JP2011024029A - Image reading apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately detect the sub-scanning position of a carriage. <P>SOLUTION: The image reading apparatus (scanner 13) comprises: a CCD 9 for performing photoelectric conversion on image information obtained by optically reading a document; a carriage 6 for moving the CCD 9 in a sub-scanning direction with respect to the document; a member 33, of which the optical attribute may be varied in accordance with an absolute position in the sub-scanning direction, in a terminal part in a main scanning direction outside a document read area (numeral 32 in Figure); and a position detection circuit 70 for detecting a position of the carriage based on image data obtained by reading an image of the member by means of an image sensor. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image reading apparatus, and more particularly to an image reading apparatus that has a traveling body in an image reading section and reads an image by driving the traveling body, and more particularly to an apparatus that is driven and controlled by a stepping motor.

  As a conventional technique for detecting the position and moving direction of a carriage, generally, as shown in Patent Document 1, a sensor of a precision part represented by a linear scale, an encoder, or the like is attached, and linear position information and a plurality of signals A method for detecting the rotational direction from the phase difference is known. The small linear scale is an optical type, and is a precision component having a complicated internal structure due to the principle of measuring a position by reading a fine optical pattern provided on a glass-like plate. Therefore, it requires expensive optical technology, thin film formation, and mounting technology at the time of manufacture, so it is expensive as a sensor, and because it uses a glassy transparent plate, it is vulnerable to impacts. Therefore, it has a drawback of hindering the assembly productivity and maintenance service of the apparatus.

  Patent Document 1 describes a technique for detecting the position of the origin and deceleration start by providing a new specified optical pattern on a linear scale and generating a signal. However, since the optical pattern is added to the linear scale itself, it becomes a more expensive part than the part according to the prior art, and since the signal is not generated in a place other than the specified place, the current position cannot be detected and the origin position is not detected. There is a problem that cannot be handled when it is located far away.

  As a prior art of means for detecting a stepping motor drive abnormality without using dedicated parts such as the linear scale and encoder, the number of pulses is compared as in Patent Document 2, or the housing of the apparatus as in Patent Document 3. There is an example of forming a bit pattern in which black and white are alternately arranged on the body.

  Japanese Patent Laid-Open No. 2004-228688 provides pulse integration means for counting the number of drive pulses of the stepping motor inside the image reading device when the home position is returned, and the pulse count setting value for the forward path and the pulse count until the home position sensor is turned on. There is described a technique for comparing a value and detecting a step-out of a stepping motor when a comparison result is out of an allowable range. However, since Patent Document 2 uses a drive pulse inside the apparatus to compare with a set value in the forward path (during document reading), until the apparatus starts reading the document and returns to the home position. There is a problem that cannot be addressed.

  In Patent Document 3, black and white marks with a constant interval are formed at the end in the main scanning direction, and these are read and scanned together with the read original by an image reading apparatus. When the reading scanning speed changes, the reading interval of the black and white mark also changes. By monitoring this, the stepping motor step-out is detected. However, Patent Document 3 has a problem that the rotation direction cannot be detected because the marks are arranged in one line in the sub-scanning direction.

  The problem of the prior art is that the sub-scanning position of the carriage (running body) cannot be accurately detected.

  Accordingly, an object of the present invention is to accurately detect the sub-scanning position of the carriage in view of the above situation.

  In order to achieve the above object, an image reading apparatus according to the present invention includes an image sensor that photoelectrically converts image information obtained by optically reading a document, and a carriage that moves the image sensor in a sub-scanning direction with respect to the document. Based on the image data obtained by reading the image of the member whose optical attribute changes according to the absolute position in the sub-scanning direction at the end in the main scanning direction outside the document reading area, and the image of the member And position detecting means for detecting the position of the carriage.

  According to the present invention, it is possible to accurately detect the sub-scanning position of the carriage.

