JP2000299770A - Reader, method and computer-readable storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the buildup time of a CCD image sensor after starting driving from a read standby state and to suppress power consumption in a standby state in a reader employing the CCD image sensor. SOLUTION: A CCD image sensor receives a shift pulse SH and transfer clocks Φ1, Φ2. A 1st mode is set to the reader where the shift pulse SH and the transfer clocks Φ1, Φ2 are always generated in a reading operation and in a state before and after it, and a 2nd mode is set to the reader where the shift pulse SH and the transfer clocks Φ1, Φ2 are generated for optional M periods in the read standby state and the transfer clocks Φ1, Φ2 are stopped and only the shift pulse SH are generated for succeeding N periods.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a CCD image sensor, a contact image sensor, an area sensor, and the like.
The present invention relates to a reading device and method for reading optical information such as a manuscript and a bar code, and a computer-readable storage medium used in the reading device and method.

[0002]

2. Description of the Related Art As is well known in the art, a CCD image sensor is provided with a photoelectric conversion unit comprising a photodiode or the like for photoelectrically converting incident light, and a charge accumulating device for accumulating charges corresponding to the amount of incident light obtained by the photoelectric conversion. And a shift register section for temporarily holding the charge accumulated in the photosensitive section for each scanning time and sequentially outputting the charges within one scanning time. It is constituted by forming on a substrate made of.

For this reason, a reading device for reading optical information such as a read original using a CCD image sensor is required to transfer electric charges accumulated in a photosensitive portion to a shift register portion in order to operate the CCD image sensor. And a transfer clock generating unit for generating a transfer clock for sequentially outputting the charges of the respective photosensitive units transferred to the shift register unit.

[0004] The CCD image sensor reading device always generates a shift pulse and a transfer clock having a constant period regardless of whether optical information is read, and drives the CCD image sensor. In addition, since it is not necessary to drive in a standby state in which optical information is not read,
For example, in a device that requires low power consumption, such as a battery-powered portable reading device, external operation is performed by detecting a user's button operation and detecting that a document has been inserted into the document insertion slot. There is also known a device in which a CCD image sensor is driven only when a command to read optical information is input from a personal computer.

However, a start-up time is required when driving the CCD image sensor. Because CC
Immediately after D drive, the photosensitive portion is full of electric charges that have been photoelectrically converted when the drive is off, and the shift register portion is also full of electric charge overflowing from the photosensitive portion. This is because it is necessary to sweep out the charge from the photosensitive section and the shift register section so that the optical information can be read by using the above.

[0006] Such discharge of electric charges may be performed by executing ordinary drive control for inputting a transfer clock and a shift pulse to the CCD image sensor. That is, CC
If a shift pulse is input to the D image sensor, the charge accumulated in the photosensitive unit is transferred to the shift register unit,
When the transfer clock is input to the D image sensor, the charges in the shift register section are sequentially discharged in synchronization with the transfer clock, so that the transfer clock and the shift pulse are input to the CCD image sensor as in the normal reading. When the power is turned off, the electric charges accumulated in the photosensitive section and the shift register section are discharged, and the CCD image sensor can be started up in a state where optical information can be read.

[0007] The rise time until the CCD image sensor can read optical information is equal to the rise time of the CCD image sensor.
After the start of driving, the transfer clock is determined by a transfer clock shift pulse and a transfer clock of one cycle or more input to the CCD image sensor.

[0008]

As is apparent from the above description, the CCD and the clock generator are always used when the driving is always performed by the shift pulse and the transfer clock having a constant period regardless of the reading of the optical information. In this case, there is a problem that the switching current continues to flow, and wasteful power consumption increases at the time of reading standby.

