric charges,
33.

The image reading apparatus also includes a control signal DS for controlling the shutter drains 13, 23, and 33 and a control area 11a for each of the shift gates 11, 21, and 31.
, 11a, 21a to 21c, 31a to 31c, a vertical transfer pulse generation circuit 101 for generating shift pulses SH1, SH2, SH3, horizontal transfer registers 12, 22,
A horizontal transfer pulse generating circuit 102 for generating transfer pulses φ1 and φ2 for driving the PDP 32; charge-to-voltage converters 14, 24, 34 for converting transferred charges into voltages, such as a floating diffusion configuration, analog amplifiers 15, 25,
35, A / D converters 16, 26 and 36 for converting analog signals into digital signals, and a signal processing circuit 103 for processing digital signals.

As in the first embodiment, each of the linear image sensors 10, 20, and 30 has a plurality of pixel units corresponding to the sampling density of image reading arranged at a length corresponding to the size of the read document. Used.

The shutter drains 13, 23, 3
3 is controlled by a control signal DS applied from the vertical transfer pulse generation circuit 101, and discharges the charge of the pixel portion based on the application of the control signal DS.

The horizontal transfer registers 12, 22, and 32 transfer the pixel-based charges read out via the shift gates 11, 21, and 31 to transfer pulses φ 1 having different phases applied from the horizontal transfer pulse generating circuit 102. , Φ2, and sequentially transferred in the horizontal direction in FIG.
4 and 34.

Further, in the image reading apparatus according to the second embodiment, each of the control areas 11a to 11c, 2 of the shift gates 11, 21, and 31 divided into a plurality of control areas.
Shift pulses SH1, SH2, and SH3 are applied from the vertical transfer pulse generation circuit 101 to 1a to 21c and 31a to 31c, and control regions 11a to 11c and 21a to 21c are applied in accordance with the application of the shift pulses SH1, SH2, and SH3.
c, the reading of the charges of the pixel portions corresponding to 31a to 31c is controlled.

That is, the shift pulses SH1, SH2,
When SH3 becomes High level, the corresponding control areas 11a to 11c, 21a to 21c, 31a to 31c
Are read out through the gates, and when the charges become low level, the corresponding control areas 11a to 11c and 21a
To 21c and 31a to 31c.

The shift pulses SH1, SH2, SH3
, The charge can be read out for each of the control regions 11a to 11c, 21a to 21c, and 31a to 31c.

For example, all the shift pulses SH1, SH
2. When SH3 is at the high level, all the charges are read by the shift gates 11, 21, and 31, that is, the read of the read width A and the number of read stages H0 are performed.

When only the shift pulse SH1 is at the low level and the other shift pulses SH2, SH3 are at the high level, the control regions 11b, 11c, 21b, 21c, 31b, 31 in the shift gates 11, 21, 31 are shifted.
The reading of the electric charge, that is, the reading of the read width B and the number of read steps H1 is performed via c.

The shift pulses SH1 and SH2 are Lo.
When the shift pulse SH3 is at the high level at the w level, the charge is read out via the control regions 11c, 21c, 31c in the shift gates 11, 21, 31;

Next, a specific timing in image reading will be described with reference to FIG. In the timing chart shown in the upper diagram of FIG. 4, the interval between the control signals DS is the exposure cycle length T.
And the exposure cycle length T from the fall of the control signal DS.
The number of transfer clocks corresponds to the number of transfer clocks N until the last transfer pulse φ2 falls.

At such timings, the shift pulses SH1, SH2, and SH3 are set to the high level, thereby causing the linear image sensors 10, 20, 3 shown in FIG.
The charge is read out from the pixel portion 0 to the horizontal transfer registers 12, 22, and 32 via the shift gates 11, 21, and 31, and the charge is discharged by the control signal DS. By repeatedly applying the charges to the horizontal transfer registers 12, 22, 32, the charges are sequentially transferred in the horizontal transfer direction.

In the second embodiment, the shift pulses SH1, SH2, and SH3 are set at such timings before the control signal DS is set to the high level and the electric charges are discharged (see a two-dot chain line in the figure). By appropriately controlling, the read widths A, B, and C of the charges are controlled.

As shown in the lower diagram of FIG.
High level (H) of H1, SH2, SH3, Low
Reading width A, B, C by combination of level (L)
Can be controlled.

