JP2007184907A - Image reading apparatus and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reading apparatus and a method in which an image can be accurately read while keeping high reliability. <P>SOLUTION: After a light source is lit for a predetermined time synchronously with a relative position signal indicating a relative position while a reader which optically reads an image moves, control is performed to output an image signal corresponding to the image read by the reader in synchronism with a control signal for outputting the image signal. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image reading apparatus and an image reading method, and more particularly to an image reading apparatus that optically reads an image recorded on a sheet-like recording medium using a linear image sensor and an image reading method applied to the apparatus.

  A CCD line sensor is used in a conventional image reading apparatus (see, for example, Patent Document 1 and FIG. 2). In such a conventional image reading apparatus, for the purpose of improving the reading position accuracy of the linear image sensor, a position sensor is arranged in the vicinity of the moving image original, and the reading timing of the image sensor is controlled by the output signal of the position sensor. There was a thing (for example, refer to patent documents 2).

  When reading an image document, a photoelectric conversion start signal is forcibly generated in response to an output from a rotary encoder that generates a pick-up pulse every time the CCD line sensor moves a certain distance in the mechanical movement direction. There was also a thing (for example, refer to patent documents 3).

Furthermore, with respect to the moving direction of the line sensor, the reading speed of the image original is measured, the horizontal synchronization signal of the line sensor is generated, and the horizontal synchronization signal is resynchronized according to the drive of the motor that moves the line sensor relative to the image original Some have become (for example, Patent Document 4).
JP-A-6-105135 JP-A-63-287167 Japanese Patent Publication No. 3-70213 Japanese Patent No. 3585976

  However, the above conventional example has the following problems.

  Japanese Patent Application Laid-Open No. H10-228561 describes that when a movement of one dot pitch is detected from a position sensor, image data accumulated in the line sensor is transferred by this signal. However, since the position sensor output is not synchronized with the accumulation timing of the line sensor, there is a problem that the position accuracy of the reading line is lowered.

  The apparatus disclosed in Patent Document 3 employs a configuration in which a photoelectric conversion signal of an image sensor is forcibly generated by an output signal of a rotary encoder, thereby improving position accuracy. However, in this configuration, the photoelectric conversion signal of the image sensor cannot be generated by the output signal of the rotary encoder during the output period of the read analog image signal, and it is impossible to synchronize with the rotary encoder sensor output. . For this reason, there is a drawback in that normal operation cannot be performed and high-speed reading cannot be performed unless the output period of the rotary encoder is equal to or greater than the sum of the photoelectric conversion period and the image signal output period. In addition, if the photoelectric conversion signal is forcibly generated, a charge overflow in the charge transfer unit inside the image sensor or an output value exceeding the expected value may occur, which may adversely affect subsequent circuit operations. .

  In the apparatus disclosed in Patent Document 4, only the first line from which reading is started can be read continuously in synchronization with the main scanning synchronization signal by resynchronizing the horizontal synchronization signal. However, since this synchronization is the synchronization of only the reading start line, there is a drawback that the reading position fluctuation caused by the fluctuation of the driving speed during the continuous line reading cannot be removed.

  In any of the above, it is indispensable that the period of the main scanning synchronization signal at the time of reading is constant, and if it fluctuates, there is a problem that the image cannot be read correctly.

  SUMMARY An advantage of some aspects of the invention is that it provides an image reading apparatus and an image reading method capable of accurately reading an image while maintaining high reliability.

  In order to achieve the above object, an image reading apparatus of the present invention has the following configuration.

  That is, an image reading apparatus for reading an image recorded on an original, wherein the original is irradiated with light from a light source to optically read the image recorded on the original, and the reading is performed on the original. Moving means for relatively moving the means, position signal generating means for outputting a position signal in accordance with movement of the reading means by the moving means, and lighting the light source in a first period in synchronization with the position signal A lighting control means for controlling the light source, and a control signal for outputting an image signal of an image read by the reading means after the light source is lit for the first period, and in synchronization with the control signal Output control means for controlling to output the image signal for a period of 2.

  According to another invention, there is provided an image reading apparatus for reading an image recorded on a document, comprising a photoelectric conversion element array in which photoelectric conversion elements are arranged and a shift register, and irradiating light from a light source to the document. Reading means for optically reading an image recorded on the original, moving means for moving the reading means relative to the original, and outputting a position signal in accordance with movement of the reading means by the moving means Position signal generating means, lighting control means for controlling the light source to light for a first period in synchronization with the position signal, and the light source is stored in the photoelectric conversion element after the first period lighting. A timing signal is transferred to the shift register, and after the timing signal is generated, the reading means is controlled to output the charge through the shift register for a second period. And having an output control means for.

