Image reading apparatus

An image reading apparatus includes a sensor including a plurality of photoelectric converters for reading information on a document, a detecting circuit for detecting movement of a document cover, a drive circuit for supplying driving pulses for driving the sensor, and a control circuit for controlling the drive circuit so that the driving pulses are changed according to a detection result generated by the detecting circuit.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image reading apparatus such as a copying machine.

2. Description of the Related Art

Hitherto, image reading apparatuses using a charge-coupled device (CCD) line sensor for scanning and reading a document placed on a glass table have been known. Some of these image reading apparatuses have a function of automatically detecting the size of a document placed on the glass table. Also, the size of paper to be copied and the scale are automatically set.

A variety of methods can be used in order to detect the size of a document. According to one of the methods, a reflective sensor for detecting the size of a document is placed at a specific position in the main and sub scanning directions under the glass table. Then, the existence of the document at the specific position is detected by the sensor so as to determine the size of the document based on the detection result. According to another method, when a command of reading a document is output, the whole document area is scanned and read (pre-scan) before reading, and the size of the document is detected based on the output image signal.

In the method using only the reflective sensor, many sensors corresponding to various sizes of a document that can be placed on the glass table are necessary, and thus the configuration becomes complicated and the cost increases. On the other hand, in the method using a pre-scan, the pre-scan must be performed every time a document is placed on the glass table. Therefore, it takes time from when a command for starting reading is output until image reading is completed.

Accordingly, a method in which the above-described two methods are combined has been proposed. In this method, an open/closed state of a cover for covering a glass table is recognized and image data when the cover is half-closed is compared with image data when the cover is completely closed. Accordingly, the size in the main scanning direction is detected, and the size in the sub scanning direction is detected by using the known reflective sensor.

In this method, when the cover is half-closed, the area other than the document area does not reflect the light from a light source, and is read as black. On the other hand, when the cover is completely closed, the area other than the document area is read as white (when the rear side of the cover is white). Thus, by comparing the image data, the document area can be recognized and thus the size of the document can be detected.

In this method, only a reflective sensor for sub scanning direction is required and pre-scan need not to be performed, and thus time for reading the document is shortened. In the above-described method, however, data read by a CCD is used in order to detect the size in the main scanning direction. Accordingly, the CCD must be driven during a standby mode in which reading is not performed so as to read a document.

In the above-described method of detecting the size of a document, the CCD is always driven even when reading is not performed, and thus electrical power is wasted. Also, the temperature of the CCD rises when the CCD is driven. In a color sensor, in particular, temperature degradation in a color filter may be caused. The degradation in a color filter results in variation in the spectral characteristic, and may have a bad effect on a read color image. Also, a fan may be provided in the apparatus in order to suppress rise in the temperature of the CCD. In this case, however, vibration caused by rotation of the fan badly affects the image, for example, color drift is caused. Further, the cost increases.

SUMMARY OF THE INVENTION

The present invention provides an image reading apparatus in which power consumption and heat generated in a sensor can be reduced.

In particular, the present invention provides an image reading apparatus comprising a sensor including a plurality of photoelectric converters for reading information on a document; a detecting circuit for detecting movement of a document cover; a drive circuit for supplying driving pulses for driving the sensor; and a control circuit for controlling the drive circuit so that the driving pulse is changed according to a detection result generated by the detecting circuit.

Also, the present invention provides a method for controlling an image reading apparatus comprising a sensor having a plurality of photoelectric converters for reading information on a document. The method comprises a step of detecting a movement of a document cover; a step of supplying a driving pulse for driving the sensor; and a step of changing the driving pulse according to a result of the step of detecting the movement of the document cover.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Hereinafter, a preferred embodiment of an image reading apparatus according to the present invention will be described with reference to the drawings.