1 is a diagram illustrating a schematic configuration of an image reading apparatus to which the present invention can be applied. It is a perspective view which shows schematic structure of the reading part 12 of FIG. It is a conceptual diagram for demonstrating the drive pattern of the reading part 12 of FIG. It is a block diagram which shows the function structure of the scanner 13 of FIG. FIG. 5 is a diagram for explaining a configuration of a motor drive control circuit 502 that performs drive control of the stepping motor 63 in FIG. 4. FIG. 5 is a diagram for explaining a configuration of a light source drive control circuit 504 that performs lighting drive control of the light source 2 that illuminates the original in FIG. 4. 2 is a flowchart showing a flow of initialization operation of the scanner 13 of FIG. 1. It is a figure which shows the structure of the 1st Embodiment of this invention. It is a figure for demonstrating the characteristic of the density | concentration board or density | concentration chart 33 of FIG. It is a figure which shows the structure of the 2nd Embodiment of this invention. It is a figure for demonstrating the characteristic of the mark member of FIG. It is a block diagram which shows the function structure of the 3rd Embodiment of this invention. FIG. 9 is a diagram for explaining an operation in the case of the configuration of FIG. 8 in the third embodiment of the present invention. FIG. 11 is a diagram for explaining an operation in the case of the configuration of FIG. 10 in the third embodiment of the present invention. It is a block diagram which shows the function structure of the 4th Embodiment of this invention. FIG. 9 is a diagram for explaining an operation in the case of the configuration of FIG. 8 in the fourth embodiment of the present invention. FIG. 11 is a diagram for explaining an operation in the case of the configuration of FIG. 10 in the fourth embodiment of the present invention. It is a figure for demonstrating the structure of the motor speed setting part 57 of FIG. It is a flowchart which shows the flow of the initialization operation | movement of the 4th Embodiment of this invention.

  Hereinafter, an embodiment in which the present invention is suitably implemented will be described with reference to the drawings.

  First, an image reading apparatus to which the present invention can be applied will be described.

  Conventionally, image information of a document or the like is line-scanned in the sub-scanning direction, the image information is imaged on a sensor surface of a photoelectric conversion means (CCD) as a reading means, and an output signal obtained from the photoelectric conversion means is used. Various image reading apparatuses that read image information such as originals have been proposed. FIG. 1 is a diagram showing a schematic configuration of a scanner 13 according to an image reading apparatus to which the present invention can be applied.

  A scanner 13 shown in FIG. 1 has a reading unit 12 and an ADF (auto document feeder) 20 attached to the upper part of the reading unit 12. Since the configuration of the ADF 20 is well known to those skilled in the art and is not a main part of the present invention, the description thereof is omitted.

  The reading unit 12 includes a contact glass 1 on which a document is placed as a document table, a first carriage 6 including a document exposure illumination lamp 2 (hereinafter referred to as “light source 2”), and a first reflecting mirror 3. A second carriage 7 comprising a second reflecting mirror 4 and a third reflecting mirror 5, a lens unit 8 for forming an image on a CCD linear image sensor 9 (hereinafter referred to as CCD), a sensor board 10 on which the CCD 9 is mounted, and reading It is composed of a white reference plate 32 for correcting various distortions caused by the optical system and adjusting the white level. When the original is placed and fixed on the contact glass 1, the first carriage 6 moves forward (in the direction of the arrow A) at a constant speed, and the second carriage 7 is half of the first carriage 6. The original on the contact glass 1 is optically scanned by moving forward following the first carriage 6 at a speed. After the reading of the document is finished, the position Y of the first carriage 6 and the second carriage 7 is the home position (standby position) of the first carriage 6. The reading unit 12 also has a motor drive system (not shown) for moving the first carriage 6 and the second carriage 7.

  FIG. 2 is a perspective view illustrating a schematic configuration of the reading unit 12.