On the other hand, the CCD image sensor is driven only when a command for reading optical information is inputted from outside by, for example, detecting a user's operation of a switch and insertion of a document into the document insertion slot. In the conventional reading device described above, unexpected external light may be input during standby. At this time, the photosensitive section is full of electric charges that have been photoelectrically converted when the drive is turned off, and the shift register section is also full of electric charges that have overflowed from this photosensitive section. In order to be able to read information, it is necessary to sweep out charges from the photosensitive section and the shift register section. Since the presence or absence of external light cannot be determined, a transfer clock and a shift pulse are generated several times at a fixed period. Therefore, after the CCD image sensor starts to be driven, until the CCD image sensor can read optical information. There was a problem that it took a long time to rise.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem. In an apparatus for reading optical information by using a CCD image sensor, the C
It is an object of the present invention to shorten the rise time of the CD image sensor and reduce the power consumption of the apparatus during standby.

[0011]

In order to achieve the above-mentioned object, a reading apparatus according to the present invention is arranged in a one-dimensional or two-dimensional direction, photoelectrically converts incident light, and obtains a charge obtained by the photoelectric conversion. And a shift register for holding the charges stored in each of the photosensitive units by an externally input shift pulse and sequentially outputting the held charges by a transfer clock input from the outside. And an image sensor that outputs a charge from the shift register unit as an image signal.
Transfer clock generating means for generating the transfer clock at a predetermined cycle; and a shift for generating the shift pulse having a period of time during which the transfer clock generating means outputs the transfer clocks equal to or more than the number of photosensitive units in the image sensor. A pulse generating means, a first mode for constantly generating the transfer clock and the shift pulse, an arbitrary M period for generating the transfer clock and the shift pulse, and the following N periods for stopping the transfer clock and only the shift pulse The transfer clock generating means and the shift pulse generating means perform the second mode for generating the image signal. The first mode is set during the image signal reading operation and before and after the image signal reading operation. Control means for setting the mode to the second mode.

Further, in the reading method according to the present invention, a plurality of photosensitive portions arranged one-dimensionally or two-dimensionally, photoelectrically converting incident light, and accumulating charges obtained by the photoelectric conversion, A shift register unit for holding the stored charges by a shift pulse input from the outside, respectively, and sequentially outputting the held charges by a transfer clock input from the outside, wherein the charge from the shift register unit is A first mode in which the transfer clock and the shift pulse are constantly generated using an image sensor that outputs an image signal, and the transfer clock and the shift pulse are generated for any M periods, and the transfer clock is stopped for the next N periods. A second mode for generating only the shift pulse is provided during and before and after the image signal reading operation. In the state set to the first mode, the reading standby state is to be set in the second mode.

Further, in the storage medium according to the present invention,
A plurality of photosensitive units arranged one-dimensionally or two-dimensionally, photoelectrically convert incident light, and accumulating charges obtained by the photoelectric conversion, and charge accumulated in each photosensitive unit is shifted by a shift pulse input from outside. A shift register unit for holding the respective charges and sequentially outputting the held charges according to a transfer clock input from the outside, wherein the transfer clock in the image sensor for outputting the charges from the shift register unit as an image signal is set to a predetermined value. A first mode in which the shift pulse is generated with a period of time during which the transfer clocks equal to or more than the number of the photosensitive units are generated, and a first mode in which the transfer clock and the shift pulse are constantly generated. , An arbitrary M period generates the transfer clock and the shift pulse, and the following N periods stop the transfer clock and shift the shift clock. A second mode for generating only a pulse, a process for setting the first mode during and before and after the image signal reading operation, and a process for setting the second mode during the reading standby state; Is stored.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. First, the principle of the CCD applied to the present invention will be described. As shown in FIG. 2, the basic structure of a CCD is a MOS capacitor having an electrode provided on an insulating film on the surface of a semiconductor substrate such as P-type silicon. When a voltage is applied to the electrode, a depletion layer is formed in the vicinity of the interface between the insulating film and the semiconductor substrate. This is called a potential well (potential well). When signal charges generated by light incidence are injected into the well of this potential, these are temporarily stored and recorded as analog quantities.