FIG. 1is a schematic view showing the overall configuration of an image reading apparatus of the embodiment. InFIG. 1, reference numeral101denotes a document. The image reading apparatus includes a glass table102on which the document101is placed and a cover103which covers the glass table102and which can be opened and closed. In the image reading apparatus, the document101placed on the glass table102is illuminated by a lamp104, and the light reflected at the document101is focused onto a charge-coupled device (CCD)109through a first mirror105, a second mirror106, a third mirror107, and a lens108.

In order to read the document101, a first mirror unit110, indicated by a broken line, moves in the sub scanning direction along the glass table102while the lamp104illuminates the document101so that the whole area of the document101on the glass table102can be scanned. The light reflected at the document101is focused onto the CCD109, as described above, and is then photoelectrically converted. An output signal from the CCD109is processed in a circuit at the subsequent stage to form an image.

FIG. 2Ashows the cover used in the image reading apparatus shown inFIG. 1. A cover203is configured so as to cover a document201and a glass table202. A detecting member204for detecting the open/closed state of the cover203is provided in the cover203. Also, two photosensors205are provided near the detecting member204, as shown inFIG. 2B. The open/closed state of the cover203, that is, the movement of the cover203can be recognized when the photosensors205are obstructed by the detecting member204by opening or closing the cover203. With the configuration shown inFIGS. 2A and 2B, a half-open state and a closed state of the cover203can be detected.

FIG. 3shows the configuration of a three-color line sensor used in the image reading apparatus. In this line sensor, instead of a CCD transfer unit being provided adjacent to each of RGB photoreceivers, CCD transfer units sandwich the RGB photoreceivers (for use in an in-pixel transfer method). In this configuration, since CCD transfer units need not be provided between the RGB photoreceivers, the gap between the photoreceivers can be reduced compared to a known line sensor. In this embodiment, the configuration shown inFIG. 3will be described in detail later. A CCD-type line sensor in which a CCD transfer unit is provided adjacent to each of the RGB photoreceivers may be used.

InFIG. 3, the line sensor includes an R-photoreceiver301having a red color filter, a G-photoreceiver302having a green color filter, and a B-photoreceiver303having a blue color filter. Also, shift gates304,305, and306for vertically transferring signal charge accumulated in each of the RGB photoreceivers to corresponding CCD transfer units307,308, and309are provided. The CCD transfer units307,308, and309horizontally transfer the signal charge transferred from the RGB photoreceivers through the shift gates304,305, and306, respectively, to output terminals. Also, the CCD transfer units307,308, and309are driven by two pulse signals, that is, φ1and φ2.

For simplicity, one CCD transfer unit is provided for one photoreceiver in this embodiment. In a general line sensor, however, signal charge is transferred by dividing it into odd-numbered and even-numbered charges.

Further, the line sensor includes a transfer gate310for transferring the signal charge from one of the CCD transfer units to another, and amplifiers311,312, and313for converting the signal charges transferred from the CCD transfer units307,308, and309, respectively, to voltage signals.

Next, scanning performed by the line sensor by the in-pixel transfer method will be described with reference to a timing chart of driving pulse signals shown inFIG. 4. SH-B is a control pulse signal for the shift gate306and controls vertical transfer of the signal charge in the B-photoreceiver303to the CCD transfer unit308. Likewise, SH-G and SH-R are shift pulse signals for controlling the shift gates305and304, respectively. φ1and φ2are pulse signals for driving the CCD transfer units307,308, and309. TG is a pulse signal for controlling the transfer gate310.

During period 1, the shift gate306is turned ON by pulse signal SH-B so that the B-signal charge accumulated in the B-photoreceiver303is moved to the shift gate306. During period 2, the shift gate306is turned OFF so that the B-signal charge in the shift gate306is moved to the CCD transfer unit308. Accordingly, the B-signal charge accumulated in the B-photoreceiver303is vertically transferred to the CCD transfer unit308.

During period 3, the B-signal charge moves from φ1to φ2inside the CCD transfer unit308. Then, during period 4, φ2is turned OFF and pulse signal TG is turned ON so that the B-signal charge is transferred to the transfer gate310. Likewise, the shift gate305is turned ON by using pulse signal SH-G during period 3, and G-signal charge accumulated in the G-photoreceiver302is transferred to the B-photoreceiver303during period 4.