  Both ends of the first carriage 6 are fixed to two symmetrically stretched wires 61 so that the first carriage 6 can reciprocate along with the movement of the wires 61, and the second carriage 7 has a first carriage at both ends thereof. A wire 61 on which the wire is fixed is stretched, and a pulley on which the stretched wire 61 is stretched is provided in the opposite direction. A timing belt pulley 65 is provided at one end of the drive shaft 67, and the timing belt 62 is stretched between the motor 63. In the above configuration, when the power switch is turned ON, the stepping motor 63 is started for homing, the driving force is transmitted to the timing belt pulley 65 via the timing belt 62, and the driving integrated with the timing belt pulley 65 is performed. The shaft 67 rotates in the rotation direction of the stepping motor. Further, the wire moves accordingly, and the first carriage 6 fixed to the wire 61 moves in the forward direction. The second carriage 7 moves in the same direction at half the speed of the first carriage 6. When the carriages 6 and 7 move by a certain distance, the stepping motor 63 starts reverse rotation (return), detects that the detection unit 66 in the first carriage has entered the home position sensor 60, and motor drive control described later. It stops when it moves a predetermined distance after detection by means. This stopped position becomes the home position, and control for stopping the first carriage 6 at this home position (standby position) is called homing.

  FIG. 3 is a diagram for explaining a drive pattern of the reading unit 12. FIG. 3 shows a typical velocity diagram (basic drive pattern for scanner driving) used for running control of the reading unit 12.

  The stepping motor 63 is driven and controlled according to the speed diagram shown in the figure, and the reading of the document is performed during the forward period in which the document travels at a constant speed through the slow-up operation as shown in the figure. During this time, the speed must be stabilized most. When the reading of the original is completed, the process proceeds to a return process and the stepping motor 63 starts reverse rotation. In order to return in as short a time as possible, the first carriage 6 is moved at a high speed, and the second carriage 7 is returned at a half speed. If the return side moving distance is returned by the distance moved on the forward side, it will return to the home position.

  A functional configuration of the scanner 13 (system configuration of the image reading apparatus) will be described with reference to FIG.

  The CCD 9 is a color 3-line CCD in which three rows of CCD sensors covered with RGB filters are arranged. The analog processing circuit 43 samples the signal portion of the analog waveform output from the CCD 9 and incorporates an amplifier to adjust the signal gain. The A / D converter 44 outputs R, G, and B color analog image signals to the image processing unit 41 as 8-bit color digital image information. In the case of the 3-line CCD 9, the signal output from the CCD 9 has a positional shift of 4 lines at the same magnification. That is, there is a positional deviation of 8 lines between R and B, and the interline correction unit 45 corrects the deviation of the reading line for each RGB of the CCD and aligns the read image. In the black correction 46, the offset data added to the image data is subtracted. In the shading correction unit 47, correction of output data variation for each pixel such as density unevenness of the optical system and sensitivity variation of the CCD 9 is performed on each RGB signal.

Each RGB signal may be further subjected to other correction processing.
Further, as illustrated, the reading unit 12 includes a stepping motor 63 for driving each carriage and the light source 2. In addition, the scanner 13 includes a control unit 50 that controls the operation of the stepping motor 63 and the light source 2 based on a control signal from the external interface 60 and the like. The control unit 50 includes a motor control unit 501 and a motor drive control circuit 502 that control the operation of the stepping motor 63, and a light source control unit 503 and a light source drive control circuit 504 that control the operation of the light source 2.

  FIG. 5 is a diagram for explaining the configuration of a motor drive control circuit 502 that controls the drive of the stepping motor 63.

  The stepping motor is supplied from the motor control unit 501 of the control unit 50 to the motor drive control circuit 502 with a motor drive clock, a forward / reverse signal in the motor rotation direction, a switching signal for the drive current flowing in each phase of the stepping motor 63, microstep drive (motor rotation). A division number switching signal (excitation setting signal) for controlling the electrical division of the corners is input, and based on these, the drive current flowing in each phase of the stepping motor is controlled, and the drive control of the stepping motor 63 is performed. For example, in the state where the number of divisions of the motor rotation angle is the same, the phase switching timing of the stepping motor 63 is faster when the driving clock frequency is higher, and is slower when the driving clock frequency is lower. Further, when the number of motor rotation angles is reduced, the amount of carriage movement per motor rotation is increased. Therefore, when the carriage movement speed is not changed, the drive clock frequency is lowered. By controlling the drive clock frequency in this way, a wide variety of slow-ups and slow-downs of the stepping motor 63, and thus the carriage, are possible. That is, the drive current is controlled to be switched depending on states such as slow-up, slow-down, reading operation, return, and standby, and the position of the stepping motor 63 can be controlled by the number of drive clocks.