Next, the operation principle of the CCD linear image sensor will be described. In the CCD linear image sensor, signal charges photoelectrically converted and accumulated by a photodiode array are transferred by a CCD analog shift register and sequentially read. The photosensitive section is composed of a photodiode, a MOS capacitor and a shift electrode as shown in FIG. The input light is photoelectrically converted by a photodiode into a photocurrent, which is stored in a MOS capacitor to become a signal charge. This signal charge is transferred to the transfer section through the shift electrode.

Generally, two phases are used as clock pulses for transferring electric charges. In this case, as shown in FIG. 4, one potential well has a role of accumulating charges, and a well adjacent thereto has a role of separating charges of each pixel. In other words, since two wells operate as a set, one pixel of the photosensitive section corresponds to two potential wells. Therefore, the image signal is output for one pixel for one cycle of the transfer clock pulse.

FIG. 5 shows a configuration diagram of a single channel register. A simple example is a configuration of a 4-pixel CCD. FIG. 6 shows an operation timing chart thereof.

Next, the operation of the embodiment of the present invention when driving only the shift pulse when the transfer clock is stopped will be described. In the description of the operation principle of the CCD, the input light to the photosensitive unit is photoelectrically converted by a photodiode into a photocurrent, accumulated in a MOS capacitor to become a signal charge, and the signal charge is transferred to a transfer unit through a shift electrode. Therefore, each time a shift pulse is input, a signal charge proportional to the input light is accumulated in the transfer unit. If this operation is repeated, the electric charge in the transfer section overflows and flows into another block.

At the time of normal reading, the transfer clock is input, and after the transfer of all the pixels is completed, the empty clock is input, and then the shift pulse is input so that no overflow occurs.

FIG. 1 is a block diagram showing a configuration of a reading apparatus according to an embodiment of the present invention. In FIG. 1, 1
Is a light source for illuminating the original, 2 is a CCD for reading the illuminated original, 3 is an image processing unit, 4 is a shift pulse generator, 5 is a transfer clock generator, 6 is a stop / drive control unit,
Reference numeral 7 denotes a mode transition determination unit, 8 denotes a cover sensor for detecting opening / closing of a document cover, 9 denotes a document detection sensor for detecting that a document has been inserted into a document insertion port, 10 denotes a control unit for controlling the entire apparatus, 11 Reference numeral 12 denotes an operation unit on which a start button for reading start is arranged, and 12 denotes a shift pulse cycle setting unit.

The shift pulse generator 4 supplies a shift pulse SH to the CCD 2. The control unit 10 controls the start and stop of the shift pulse, and normally drives constantly. The transfer clock generator 5 supplies two-phase transfer clocks Φ1 and Φ2 to the CCD 2. The stop / drive of the supply is controlled by the stop / drive control unit 6. The timing is controlled so as to synchronize with the shift pulse as shown in FIGS.

The mode transition determining unit 7 instructs the stop / drive. The mode transition determination unit 7 determines whether the mode is the first mode or the second mode based on the device state signal from the control unit 10. In the present embodiment, the first mode is a mode in which a transfer clock and a shift pulse are constantly generated, and the second mode is a mode in which a transfer clock and a shift pulse are generated for an arbitrary M period, and the subsequent N periods are for a transfer period. In this mode, the clock is stopped and only the shift pulse is generated.
The mode shift determination unit 7 instructs the stop / drive control unit 6 according to the determination result.

Each signal by pressing the reading start button of the cover sensor 8, the document detection sensor 9, and the operation unit 11 is input to the control unit 10. The control unit 10 generates a state signal of the device according to the current state of the apparatus, for example, a state of “reading / standby” and each input signal, and sends the signal to the mode transition determination unit 7.

Next, the drive timing of the transfer clock and the shift pulse by each unit in FIG. 1 will be described in detail.
After the reading is completed, the light source 1 is turned off, and when the reading is not started even after the elapse of a certain time, the stop / drive control unit 6 as shown in FIG. Stop Φ2. The charge is t3 in FIG.
Is the state stored in the transfer unit. At this time, since the light source 1 has already been turned off, the input light is close to zero.