  According to still another invention, there is provided an image reading apparatus for reading an image recorded on a document, comprising a photoelectric conversion element array in which photoelectric conversion elements are arranged and a shift register, and irradiating light from a light source to the document. Reading means for optically reading an image recorded on the original, moving means for moving the reading means relative to the original, and outputting a position signal in accordance with movement of the reading means by the moving means A position signal generating means for enabling, in a state where the light source is turned on, a permission signal control means for generating a permission signal for allowing the photoelectric conversion element to accumulate charges in a first period in synchronization with the position signal; After the permission signal is generated for the first period, a timing signal is generated to transfer the charge accumulated in the photoelectric conversion element to the shift register, and after the generation of the timing signal, the second period Characterized in that through the shift register and an output control means for controlling to output the charges from the reading means.

  According to still another invention, an image recorded on the original is optically irradiated by irradiating the original with light from a light source using a reading unit including a photoelectric conversion element array in which photoelectric conversion elements are arranged and a shift register. An image reading method for reading, wherein a moving step of moving the reading unit relative to the document, and a position signal generating step of outputting a position signal according to the movement of the reading unit by the moving step, A lighting control step for controlling the light source to light for a first period in synchronization with the position signal, and the charge accumulated in the photoelectric conversion element after the light source is lighted for the first period is shifted. An output control step of generating a timing signal to be transferred to the register and controlling to output the charge from the reading unit through the shift register for a second period after the generation of the timing signal. And features.

  According to still another invention, an image recorded on the original is optically irradiated by irradiating the original with light from a light source using a reading unit including a photoelectric conversion element array in which photoelectric conversion elements are arranged and a shift register. An image reading method for reading, wherein a moving step of moving the reading unit relative to the document, and a position signal generating step of outputting a position signal according to the movement of the reading unit by the moving step, A permission signal control step of generating a permission signal for allowing the photoelectric conversion element to accumulate charges in a first period in synchronization with the position signal in a state where the light source is turned on; and the permission signal is the first signal A timing signal for transferring the charge accumulated in the photoelectric conversion element to the shift register is generated, and after the timing signal is generated, a second period is generated via the shift register. And having an output control step of controlling to output the charges from the serial reading section.

  Therefore, according to the present invention, the image signal of the image read by the reading unit after the light source is turned on for a predetermined time in synchronization with the relative position signal indicating the relative position of the reading unit that optically reads the image. The image signal is controlled to be output in synchronization with the control signal for outputting. Therefore, even if the speed during movement of the reading unit fluctuates, it is possible to accurately read an image corresponding to the position.

  Further, the length of the cycle for generating the relative position signal can be made shorter than the sum of the photoelectric conversion period and the output period of the photoelectric conversion element, and the speed of the reading operation can be improved.

  Hereinafter, preferred embodiments of the present invention will be described more specifically and in detail with reference to the accompanying drawings.

  FIG. 1 is an external perspective view of a flat bed type image reading apparatus 100 (optical scanner) which is a typical embodiment of the present invention. As shown in FIG. 1, the image reading apparatus is provided with an LCD 110 with a backlight. When reading an image, the backlight of the LCD 110 can be turned on to display simple character information and an image. The LCD display screen 111 shown in FIG. 1 displays a reading resolution, a scan mode, a meter indicating the reading progress, and the like. The image reading apparatus 100 is connected to an external apparatus such as a host computer (hereinafter referred to as a host) via a USB interface, and power for operating the image reading apparatus is supplied from the external apparatus via the USB interface. A typical host is a personal computer or the like.

  The present invention is applied not only to a flat bed type image reading apparatus as shown in FIG. 1 but also to a scanner incorporated in a multifunction printer (MFP) integrated with a printer or a facsimile.

  FIG. 2 is a side sectional view showing the internal configuration of the image reading apparatus 100 shown in FIG.

  As shown in FIG. 2, the image reading apparatus 100 includes an optical unit 101, a circuit board 102 electrically connected to the optical unit 101, a belt 103 mounted with the optical unit 101 and scanned in the direction of arrow B, and an image original 108 A document table glass 104 is provided. The optical unit 101 includes a linear image sensor (LIS) 106 that irradiates the image original 108 with light, receives the reflected light, and converts it into an electrical signal.

  The belt 103 is rotated by a DC motor 105. A rotary encoder (not shown) is attached to the rotating shaft of the DC motor 105, and the rotary encoder sensor 107 outputs a position signal of the rotary encoder. Based on this position signal, the position of the LIS 106 is detected.

