JP2007060211A - Document size detection device - Google Patents

Abstract

The present invention relates to a document size detection apparatus that shortens a rise time.
An image reading apparatus turns on a light source without waiting for completion of startup of a signal processing circuit, and inputs a comparison reference voltage from a reference voltage input unit to a comparator of a document size detection unit. The image signal from the CCD 9 is signal-processed by the signal processing circuit 22 before completion of rising, and compared with the comparison reference voltage by the comparator of the document size detection unit 24, and the comparison result is used as the edge position detection result signal to detect the document size. Store in the memory of the unit 24. The image reading apparatus 1 discriminates the document size based on the end position detection result signal in the memory of the document size detection unit 24 after the start-up is completed. Accordingly, without waiting for completion of the start-up of the signal processing circuit 22, information necessary for detecting the size of the document can be acquired, the document size can be quickly determined, and the rise time can be shortened.
[Selection] Figure 3

Description

  The present invention relates to a document size detection apparatus, and more particularly, to a document size detection apparatus that quickly detects a document size and shortens a rise time of an image reading apparatus.

  In recent years, it has become important to improve the energy consumption efficiency of equipment for the purpose of environmental conservation. In addition, for the user, the energy consumption of the device when not in use is economically wasteful.

  Therefore, in image reading apparatuses such as scanners, facsimile apparatuses, copying apparatuses, and multi-function apparatuses, in order to reduce power consumption, those equipped with an energy saving mode have conventionally appeared and are in a standby state other than during an image reading operation. When the standby state elapses for a predetermined time, the image reading apparatus is moved to the energy saving mode by hiding the liquid crystal display on the operation panel, reducing or stopping the supply of power to the reading unit, etc. The power consumption of the entire system is reduced.

  Further, such an image reading apparatus detects the opening / closing operation of the document pressing plate when the document pressing plate (pressure plate) is opened / closed in order to set the document on the contact glass in the energy saving mode. The energy saving mode is returned to the standby mode, and the time required for returning from the energy saving mode to the standby mode, that is, the reduction of the return time is also required.

  Therefore, conventionally, when the scanning body is moved under the white reference plate prior to shifting from the standby state (standby mode) to the power saving state (energy saving mode), the image is returned when returning from the power saving state to the standby state. The reading unit reads this white reference plate to perform a predetermined restoration process, and when the document pressing member is closed, the lamp (light source of the image reading unit) is turned on instantaneously to read the image for one line. A technique for automatically detecting the size of a document based on data has been proposed (see Patent Document 1).

  That is, according to this conventional technique, when returning from the energy saving mode, the document size detection function is effectively activated at an earlier timing to shorten the return time.

JP 2004-109639 A

  However, in the above-described prior art, the delay in the timing for detecting the document size is the cause of sending the return time from the energy saving mode of the image reading apparatus, and the cause of the delay in the timing for detecting the size of the document However, at the time of return, it is assumed that the carriage (scanning body) on which the optical elements such as the light source and the mirror are mounted is moved below the white reference plate. Since the document size is detected by moving the light source and turning on the light source during the closing operation of the document pressing plate, the delay in the detection timing of the document size cannot be sufficiently solved, and there is a need for improvement.

  That is, when returning from the energy saving mode, a delay in timing for detecting the size of the document occurs even if the signal processing circuit outputs the signal output from the optical element.

  Therefore, the present invention eliminates the delay in the document size detection timing caused by the signal processing circuit, detects the document size quickly, and reduces the return time from the energy saving mode of the image reading apparatus. The object is to provide a device.

  The document size detection apparatus according to the first aspect of the present invention is directed to irradiating light from a light source to a document, receiving light reflected by the document by a photoelectric conversion element, converting the light into an image signal, and outputting an image output from the photoelectric conversion element The signal is processed by the signal processing means, and the comparison means compares the processed image signal with a predetermined comparison signal value to detect the edge position of the document, and detects the edge position output from the comparison means. A document size detecting device for detecting a document size based on a result signal, wherein a storage means for storing an end position detection result signal output from the comparison means, and a predetermined comparison reference as a comparison signal value in the comparison means Reference value input means for inputting a signal value, and before the completion of startup of the signal processing means, the light source is turned on, and the comparison reference signal is input from the reference value input means to the comparison means. This By comparing the image signal signal-processed by the signal processing means before completion of rising with the comparison reference signal value by the comparison means, and storing the end position detection result signal output by the comparison means in the storage means Has achieved the above objectives.

  In this case, for example, as described in claim 2, the signal processing unit includes a gain adjustment unit that adjusts a gain of the image signal, and the document size detection device includes a predetermined fixed gain in the gain adjustment unit. Gain fixing means for setting a value, the gain fixing means sets the fixed gain in the gain adjusting means, and the gain adjusting means sets the gain fixing means in a period before completion of the start-up. The gain of the image signal from the photoelectric conversion means may be adjusted with a fixed gain value.

  Further, for example, the signal processing unit includes an offset adjustment unit that adjusts an offset level of the image signal, and the document size detection device includes a predetermined fixed offset in the offset adjustment unit. Offset fixing means for setting a value, and during the period before the completion of startup, the offset fixing means sets the fixed offset value in the offset adjusting means, and the offset adjusting means sets the offset fixing means. The image signal from the photoelectric conversion means may be offset adjusted with a fixed offset value.

  Further, for example, as described in claim 4, the document size detection device is configured to specify an end position specification for specifying the document end position necessary for detecting the document size as a comparison target position with respect to the comparison unit. The comparison means compares the image signal with the comparison reference signal value only at the comparison target position designated by the end position designation means, and the storage means detects the end position detection result of the comparison means. A signal may be stored.

  Further, for example, as described in claim 5, the document size detection device provides the comparison unit with a comparison target area having a predetermined width including a document edge position necessary for detecting the document size as a comparison target position. An edge position designation means for designating and a counting means for counting the number of edge position detection result signals indicating the presence of the document of the comparison means, and the comparison means is designated by the edge position designation means. The image signal is compared with the comparison reference signal value only in the comparison target area, the number of times of the edge position detection result signal with the document of the comparison means is counted by the counting means, and the storage means The count result of the means may be stored, and the document size may be detected based on the count result of the storage means.

  According to the document size detecting apparatus of the present invention, the light source is turned on before the start-up of the signal processing means, and the image signal processed by the signal processing means before the start-up is input from the reference value input means. Since the edge position detection result signal is stored in the storage means in comparison with the comparison reference signal, the document size is discriminated based on the edge position detection result signal of the storage means after the start-up is completed. The document size can be detected quickly without waiting for the signal processing means to complete the start-up, and the start-up time such as the return time from the energy saving mode can be shortened.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, since the Example described below is a suitable Example of this invention, various technically preferable restrictions are attached | subjected, However, The scope of the present invention limits this invention especially in the following description. As long as there is no description of the effect, it is not restricted to these aspects.

  1 to 13 are diagrams showing an embodiment of a document size detection apparatus according to the present invention. FIG. 1 is a schematic diagram of a main part of an image reading apparatus 1 to which an embodiment of the document size detection apparatus according to the present invention is applied. It is a block diagram.