  FIG. 6 is a diagram for explaining the configuration of the light source drive control circuit 504 that controls the lighting drive of the light source 2 that illuminates the document.

  The light source 2 receives a light source drive clock and a light source lighting signal from the light source control unit 503 of the control unit 50 to the light source drive control circuit 504, and based on these, the light source is driven to turn on and control power consumption.

  The above is the schematic configuration of each unit of the scanner 13. Meanwhile, the scanner 13 performs the operation as described above, while performing the initialization operation of the apparatus when the power is turned on or at the time of automatic return after occurrence of an abnormality.

  In the initialization operation process, the reading unit 12 performs homing (carriage initialization process) and adjustment of signal processing characteristics of the read image. In the adjustment of the signal processing characteristics of the read image, the output level is made constant by adjusting the processing characteristics of an analog signal processing unit of an image sensor (usually a CCD linear image sensor) that performs photoelectric conversion of the image. This adjustment is performed in consideration of deterioration of the light source and environmental fluctuations, and the adjustment of the analog signal processing unit includes black level adjustment and white level adjustment. The black level adjustment is performed using the read black level signal. The white level adjustment is performed by adjusting a white level signal (usually based on a peak value) obtained by reading a white reference plate illuminated by a light source to a target value.

  FIG. 7 is a flowchart showing a flow of initialization operation of the scanner 13.

  First, initial value setting is performed (S101). In the initial value setting, initial values necessary for reading scanning of the scanner unit and processing of the read image signal are set in each circuit. Next, homing is performed (S102). The homing is an operation of positioning a carriage equipped with a reading unit at a home position serving as a reference for scan control (determining a mechanical origin). Since this position is the position of the carriage in the standby state, it is referred to as a standby position. Thereafter, an operation for adjusting the black level and the white level is started. Since the CCD 9 always photoelectrically converts the read image and outputs an image signal, the OPB (Optical Black) provided in a part of the CCD 9 is taken at an appropriate time until the white reference plate 11 (reference white plate) is read. ), That is, the black level is detected by reading the image signal output from the pixel portion where the external light is blocked, and the black level is adjusted. The light source 2 (illumination lamp 2) is turned on (S103), and the carriage is moved to read the reference white plate from the home position (S104). An adjustment value for setting the white level to the target value is determined from the white level image signal obtained by reading the reference white plate, and the value is set as a value for adjusting the gain of the amplifier of the analog processing circuit. At this time, the feedback loop operation is repeated to obtain an adjustment value (S105). After the adjustment process is finished, the light source 2 is turned off (S106), the carriage is moved to the standby position (S107), and the sequence is finished.

  In the above-described image reading apparatus, when the signal port of the motor control signal fails during the drive control of the stepping motor, there is no means for externally detecting the actual position and rotation direction of the carriage, so that it can be determined as the original setting. It is difficult and cannot be detected as an abnormality during driving. If this occurs during the forward movement of the document reading, the carriage may collide with the housing of the apparatus or the image data may be defective.

  Also, if an abnormality occurs during document reading, the device initialization operation is performed when the user turns off the power to turn it back on to try to return it, or when the device automatic return processing is executed. Since there is no means to detect the current position of the motor and the distance to return to the home position is unknown, high-speed driving due to slow-up and slow-down is not possible, and the stepping motor is driven at a low speed within the self-starting area, causing the carriage to move out of the home position due to an abnormality. If the vehicle is stopped at a certain position, there is a problem that the waiting time until the device starts up becomes long and the user feels uncomfortable.

