JP2001197272A - Image reader, image forming device, image reading method and computer readable storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the electric charges overflowing a photoelectric conversion means such as a CCD. SOLUTION: When a normal SH signal having a read cycle SH defined as T+T1 is transmitted to a CCD part 107, a pseudo SH signal is transmitted from a pseudo SH signal generation part 127 at a time T after the normal SH signal is transmitted. Receiving the pseudo SH signal, when the part 107 receives the pseudo signal, the part 107 transfers the hitherto accumulated electric charge at the time T and accordingly can accumulate the electric charges equivalent to the time T1 that would overflow in a conventional case.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an image reading apparatus using photoelectric conversion means such as a CCD, an image forming apparatus having the image reading apparatus, an image reading method, and a computer-readable storage medium. It is suitable for use in preventing saturation of photoelectric conversion means such as a CCD.

[0002]

2. Description of the Related Art FIG. 5 shows the structure of an image reading apparatus 100. The image reading apparatus 100 includes a transparent document table 104 using glass or the like for setting a document 110, an optical unit 105, an optical unit driving motor 101 for moving the optical unit 105 in the sub-scanning direction of the document, and an optical unit. Home position sensor 10 for detecting that 105 is at the image reading start position (home position)
2 is provided. The optical unit 105 includes a light source 106 for irradiating a document, a reflection mirror 108, a condenser lens 103, and a CCD unit 107 for accumulating charges corresponding to incident light.
Consists of

In the image reading apparatus 100 as described above, the optical unit 105 is driven by the optical unit driving motor 1 while the original 110 is placed at a predetermined position on the original table 104.
While scanning in the horizontal direction according to 01, the light source 106 is irradiated to read the image of the original 110.

The speed at which a document is read differs depending on the resolution. Generally, the higher the resolution, the lower the reading speed.

[0005]

However, when the reading speed is reduced, the light from the original
The time input to D section 107 becomes longer, and CC
The amount of charge stored in the D section 107 increases. Therefore, C
In some cases, the charge overflowed from the CD unit 107, causing the image to become white in the main scanning direction or to be read as a black image.

The present invention has been made in view of the above situation, and has as its object to prevent charges from overflowing from the CCD unit 107.

[0007]

First, an image reading apparatus according to the present invention comprises: a photoelectric conversion means for accumulating electric charges corresponding to incident light; And a first accumulation start signal means for generating a first accumulation start signal for starting accumulation of the electric charges, wherein the image reading apparatus determines an accumulation time of the photoelectric conversion means by a generation cycle of the first accumulation start signal. When the accumulation time of the photoelectric conversion means, which is determined by the generation cycle of the first accumulation start signal, is longer than a predetermined time, the transfer of the charge accumulated in the photoelectric conversion means is started, and a new charge is started. It is characterized in that a second accumulation start signal generating means for generating a second accumulation start signal for starting the accumulation of electric charges is provided.

[0008] Second, the second accumulation start signal generating means generates a first accumulation start signal after the first accumulation start signal is generated by the first accumulation start signal generation means. It is characterized in that the second accumulation start signal is generated until it is generated.

Thirdly, there is provided a clock signal generating means for generating a clock signal for controlling a transfer time of the electric charge transferred by the first and second accumulation start signals, and the frequency of the clock signal is variable. It is characterized by

Fourthly, the clock signal generation means changes the frequency of the clock signal to the first frequency when the second accumulation start signal generation means generates the second accumulation start signal.
To increase from the frequency of the second to the second frequency,
It is characterized in that the transfer time of the charges whose transfer has been started by the second accumulation start signal is shortened.

Fifth, the clock signal generating means may be configured such that after the second accumulation start signal generating means generates the second accumulation start signal, the first accumulation start signal generating means outputs the next signal. It is characterized in that the frequency of the clock signal is returned from the second frequency to the first frequency when one accumulation start signal is generated.

A sixth feature of the present invention is that an image processing means for performing image processing on a signal output from the photoelectric conversion means is provided.

A seventh feature is that the image of the subject is read by relatively moving the photoelectric conversion means and the subject.

Eighthly, an image forming apparatus according to the present invention comprises an image reading device according to any one of claims 1 to 7, and a printer unit for recording an image read by the image reading device on a recording medium. Has features.