  In FIG. 1, the image reading apparatus 1 has a contact glass 3 disposed on an upper portion of a main body housing 2, and a document to be read is set on the contact glass 3. In the image reading apparatus 1, a pressure plate 4 that presses a document set on the contact glass 3 against the contact glass 3 is attached to the back side of the image reading apparatus 1 so as to be openable and closable as shown in FIG. A pressure plate angle detection unit 5 that detects an opening / closing angle of the pressure plate 4 is disposed on the upper portion of the housing 2.

  The image reading apparatus 1 includes a first carriage 6 and a second carriage 7 that move in the sub-scanning direction (left-right direction in FIG. 1) below the contact glass 3 and in the main body housing 2. An optical element 11 for housing a sensor board unit (hereinafter referred to as SBU) 10 and the like on which an imaging lens 8 and a CCD (Charge Coupled Device) 9 as a photoelectric conversion element are mounted.

  The first carriage 6 is equipped with a light source (such as a xenon lamp) 12 that irradiates reading light onto a document placed on the contact glass 3 and a first mirror 13, and the second carriage 7 is equipped with a second mirror 14. The third mirror 15 is mounted. The first carriage 6 and the second carriage 7 are moved in the sub-scanning direction by a motor (not shown), and when reading a document on the contact glass 3, the speed ratio between the first carriage 6 and the second carriage 7 is 2. The distance from the original surface to the image formation surface of the CCD 9 of the optical element 11 is controlled to be constant.

  The SBU 10 is connected to a main control unit 18 disposed in the main body unit 17 in the main body housing 2, and outputs a photoelectrically converted image signal of the CCD 9 to the main control unit 18.

  In the image reading apparatus 1, a white reference plate 19 is disposed on the upstream side in the movement direction of the first carriage 6 with respect to the original reading point of the contact glass 3, and a reference for shading correction is used as a reference for the white reference plate 19. It can be set based on the density. That is, the image reading apparatus 1 moves the first carriage 6 and the second carriage 7 to the reading position of the white reference plate 19 before reading the document, and irradiates the white reference plate 19 with light from the light source 12. The reflected light from the white reference plate 19 is sequentially reflected by the first mirror 13, the second mirror 14, and the third mirror 15 and is incident on the imaging lens 8, and is reduced and formed on the CCD 9 by the imaging lens 8. Obtains shading correction data by photoelectrically converting incident light.

  Thereafter, the image reading apparatus 1 moves the first carriage 6 and the second carriage 7 to the home position, and irradiates light from the light source 12 onto the document placed on the contact glass 3 from the home position. However, as described above, the first carriage 6 and the second carriage 7 are moved in the sub-scanning direction at a speed ratio of 2: 1, and the reflected light reflected from the original is reflected by the first mirror 13 and the second mirror. 14, sequentially reflected by the third mirror 15 and made incident on the imaging lens 8, and reduced and focused on the CCD 9 by the imaging lens 8, and the CCD 9 photoelectrically converts the incident light, thereby reading the image of the document.

  When the image reading apparatus 1 finishes reading the document, the image reading device 1 performs the return operation of returning the first carriage 6 and the second carriage 7 to the home position, which is the reading start position, and preparing for the next document reading.

  As shown in FIG. 3, the image reading apparatus 1 is configured as a block, and includes the SBU 10, the light source 11, the pressure plate angle detection unit 5, the power saving return SW 20, the motor control unit 21, the main body unit 17, and the like. In addition to the CCD 9, the SBU 10 includes a signal processing circuit 22, a signal processing circuit control unit 23, a document size detection unit 24, a drive circuit 25, and the like. The main body unit 17 includes the main control unit 18, a power saving control unit 26, an image processing unit 27, and the like. The main control unit 18 includes a start-up control unit 28.

  The main control unit 18 controls the lighting of the light source 12, the detection signal of the pressure plate angle detection unit 5 is input, and the detection signal of the pressure plate angle detection unit 5 is also input to the power saving control unit 26. The pressure plate angle detection unit 5 opens and closes the surface of the contact glass 3 to open and close the pressure plate 4 in order to open and close the surface of the contact glass 3 to set and remove the original on the contact glass 3. The angle is detected, and a detection signal is output to the main control unit 18 and the power saving control unit 26. The power saving return SW 20 is a switch for returning the image reading apparatus 1 in the energy saving mode to the normal mode, and is provided in an operation unit (not shown) or the like, and outputs an operation signal to the power saving control unit 26. The motor control unit 21 drives and controls a motor that drives the first carriage 6 and the second carriage 7, and is controlled by the main control unit 18.

  The signal processing circuit (signal processing means) 22 receives an image signal output from the CCD 9, operates under the control of the signal processing circuit control unit 23, performs necessary signal processing on the image signal from the CCD 9, and performs the SBU10. Output to the document size detection unit 24 and the image processing unit 27 of the main body unit 17 functioning as a document size detection output device.

  The start control unit 28 controls the start of the signal processing circuit control unit 23 by serial control, and the document size detection unit 24 and the signal processing circuit 22 output the outputs to the serial port of the main body unit 17.

  The SBU 10 is configured as a block as shown in FIG. 4 and includes the signal processing circuit 22, signal processing circuit control unit 23, document size detection unit 24, and drive circuit 25, and is connected to the subsequent stage of the CCD 9. The analog processing circuit 29 is provided. The analog processing circuit 29 amplifies the analog image signal output from the CCD 9 and outputs it to the signal processing circuit 22.

  The signal processing circuit 22 includes a clamp circuit 31, an AGC (automatic gain control, PGA) circuit 32, an ADC (analog / digital converter) circuit 33, and an offset adjustment circuit 34.

  The clamp circuit 31 receives the image signal of the CCD 9 amplified by the analog processing circuit 29, performs a DC clamp process on the image signal, and outputs the image signal to the AGC circuit 32. The direct current clamp process is a process in which only an alternating current (AC) component that is a signal component of the output of the CCD 28 is transmitted, and the direct current (DC) component is superimposed with a (desired) potential different from the output of the CCD 9. The AGC circuit (gain adjusting means) 32 is designed so that the data after AD conversion becomes substantially the same level for the purpose of absorbing variations in the maximum level (white level) of the output signal of the CCD 28 subjected to DC clamp processing by the clamp circuit 31. The gain is programmable and output to the ADC circuit 33. The ADC circuit 33 performs AD (analog / digital) conversion of the image signal set to a desired gain by the AGC circuit 32, and the offset adjustment circuit 34, The data is output to the document size detection unit 24 and the image processing unit 27 of the main body unit 17. The offset adjustment circuit (offset adjustment means) 34 performs offset adjustment based on the digitally converted image signal from the ADC circuit 33 and feeds it back to the AGC circuit 32. The offset adjustment here is a process of stabilizing the black reference level to a desired numerical value for the data after AD conversion.

  The signal processing circuit control unit 23 includes an initial setting circuit 35, a serial / parallel conversion unit (serial-parallel conversion unit) 36, a switching circuit 37, a control signal generation circuit 38, and the like.

  The initial setting circuit 35 is a circuit that determines a setting signal (output) only by turning on the power supply, and acts on the control signal generation circuit 38 only during the reset period. The control signal generation circuit 38 sets the output signal so that at least the presence or absence of the document can be determined with respect to the signal processing circuit 22 during the reset period by the setting by the initial setting circuit 35. The control signal generation circuit 38 also outputs a control signal such as an accumulation time of the CCD 9, a charge transfer clock, a reset pulse, and a bit clamp pulse to the drive circuit 25 of the CCD 9, and has a drive control function of the CCD 9.