  Next, an image reading apparatus according to an embodiment of the present invention will be described. The image reading apparatus according to the embodiment of the present invention conforms to the configuration shown in FIGS. An image sensor that photoelectrically converts image information obtained by optically reading a document, a light source that illuminates the document, a device that controls driving of the light source, a stepping motor that moves the carriage in the sub-scanning direction relative to the document, and a motor A device for controlling the drive is mounted, and when the carriage is reciprocated, drive control means for setting the drive clock frequency of the stepping motor according to the setting of the rotation resolution and speed is provided.

<First Embodiment>
The configuration and operation of the first embodiment will be described with reference to FIGS.

  The reading range in the main scanning direction of the image reading apparatus according to the present embodiment is set wider than the actual document size in order to satisfy the image quality of the document, and the range outside the document reading area can also be read. As shown in FIG. 8, the reading unit 12 of the image reading apparatus (scanner 13) according to the present embodiment has a density plate or density chart 33 disposed at an end in the main scanning direction outside the document reading area 32. As shown in FIG. 9, the density plate or density chart 33 has a characteristic in which the intensity of reflected light incident on the CCD 9 increases in proportion to the absolute position of the first carriage 6 in the sub-scanning direction (hereinafter referred to as sub-scanning position). It has.

  As the system configuration of this embodiment, the system configuration shown in FIG. 12 or FIG. 15 can be used. A more detailed description of the configuration shown in FIG. 12 or FIG. 15 will be described in the third and fourth embodiments, and here, portions related to the present embodiment will be mainly described.

  As shown in FIG. 12 or FIG. 15, the reflected light incident on the CCD 9 is photoelectrically converted into an analog signal waveform and input to the analog processing circuit 43. The analog processing circuit 43 samples the signal portion of the analog waveform output from the CCD 9 and incorporates an amplifier to adjust the signal gain. The A / D converter 44 outputs R, G, and B color analog image signals to the image processing unit 41 as 8-bit color digital image information. In the case of the 3-line CCD 9, the signal output from the CCD 9 has a positional shift of 4 lines at the same magnification. That is, there is a positional deviation of 8 lines between R and B, and the interline correction unit 45 corrects the deviation of the reading line for each RGB of the CCD 9 and aligns the read image. In the black correction 46, the offset data added to the image data is subtracted. In the shading correction unit 47, correction of output data variation for each pixel such as density unevenness of the optical system and sensitivity variation of the CCD 9 is performed on each RGB signal.

  When the reading scan is executed, the intensity of the light reflected on the density plate or density chart 33 and incident on the CCD 9 increases as the first carriage 6 moves in the sub-scanning direction according to the characteristics shown in FIG. The level of image data output obtained later increases proportionally. That is, since the level of image data output changes when the first carriage 6 moves, it becomes possible to detect the sub-scanning position of the first carriage 6 at that level. The position of the first carriage 6 can be obtained while moving without using parts.

  From the above, since the position of the first carriage 6 can be known, the actual moving speed and direction of the first carriage 6 can be detected. In addition to monitoring inside the control, it is possible to monitor the movement speed and direction of the carriage from the outside of the control, so abnormalities such as step-out in cases where it is difficult to distinguish from the original setting or signal port failure Occurrence can be detected, and abnormality detection in the drive control of the stepping motor 63 can be enhanced.

  On the other hand, if the position of the first carriage 6 can be obtained, the distance to return to the home position is known, so the speed at the time of homing return movement can be set to a high speed setting by slow-up and through-down faster than the conventional low speed. It becomes possible. If the carriage stops at a position that deviates from the home position when recovering from an error that occurred during document scanning, the waiting time until the device starts up can be greatly reduced. Pleasure can be reduced. Furthermore, the fact that the waiting time during the homing return movement can be shortened leads to a reduction in the operating time of the stepping motor 63, so that it is possible to reduce the power consumption during the operation, which is advantageous in terms of environmental considerations. .

  In addition, since a member formed of a mark or a pattern is used, it does not have a complicated internal structure and is excellent in impact resistance, and an existing image sensor is used, so that the cost can be reduced.