Ninth, according to the image reading method of the present invention, a first accumulation start signal for starting transfer of electric charges accumulated in the photoelectric conversion means and starting accumulation of new electric charges is generated.
An image reading method having a procedure for determining the accumulation time of said photoelectric conversion means by the generation cycle of said accumulation start signal, wherein the accumulation time of said photoelectric conversion means is determined by the generation cycle of said first accumulation start signal. It is characterized in that it has a procedure of generating a second accumulation start signal for starting transfer of electric charges accumulated in the photoelectric conversion means and starting accumulation of new electric charges when the time is longer than the time.

Tenth, the computer-readable storage medium of the present invention generates a first accumulation start signal for starting transfer of electric charges accumulated in the photoelectric conversion means and for starting accumulation of new electric charges, A computer-readable storage medium storing a program for executing a procedure for determining an accumulation time of the photoelectric conversion unit based on a generation cycle of the first accumulation start signal, wherein When the determined accumulation time of the photoelectric conversion means is longer than a predetermined time, a second accumulation start signal for starting transfer of the electric charge accumulated in the photoelectric conversion means and starting accumulation of new electric charge is generated. The feature is that a program for executing the procedure is stored.

According to the present invention as described above, the second accumulation start signal is generated before the electric charge overflows from the photoelectric conversion means which has started the accumulation by the first accumulation start signal, so that the photoelectric conversion is performed until then. By transferring the accumulated charge to the means, it is possible to accumulate the charge that is about to overflow.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram illustrating a configuration of an image forming apparatus according to the present embodiment.
Denotes a printer unit.

An image reading unit 100 includes a transparent document table 104 using glass or the like for setting a document 110, an optical unit 105, and an optical unit drive motor 101 for moving the optical unit 105 in the sub-scanning direction of the document. ,
Home position sensor 10 for detecting that the optical unit is at the image reading start position (home position)
2 is provided. The optical unit 105 includes a light source 106 for irradiating a document, a reflection mirror 108, a condenser lens 103, and a CCD unit 107 for accumulating charges corresponding to incident light.
Consists of In the present embodiment, the CCD unit 107 corresponds to a photoelectric conversion unit according to the present invention.

In the image reading section 100 as described above,
With the document 110 placed at a predetermined position on the document table 104, the optical unit 105 is
1 to scan in the horizontal direction.

Specifically, the light source 1 of the optical unit 105
The light 06 is applied to the original 110 on the original table 104, and the reflected light from the original 110 enters the CCD 107 via the reflection mirror 108 and the condenser lens 103. CCD
The light incident on the unit 107 is converted into an electric signal according to the intensity, and is transferred to the first control unit 111 to perform image processing. Further, the first control unit 111 reads the entire document 110 by causing the optical unit 105 to scan in the sub-scanning direction by the optical unit driving motor 101 at the same time as the above operation. The details of the first control unit 111 will be described later.

The printer unit 200 includes the paper feed cassette 20
1. Paper 202 serving as a recording medium, a paper feed roller 203, a registration roller 204, an image carrier (photosensitive drum), and a toner cartridge 20 including a charging unit and a developing unit (not shown)
5, a transfer roller 206, a conveyance path 207 for the paper 202, a polygon scanner (not shown), a laser scanner unit 208 including a semiconductor laser, a fixing unit 209 for fixing toner on the paper 202, and a paper discharge tray 210. And a second control unit 211.

The image data on which the image processing has been performed by the first control unit 111 of the image reading section 100 is sent to the second control unit 211 of the printer section 200. The second control unit 211 causes the laser scanner unit 208 to perform laser beam scanning exposure corresponding to a target image pattern on the basis of the image data, so that the image carrier (photosensitive drum) in the toner cartridge 205 is An electrostatic latent image is formed.

The paper 202 in the paper feed cassette 201
Are separated and fed by the cooperation of the sheet feeding roller 203 and a separating member (not shown). The registration roller 204 corrects the skew of the fed paper 202 and feeds the paper 202 to the transfer roller 206 at an appropriate timing in synchronization with image formation on the image carrier (photosensitive drum) side.