  A serial control signal is input to the serial / parallel conversion unit 36 from the start-up control unit 28 of the main body unit 17, and the serial / parallel conversion unit 36 converts the serial control signal into parallel and outputs it to the switching circuit 37. The switching circuit 37 receives an initial setting signal from the initial setting circuit 35 and a parallel control signal from the serial / parallel conversion unit 36, and the switching circuit 37 receives the initial setting circuit 35 based on the reset signal from the main body unit 17. 1 is selected and output to the control signal generation circuit 38. When the reset signal input from the main body 17 is in the active state, the initial setting circuit 35 is selected. When the setting signal from the control unit 28 is selected and in the non-active state, the serial control signal from the startup control unit 28 of the main body control unit 17 is selected.

  The control signal generation circuit 38 sets initial setting values set in advance by the initial setting signal from the initial setting circuit 35 input via the switching circuit 37 in the signal processing circuit unit 22 and the drive circuit unit, and particularly At the time of return from the energy saving mode, the reference voltage signal from the initial setting circuit 35 is set to a state in which at least an output signal capable of determining the presence or absence of a document is obtained by the output of the CCD 9 to the signal processing circuit 22 during the return period. To do.

  The control signal generation circuit 38 outputs control signals such as an accumulation time of the CCD 9, a charge transfer clock, a reset pulse, and a bit clamp pulse to the drive circuit 25 of the CCD 9, and drives the CCD 9 via the drive circuit 25. Control.

  The signal processing circuit 22 and the signal processing circuit control unit 23 are configured in detail as shown in FIG. 5, and in particular, the signal processing circuit 22 includes the clamp circuit 31, the AGC (PGA) circuit 32, An ADC 33, an ADC circuit 33, and an offset adjustment circuit 34 are provided with an offset level setting unit 34a, a DAC (digital analog converter) 34b, an adder 22a, and the like.

  In the signal processing circuit control unit 32, a gain fixing unit (gain fixing unit) 40 and an offset fixing unit (offset fixing unit) 41 are connected to the initial setting circuit 35. The gain fixing unit 40 outputs a gain fixing signal that fixes the gain of the signal processing circuit 22 at the time of startup to an arbitrary gain value (fixed gain value) to the initial setting circuit 35. At the start-up of the apparatus 1, before the start-up of the signal processing circuit 22 is completed, the light source 12 is turned on and output from the CCD 9, and the image signal gain-adjusted with the gain set by the gain fixed signal in the signal processing circuit 22 A sufficient gain is set to provide a signal necessary to detect the size of the document. The offset fixing unit 41 outputs to the initial setting circuit 35 an offset fixing signal that fixes the offset of the signal processing circuit 22 at the time of startup to an arbitrary offset value (fixed offset value). At the start-up of the apparatus 1, before the start-up of the signal processing circuit 22 is completed, the light source 12 is turned on and output from the CCD 9, and the image signal offset-adjusted by the offset set by this offset fixed signal in the signal processing circuit 22 Therefore, an appropriate offset is set to obtain a signal necessary for detecting the size of the document with high accuracy.

  As described above, the initial setting circuit 35 outputs the initial setting signal to the switching circuit 37. At this time, the initial setting circuit 35 outputs the gain fixing signal from the gain fixing unit 40 to the switching circuit 37, and from the offset fixing unit 41. Is output to the switching circuit 37. As described above, the switching circuit 37 selects the initial setting signal from the initial setting circuit 35 and outputs it to the control signal generation circuit 38 when the reset signal input from the main body 17 is in the active state. In this case, the serial control signal from the startup control unit 28 of the main body control unit 17 is selected and output to the control signal generation circuit 38. FIG. 5 shows a state in the rising period, in which the switching circuit 37 selects the initial setting circuit 35 side.

  The control signal generation circuit 38 outputs a control signal (clock, pulse, command, etc.) to the signal processing circuit 22 based on the control signal input from the switching circuit 37.

  The signal processing circuit 22 adjusts the offset of the image signal digitally converted by the ADC circuit 33 by the offset level setting unit 34a according to the offset value set by the control signal generation circuit 38, and outputs it to the DAC 34b. The offset adjusted image signal is digitally converted and output to the adder 22a. The adder 22a further receives an image signal that has been DC clamped by the clamp circuit 31, and the adder 22a adds the image signal from the clamp circuit 31 and the image signal from the DAC 34b, and outputs the result to the PGA 32. . The AGC (PGA) circuit 32 sets the gain of the image signal from the adder 22a with the gain value from the control signal generation circuit 38 of the signal processing circuit control unit 23, and outputs the gain to the ADC circuit 33. The ADC circuit 33 The AGC circuit 32 AD-converts the image signal set to a desired gain and outputs it to the offset adjustment circuit 34, the document size detection unit 24, and the image processing unit 27 of the main body unit 17.

  The document size detection unit 24 then detects the document end position (document end position) necessary for determining the document size set on the contact glass 4 based on the image signal from the ADC circuit 33 of the signal processing circuit 22. (Hereinafter referred to as document size detection if necessary), as shown in FIG. 6, a comparator 51, a reference voltage input unit 52, a counter 53, a RAM (Random Access Memory) not shown, and the like. Memory (storage means). The reference voltage input unit (reference value input means) 52 inputs a predetermined comparison voltage (comparison signal value) to the comparator 51 in a state where the rise of the image reading apparatus 1 is completed, and returns from the energy saving mode. For example, the comparator 51 determines the edge of the document from the image signal for one line from the ADC circuit 33 of the signal processing circuit 22 that has not been completed (image signal when the document size is detected). An appropriate comparison reference voltage (comparison reference signal value) is output to the comparator 51 as a comparison voltage (comparison signal value).

  In addition to the comparison voltage from the reference voltage input section 52, the comparator (comparison means) 51 receives an image signal for one line at the time of document size detection from the ADC circuit 33, and further, a sampling clock, although not shown. A comparison target position designation signal for designating a comparison target position is input from the main control unit (end position designation means) 18. The comparison target position designation signal is input from the main control unit 18 at least at the time of start-up, and the document edge position is designated for each pixel, and the document edge position is designated by a comparison target area for a predetermined number of pixels. There is a case. When the comparator 51 rises, the sampling clock is counted from the head of one line, and when the comparison target position designated by the comparison target position designation signal from the main control unit 18 is reached, the image signal from the ADC circuit 33 is converted to the reference voltage. Compared with the comparison reference voltage (comparison reference signal value) from the input unit 52, the data for one line of the end position detection result signal is output to the memory of the main body unit 17 (not shown), and also in the document size detection unit 24 Is stored in a memory (not shown), and an end position detection result signal is output to the counter 53. That is, the comparator 51 compares the image signal for one line from the signal processing circuit 22 with the comparison voltage during the normal operation in which the comparison target position designation signal is not input from the main control unit 18, and compares the end portion for one line. The position detection result signal is output to the memory of the main body unit 17 and the image signal from the signal processing circuit 22 is output at the time of rising when the comparison target position specifying signal for specifying the position of the document edge for each pixel is input from the main control unit 18. Of these, only the image signal at the comparison target position is compared with the comparison reference voltage, and the edge position detection result signal is stored in a memory (storage means) (not shown) in the document size detection unit 24 or output to the counter 53. The image from the signal processing circuit 22 at the time of start-up when a comparison target position designation signal for designating a document edge position in a comparison target area for a predetermined number of pixels is input from the main control unit 18. Compared to the image signal only a comparison reference voltage of the comparison regions of the item, and outputs the edge position detection result signal in the memory or counter 53 in the memory (storage means) of the document size detection unit 24.