<Second Embodiment>
The configuration and operation of the second embodiment will be described with reference to FIGS.

  The reading range in the main scanning direction of the image reading apparatus is set wider than the actual document size in order to satisfy the image quality of the document, and the range outside the document reading area can also be read. In the reading unit 12 of FIG. 10, a mark member 34 is arranged at the end in the main scanning direction outside the document reading area 32. As shown in FIG. 11, the mark member 34 has a characteristic that the range in which the reflected light incident on the CCD 9 changes is proportionally increased depending on the absolute position of the first carriage 6 in the sub-scanning direction (hereinafter referred to as sub-scanning position). I have.

  As shown in FIG. 12 or FIG. 15, the reflected light incident on the CCD 9 is photoelectrically converted into an analog signal waveform, and the subsequent processing is as described above until the shading correction processing.

  When the reading scan is executed, according to the characteristics of FIG. 11, as the first carriage 6 moves in the sub-scanning direction, the range of the light intensity that is reflected by the mark member 34 and incident on the CCD 9 increases. The range in which the image data output obtained after the shading correction changes in the main scanning direction increases in proportion. That is, when the first carriage 6 moves, the range of image data output that changes in the main scanning direction changes, so that the sub-scanning position of the first carriage 6 can be detected with the range width at that time. The current position of the first carriage 6 can be obtained while moving without using dedicated parts such as a linear scale and an encoder.

  As described above, since the current position of the first carriage 6 can be known, it is possible to enhance the abnormality detection of the motor drive control and shorten the waiting time at the time of initialization of the apparatus as described above.

<Third Embodiment>
In the image reading apparatus according to the first and second embodiments, the third embodiment detects the sub-scanning position of the carriage based on the range in which the image data obtained by the output from the image sensor changes in the main scanning direction. Realize that. The system configuration of this embodiment is shown in FIG.

  As shown in FIG. 12, the reflected light incident on the CCD 9 is photoelectrically converted into an analog signal waveform, and the subsequent processing is as described above up to the shading correction processing. The image data that has been subjected to the inter-line correction 45, the black correction 46, and the shading correction 47 by the image processing unit 41 is input to the position detection circuit 70.

  In the apparatus configuration of FIG. 8, the position detection circuit 70 has a function of converting the output of image data into a sub-scanning position as shown in FIG. 13, and the image data input to the position detection circuit 70 is motor-driven. It is detected at a timing synchronized with the rising edge (or falling edge) of the clock, and the output of the detected image data is converted to the opposite sub-scanning position.

  In the apparatus configuration of FIG. 10, as in the configuration of FIG. 8, the position detection circuit 70 has a function of converting the change width of the image data in the main scanning direction into the sub-scanning position as shown in FIG. Then, the image data input to the position detection circuit 70 is detected at a timing synchronized with the rise (or fall) of the motor drive clock, and the change width of the detected image data in the main scanning direction is the opposite sub-scanning position. Converted.

  Since the motor drive clock is set according to the rotation resolution and speed settings of the stepping motor, if there are multiple stepping motor drive control patterns such as document reading magnification / resolution setting and switching according to the specified operation, The sub-scanning position can be detected more simply than adding a timer counter.

  The sub-scanning position data obtained by the position detection circuit 70 is stored in the memory 71 and also input to the movement distance calculation unit 72.

  The movement distance calculation unit 72 reads out the data at the sub-scanning position one clock before from the memory 71 and obtains the movement distance from the difference from the data at the current sub-scanning position. The obtained movement distance is input to the motor (acceleration) speed detection unit 51 and the motor rotation direction detection unit 53.

  As shown in FIG. 13, the motor (acceleration) speed detection unit 51 can detect the current speed by dividing the movement distance by the cycle time of the motor drive clock. Further, since the speed change can be found from the difference from the speed one clock before the present time, the acceleration can be detected by dividing by the period time of the motor drive clock. The detected speed and acceleration are each input to the comparison circuit 52 and compared with a set value in the control unit 50. The comparison result is input to the abnormality determination unit 55.