  A home position sensor 109 is provided at the end of the scanning path of the optical unit 101, and outputs a home position signal when the optical unit 101 reaches a predetermined home position (HP).

  The rotational speed of the DC motor 105 is controlled by the voltage or current supplied from the circuit board 102. The position signal of the rotary encoder output from the rotary encoder sensor 107 is transferred to the circuit board 102.

  At the time of image reading, the image recorded on the image original 108 is read by the optical unit 101 scanning the image original 108 placed on the platen glass 104 in the direction of arrow B (sub-scanning direction).

  FIG. 3 is a side sectional view showing a detailed structure of the linear image sensor (LIS) 106.

  As shown in FIG. 3, the LIS 106 includes a red LED 202 that emits R (red) light, a green LED 203 that emits G (green) light, and a blue LED 204 that emits B (blue) light. And. When reading a document, each color LED is turned on in a time-sharing manner for each line, and the lit light is uniformly applied to the document through the light guide pair 205, and the reflected light is condensed by the SELFOC lens 201 for each pixel and photoelectrically converted. The element converts the light into an electrical signal. In this manner, an image signal for one line composed of RGB color component color signals is output. The entire surface of the original is read by moving the LIS unit in the sub-scanning direction.

  Here, the linear image sensor LIS 106 includes a diode array (photoelectric conversion element), a shift register, and an output unit. The diode array includes a photodiode and a charge storage unit.

  FIG. 15 is a diagram illustrating processing blocks for reflected light of R (red) light as an example. Reference numeral 1601 denotes a diode array, 1062 denotes a shift register, and 1063 denotes an output unit. The output unit 1063 is output to the amplifier (AMP) 404. The processing blocks of G (green) color and B (blue) color have the same configuration, and thus the description thereof is omitted.

  The direction of the arrow A indicating the arrangement direction of each cell of the SELFOC lens 201 is referred to as a main scanning direction. The main scanning direction and the sub scanning direction are orthogonal to each other. In FIG. 2, the main scanning direction is a direction perpendicular to the paper surface.

  FIG. 4 is a block diagram showing the configuration of the control circuit of the image reading apparatus.

  In FIG. 4, the same reference numerals are assigned to the components already described in FIGS. 1 to 3, and description thereof is omitted.

  The LIS 106 reads the color images in order of RGB lines by switching and lighting the LEDs 202 to 204 of each color for each line in the LED drive circuit 403. The LEDs 202 to 204 are light sources capable of changing the amount of light irradiated on the document. An amplifier (AMP) 404 amplifies the signal output from the LIS 106, and an A / D converter 405 performs A / D conversion on the amplified electrical signal, for example, digital image data of 16 bits for each color component of each pixel. Output.

  The shading RAM 407 stores data used to perform shading correction by reading a standard white plate (not shown) attached to the back surface of an indicator plate (not shown) attached to the original glass 105. The shading correction circuit 406 performs a shading correction process on the image data output from the A / D converter 405 based on the data stored in the shading RAM 407. Further, the gamma conversion circuit 408 performs gamma conversion on the image data subjected to the shading correction according to a gamma curve preset by the host.

  The buffer RAM 410 is a RAM for temporarily storing image data in order to match the actual reading operation and the timing in communication with the host. The packing / buffer RAM control circuit 411 performs packing according to an image output mode (binary, 8-bit gray, 24-bit color (RGB each 8 bits), 48-bit color (RGB each 16 bits)) preset by the host. Process. Further, the packed image data is written into the buffer RAM 410, and the image data is read from the buffer RAM 410 and output to the interface control circuit 411.

  The interface control circuit 411 exchanges control data and outputs image data with the host which is the external device 417.

  The series of processes as described above is controlled by the CPU 414. The control is executed by the CPU 414 reading out the processing program stored in the ROM 415 and executing it using the RAM 416 as a work area.

  Further, in FIG. 4, reference numeral 412 is a reference signal oscillator (OSC) such as a crystal oscillator, for example, and 413 is various timing signals that are the basis of the operation by dividing the output of the reference signal oscillator 412 according to the setting of the CPU 414. Is a timing signal generation circuit for generating A rotary encoder 421 outputs a signal according to the movement of the LIS 106. This signal is input to the timing signal generation circuit 413. The timing signal generation circuit 413 generates the output timing of a main scanning synchronization signal (MSYNC) described later, the output timing of a reading light source lighting signal (LEDR), the output timing of an analog image signal (AIMG), and the like.