When reading charges with the read width A, the shift pulses SH1, SH2, and SH3 are all set to Hig.
h level (H). Thereby, even when the control signal DS is applied, the shutter drains 13, 23,
Before the discharge at 33, all the charges are read out to the horizontal transfer registers 14, 24, and 34, so that the charges can be read out at the readout stage number H0.

When the charge is read with the read width B, the shift pulse SH1 is set to the low level (L), and the shift pulses SH2 and SH3 are set to the high level (H). Thereby, before the control signal DS is applied, the control region 1 in the shift gates 11, 21, 31 shown in FIG.
The charge of the pixel portion corresponding to 1b, 11c, 21b, 21c, 31b, 31c can be read. Also, the received charges corresponding to the unread control areas 11a, 21a, 31a are discharged by application of the control signal DS. That is, it is possible to perform charge readout with the number of readout stages H1.

When reading charges with the read width B, the shift pulses SH1 and SH2 are set to the low level (L), and the shift pulse SH3 is set to the high level (H). Thus, before the control signal DS is applied, FIG.
In the shift gates 11, 21, and 31 shown in (1), the charges in the pixel portions corresponding to the control regions 11c, 21c, and 31c can be read. Also, the received light charges corresponding to the unread control regions 11a, 11b, 21a, 21b, 31a, 31b are discharged by applying the control signal DS. That is, it is possible to perform charge reading with the number of reading stages H2.

By such readout, horizontal transfer of electric charges according to the number of readout stages can be performed as in the first embodiment. That is, since the transfer clock number N can be reduced as the read width becomes shorter, the read speed can be increased.

Next, a third embodiment of the image reading apparatus of the present invention will be described. FIG. 5 is a configuration diagram illustrating the third embodiment, and FIG. 6 is a timing chart illustrating the third embodiment.

As shown in FIG. 5, the image reading apparatus according to the third embodiment has a linear image sensor 10 for reading image information, and two shift gates 111 and 112 provided on both sides of the linear image sensor 10.
And two horizontal transfer registers 121 and 122 for transferring the charges of the pixel portion read alternately through the shift gates 111 and 112 in the horizontal direction in the drawing, respectively, and a shutter drain 131 for discharging the charges. 132.

The image reading apparatus also includes a vertical transfer pulse generating circuit 101 for generating a control signal DS for controlling the shutter drains 131 and 132 at a predetermined timing and a shift pulse SH for controlling the shift gates 111 and 112. A horizontal transfer pulse generating circuit 102 for generating transfer pulses φ1 and φ2 for driving the registers 121 and 122; a charge-to-voltage converter 14 for converting transferred charges into a voltage such as a floating diffusion configuration;
1, 142, analog amplifiers 151, 152, A / D converters 161, 1 for converting analog signals into digital signals
62 and a signal processing circuit 10 for processing digital signals
3 is provided.

As the linear image sensor 10, a plurality of pixel portions corresponding to the sampling density of image reading are provided.
A document arranged at a length corresponding to the size of the read document is used.

The shift gates 111 and 112 are controlled by a shift pulse SH applied from the vertical transfer pulse generation circuit 101, and transfer the charge of the pixel portion every other pixel to the horizontal transfer register 1 based on the application of the shift pulse SH.
21 and 122.

The horizontal transfer registers 121 and 122 transfer the electric charge of each pixel read through the shift gates 111 and 112 by transfer pulses φ 1 and φ 2 having different phases applied from the horizontal transfer pulse generating circuit 102. The charge-to-voltage converters 141, 1 are sequentially transferred in the horizontal direction in the drawing.
The electric charge is output to the reference numeral 42.

Further, in the image reading apparatus according to the third embodiment, the charges are transferred by the horizontal transfer registers 121 and 122 by the number of stages corresponding to the reading width, and the remaining charges are output without being discharged to the shutter drains 131 and 13.
2 to output only the charge corresponding to the reading width.

For example, when transferring charges read from all the pixel units of the linear image sensor 10 (read width A, readout stage number H0), the horizontal transfer register 12
As the transfer pulses φ1 and φ2 for driving 1, 122, charges are transferred by the number of stages corresponding to the number of readout stages H0, and after all the charges are output, a control signal DS for controlling the shutter drains 131 and 132 is generated. To discharge the charge.