  As shown in FIG. 13, the motor rotation direction detection unit 53 knows that the carriages 6 and 7 are moving in the forward direction when the value of the movement distance is positive, and the return direction when the value is negative. The direction can be detected. The detected rotation direction is input to the comparison circuit 54 and compared with the set direction in the control unit 50. The comparison result is input to the abnormality determination unit 55. The abnormality determination unit 55 determines that the comparison result is out of the allowable value range, determines that it is abnormal, stops the operation of the motor control unit, and notifies the upper system via the external interface 60 of the abnormality.

  From the above, it is possible to detect the speed and acceleration and the rotation direction of the carriages 6 and 7 adapted to the content of the drive control of the stepping motor, so that it is possible to determine abnormality of the motor drive by comparing with the set value. That is, as described above, it is possible to enhance the abnormality detection of the motor drive control.

<Fourth Embodiment>
In the image reading apparatus according to the first and second embodiments, the fourth embodiment detects the current position of the carriage at the time of initializing the apparatus, thereby realizing a high speed homing (returning movement) operation. The system configuration of this embodiment is shown in FIG.

  As shown in FIG. 15, the reflected light incident on the CCD 9 is photoelectrically converted into an analog signal waveform, and the subsequent processing is as described above up to the shading correction processing. The image data that has been subjected to the inter-line correction 45, the black correction 46, and the shading correction 47 by the image processing unit 41 is input to the position detection circuit 70.

  In the apparatus configuration of FIG. 8, the position detection circuit 70 has a function of converting the output of the image data into the sub-scanning position as shown in FIG. 16, and the image data input to the position detection circuit 70 is turned on by the light source. It is detected at a timing synchronized with the fall (or rise) of the signal, and the output of the detected image data is converted to the opposite sub-scanning position.

  In the apparatus configuration of FIG. 10, as in the configuration of FIG. 8, the position detection circuit 70 has a function of converting the change width of the image data in the main scanning direction into a corresponding sub-scanning position as shown in FIG. The image data input to the position detection circuit 70 is detected at a timing synchronized with the fall (or rise) of the light source lighting signal, and the change width in the main scanning direction of the detected image data is the opposite sub-scanning. Converted to position.

  The sub-scanning position data obtained by the position detection circuit 70 is input to the homing distance calculation unit 73.

  The homing distance calculation unit 73 has setting data of a position (deceleration start position) at which normal low-speed driving is started during the return movement of the homing operation, and obtains the distance by a difference from the data of the current sub-scanning position. The obtained distance is input to the comparison circuit 56, and is compared with setting data of a moving amount that can be driven at high speed. The comparison result is input to the motor speed setting unit 57. When the comparison result exceeds a predetermined movement amount, the motor speed setting unit 57 determines that high-speed driving at the time of homing return movement is possible, and an operation pattern of high-speed drive control up to the deceleration start position as shown in FIG. To reflect to the motor controller. At this time, the distance obtained by the homing distance calculation unit 73 is converted into the number of movement pulses of the stepping motor and set as the movement amount. If the comparison result does not exceed, it is determined that the amount of movement necessary for high-speed driving cannot be secured, so that the normal low-speed driving setting is maintained in the motor control unit.

  FIG. 19 is a flowchart showing the flow of the initialization operation of the apparatus according to the present embodiment. The same reference numerals are assigned to processes common to those in FIG.

  First, initial value setting is performed (S101). In the initial value setting, initial values necessary for reading scanning of the scanner unit and processing of the read image signal are set in each circuit. At that time, the result of the adjustment (S105) obtained in the previous initialization process is reflected. Next, the light source 2 is turned on (S201), image data outside the document reading area is acquired at a timing synchronized with the lamp lighting signal input to the position detection circuit 70, and the sub-scanning position of the carriage is determined from the obtained image data. It detects (S202).