  Further, reference numeral 417 denotes an operation unit including operation buttons, and an output signal thereof is connected to an input port of the CPU 414. Reference numeral 419 denotes an LED serving as a backlight light source of the LCD 110, and lighting control is performed by a lighting signal output from the timing signal generation circuit 413. A motor driver 420 drives and controls the DC motor 105 based on an instruction from the CPU 414.

  Next, an image reading operation in the image reading apparatus having the above configuration will be described in detail. In order to simplify the description, a case where image reading is performed with only one LED turned on will be described. In this embodiment, the image reading operation is controlled in synchronization with each signal pulse from the rotary encoder sensor 107.

  FIG. 5 is a time chart of each signal showing the image reading operation. In FIG. 5, it is assumed that time elapses from the left to the right, and the state of shifting from the non-reading state to the reading state is described. For example, the LIS 106 is in the non-reading state in the acceleration control region, and the LIS 106 shifts to the reading state in the constant speed control region.

  First, when the image reading operation is not performed, the CPU 414 outputs a main scanning synchronization signal (MSYNC) having a predetermined period (t) to the LIS 106 as shown in FIG. On the other hand, the LIS 106 accumulates and converts the optical signal exposed during the main scanning synchronization signal period into an analog electric signal, and outputs the charge accumulated during the next main scanning synchronization signal period as an analog image signal (AIMG) for one main scanning. . For example, the diode array 1061 accumulates the charge during the period from the output timing of the previous MSYNC to the output timing of the next MSYNC. Then, when MSYNC at timing 503 is output in the reading operation section, the diode array 1061 outputs the accumulated charge to the register 1062. Then, the charge output to the register 1062 starts output (transfer) to the amplifier 404 in synchronization with MSYNC. In this output process, the output signal is output to the amplifier 404 via the output unit 1063 based on a clock signal for output (transfer). Here, the analog image signal (AIMG) output at the timing 504 is a signal corresponding to the timing 502 of the LEDR. When the reading operation is not performed, the light source LEDs 202 to 204 are turned off. Therefore, as shown by the shaded analog image signal (AIMG) in FIG. 5, the analog image signals (AIMG0, AIMG1, AIMG2) output from the LIS 106 are almost zero (full black).

  The CPU 414 controls the driving of the DC motor 105 via the motor driver 420 and moves the LIS 106 relative to the image original 108. At this time, prior to the image reading operation, counting of signal pulses from the rotary encoder sensor 107 is started when a signal from the home position sensor 109 is detected. When the count value of the signal pulse from the rotary encoder sensor 107 that has started counting reaches a predetermined numerical value (that is, when it reaches a predetermined reading start position), the reading operation is started.

  As shown in FIG. 5, for example, when the count value of the pulse signal (REPLS) reaches a predetermined count value immediately before timing 501, a read command (RCMD) is issued at timing 500. Next, image reading is started at timing 501, and in synchronization with the pulse signal (REPLS), the reading light source lighting signal (LEDR) is output for a predetermined period (t 1) at timing 502, and then the main scanning synchronization signal (MSYNC). ) Is output at timing 503. That is, the CPU 414 performs control to output the main scanning synchronization signal (MSYNC) after time t1 with the pulse signal (REPLS) as a trigger. Following the output of the main scanning synchronization signal (MSYNC), an analog image signal (AIMG) is output at a timing 504 for a period (t2). Referring to FIG. 15, the charge held in the period (t2) register 1602 is output via the output unit 1063 at the timing 504. Thereafter, the reading operation of each line is continuously performed in accordance with the output timings 505 and 506 of the pulse signal (REPLS). Normally, in order to perform continuous image reading, at least in the image reading operation section, the period (t) of the main scanning synchronization signal (MSYNC) is t ≧ t1 and t ≧ t2. Further, when the period of REPLS is tr, tr> t1.

  FIG. 6 is a time chart of each signal showing the image reading operation following FIG.

  In FIG. 6, the same reference symbols are used for the same signals as those shown in FIG. 5, and the same reference numerals are used for the same timing.

  FIG. 6A is an explanatory diagram when the interval between output pulses (REPLS) becomes longer. The time from the output timing 506 of the previous output pulse (REPLS) to the output timing 508 of the next output pulse (REPLS) is longer than the period (t) of the main scanning synchronization signal (MSYNC) in the non-reading operation section. . As a supplement, the timing from the output timing 506 of the previous output pulse (REPLS) to the output timing of the next output pulse (REPLS) is equal to the period (t) of the main scanning synchronization signal (MSYNC) in the non-reading operation section. 507. The timing at which the output pulse (REPLS) is actually output is timing 508 delayed by Δt. For this reason, the reading light source lighting signal (LEDR) output at the timing 515 shown in FIG. 6B is output with a delay of Δt from the timing 509 indicated by the broken line in FIG.