The paper 2 passing through the transfer roller 206
Reference numeral 02 denotes a sheet on which the electrostatic latent image on the image carrier (photosensitive drum) is transferred, and then passes through the fixing unit 209 and is discharged to the sheet discharge tray 210.

FIG. 2 shows an outline of the first control unit 111 on the image reading section 100 side. A series of controls described below are performed by the control unit 126. A normal SH (reading cycle) signal is sent from the control unit 126 to the CCD unit 107. The SH signal is a signal for starting the transfer of the charges stored in the CCD unit 107 and starting the storage of new charges. That is, the CCD unit 107 accumulates electric charges for a time determined by the generation cycle of the SH signal. In the present embodiment, this normal SH signal corresponds to the first accumulation start signal according to the present invention.

A clock signal is sent from the clock signal generator 128 to the CCD unit 107. This clock signal is a signal for controlling the transfer time of the charges accumulated in the CCD unit 107.

CC for accumulating and transferring charges as described above
The electric signal output from the D unit 107 is
, And is converted to a digital image signal by the A / D converter 122. The digital image signal is supplied to the light source 106 and the lens 10 by the shading correction unit 123.
3 and the CCD unit 107 are subjected to shading correction. The shading correction of the digital image signal corrects the spectral characteristics of the light source 106 and the CCD unit 107 in the masking correction unit 124, and outputs the L signal in the LOG conversion unit 125.
OG conversion is performed, and the result is sent to the second control unit 211 as described above.

Here, when the charges are likely to overflow from the CCD unit 107, that is, when the accumulation time determined by the regular SH signal becomes long, the details will be described later, but separately from the SH signal, Pseudo SH generator 127
Sends a pseudo SH signal. This pseudo SH signal is represented by C
This is a signal for starting transfer of charges stored in the CD unit 107 and starting storage of new charges. In this embodiment, the pseudo SH signal corresponds to the second accumulation start signal according to the present invention.

When the pseudo SH signal is sent, the clock signal generator 128 sends a clock signal with a changed frequency.

Hereinafter, the operation of the image reading section 100 of the image forming apparatus will be described. FIG. 3 shows the operation timing of the image reading unit 100. FIG. 3A shows a case where the reading speed is low, and FIG. 3B shows a case where the reading speed is high. 3 (a) and 3 (b), (A) shows CC
The reading cycle SH of the D unit 107, (B) the drive pulse of the optical unit drive motor 101, and (C) the CCD unit 107
(D) is image data transferred from the CCD unit 107 to the first control unit 111, and (F) is a clock for transferring the charge (image data). As shown in (A) and (B), the read cycle SH (charge accumulation time) of the CCD unit 107 and the drive pulse of the optical unit drive motor 101 are synchronized.

In the CCD 107 of this embodiment, when the reading cycle SH (charge storage time) exceeds the time T, the charges overflow.

First, the case where the reading speed is high and the reading cycle SH of the CCD unit 107 is T will be described. In this case, the reading cycle SH of the CCD unit 107 is T
, The charge does not overflow from the CCD unit 107 (the CCD unit 107 does not saturate).

The control unit 126 sends a normal SH signal to the CCD unit 107 with the read cycle SH as T. Therefore, as shown in FIG.
Starts the accumulation of charges (image data A) upon receiving the SH signal (n-th). Then, if the next regular SH signal (n + 1) is received after time T,
The charge (image data A) accumulated so far is transferred to the first control unit 111 side, and the accumulation of new charge (image data B) is started. Thereafter, the above operation is repeated until reading is completed.

The transfer of charges from the CCD unit 107 is performed based on a clock signal from the clock signal generation unit 128, and the transfer clock at this time is f1.

Next, a case where the reading speed is slow and the reading cycle SH of the CCD unit 107 exceeds T and becomes T + T1 will be described. In this case, since the reading cycle of the CCD unit 107 exceeds the time T, the charge overflows from the CCD unit 107 as it is (the CCD unit 107 is saturated). Therefore, the control unit 126 performs the processing shown in the flowchart of FIG. 4 to control the charge so as not to overflow from the CCD unit 107.

The control unit 126 sends a normal SH signal to the CCD unit 107 with a read cycle SH of T + T1. Therefore, as shown in FIG.
07 starts accumulation of charges (image data A) when receiving the SH signal (n-th).