During period 5, the B-signal charge in the transfer gate310is transferred to the CCD transfer unit309by turning OFF pulse signal TG and turning ON pulse signal φ1. Also, during periods 5 and 6, the G-signal charge in the B-photoreceiver303is transferred to the CCD transfer unit308by turning ON pulse signal SH-B. Further, by turning ON the shift gate304by using pulse signal SH-R, R-signal charge accumulated in the R-photoreceiver301is transferred to the CCD transfer unit307.

As described above, the signal charge accumulated in each photoreceiver is vertically transferred to the corresponding CCD transfer unit. Then, during period 7, each of the CCD transfer units is driven at high-speed by pulse signals φ1and φ2, and the signal charges are horizontally transferred to the output terminals.

In general, each of the CCD transfer units is a large capacitive load and thus a large amount of electrical power is required in order to drive the CCD transfer units at high-speed. Further, the heat value of the CCD is very high at this time. Accordingly, the reading unit should be controlled so that horizontal transfer, in which the CCD transfer units are driven at high-speed, is not performed when reading is unnecessary.

Next, a control unit in the reading unit of the image reading apparatus will be described with reference to a block diagram shown inFIG. 5. InFIG. 5, the control unit includes a CCD line sensor501(CCD109inFIG. 1), which is driven by a driver502. A timing generation circuit503generates various CCD-driving pulses and also generates the driving pulse signals shown inFIG. 4. Pulse signals φ1and φ2for driving the CCD transfer units output from the timing generation circuit503have two modes: a mode for outputting only pulses for performing vertical transfer; and a mode for outputting pulses which are input to the CCD during normal reading. Each of the two modes is controlled by a CPU504.

The signal output from the CCD501is gain/offset-adjusted by an analog processing IC505and is transmitted to an AD converter506at the subsequent stage. The analog signal is converted to a digital signal in the AD converter506. An image processing IC507receives the digital signal from the AD converter506and performs various processes such as shading correction and inter-line correction. The timing generation circuit503supplies a timing signal to the above-described ICs so as to control the timing of the operation thereof.

Reference numeral508denotes a cover sensor (detecting member204and photosensors205), which detects whether the cover is opened/closed at a predetermined angle or whether the cover is closed for detecting the size of a document and transmits a detection signal to the CPU504. A lamp509(lamp104inFIG. 1) and a motor510are controlled by the CPU504and operate in response to commands from the CPU504in order to read a document or detect the size of the document. The CPU504contains a program for detecting the size of a document. The size of the document is detected by comparing image data when the cover is opened/closed at a predetermined angle with image data when the cover is closed.

Next, a method for generating pulse signals φ1and φ2for driving the CCD transfer units in the timing generation circuit503will be described.FIG. 6shows a circuit for generating pulse signal φ1andFIG. 7shows waveforms of the pulse signal generated in each unit. InFIG. 6, the pulse signal generation circuit includes a counter601which operates in synchronization with a clock signal CLK, and a blank setting unit602for generating a pulse signal which becomes low at the starting and ending points of the vertical transfer period of pulse signal φ1. The blank setting unit602includes two registers which set the counter values at the starting and ending points of the vertical transfer period of pulse signal φ1. The set register value is compared to the value of the counter601by a comparator (not shown) and the above-described pulse signal is generated based on the comparison result. The output pulse signal is shown in (a) ofFIG. 7.

A vertical transfer pulse generating unit603generates pulses in the vertical transfer period of pulse signal φ1. The basic configuration thereof is the same as that of the blank setting unit602. The vertical transfer pulse generating unit603includes a plurality of registers which set the counter values at the leading edge and the trailing edge of the vertical transfer period of pulse signal φ1. The set value is compared to the value of the counter601and a vertical transfer pulse is generated based on the comparison result ((c) inFIG. 7).