The read width B shorter than the read width A
When the charge transfer is performed at (the number of readout stages H1), the transfer pulse φ1, which drives the horizontal transfer registers 121 and 122,
As φ2, charge transfer is performed according to the number of stages corresponding to the number of readout stages H1. The charge corresponding to the read width B is output by the read stage number H1, and then the control signal DS for controlling the shutter drains 131 and 132 is output.
And the horizontal transfer registers 121, 1
The charge remaining in 22 is discharged.

Further, the read width C which is shorter than the read width B
When the charge transfer is performed with (the number of readout stages H2), the transfer pulse φ1 for driving the horizontal transfer registers 121 and 122,
As φ2, charges are transferred by the number of stages corresponding to the number of readout stages H2. The charge corresponding to the read width C is output by the read stage number H2, and then the control signal DS for controlling the shutter drains 131 and 132 is output.
And the horizontal transfer registers 121, 1
The charge remaining in 22 is discharged.

Next, a specific timing for reading an image will be described with reference to FIG. In the timing chart shown in the upper part of FIG. 6, the interval between the shift pulses SH corresponds to the exposure cycle length T, and the number of transfer clocks is from the fall of the shift pulse SH to the fall of the last transfer pulse φ2 within the exposure cycle length T. N.

At such a timing, the shift pulse SH becomes High level, so that the pixel portion of the linear image sensor 10 shown in FIG.
1 and 112, the charges are alternately transferred to the horizontal transfer register 12
1 and 122, and repeatedly transfer pulses φ1 and φ2 having different phases, respectively, to horizontal transfer registers 121 and 122.
, The charges are sequentially transferred in the horizontal transfer direction.

In the third embodiment, a control signal DS for driving the shutter drains 131 and 132 (see FIG. 5) is generated after generating a predetermined number N of transfer clocks at such timing, and Read width A, B, C
After reading out the charges, the remaining charges are discharged.

As shown in the lower diagram of FIG. 6, the read widths A, B and C can be controlled by making the transfer clock number N correspond to the read stage numbers H0, H1 and H2.

That is, in the case of reading charges with the read width A, charges are read from all the pixel portions of the linear image sensor 10 into the horizontal transfer registers 121 and 122 by the shift pulse SH, and then transferred according to the number of read stages H0. The transfer pulses φ1 and φ2 having the number N of clocks are generated. The transfer pulses φ1 and φ2 of the read stage number H0
Thereby, transfer and output of the charge corresponding to the read width A are performed. Then, at the stage when this transfer is completed, the control signal DS is generated, and the shutter drains 131 and 13 are generated.
2 is driven to discharge the remaining charge.

When electric charges are read with the read width B, electric charges are transferred from all the pixel portions of the linear image sensor 10 to the horizontal transfer register 12 by the shift pulse SH.
After reading the data to 1, 122, transfer pulses φ1 and φ2 having the number N of transfer clocks corresponding to the number of read stages H1 are generated. The transfer and output of the charge corresponding to the read width B are performed by the transfer pulses φ1 and φ2 of the read stage number H1. Then, at the end of this transfer, a control signal DS is generated, and the shutter drains 131 and 132 are driven to discharge the remaining charge. As a result, even if the charges of the next line are read out to the horizontal transfer registers 121 and 122, mixing with the remaining charges of the previous line can be avoided.

Similarly, when electric charges are read with the read width C, the electric charges are transferred from all the pixel portions of the linear image sensor 10 to the horizontal transfer register 1 by the shift pulse SH.
After reading the data into the readout stages 21 and 122, transfer pulses φ1 and φ2 having a transfer clock number N corresponding to the readout stage number H2 are generated. By the transfer pulses φ1 and φ2 of the readout stage number H2, the transfer and output of the charge corresponding to the readout width C are performed. Then, at the stage when this transfer is completed, a control signal DS is generated, and the shutter drains 131, 132
To discharge the remaining charge. by this,
Even if the charges of the next line are read out to the horizontal transfer registers 121 and 122, it is possible to avoid mixing with the remaining charges of the previous line.

As described above, the number N of transfer clocks by the transfer pulses φ1 and φ2 and the shutter drains 131 and 1
In accordance with the timing of the control signal DS for controlling the control signal 32, it is possible to output charges of the number of stages corresponding to the read width.
That is, as the read width is shorter, the number of transfer clocks can be reduced, and the charge of the next line can be read immediately after transferring a predetermined number of charges, so that the read speed can be increased.