Therefore, even if a few shift pulses are input after the transfer clock is stopped, the charges in the transfer section do not overflow.
That is, the states of t2 and t3 in FIG. 3 are repeated. However, since there is almost no charge in the light receiving portion (hatched portion in FIG. 3), the charge accumulated in the photosensitive portion in FIG. Even if it is done, it does not overflow from the photosensitive section.

However, if the transfer clock is stopped as it is, the overflow will occur sometime. Therefore, as shown in FIG. In this case, one cycle is set so that a transfer clock is input. This allows
The overflow can be prevented, and the switching current of the MOS is not consumed only during the stop period of the transfer clock.

Assuming that the current value of the CCD 2, the shift pulse generator 4 and the transfer clock generator 5 at the time of input of the transfer clock is IH, and the current value of the transfer clock stop is IL, the average current IM = IH * M / ( M + N) + IL * N / (M
+ N) If M = 1 and N = 99, IM = 0.01I + 0.99IL Since the conventional current value is IH, the difference is: IH−IM = IH−0.01I−0.99IL = 0.99IH−0 Since .99IL IL≪IH, a 99% reduction in current consumption can be realized.

In a conventional reading apparatus in which the transfer clock of the CCD image sensor is constantly generated, unexpected external light may be input during standby. However, according to the present embodiment, the transfer is performed at regular intervals. Since the clock is stopped and driven, it is possible to quickly return to the normal state.

Further, when there is a possibility that the reading position is opened and external light is input by opening the document cover or the like when the document reading unit releases the document, a cover release sensor is provided to detect the release. Sometimes, control is performed so as to immediately drive the transfer clock. As a result, it is possible to prevent an overflow due to unexpected external light or the like.

Next, a description will be given of a case where an optical information reading command is input from the outside by, for example, operating the reading start button by the user during standby and detecting that a document has been inserted into the document insertion slot. Insert a manuscript from the main body,
Alternatively, when a reading start signal is input by the reading start button after the original is inserted, the control unit 10 in FIG.

The mode shift determining unit 7 determines that the mode shifts to the second mode when the reading start signal is input when the apparatus is in the second mode state. And
The stop / drive control unit 6 is instructed to shift to the second mode, and the transfer clock of the CCD 2 is immediately driven. When there is a driving instruction, the transfer clock generator 5 transfers the transfer clocks Φ1 and Φ1 while maintaining the phase as shown in FIG.
2 is driven in synchronization with the shift pulse. Control unit 10
When a transfer clock of one cycle or more is input to the CCD 2, the light source 1 is turned on, and after the light amount is stabilized, document feeding, prescan shading correction, and the like are performed, and a reading operation is started.

The drive timing of the transfer clock at the start of reading shown in FIG. 8 is performed in the same manner when the danger of external light input due to release of the document cover or the like is detected. However, the operation after turning on the light source 1 is not performed.

Since the number M of shift pulses and the number N of the shift pulses in the above embodiment are arbitrary, if the specifications such as the dark current of the CCD are remarkably excellent, N can be increased as much as possible, which considerably contributes to the reduction of current consumption. I do.

In order to prevent erroneous recognition of a cover sensor or the like, a photo sensor may be separately installed near the CCD, and the mode transition determination may be performed using a light detection signal from this sensor. Further, the shift pulse period in the standby state can be optimally controlled according to the light amount detection amount of the photo sensor. This is an effective control method for avoiding the overflow of the charge of the transfer electrode.

Further, even if the CCD in the present embodiment is replaced with a contact image sensor of a contact type,
It goes without saying that the same effect as in the above-described embodiment can be obtained even if the area sensor is replaced with a two-dimensional area sensor.

Next, the storage medium according to the present invention will be described. The system including the blocks in FIG. 1 can be configured by a computer system including a CPU and a memory. In that case, the memory configures a storage medium according to the present invention. The storage medium stores a program for executing a processing procedure for controlling the operation described in the above embodiment.

As the storage medium, ROM, R
Semiconductor memory such as AM, optical disk, magneto-optical disk,
A magnetic medium or the like may be used, and these may be configured and used in a CD-ROM, a floppy disk, a magnetic medium, a magnetic card, a nonvolatile memory card, or the like.