  The counter (counting means) 53 counts the number of times that the edge position detection result signal input from the comparator 51 indicates that there is a document, that is, the number of documents present, and the count result is stored in the document size detection unit 24. Is stored in a memory (storage means) (not shown).

  The main control unit (document size determination means) 18 stores the end position detection result signal for one line sent from the comparator 51 of the document size detection unit 24 in the memory of the main body unit 17 during normal operation. Then, the document size is determined based on the edge position detection result signal in the memory, and the edge position detection result signal for each pixel is stored in the memory in the document size detection unit 24 at the time of start-up. If it is, the document size is determined based on the edge position detection result signal of the memory, and the count number of the counter 53 is stored in the memory in the document size detection unit 24 at the time of start-up. If the number of counts of the comparison target area in the memory is equal to or greater than a preset number, it is determined that the document end position exists in the comparison target area, and the document size is determined. Processing is carried out.

  Then, the image reading apparatus 1 according to the present embodiment hides the liquid crystal display on the operation panel or supplies power to the reading unit when the standby state elapses for a predetermined time in the standby state other than during the image reading operation. An energy saving mode for reducing the power consumption of the entire system as the image reading apparatus 1 by reducing or stopping the image reading apparatus 1 is provided. In this energy saving mode, the pressure plate angle detector 5 detects that the pressure plate 4 has been opened more than a predetermined angle. Is detected or when the power saving return SW 20 is turned on (turned on), a return process such as resumption of the supply of power to each unit is performed, thereby returning from the energy saving mode to the standby state.

  The image reading apparatus 1 according to the present embodiment has a startup in which the main control unit 18 is not fully started up when starting up to the normal mode when the power switch is turned on or when starting up to return from the energy saving mode to the normal mode. This is characterized in that document detection necessary for document size determination is performed with high accuracy at an intermediate timing.

  First, transition processing from the standby state to the energy saving mode and transition processing accompanying the document size detection processing from the energy saving mode to the standby state will be described with reference to FIG.

  In the normal reading state (step S101), the image reading apparatus 1 checks whether the main control unit 18 has not performed an operation such as operation of the operation unit or setting of a document and a preset power saving transition time has elapsed. However, when the power saving transition time has not elapsed, the process returns to step S101 to check whether the power saving transition time has elapsed again until the power saving transition time has elapsed (steps S101, S102). ).

  When the power saving transition time elapses in step S102, the main control unit 18 moves the first carriage 6 to a predetermined position (original size detection position) (step S103), and stops or reduces the supply of power to each main unit. Shift to the energy saving mode (power saving mode) to be performed (step S104). In this energy saving mode, the supply of power to the main control unit 18, the image processing unit 27, the SBU 10, and the motor control unit 21 is stopped or reduced, but at least the power saving control unit 26, the power saving return SW 20 and the pressure plate Power is supplied to the angle detector 5.

  When shifting to the power saving mode, the power saving control unit 26 always monitors the return factor (step S105), and the pressure plate 7 is released from the detection signal of the pressure plate angle detecting unit 5 or the power saving return SW 20 is turned on. It is checked (step S106), and when either the pressure plate 7 is opened or the power saving return SW 20 is detected, the main controller 18 is activated (step S107).

  When activated, the main control unit 18 turns on the light source 12 when the pressure plate 7 is closed based on the detection signal of the pressure plate angle detection unit 5 (step S108), and the document size detection unit 24 determines the document size. After performing document detection (document size detection) necessary for discrimination (step S109), the light source 12 is turned off (step S110).

  In the document size detection by the document size detection unit 24, the light source 12 is turned on before the start of the signal processing circuit 22 is completed, and a comparison reference voltage is input from the reference voltage input unit 52 to the comparator 51, and the CCD 9 The comparator 51 compares the image signal photoelectrically converted by the signal processing circuit 22 and stores the comparison result in the memory in the document size detection unit 24 as an edge position detection result signal.

  Then, the main control unit 18 moves the first carriage 6 to the home position (step S111), and starts up the drive circuit 25 and the signal processing circuit 22 (step S112). The document size information for determining the document size is confirmed based on the edge position detection result signal of the memory (step S113), and the process waits until the document reading starts.

  And the operation process in SBU10 at the time of a return from the said energy saving mode is demonstrated based on FIG.

  When returning from the energy saving mode (power saving mode), the SBU 10 initializes the signal processing circuit 22 when reset is released after the main power supply is turned on, and the detected angle of the pressure plate 4 exceeds the predetermined angle A from the predetermined angle. The light source 12 is turned on even when the signal processing circuit 22 has not finished rising in response to a signal indicating that A or less. Further, when the detection angle of the pressure plate becomes equal to or smaller than the predetermined angle B, the SBU 10 performs signal processing on the output signal (image signal) of the CCD 9 to detect the document size, and then receives the start signal and then the signal processing circuit 22. When the reading instruction signal is received thereafter, the light source 12 is turned on, the output signal of the CCD 9 is processed, and image data is sent to the image processing unit 27.

  That is, as shown in FIG. 8, when the main control unit 18 returns from the power saving mode (step S201), the main control unit 18 controls the drive circuit 25 and the signal processing circuit 22 based on information from the initial setting circuit 35. Initial setting is performed (step S202). In this initial setting, the clamping circuit 31 has a clamping period and a clamping pulse, the AGC circuit 32 has a gain, the offset adjustment circuit 34 has an offset detection period and a target value, and the ADC circuit 33 has a sampling clock. Set to a state where can be determined.

  Then, the main control unit 18 detects the angle of the pressure plate 7 by the pressure plate angle detection unit 5 and checks whether the angle (opening angle) of the pressure plate 7 with respect to the contact glass 3 is equal to or less than a predetermined angle A set in advance ( Step S203).

  If the angle of the pressure plate 7 is equal to or smaller than the predetermined angle A in step S203, the main control unit 18 turns on the light source 12 via the signal processing circuit control unit 23 and the drive circuit 25 (step S204), and reads it by the CCD 9. The image signal (AD data) output from the ADC circuit 33 of the signal processing circuit 22 is taken into the document size detection unit 24 of the SBU 10 (Step S205), and the angle of the pressure plate 7 is set to a predetermined value that is smaller than the predetermined angle A. It is checked whether the angle is equal to or smaller than B (step S206). When the angle of the pressure plate 7 is larger than the predetermined angle B in step S206, the main control unit 18 returns to step S206 and continues to take in AD data, and checks again whether it is equal to or smaller than the predetermined angle B (step). S205, S206).

  When the angle of the pressure plate 7 becomes equal to or smaller than the predetermined angle B in step S206, the main control unit 18 performs document size detection necessary for document size determination by the document size detection unit 24, and stores the memory in the document size detection unit 24. Is stored (confirmed) (step S207).