FIGS. 7A and 7B are diagrams for explaining the relationship between the reading width and the document width. FIG. 7A is a diagram of the document arrangement viewed from above, and FIG.
Is the document width (Lx) and (Lx / L) according to the document type
FIG.

When the image reading apparatus in the above embodiment is applied to a copying machine, a scanner or the like, originals of various sizes are handled as shown in FIG. 7 (a). Be a guide. That is, the document is arranged so that the corners of the document match the corner register formed by the document position regulation guide.

At this time, assuming that the maximum length of original reading along the vertical direction in the drawing is the reading width (L) and the length of the placed original along the vertical direction in the drawing is the original width (Lx), FIG.
As shown in (b), the original width (Lx) differs depending on the type and arrangement direction of various originals.

For example, in the case of A2 / A3 landscape along the paper size according to JIS, the document width (Lx) is 420 mm and B3
/ B4 horizontal document width (Lx) is 358mm, A3 / A
The document width (Lx) is 297 mm for 4-width document, the document width (Lx) is 252 mm for B4, and the document width (Lx) is 2 for A4.
It is 10 mm.

As a result, the ratio (Lx / L) between the maximum reading width (L) and each document width (LX) is (Lx / L) is 1 for A2 / A3 landscape, and (Lx / L) for B3 / B4 landscape. /
L) is 0.85, (Lx / L) is 0.71 for A3 / A4 landscape, (Lx / L) is 0.60 for B4, and (Lx / L) is 0.50 for A4.

In the image reading apparatus according to the above-described embodiment, the reading widths A, B, and C described above are changed by the ratio (Lx / Lx) between the maximum reading width (L) and each document width (LX).
Set according to L). At this time, the reading widths A, B, and C are set based on the ends of the linear image sensors 10, 20, and 30 corresponding to the positions of the corner registers.

That is, the linear image sensors 10, 2
When the reading width A at 0 and 30 corresponds to the maximum reading width (L) shown in FIG. 7, the reading widths B and C of the linear image sensors 10, 20, and 30 are compared with the reading width A. (Lx / L).

For example, the linear image sensors 10, 2
When the length of the reading width A at 0 and 30 is “1”, the length of the reading width B is “0.85”, and the reading width C is
Is set to “0.71”. Note that other values (Lx / L) may be set.

Thus, the linear image sensor 1
The number of stages of reading the electric charges at 0, 20, and 30 can be adjusted to the size of the original to be read, and the reading speed can be improved by preventing useless reading of the electric charges.

FIG. 8 is a diagram for explaining the correction circuit. In this figure, only a portion for correcting the signal output from the linear image sensor 10 is shown for simplicity of explanation.
The same applies to the portion that corrects the signals output from 0 and 30.

That is, in the image reading apparatus of the present embodiment, the reading speed can be increased as the reading width becomes shorter, but the exposure time per one line of reading is reduced in inverse proportion to the increase in the reading speed.

Therefore, in the present embodiment, a shading corrector 17 is provided at a stage subsequent to the analog amplifier 15 and the A / D converter 16 to suppress a decrease in sensitivity due to a reduction in exposure time. That is, in the shading corrector 17, the data read from the white reference plate is stored in the memory 17a in advance, and this data is stored in the memory 1a when the original is read.
By reading from 7a and performing division, a change in the amount of illumination light, an uneven light distribution characteristic, a variation in sensitivity between pixel portions, and the like are corrected.

That is, the read data of the white reference plate is obtained in advance at each reading speed, and the read data of the white reference plate corresponding to the original reading at each reading speed is read from the memory 17a and divided. Variations in sensitivity due to differences in reading speed can be suppressed.

The exposure time per line is reduced in inverse proportion to the increase in the reading speed, and the sensor output is also reduced. However, by increasing the gain of the analog amplifier 15 in accordance with the reading speed, the A / D conversion is performed. The quantization error in the unit 16 can be suppressed.

Further, the S / N of the sensor itself deteriorates as the exposure time is reduced due to the increase in the reading speed. However, a predetermined exposure amount can be maintained by increasing the amount of illumination in accordance with the reading speed.