Therefore, this storage medium can be used in a system or apparatus other than the system or apparatus shown in FIG. 1, and the system or computer reads out and executes the program code stored in this storage medium. The same functions as those of the above-described embodiment can be realized, the same effects can be obtained, and the object of the present invention can be achieved.

An OS running on a computer
Perform part or all of the processing, or after the program code read from the storage medium is written into the memory provided in the extended function board inserted into the computer or the extended function unit connected to the computer. ,
Even when the CPU or the like provided in the extended function board or the extended function unit performs a part or all of the processing based on the instruction of the program code, the same functions as those of the above embodiment can be realized and the same effects can be obtained. You can get
The object of the present invention can be achieved.

[0040]

As described above, according to the present invention,
A first mode in which a transfer clock and a shift pulse used in an image sensor are constantly generated, and the transfer clock and the shift pulse are generated at an arbitrary M period, and the following N periods stop the transfer clock and generate only a shift pulse. A second mode is provided, and the first mode is set during and before and after the reading operation, and the second mode is set during the reading standby state. Even if it is performed, the photosensitive portion is not filled with the charge photoelectrically converted when the drive is turned off, and the shift register portion is not filled with the charge overflowing from the photosensitive portion. There is no need to sweep out charges from the photosensitive section and the shift register section.

Therefore, there is no need to generate several cycles of the transfer clock and the shift pulse at a constant cycle after the start of driving as in the prior art. When the driving of the image sensor is started, the rise time of the image sensor can be shortened, and the standby time of the apparatus can be reduced. It is possible to achieve both suppression of power consumption at the time.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a reading device according to an embodiment of the present invention.

FIG. 2 is a configuration diagram showing a basic structure of a CCD.

FIG. 3 is a configuration diagram illustrating a cross-sectional structure and an operation principle of a photosensitive unit.

FIG. 4 is a configuration diagram and a timing chart showing an operation principle of two-phase driving.

FIG. 5 is a configuration diagram of a single channel register.

FIG. 6 is a timing chart showing the operation of a single channel register.

FIG. 7 is a timing chart showing the operation at the end of reading.

FIG. 8 is a timing chart showing an operation at the start of reading.

FIG. 9 is a timing chart showing an operation in a standby state.

[Explanation of symbols]

 Reference Signs List 1 light source 2 CCD 3 image processing unit 4 shift pulse generator 5 transfer clock generator 6 drive / stop control unit 7 mode transition determination unit 8 document cover cover sensor 9 document document detection sensor 10 control unit 11 operation unit

Claims (15)