  On the other hand, when the angle of the pressure plate 7 with respect to the contact glass 3 is larger than the predetermined angle A in step S203, the main control unit 18 waits for the start key of the operation unit to be turned on (steps S208 and S203). When the start key is turned on, at this timing, the light source 12 is turned on (step S209), the output (AD data) of the ADC circuit 33 is taken in (step S210), and the document size detector 24 detects the document size. To confirm (step S207).

  Then, in the detection and determination of the document size by the document size detection unit 24, as described above, the light source 12 is turned on and the reference voltage input unit 52 to the comparator 51 before the start of the signal processing circuit 22 is completed. The comparison reference voltage is input to the image signal, which is photoelectrically converted by the CCD 9 and processed by the signal processing circuit 22 before the completion of the rise, is compared by the comparator 51, and the comparison result is compared with the end position detection result. The signal is stored in a memory in the document size detection unit 24 as a signal.

  When the main controller 18 determines (determines) the document size, the light source 12 is turned off (step S211), the first carriage 6 is moved to the home position (step S212), and the drive clock and signal processing circuit controller 23 operates. The reset is released (step S213). That is, in each process from step S201 to step S212, the signal processing circuit control unit 23 is in a reset state.

  In step S203, the light source is turned on when the angle of the pressure plate 7 is equal to or smaller than the predetermined angle A, or when the start key is on (naturally, the pressure plate 7 is closed) (step S204). , S209), the light source 12 is not turned on when the pressure plate 7 is completely opened, but is turned on when the pressure plate 7 is to be closed, thereby making it difficult for light to enter the eyes of the user.

  When the reset of the signal processing circuit control unit 23 is released, the main control unit 18 performs initial setting of the SBU 10 including the signal processing circuit 22, that is, a start-up operation (step S214). The start-up operation is a normal read operation for each of the clamp period and the clamp pulse for the clamp circuit 31, the gain for the AGC circuit 32, the offset detection period and the target value for the offset adjustment circuit 34, and the sampling clock for the ADC circuit 33. Set to a state where

  When the initial setting is completed, the main control unit 18 determines the document size (confirms the document size information) based on the detection result of the document size detection unit 24 (step S215), and waits for the start key to be turned on. When the start key is turned on (step S216), the light source is turned on at this point (step S217), and the document reading operation is started (step S218). When the main control unit 18 starts the document reading operation, the main control unit 18 outputs the AD data obtained by reading to the image processing unit 27 from the ADC conversion 33 (step S219).

  9 shows an angle detection signal (off → on → off, a period just turned off), a power control signal (power saving → standby), and size detection in the platen angle detection unit 5 in the processing of FIGS. 4 is a timing chart showing a signal (off → on), a rising signal (rising control), and a movement timing of the first carriage 6, respectively.

  As can be seen from the timing chart of FIG. 9, the angle detection signal rises in the process of opening the pressure plate 7, the power source shifts from the energy saving mode to the standby state (standby state) (steps S106 and S107 in FIG. 7), and the size detection signal. Is turned on. When the pressure plate 7 is closed, the angle detection signal falls, the light source 12 is turned on at the timing of the predetermined angle A (step S108 in FIG. 7, step S204 in FIG. 8), and the document size is detected. (Step S109 in FIG. 7, Step S205 in FIG. 8) When the pressure plate 7 is closed to a predetermined angle B (Step S206 in FIG. 8), the size detection signal is turned off to determine the size (Step in FIG. 8). S207). Thereafter, the light source 12 is turned off (step S110 in FIG. 7 and step S211 in FIG. 8), and the movement of the first carriage 6 from the size detection position to the home position is started (step S111 in FIG. 7 and step S212 in FIG. 8). ), The reset state of the signal processing circuit control unit 23 is released (step S213 in FIG. 8), and the start-up control of the signal processing circuit 22 is executed using the reset release as a trigger (steps S112 and FIG. 8 in FIG. 7). Step S214). During the start-up control of the signal processing circuit 22, the first carriage 6 reaches the home position and stands by at the home position. At this standby time, the light source 12 is turned on again for AGC processing, and data for AGC processing is acquired. When the start-up is completed, the light source 12 is turned on again for reading the document, the document reading is started, and the first carriage 6 also starts moving scanning in the sub-scanning direction.

  FIG. 10 is an explanatory diagram of the start-up operation of the signal processing circuit 22 and shows the signal output timing and the circuit configuration of the signal processing circuit 22. 10, the signal processing circuit 22 includes the clamp circuit 31, the AGC (PGA) circuit 32, the ADC circuit 33, and the offset adjustment circuit 34, as described above. The offset adjustment circuit 34 includes an offset level setting unit 34a, It consists of DAC 34b. The signal processing circuit 22 adds the clamp output obtained by clamping the image signal input from the CCD 9 to the clamp circuit 27 via the analog circuit 26 by the clamp circuit 27 and the DAC output of the offset adjustment circuit 34 by the adder 22a. Input to the PGA 32.

  As shown in FIG. 10, the operation timing of each part at this time is as follows. First, the power is turned on, the output of the CCD 9 (CCD output), the output of the analog circuit 29 (analog circuit output), and the output of the clamp circuit 31 (clamp circuit). Output) rises, and the input / output (PGA input, PGA output) of the AGC (PGA) circuit 32 rises.

  The CCD output is generated for each line, but the analog circuit output amplifies the CCD output, so that the output level rises before the reading output from the CCD 9. The analog circuit output is clamped by the clamp circuit 27 and input to the AGC (PGA) circuit 32 as a clamp circuit output (PGA input). Based on the output of the clamp circuit, the black level is adjusted by the PGA circuit input. The circuit output gain is adjusted. In the clamp circuit 31, the clamp pulse output period is optimized.

  On the other hand, the light source 12 is turned on after the CCD 9 is turned on, and in the process of resetting the signal processing circuit reset signal, the clamp pulse output period is optimized, the clamp pulse of the clamp circuit output, the black level of the PGA circuit input Adjustment, gain adjustment of the PGA circuit output, and phase adjustment of the AD sampling clock output period are performed, and a normal document reading operation is performed. At this time, the sampling point of the ADC circuit 29 is also optimized and set to the timing at which the peak value can be sampled when the sampling clock rises.

  As described above, the signal processing circuit 22 of the SBU 10 starts the start-up after signal processing and outputting the output of the CCD 9 (original size detection image signal) when the light source 12 is turned on before the start-up is completed. Further, the ADC circuit 29 performs signal sampling in the signal output period so that the output of the CCD 9 can be sampled immediately when the image reading apparatus 1 returns from the energy saving mode (power saving mode) to the standby state (standby state). The operation starts at the same time as the return from the energy saving mode. This start-up is a return from the energy saving mode by a circuit whose state is determined only by releasing the reset signal from the outside to the SBU 10 or a circuit whose state is determined when the main power source of the image reading apparatus 1 is started. This can be realized by configuring the sampling state to be determined at the same time.