The circuit also includes a JK flip-flop604. A pulse generated at the blank setting unit602is input to a K-terminal thereof. The J-terminal is set to high (H), and thus a signal shown in (b) ofFIG. 7is output.

The blank setting unit602, the vertical transfer pulse generating unit603, and the JK flip-flop604operate in synchronization with the clock signal CLK. Also, the registers in the blank setting unit602and the vertical transfer pulse generating unit603are set by the CPU when an initial setting is performed, for example, when the power of the apparatus is turned on. The outputs of the JK flip-flop604and the vertical transfer pulse generating unit603are input to an AND circuit605. The output from the AND circuit605is shown in (d) ofFIG. 7, and a pulse signal including vertical transfer pulses and horizontal transfer pulses is generated.

A selector606selects one of the two inputs and outputs the selected input. The signal from the AND circuit605and the signal from the vertical transfer pulse generating unit603are input to the selector606, which selects the signal to be output based on the control of the CPU. That is, the selector606selects one of pulse signal φ1having only the vertical transfer pulses and pulse signal φ1having both the vertical transfer pulses and the horizontal transfer pulses, and supplies the selected pulse signal to the CCD driver502(FIG. 5). Pulse signal φ2is generated in the same way as in the case of pulse signal φ1, and one pulse signal can be selected from two types of pulse signals so as to be output.

Herein, regarding pulse signals φ1and φ2for driving the CCD transfer units, a mode in which a pulse signal including only the vertical transfer pulses is output is referred to as mode 1, and a mode in which a pulse signal including the vertical transfer pulses and the horizontal transfer pulses used for normal reading is output is referred to as mode 2. Next, a method for controlling each mode when the size of a document is detected will be described.

When the image reading apparatus is not operated, that is, in a standby mode, the CCD501is not required to be in a reading mode. Thus, the timing generation circuit503is set to mode 1 by the CPU504. Also, the CPU504drives the motor510so that the first mirror unit110moves to the size detecting position.

At this time, the user opens the cover (the cover is opened to a predetermined angle or more). The cover sensor508detects that the cover is opened and the CPU504recognizes that the cover is opened. The CPU504sets the timing generation circuit503to mode 2 so that the CCD501is set to a reading mode. Then, when the user puts a document on the glass table202and the cover is closed to a predetermined angle, the cover sensor508detects that fact and transmits it to the CPU504. The CPU504controls the illumination of the lamp509and also controls the reading of the document placed on the glass table202.

After that, when the cover is completely closed, the cover sensor508detects that fact and transmits it to the CPU504. The CPU504controls the illumination of the lamp509again when it detects that the cover is completely closed, and controls reading of the document placed on the glass table202.

The CPU504compares image data which is previously read with image data when the cover is completely closed so as to detect the size in the main scanning direction of the document placed on the glass table202. When the size of the document has been detected, the CPU504drives the motor510and controls the first mirror unit110so that the first mirror unit110moves to the home position (position for reading a standard white for shading correction). According to requirements, the standard white for shading correction may be read and gain/offset-adjustment may be performed. When the user presses a start key, the CPU504controls each unit so as to read the whole document area.

After the document has been read, the CPU504sets the timing generation circuit503to mode 1 so that the CCD501enters a standby mode. Then, the first mirror unit110is moved to the size detecting position so as to enter a mode for preparing for the next size-detecting operation. In this embodiment, only the vertical transfer pulses are supplied to the CCD line sensor109during the standby mode. This is because the frequency of the vertical transfer pulse is not so high and thus does not have a great influence on power consumption. Further, by supplying the vertical transfer pulses to the CCD line sensor109, the configuration of the timing generation circuit503and so on can be simplified. Incidentally, the vertical transfer pulses need not be supplied to the CCD line sensor109during the standby mode, although the circuit configuration becomes more complicated, which is disadvantageous.