  After completing the carriage position detection process, the lamp is turned off (S203). A distance is obtained by a difference calculation process from the detected sub-scanning position to the deceleration start position (S204). The obtained distance is compared with the set value of the moving amount that can be driven at high speed (S205), and if it exceeds, it is set to drive control in which the speed at the time of homing return movement to the deceleration start position is higher than usual (S206), If not, the homing operation is executed with the normal low-speed drive setting (S102). The homing is an operation of positioning a carriage equipped with a reading unit at a home position serving as a reference for scan control (determining a mechanical origin). Since this position is the position of the carriage in the standby state, it is referred to as a standby position.

  Thereafter, an operation for adjusting the black level and the white level is started. Since the CCD always photoelectrically converts the read image and outputs an image signal, the OPB (Optical Black) part provided in a part of the CCD, that is, outside light, at an appropriate time until the reference white plate is read. The black level is detected by reading the image signal output from the pixel portion where the signal is cut off, and the black level is adjusted. The lamp is turned on (S103), and the carriage is moved to read the reference white plate from the home position (S104). An adjustment value for setting the white level to the target value is determined from the white level image signal obtained by reading the reference white plate, and the value is set as a value for adjusting the gain of the amplifier of the analog processing circuit. At this time, the feedback loop operation is repeated to obtain an adjustment value (S105). Here, the content of the obtained adjustment result is reflected in the initial setting. After the adjustment process is finished, the lamp is turned off (S106), the carriage is moved to the standby position (S107), and the sequence is finished.

  As described above, since the current positions of the carriages 6 and 7 can be detected at the time of initialization of the apparatus, it is possible to perform high-speed driving at the time of homing feedback movement by comparison with the set value. That is, as described above, the waiting time at the time of device initialization can be shortened.

  Note that the configurations of the above-described embodiments can be combined with each other.

1 Contact glass 2 Light source (lighting lamp)
6 First Carriage 7 Second Carriage 9 CCD (Line CCD Sensor)
10 Sensor board 12 Reading section (scanner)
32 Out of document reading area 33 Density plate or density chart 34 Mark member 43 Analog processing circuit 50 Control unit 501 Motor control unit 502 Motor drive control circuit 503 Light source control unit 504 Light source drive control circuit 51 Motor (acceleration) speed detection unit 53 Motor rotation Direction detection unit 52, 54, 56 Comparison circuit 55 Abnormality determination unit 57 Motor speed setting unit 63 Motor (stepping motor)
70 Position Detection Circuit 71 Memory 72 Moving Distance Calculation Unit 73 Homing Distance Calculation Unit

Japanese Patent Laid-Open No. 02-39208 Japanese Patent Laid-Open No. 09-102850 Japanese Patent Laid-Open No. 04-336854

Claims (5)

An image sensor that photoelectrically converts image information obtained by optically reading a document;
A carriage for moving the image sensor in the sub-scanning direction with respect to the document;
A member whose optical attribute changes according to an absolute position in the sub-scanning direction at an end portion in the main scanning direction outside the document reading area;
Position detecting means for detecting the position of the carriage based on image data obtained by reading an image of the member by the image sensor;
An image reading apparatus comprising:   The image reading apparatus according to claim 1, wherein the member is a density plate or a density chart having a characteristic that reflected light increases or decreases in the same direction according to a sub-scanning position.   The image reading device according to claim 1, wherein the member is a mark having a characteristic that a shape thereof changes according to a sub-scanning position and a range in which reflected light changes increases or decreases in the same direction. apparatus. A stepping motor for driving the carriage;
The position detecting means detects the sub-scanning position of the carriage in synchronization with the driving clock signal of the stepping motor, and an abnormality has occurred when the change in the position of the carriage deviates from a predetermined allowable range. An abnormality detection means for determining the effect,
The image reading apparatus according to claim 1, further comprising:   Before starting a homing operation to be executed when the apparatus is initialized, a light source is activated to detect a sub-scanning position of the carriage, and drive control of the homing operation is adjusted according to the sub-scanning position of the carriage. The image reading apparatus according to claim 1, wherein:

Images