  Therefore, in order to start the signal sampling operation simultaneously with the return from the energy saving mode, a circuit (not shown) having the above-described function is provided. Similarly, the clamp circuit 31 also starts the clamping operation simultaneously with the return from the energy saving mode so that the output of the CCD 9 can be immediately clamped when the energy saving mode returns to the standby state. In this start-up, the state is determined only by releasing the reset signal from the outside to the SBU 10, or the state is determined by the rise of the main power supply of the image reading apparatus 1, and the return from the energy saving mode is performed. This can be realized by configuring the clamp state to be determined at the same time. Therefore, in order to start the clamping operation simultaneously with the return from the energy saving mode, a circuit (not shown) having the above-described function is provided. Similarly, when the AGC (PGA) circuit 32 returns from the energy saving mode to the standby state, the gain is adjusted simultaneously with the return from the energy saving mode so that the ADC circuit 33 can perform AD conversion immediately without saturating the output of the CCD 9. The gain is fixed by a gain fixing signal output from the gain fixing unit 40. The gain value is determined when the state is determined only by releasing the reset signal from the outside to the SBU 10 or when the state is determined by the main power supply rising, and the gain state is set simultaneously with the return from the energy saving mode. It can be realized by configuring so as to be fixed. Therefore, in order to determine and start the gain of the AGC (PGA) circuit 32 at the same time as the return from the energy saving mode, a circuit (not shown) having the above-described function is provided. Further, the offset adjustment circuit 34 outputs the offset output from the offset fixing unit 41 simultaneously with the return from the energy saving mode so that the output of the CCD 9 immediately becomes an appropriate detection value when the energy saving mode returns to the standby state. Confirm with a fixed signal. This offset is determined by the circuit that determines the state only by releasing the reset signal from the outside to the SBU 10 or the circuit that determines the state when the main power supply starts up and the offset state is set simultaneously with the return from the energy saving mode. This can be realized by configuring to be fixed. Therefore, in order to determine and start the offset of the offset adjustment circuit 34 simultaneously with the return from the energy saving mode, a circuit (not shown) having the above-described function is provided. The setting and adjustment of the gain and offset will be described in detail later.

  Further, as shown in the flowchart of FIG. 7, in step S109, the document size detection unit 24 detects the size of the document (document edge position detection). Not raised. The start-up operation of the signal processing circuit 22 is performed in step S112 in FIG. Similarly, in the flowchart of FIG. 8, after the document size is determined by the document size detection unit 24 in step S207, the signal processing circuit 22 is started up in step S214. That is, as can be seen from the timing chart of FIG. 9, the document size information is signal-processed before the start of the signal processing circuit 22, and the signal processing before the start of the signal processing circuit 22 is shown in FIG. This is based on the function of the initial setting circuit 35 shown in FIG.

  As described above, the image reading apparatus 1 according to the present embodiment turns on the light source 12 before starting up the signal processing circuit 22 and outputs the image signal signal-processed by the signal processing circuit 22 before starting up. Compared with the comparison reference signal (comparison reference voltage) input from the reference voltage input unit 52, the end position detection result signal is stored in the memory of the document size detection unit 24.

  Therefore, after completion of the start-up, the document size is determined based on the end position detection result signal in the memory of the document size detection unit 24, so that the document size can be quickly determined without waiting for the signal processing circuit 22 to complete the start-up. And the rise time such as the return time from the energy saving mode can be shortened.

  When the start-up occurs during the signal processing of the size information, the processing is performed as shown in FIG.

  That is, as shown in FIG. 11, the main control unit 18 lapses a preset power saving transition time in a normal standby state (step S <b> 301) in which no operation such as operation of the operation unit or document setting is performed. If the power saving transition time has not elapsed, the process returns to step S301 to check again whether the power saving transition time has elapsed until the power saving transition time has elapsed (step S302). S301, S302).

  When the power saving transition time elapses in step S302, the main control unit 18 moves the first carriage 6 to a predetermined position (original size detection position) (step S303), and then stops supplying power to the main units. Or it transfers to the energy saving mode (power saving mode) to reduce (step S304).

  When the mode is shifted to the power saving mode, the power saving control unit 26 always monitors the return factor, here, opening / closing of the pressure plate 7 by a detection signal from the pressure plate angle detection unit 5 (step S305). It is checked from the detection signal whether the pressure plate 7 is opened by a predetermined angle B or more with respect to the contact glass 3 (step S306). When it is detected that the pressure plate 7 is opened by the predetermined angle B or more, the energy saving mode is restored (step S307). Then, it is checked whether or not the pressure plate 7 is closed to a predetermined angle A or less by a detection signal from the pressure plate angle detection unit 5 (step S308).

  In step S308, when the pressure plate 7 is closed to a predetermined angle or less, the main control unit 18 turns on the light source 12 (step S309), and the output signal (read from the ADC circuit 33 of the signal processing circuit 22) read by the CCD 9 is output. (AD data) is taken into the document size detector 24 of the SBU 10 (step S310), and it is checked whether the angle of the pressure plate 7 is equal to or smaller than a predetermined angle B that is smaller than the predetermined angle A (step S311). When the angle of the pressure plate 7 is larger than the predetermined angle B in step S311, the main control unit 18 returns to step S310 and continues to take in AD data, and checks again whether the angle is equal to or smaller than the predetermined angle B (step). S310, S311).

  When the angle of the pressure plate 7 becomes equal to or smaller than the predetermined angle B in step S311, the main control unit 18 detects and determines the document size by the document size detection unit 24 (step S312).

  On the other hand, when the angle of the pressure plate 7 with respect to the contact glass 3 is larger than the predetermined angle A in step S308, the main control unit 18 waits for the start key of the operation unit to be turned on (steps S308 and S313). When the start key is turned on, at this timing, the light source 12 is turned on (step S314), and the output (AD data) of the ADC circuit 33 is taken in (step S315). Is detected (stored) in a memory in the document size detection unit 24 (step S312).

  When the main control unit 18 determines the document size, the light source 12 is turned off (step S316), the first carriage 6 is moved to the home position (step S317), and the SBU 10 including the signal processing circuit control unit 23 is initialized. That is, a start-up operation is executed (step S318).

  When the initial setting is completed, the main control unit 18 determines the document size (confirms the document size information) based on the end position detection result signal in the memory which is the detection result of the document size detection unit 24 (step S319). After waiting for the start key to be turned on (step S320), when the start key is turned on, the light source is turned on at this time, and the document reading operation is started.

  In the flowchart of FIG. 11, as can be seen from the determination processing in step S308 and step S313, after the return from the energy saving mode, unless the angle of the pressure plate 7 is equal to or smaller than the predetermined angle A or the start key is not pressed, step S318 is performed. Thus, the start-up operation is not executed for the signal processing circuit 22, and the start-up operation is not started during the signal processing of the document size information. Further, since the start key on is a reading operation start condition in step S320, even if the start key is turned on once in step S313 when the pressure plate 7 is opened in step S306, it is again. If the start key is not turned on (step S320), the document reading operation is not started.

  As described above, the image reading apparatus 1 according to the present embodiment turns on the light source 12 and outputs an image signal from the CCD 9 without waiting for completion of the start of the signal processing circuit 22, thereby starting up the signal processing circuit 22. Without waiting for completion, it is possible to obtain a signal (edge position detection result signal) necessary to detect at least the document edge position and detect the document size. Therefore, a delay in the document size detection timing due to the start-up time of the signal processing circuit 22 can be eliminated. As long as a signal (edge position detection signal) necessary for detecting the size of the document is obtained, the main control unit 18 may determine the size of the document based on the signal.