[Claims] 1. A plurality of photosensitive units arranged one-dimensionally or two-dimensionally, photoelectrically converting incident light and storing charges obtained by the photoelectric conversion, and inputting charges stored in the respective photosensitive units from the outside. And a shift register unit for sequentially holding the held charges and sequentially outputting the held charges by a transfer clock input from the outside,
An image sensor that outputs the charge from the shift register unit as an image signal; a transfer clock generation unit that generates the transfer clock at a predetermined cycle; and a transfer clock that is equal to or more than the number of the photosensitive units is output from the transfer clock generation unit. Shift pulse generating means for generating the shift pulse having a period of one cycle, a first mode for constantly generating the transfer clock and the shift pulse, and an arbitrary M period for generating the transfer clock and the shift pulse. In the following N periods, the transfer clock is stopped and the second mode of generating only the shift pulse is performed by the transfer clock generating means and the shift pulse generating means. Control means for setting the first mode and setting the second mode in the reading standby state Reader, wherein a is provided. 2. The reading device according to claim 1, wherein the control means shifts from the second mode to the first mode when a read start signal is input. 3. A light shielding means for shielding external light from entering the photosensitive portion of the image sensor, and a detecting means for detecting that the light shielding by the light shielding means is released, wherein the control means comprises: 2. The reading apparatus according to claim 1, wherein a transition is made from the second mode to the first mode in response to the detection of the means. 4. The image sensor according to claim 1, wherein the image sensor reads an original image irradiated by a light source.
After the start signal is input, at least one cycle of the shift pulse immediately before the start of lighting of the light source is at least one cycle of the first pulse.
3. The reading apparatus according to claim 2, wherein the mode shifts to the first mode, and then the lighting of the light source is started. 5. The detecting means comprises a light receiving means provided near the image sensor, and the control means determines a stop cycle N of the transfer clock in accordance with an amount of light received by the light receiving means. The reading device according to claim 3, wherein 6. A plurality of photosensitive units arranged one-dimensionally or two-dimensionally, photoelectrically converting incident light and storing charges obtained by the photoelectric conversion, and inputting charges stored in each of the photosensitive units from outside. And a shift register unit for sequentially holding the held charges and sequentially outputting the held charges by a transfer clock input from the outside,
A first mode in which the transfer clock and the shift pulse are constantly generated using an image sensor that outputs the charge from the shift register unit as an image signal, and an arbitrary M period generates the transfer clock and the shift pulse, and continues. A second mode in which the transfer clock is stopped and only the shift pulse is generated for the N periods is provided. The first mode is set during the image signal reading operation and before and after the image signal reading operation. A reading method, wherein the reading mode is set to the second mode. 7. The reading method according to claim 6, wherein when the start signal for starting reading is input, the mode is shifted from the second mode to the first mode. 8. When the light blocking by light blocking means for blocking external light from entering the photosensitive portion of the image sensor is released,
7. The reading method according to claim 6, wherein the mode is shifted from the second mode to the first mode. 9. The image sensor according to claim 1, wherein the image sensor reads a document image irradiated by a light source, and after the activation signal is input, at least one cycle of the shift pulse immediately before the start of lighting of the light source. 7. The reading method according to claim 6, wherein the mode is shifted to the first mode, and then the lighting of the light source is started. 10. The method according to claim 8, wherein the release of light shielding by said light shielding means is detected by a light receiving means provided near said image sensor, and a stop cycle N of said transfer clock is determined according to a light receiving amount of said light receiving means. The reading method according to claim 8, wherein 11. A plurality of photosensitive units arranged one-dimensionally or two-dimensionally, photoelectrically converting incident light, and storing charges obtained by the photoelectric conversion, and inputting the charges stored in the respective photosensitive units from outside. A shift register unit for holding the respective shift pulses and sequentially outputting the held charges in accordance with a transfer clock input from the outside, and outputting the charges from the shift register unit as an image signal. A process of generating the transfer clock at a predetermined cycle, a process of generating the shift pulse with a period of time during which the transfer clocks equal to or more than the number of the photosensitive units are generated as one cycle, and constantly generating the transfer clock and the shift pulse In the first mode, any M periods generate the transfer clock and shift pulse, and the following N periods generate the transfer clock. The second mode is stopped and the shift mode is generated only. The first mode is set during and before and after the image signal reading operation, and the second mode is set during the reading standby state. A computer-readable storage medium storing a program for executing a setting process. 12. The computer-readable storage medium according to claim 11, wherein the setting process shifts from the second mode to the first mode when a reading start signal is input. . 13. A program for executing a process of detecting the incidence of external light on a photosensitive portion of the image sensor, wherein the setting process is performed in accordance with the detection.
The computer-readable storage medium according to claim 11, wherein the mode is shifted from the first mode to the first mode. 14. The image sensor according to claim 1, wherein the image sensor reads a document image illuminated by a light source, and the setting process is performed after the start signal is input and at least immediately before the start of lighting of the light source. 13. The computer-readable storage medium according to claim 12, wherein a transition to the first mode is performed for at least one cycle, and thereafter, a process of starting to turn on the light source is performed. 15. The method according to claim 13, wherein the detecting process detects the received light amount of the external light, and the setting process determines a stop cycle N of the transfer clock according to the received light amount. The computer-readable storage medium according to any one of the preceding claims.