At the same time, the control unit 126
It is determined that H exceeds T (step S101 in the flowchart of FIG. 4), and after a time T from sending the normal SH signal, that is, after the CCD unit 107 starts accumulating charges (image data A). After T seconds, the pseudo SH generator 12
7 to send a pseudo SH signal (step S102 in the flowchart of FIG. 4). As a result, FIG.
As shown in (a), when the CCD unit 107 receives the pseudo SH signal (the (n + 1) th), the CCD unit 107 takes time T until that time.
Is transferred to the first control unit 111 side. Therefore, the CCD unit 107 can accumulate charges (image data B) for the time T1 that should originally overflow.

Here, since the CCD section 107 receives the next normal SH signal (n + 2) after the time T1, the transfer of the charge (image data A) must be completed within the time T1. Therefore, when sending the pseudo SH signal (the (n + 1) th), the control unit 126 sets the clock signal generation unit 1
At 28, the frequency of the clock signal is increased from f1 to f2 (step S103 in the flowchart of FIG. 4). As a result, as shown in FIG. 3A, the transfer of the charge (image data A) can be completed within the time T1.

Then, as shown in FIG.
Upon receiving the next normal SH signal (the (n + 2) th), the unit 107 transfers the charge (image data B) accumulated up to that time T1 and stores the new charge (image data C). Start.

Note that the transfer of the charge (image data B) whose transfer has been started may be completed within the time T until the next pseudo SH signal (n + 3) is received.
In step 26, when the SH signal (n + 2) is sent (step S104 in the flowchart of FIG. 4), the clock signal generator 128 returns the frequency of the clock signal from f2 to the original f1 (step S105). Thereafter, the above operation is repeated until reading is completed.

As described above, according to the present embodiment,
Since the pseudo SH signal is sent before the electric charge overflows from the CCD unit 107, the electric charge is prevented from overflowing from the CCD unit 107, and the image becomes white in the main scanning direction or becomes a black image. It is possible to prevent reading. In addition, since the frequency of the clock is increased when transmitting the pseudo SH signal, the next regular SH
By the time the signal is sent, the transfer of the accumulated charge can be completed.

Note that the image forming apparatus of the above embodiment is
The image data from the image reading unit 100 is
Although the above-described apparatus functions as a copier that transfers the image data to the host computer, it also functions as a printer that prints image data from a host computer (not shown) or transmits image data from the image reading unit 100 to the host computer. It may function as a scanner.

(Other Embodiments) Even if the present invention is applied to a system composed of a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.), one device (for example, a copying machine, a facsimile, etc.) Device).

Also, the functions of the above-described embodiments are implemented in a device connected to the various devices or a computer in a system so that various devices are operated to realize the functions of the above-described embodiments. The present invention also includes a program which is provided by supplying program code of software for operating the above various devices in accordance with a program stored in a computer (CPU or MPU) of the system or apparatus.

In this case, the software program code itself implements the functions of the above-described embodiment, and the program code itself and means for supplying the program code to the computer are provided.
For example, a recording medium storing such a program code constitutes the present invention. As a recording medium for storing such a program code, for example, a floppy disk, hard disk, optical disk, magneto-optical disk, CD-ROM,
A magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.

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

Further, after the supplied program code is stored in a memory provided in a function expansion board of a computer or a 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. It is needless to say that the present invention also includes a case where the CPU or the like provided for performs part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.

It should be noted that the shapes and structures of the respective parts shown in the above-described embodiment are merely examples of the embodiment for carrying out the present invention, and the technical scope of the present invention is thereby reduced. It should not be interpreted restrictively. That is, the present invention can be implemented in various forms without departing from the spirit or main features thereof.

[0050]

As described above, according to the present invention, it is possible to prevent the electric charges from overflowing from the photoelectric conversion means, so that the image becomes white in the main scanning direction or is read as a black image. Can be prevented beforehand.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of an image forming apparatus according to a first embodiment.

FIG. 2 shows a first control unit 111 of the image reading unit 100.
FIG.

FIG. 3 is a diagram illustrating operation timings of an image reading unit of the image forming apparatus.

FIG. 4 is a flowchart illustrating a process performed when a reading cycle SH (charge storage time) of a CCD unit 107 exceeds T.