  Further, due to the serial communication between the start control unit 28 and the signal processing circuit control unit 23, the start of the signal processing circuit 22 may be further delayed, but the start control unit 28 returns from the energy saving mode to the standby state. In this case, since the start of the signal processing circuit 22 is started, the influence of the rise delay can be avoided.

  In the process of FIG. 7, the start control unit 28 can obtain a certain amount of image output, and the document size detection (document edge position detection) is performed based on this data.

  However, in order to further improve the accuracy, in this embodiment, as described above, the comparator 51 that detects the position of the document edge of the document size detection unit 24 at the time of startup is supplied from the reference voltage input unit 52 to the comparison reference. In addition to setting the comparison voltage (comparison signal value) of the comparator 51 to the comparison reference voltage (comparison reference signal value), the AGC (PGA) of the signal processing circuit 22 as shown in FIG. The gain of the circuit 32 is set by the gain fixing unit 40, and the offset of the offset adjustment circuit 34 of the signal processing circuit 22 is further set by the offset fixing unit 41. In FIG. 12, the same processing steps as those in FIG. 7 are denoted by the same step numbers, and the description thereof is simplified.

  That is, as shown in FIG. 12, in the image reading apparatus 1, in the normal standby state (step S <b> 101), the state where the main control unit 18 does not perform operations such as operation of the operation unit or document setting is shifted to power saving. When the time has elapsed (step S102), the first carriage 6 is moved to a predetermined position (document size detection position) (step S103), and the mode is shifted to the energy saving mode (power saving mode) (step S104). When shifting to the power saving mode, the power saving control unit 26 always monitors the return factor (step S105), and when either the pressure plate 7 is opened or the power saving return SW 20 is detected (step S107), the main control is performed. The unit 18 is activated (step S107).

  When activated, the main control unit 18 inputs and sets a comparison reference voltage (comparison reference signal value) from the reference voltage input unit 52 of the document size detection unit 24 to the comparator 51 (step S401). The gain of the AGC (PGA) circuit 32 of the signal processing circuit 22 is set to a fixed gain (external setting gain) from the gain fixing unit 40 by the processing circuit control unit 23 (step S402), and further, the signal processing circuit control unit 23 The offset of the offset adjustment circuit 34 of the signal processing circuit 22 is set to a fixed offset (external setting offset) from the offset fixing unit 41 (step S403).

  When activated, the main control unit 18 turns on the light source 12 at the timing when the pressure plate 7 is closed based on the detection signal of the pressure plate angle detection unit 5 (step S108), and the comparator 51 of the document size detection unit 24. Is compared with the comparison reference voltage (comparison reference signal value) from the reference voltage input unit 52 when the document size is detected by the CCD 9 and digitally converted by the ADC circuit 33 (step S404). Then, the comparison result (edge position detection result signal) is stored in a memory such as a RAM in the document size detector 24 (step S405), and the light source 12 is turned off (step S110).

  Then, the main control unit 18 moves the first carriage 6 to the home position (step S111), and starts up the drive circuit 25 and the signal processing circuit 22 (step S112). After checking the document size information (discriminating the document size) based on the end position detection result signal of the memory (step S113), the process waits until the reading of the document starts.

  In this way, the position of the document edge can be detected more accurately and the document size can be determined more accurately even before the signal processing circuit 22 finishes rising.

  In the process of FIG. 12, since image data for one line is stored in the memory in the document size detection unit 24 when the document size is detected, a memory having a memory capacity for at least one line is required. Become.

  However, since the document size can be determined only by the change in the image data in the area necessary for detecting the document size, only the pixel data in the document size detection area is extracted as shown in FIG. The document size may be determined by storing it in a memory in the detection unit 24. In FIG. 13, the same processing steps as those in FIGS. 7 and 12 are denoted by the same step numbers, and the description thereof is simplified.

  That is, as shown in FIG. 13, in the image reading apparatus 1, in the normal standby state (step S <b> 101), the state where the main control unit 18 does not perform operations such as operation of the operation unit or document setting is shifted to power saving. When the time has elapsed (step S102), the first carriage 6 is moved to a predetermined position (document size detection position) (step S103), and the mode is shifted to the energy saving mode (power saving mode) (step S104). When shifting to the power saving mode, the power saving control unit 26 always monitors the return factor (step S105), and when either the pressure plate 7 is opened or the power saving return SW 20 is detected (step S107), the main control is performed. The unit 18 is activated (step S107).

When activated, the main control unit 18 inputs and sets a comparison reference voltage (comparison reference signal value) from the reference voltage input unit 52 of the document size detection unit 24 to the comparator 51 (step S401). The gain of the AGC (PGA) circuit 32 of the signal processing circuit 22 is set to a fixed gain (external setting gain) from the gain fixing unit 40 by the processing circuit control unit 23 (step S402), and further, the signal processing circuit control unit 23 The offset of the offset adjustment circuit 34 of the signal processing circuit 22 is set to a fixed offset (external setting offset) from the offset fixing unit 41 (step S403). The main control unit 18 sets the number of pixels of the comparison target position to be compared as the document size detection position in the counter 53 of the document size detection unit 24 (step S501), and based on the detection signal of the pressure plate angle detection unit 5, the pressure plate 7 The light source 12 is turned on at the timing when is closed (step S108),
Next, the comparator 51 starts counting the image signal for one line from the signal processing circuit 22 from the top pixel (step S502), and the comparison target position pixel which is the document detection position set in step S501. It is determined whether or not there is (step S503). If it is determined in step S503 that the pixel of the image signal is not a pixel at the comparison target position, the comparator 51 repeats the same determination process for the next image signal (step S503), and the pixel of the image signal is a pixel at the comparison target position. If so, the pixel of the image signal is compared with the comparison reference voltage (comparison reference signal value) from the reference voltage input unit 52 (step S404).

  At this time, the image signal for one line input to the comparator 51 is gain-adjusted by the AGC (PGA) circuit 32 in which the gain is set in the signal processing circuit 22, and further, the offset adjustment circuit 34 in which the offset is set. The signal is analog / digital converted by the ADC circuit 29 after being offset adjusted in FIG. Therefore, the signal processing circuit 22 can appropriately and sufficiently perform signal processing even during the start-up, and the comparator 51 can appropriately and accurately detect the edge of the document.

  When comparing the image signal with the comparison reference voltage, the comparator 51 stores the edge position detection result signal in the memory in the document size detection unit 24 (step S504).

  When the comparator 51 stores the end position detection result signal of the comparison target position in the internal memory in the document size detection unit 24, the comparator 51 checks whether the processing is completed for the pixel signal for one line (step S505). When the processing for one line is not completed, the process returns to step S503 and the same processing as described above is performed (steps S503, S404, S504, S505). When the processing for one line is completed, the light source 12 is turned off ( Step S110).

  Then, the main control unit 18 moves the first carriage 6 to the home position (step S111), performs the start-up operation of the drive circuit 25 and the signal processing circuit 22 (step S112), and sets the document size to the document size detection unit. After discrimination (confirming the document size information) based on the edge position detection result signal in the memory 24 (step S113), the process waits until the document reading starts.