In the first and second embodiments described above, a three-line sensor for reading a color image is used as an example. However, a one-line sensor or an RGB + infrared sensor for reading a monochrome image is used. The four-line sensor described above is also applicable. In the third embodiment, a one-line sensor is used as an example, but a three-line sensor may be used. That is, it is applicable regardless of the number of parallel lines.

In the first and second embodiments, a so-called single CCD type having one row of horizontal transfer registers 12, 22, 32 for each of the linear image sensors 10, 20, 30 is provided. In the third embodiment, Two rows of horizontal transfer registers 121, 1 on both sides of the linear image sensor 10.
So-called dual CCD type with 22
As a structure including a shutter drain outside the linear image sensor 10 as in the third embodiment, as shown in FIG. 9, a row of horizontal transfer registers 121 is arranged on one side of the linear image sensor 10 and A so-called single CCD having one row of shutter drains 131
Even the type is applicable.

Further, the read widths A, B, and C described in each embodiment are merely examples, and two types other than these three types are available.
Also, four or more types may be used.

[0090]

As described above, the image reading apparatus of the present invention has the following effects. That is, when reading an image smaller than the maximum reading width by using an image sensor corresponding to the maximum reading width to be read, it is possible to control the reading of the electric charges according to the reading width and to increase the reading speed. Become. Thus, an efficient image reading operation according to the reading width can be performed.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating a first embodiment.

FIG. 2 is a timing chart illustrating the first embodiment.

FIG. 3 is a configuration diagram illustrating a second embodiment.

FIG. 4 is a timing chart illustrating a second embodiment.

FIG. 5 is a configuration diagram illustrating a third embodiment.

FIG. 6 is a timing chart illustrating a third embodiment.

FIG. 7 is a diagram illustrating a relationship between a reading width and a document width.

FIG. 8 is a diagram illustrating a correction circuit.

FIG. 9 is a configuration diagram illustrating a modification of the third embodiment.

[Explanation of symbols]

 10, 20, 30 Linear image sensor 11, 21, 31 Shift gate 12, 22, 32 Horizontal transfer register 13, 23, 33 Shutter drain 14, 24, 34 Charge-voltage converter 15, 25, 35 Analog amplifier 16, 26, 36 A / D converter 101 Vertical transfer pulse generation circuit 102 Horizontal transfer pulse generation circuit 103 Image processing unit

Claims (6)

[Claims] 1. A light receiving means in which a plurality of pixel portions receiving image information and accumulating predetermined charges are arranged, and the electric charges accumulated in each pixel portion of the light receiving means are arranged along the light receiving means and sequentially output. Transfer means for transferring in the circuit direction; and charge discharging means which is divided into a plurality of control areas along the light receiving means and controls charge discharging in a plurality of pixel portions of the light receiving means in accordance with the division. An image reading device characterized by the above-mentioned. 2. A light receiving means in which a plurality of pixel portions for receiving predetermined image information and accumulating predetermined charges are arranged, and the electric charges accumulated in each pixel portion of the light receiving means are arranged along the light receiving means and sequentially output. Transfer means for transferring in a circuit direction; disposed between the light receiving means and the transfer means, divided into a plurality of control areas along the light receiving means, and transferred from a plurality of pixel portions of the light receiving means. Reading means for controlling charge transfer to the means according to the classification. 3. A light receiving means in which a plurality of pixel sections for receiving predetermined image information and accumulating predetermined charges are arranged, and arranged on both sides along the light receiving means, and the electric charges accumulated in each pixel section of the light receiving means are provided. Two transfer means each of which is obtained and sequentially transferred in the direction of the output circuit; and discharges of electric charges arranged along each of the two transfer means and transferred from the plurality of pixel portions of the light receiving means to the two transfer means. And an electric charge discharging means for controlling the electric charge according to a predetermined timing. 4. The image reading apparatus according to claim 1, wherein electric charges are transferred to the output circuit in accordance with the division of the control area in accordance with a size of the image information to be read. . 5. The method according to claim 1, wherein the amount of charge stored in the plurality of pixel units is changed according to the amount of charge transferred to the output circuit according to the division of the control region. An image reading device according to claim 1. 6. The method according to claim 1, wherein the charge discharging unit discharges the charge remaining in the transfer unit after the transfer of the charge according to the size of the image information to be read is performed. Item 3. The image reading device according to Item 3.