When the above-described control is performed, in a case where the cover is left opened or in a case where the start key is not pressed after the size of the document has been detected, the CCD remains in a reading mode. In order to prevent such a situation, when the cover is left opened, a timer is started when the cover is opened, and the timing generation circuit503is changed from mode 2 to mode 1 when a predetermined time has passed.

In this case, however, the CCD is not in a reading mode, and thus the size of the document cannot be detected even when the cover is closed. At this time, the user manually sets the size of the document, or the user is encouraged to open and close the cover again, so as to detect the size of the document.

If the start key is not pressed after the size of the document has been detected, the timer is started when the cover is closed, as in the above-described case. After a predetermined time has passed, the timing generation circuit503is changed from mode 2 to mode 1. In this case, when the user presses the start key, the mode is changed again, the CCD is set to the reading mode, and then an image is read.

As described above, the image reading apparatus of the present invention has a configuration in which the CCD can be switched to/from a reading mode and a standby mode according to the open/closed state of the cover. The CCD is set to the reading mode only when the CCD detects the size of a document in the main scanning direction. Other than that, the CCD may be in the standby mode. Accordingly, a rise in the temperature of the CCD can be suppressed and thus the temperature degradation in a color filter of the color sensor can be suppressed. Also, since horizontal transfer, which needs a large amount of electrical power, is not always performed by the CCD transfer units, the power consumption can be reduced. Furthermore, heat generated from the CCD and the driver for driving the CCD transfer units decreases, and thus a cooling system such as a fan need not be provided.

In this embodiment, the CCD is always turned on after the image reading apparatus is turned on. This is because the effect of suppressing a rise in the temperature when the CCD is always turned on is almost the same as when the CCD is turned on only when required. Also, in order to control the power, the time from the turning on of the power until the CCD enters the reading mode has to be considered, and thus a complicated control is required.

In this embodiment, drive control performed when the size of a document is detected has been described. However, the above-described driving modes (mode 1 and mode 2) may be applied to an image reading apparatus which does not have a function of detecting the size of a document. By pressing a start key, a horizontal transfer drive pulse may be supplied to the line sensor so as to read the document. Also, by detecting the open/closed state of the cover and by supplying a horizontal transfer drive pulse to the line sensor, the time from pressing the start key until the reading operation can be shortened.

Each functional block and processes described in the embodiment may be formed by hardware, or may be formed by a microcomputer system including a CPU or an MPU, a ROM, and a RAM, and the operation may be realized according to an operation program stored in the ROM or the RAM. Alternatively, a software program for realizing the function of each functional block may be supplied to the RAM so that each of the above-described functional blocks operates in accordance with the program.

In this case, the software program itself realizes the functions of the above-described embodiment. Also, the program itself and a system for supplying the program to a computer, for example, a storage medium storing the program, are included in the present invention. As a storage medium for storing the program, a floppy disk, a hard disk, an optical disk, a magnetooptical disk, a CD-ROM, a CD-I, a CD-R, a CD-RW, a DVD, a ZIP disk, a magnetic tape, or a nonvolatile memory card can be used as well as the ROM and the RAM.

Also, it is needless to say that the program is included in the present invention when the functions of the above-described embodiment are realized when the program cooperates with an operating system (OS) which operates in the computer or with other application software, as well as when the functions of the above-described embodiment are realized when the computer executes the supplied program.

Alternatively, after the supplied program is stored in a memory of an expansion board of a computer or an expansion unit connected to the computer, a CPU in the expansion board or the expansion unit may execute a part or whole of the actual process based on the program commands so that the process realizes the functions of the above-described embodiment.

As described above, according to the embodiment, by adequately switching the CCD between an operating mode and a standby mode at a preferred timing, a rise in the temperature can be suppressed so as to prevent temperature degradation and reduce power consumption. Accordingly, it is possible to provide an image reading apparatus in which the cost can be substantially reduced and an adequate operation can be ensured for a long period of time.

While the present invention has been described with reference to what is presently considered to be the preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiment. On the contrary, the invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.