  In this way, it is possible to reduce the capacity of the memory in the document size detection unit 24, and more accurately detect the document end position (document size detection) without being affected by the optical system. This makes it possible to determine the document size more accurately.

  In the process of FIG. 13, the main control unit 18 designates the document end position necessary for detecting the document size as a comparison target position to the comparator 51 in the pixel position, and the comparator 51 is designated. The image signal at the pixel position is compared with the comparison reference voltage. However, the image signal is not limited to pixel designation, but may be area designation.

  In this case, the main control unit 18 designates the comparison target region having a predetermined width including the document edge position necessary for detecting the document size as the comparison target position in the comparator 15, and the comparator 51 is designated. Each image signal belonging to the comparison target area is compared with a comparison reference voltage.

  When the image signal to be compared is designated as a region, the comparison result (edge position detection result signal) of the comparator 51 is stored in the memory in the document size detection unit 24, and the edge position detection in this memory is performed. The present invention is not limited to the case where the main control unit 18 determines the document size based on the result signal.

  That is, the comparator 51 outputs an end position detection result signal, which is a comparison result, to the counter 53, and the counter 53 determines whether there is a document for each comparison target area from the end position detection result signal from the comparator 51. Is checked, the number of edge position detection result signals indicating the presence of a document is counted, and the count result for each comparison target area is stored in the memory in the document size detection unit 24. Then, the main control unit 18 compares the count number for each comparison target area of the memory in the document size detection unit 24 with a preset reference count number, and compares the count number equal to or greater than the reference count number. The document size is determined with the region having the document edge position.

  In this way, the position of the document edge can be detected with high accuracy without using expensive software, regardless of the state of the document set on the contact glass 3, and the memory in the document size detector 24 can be detected. The document size can be discriminated at low cost and with high accuracy.

  The invention made by the present inventor has been specifically described based on the preferred embodiments. However, the present invention is not limited to the above, and various modifications can be made without departing from the scope of the invention. Needless to say.

  The present invention is applicable to general document size detection devices that have an energy saving mode and detect the document size when the image reading device returns from the energy saving mode due to a return factor such as a document set.

1 is a schematic configuration diagram of a main part of an image reading apparatus to which an embodiment of a document size detection apparatus according to the present invention is applied. FIG. 2 is a side view of the image reading apparatus in FIG. 1. FIG. 3 is a main block schematic block diagram of the image reading apparatus of FIGS. 1 and 2. The circuit block block diagram of SBU of FIG. The detailed circuit block block diagram of SBU of FIG. FIG. 5 is a main part circuit block configuration diagram of the document size detection unit of FIG. 4. 2 is a flowchart showing a control process until the image reading apparatus of FIG. 1 starts up from a standby state and enters an energy saving mode. 3 is a flowchart showing an operation process in the SBU when the image reading apparatus in FIG. 1 returns from the energy saving mode. 9 is a timing chart showing a detection angle signal, a power source, a light source, a size detection signal, a reset signal, a rising signal, and a first carriage position in the processing of FIGS. FIG. 6 is an explanatory diagram of a startup operation of the signal processing circuit of FIG. 5. FIG. 8 is a flowchart showing a return operation process when a start-up occurs during a size information signal process in the return operation process of FIG. 7. FIG. 8 is a flowchart showing return operation processing when external gain setting and external offset setting are performed in the return operation processing of FIG. 7. FIG. 14 is a flowchart showing a return operation process when only pixel data in the document size detection area is extracted and processed in the return operation process of FIG. 13.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image reader 2 Main body housing | casing 3 Contact glass 4 Pressure plate 5 Pressure plate angle detection part 6 1st carriage 7 2nd carriage 8 Imaging lens 9 CCD
10 Sensor board unit (SBU)
DESCRIPTION OF SYMBOLS 11 Optical element 12 Light source 13 1st mirror 14 2nd mirror 15 3rd mirror 17 Main-body part 18 Main control part 19 White reference board 20 Power saving return SW
DESCRIPTION OF SYMBOLS 21 Motor control part 22 Signal processing circuit 22a Adder 23 Signal processing circuit control part 24 Document size detection part 25 Drive circuit 26 Power saving control part 27 Image processing part 28 Start-up control part 29 Analog processing circuit 31 Clamp circuit 32 AGC (PGA) ) Circuit 33 ADC circuit 34 Offset adjustment circuit 34a Offset level setting unit 34b DAC
35 Initial setting circuit 36 Serial-parallel converter (serial-parallel converter)
37 switching circuit 38 control signal generation circuit 40 gain fixing unit 41 offset fixing unit

Claims (5)

  Light from the light source is irradiated onto the document, and the light reflected by the document is received by the photoelectric conversion element and converted into an image signal. The image signal output from the photoelectric conversion element is signal-processed by the signal processing unit, and the comparison unit Document size detection that detects the edge position of the document by comparing the image signal processed with the signal with a predetermined comparison signal value, and detects the document size based on the edge position detection result signal output from the comparison means A storage means for storing an end position detection result signal output from the comparison means; and a reference value input means for inputting a predetermined comparison reference signal value as the comparison signal value to the comparison means. Before starting up the signal processing means, the light source is turned on, and the comparison reference signal is input from the reference value input means to the comparison means, and signal processing is performed by the signal processing means before completion of the rise. By comparing the image signal with the comparison reference signal value in the comparison means, the document size detection device and to store the output edge position detection result signal to the said comparator means in said storage means.   The signal processing means includes gain adjusting means for adjusting the gain of the image signal, and the document size detecting device includes gain fixing means for setting a predetermined fixed gain value in the gain adjusting means, and the start-up is completed. In the previous period, the gain fixing unit sets the fixed gain in the gain adjusting unit, and the gain adjusting unit converts the image signal from the photoelectric conversion unit with a fixed gain value set by the gain fixing unit. 2. The document size detecting apparatus according to claim 1, wherein gain adjustment is performed.   The signal processing unit includes an offset adjustment unit that adjusts an offset level of the image signal, and the document size detection device includes an offset fixing unit that sets a predetermined fixed offset value in the offset adjustment unit. In a period before completion, the offset fixing unit sets the fixed offset value in the offset adjusting unit, and the offset adjusting unit uses the fixed offset value set by the offset fixing unit to output the image from the photoelectric conversion unit. 3. The document size detecting apparatus according to claim 1, wherein the offset of the signal is adjusted.   The document size detecting device includes an end position specifying unit that specifies a document end position necessary for detecting the document size as a comparison target position with respect to the comparing unit, and the comparing unit includes the end position specifying unit. 2. The image signal is compared with the comparison reference signal value only at a comparison target position designated by a designation means, and the storage means stores an end position detection result signal of the comparison means. The document size detection apparatus according to claim 3. The document size detecting device includes an edge position designating unit that designates a comparison target area having a predetermined width including a document edge position necessary for detecting a document size as a comparison target position with respect to the comparison unit, and the comparison Counting means for counting the number of edge position detection result signals indicating the presence of a document of the means, and the comparison means compares the image signal only in the comparison target area designated by the edge position designation means. Compared with a reference signal value, the count means counts the number of edge position detection result signals with a document of the comparison means, and the storage means stores the count result of the count means. 4. The document size detection apparatus according to claim 1, wherein the document size is detected based on a count result.

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