FIG. 5 is a diagram illustrating a configuration of an image reading apparatus.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 Image reading unit 101 Optical unit drive motor 102 Home position sensor 103 Condensing lens 104 Document table 105 Optical unit 106 Light source 107 CCD unit 108 Reflecting mirror 110 Document 111 First control unit 121 Amplifying unit 122 A / D conversion unit 123 Shading Correction unit 124 Masking correction unit 125 LOG conversion unit 126 Control unit 127 Pseudo SH generation unit 128 Clock signal generation unit 200 Printer unit 201 Paper feed cassette 202 Paper 203 Paper feed roller 204 Registration roller 205 Toner cartridge 206 Transfer roller 207 Transport path 208 Laser Scanner unit 209 Fixing unit 210 Output tray 211 Second control unit

Claims (10)

[Claims] 1. A photoelectric conversion means for accumulating electric charge according to incident light, and a first accumulation start signal for starting transfer of electric charge accumulated in the photoelectric conversion means and starting accumulation of new electric charge. A first accumulation start signal means;
An image reading device that determines an accumulation time of said photoelectric conversion means by a generation cycle of said accumulation start signal, wherein an accumulation time of said photoelectric conversion means defined by a generation cycle of said first accumulation start signal is longer than a predetermined time. A second accumulation start signal generating means for generating a second accumulation start signal for starting transfer of the electric charge accumulated in the photoelectric conversion means and starting accumulation of new electric charge when the length is long; Image reading device. 2. The method according to claim 1, wherein the second accumulation start signal generation means is configured to generate a first accumulation start signal after the first accumulation start signal generation means generates the next first accumulation start signal. 2. The image reading apparatus according to claim 1, wherein a second accumulation start signal is generated in between. 3. A clock signal generating means for generating a clock signal for controlling a transfer time of the charge whose transfer has been started by the first and second accumulation start signals, wherein the frequency of the clock signal is made variable. The image reading device according to claim 1 or 2, wherein 4. The clock signal generating means according to claim 2, wherein
When the accumulation start signal generating means generates the second accumulation start signal, the frequency of the clock signal is changed from the first frequency to the second frequency, and the frequency of the clock signal is changed by the second accumulation start signal. The image reading apparatus according to claim 3, wherein a transfer time of the charge whose transfer has been started is shortened. 5. The clock signal generating means according to claim 2, wherein:
After the first accumulation start signal generating means generates the second accumulation start signal, the first accumulation start signal generating means
5. The image reading apparatus according to claim 4, wherein when the storage start signal is generated, the frequency of the clock signal is returned from the second frequency to the first frequency. 6. The image reading apparatus according to claim 1, further comprising image processing means for performing image processing on a signal output from said photoelectric conversion means. 7. The image reading apparatus according to claim 1, wherein the image of the subject is read by relatively moving the photoelectric conversion unit and the subject. 8. An image forming apparatus comprising: the image reading device according to claim 1; and a printer unit that records an image read by the image reading device on a recording medium. apparatus. 9. A first accumulation start signal for starting transfer of electric charge accumulated in the photoelectric conversion means and starting accumulation of new electric charge is generated, and the photoelectric conversion is performed according to a generation cycle of the first accumulation start signal. An image reading method having a procedure for determining an accumulation time of the photoelectric conversion means, wherein the accumulation time of the photoelectric conversion means defined by a generation cycle of the first accumulation start signal is longer than a predetermined time. An image reading method for generating a second accumulation start signal for starting the transfer of the electric charge accumulated in the memory and starting the accumulation of new electric charge. 10. A first accumulation start signal for starting transfer of electric charge accumulated in the photoelectric conversion means and starting accumulation of new electric charge is generated, and the photoelectric conversion is performed according to a generation cycle of the first accumulation start signal. A computer-readable storage medium storing a program for executing a procedure for determining an accumulation time of a means, wherein the accumulation time of the photoelectric conversion means is determined by a generation cycle of the first accumulation start signal for a predetermined time. And storing a program for executing a procedure for generating a second accumulation start signal for starting transfer of the electric charge accumulated in the photoelectric conversion means and starting accumulation of new electric charge when the electric charge is longer. Computer-readable storage medium.