  Accordingly, as shown in FIG. 6B, the next output pulse (REPLS) from the rotary encoder sensor 107 is output at the timing 508, and in synchronization with this timing, the reading light source lighting signal (LEDR) and the main scanning are synchronized. A signal (MSYNC) is output. Then, an analog image signal (AIMG) is output at timing 516 in synchronization with the main scanning synchronization signal (MSYNC) output at timing 512. As described with reference to FIG. 6A, the REPLS output 508 is delayed by Δt from the timing 507, and therefore the timing 512 of the main scanning synchronization signal (MSYNC) is delayed by Δt from the timing 511.

  As described above, when the cycle of the output pulse (REPLS) from the rotary encoder sensor 107 becomes long, unlike the non-reading operation section, as shown by timings 510 and 512 in FIG. The period of the main scanning synchronization signal used for the fluctuates.

  Conversely, the cycle of the output pulse signal (REPLS) from the rotary encoder sensor 107 may be shortened due to the influence of servo control of the DC motor. In this case, as can be seen from the timing 505 in FIG. 5, the main scanning synchronization signal (MSYNC) is not output even if the pulse signal (REPLS) overlaps the output period of the analog image signal (AIMG). It does not affect the signal output. Therefore, the AIMG output process (t2) based on the previous MSYNC and the LEDR process (on period) based on the next MSYNC can be performed in parallel.

  On the other hand, in the conventional technique, 1601 is output from the diode array 1601 to the shift register 1602 in synchronization with the pulse signal (REPLS) of the rotary encoder sensor 107. Therefore, when the signal (REPLS) is generated during the output period of the analog image signal (AIMG), the analog image signal (AIMG) based on the current signal (REPLS) is output from the middle of the output period. In such processing, the output of the analog image signal (AIMG) in one scanning unit (one scanning) is not correctly performed.

  For this reason, in order to output the analog image signal (AIMG) in one scanning unit (one scanning), the moving speed of the line sensor is set assuming that the cycle of the output pulse signal (REPLS) is short. There is a need.

  That is, it is necessary to set the moving speed of the line sensor so as to satisfy the relationship of REPLS cycle (tr)> LEDR effective period (t1) + AIMG output period (t2). In such a conventional technique, the AIMG output process (t2) based on the previous MSYNC and the LEDR process (on period) based on the next MSYNC cannot be performed in parallel.

  As described with reference to FIG. 5, when the count value of the pulse signal (REPLS) from the rotary encoder sensor 107 reaches a predetermined value, a reading start command (RCMD) is internally issued. When the reading start command (RCMD) is issued, the LED of the LIS 106 is turned on for a certain period in accordance with the pulse signal from the rotary encoder sensor, and then the main scanning synchronization signal (MSYNC) is output and the analog image signal (AIMG) ) Is output. The analog image signal (AIMG) is amplified by an amplifier (AMP) 404, and the A / D converter 405 performs A / D conversion on the amplified electrical signal, for example, to convert digital image data of 16 bits per pixel. Output. Digital image data is subjected to image processing such as shading correction and γ conversion, and is stored in the buffer RAM 409.

  Next, the period (t) of the main scanning synchronization signal (MSYNC) of the LIS 106 during the image reading operation will be described.

  As can be seen from FIGS. 5 to 6, the period of the main scanning synchronization signal (MSYNC) used in the reading operation varies depending on the signal pulse from the rotary encoder sensor 107, and the variation range is t1 to t + t1, and the variation range is approximately t. Is equal to

  The upper limit (t + t1) of this fluctuation range will be described with reference to FIG.

  14, the same reference symbols are used for the same signals as in FIG. 6, and the same reference numerals are used for the same timing.

  FIG. 14 shows that the output timing (508) of the output pulse (REPLS) from the rotary encoder sensor 107 is output immediately before the timing 513 when the period (t) elapses from the timing 510 of the main scanning synchronization signal (MSYNC).

  In this case, since the lighting time of the reading light source lighting signal (LEDR) is t1, the main scanning synchronization signal (MSYNC) is at timing 512 when about time (t + t1) has elapsed from the output timing 510 of the main scanning synchronization signal (MSYNC). Is output. As described above, the period of the main scanning synchronization signal (MSYNC) is maximized when it is output immediately before the timing 513 when the period (t) elapses from the timing 510 of the main scanning synchronization signal (MSYNC).

  Basically, in the image reading operation, the reflected light from the light source irradiated on the image original or the transmitted light from the light source transmitted through the transparent original is photoelectrically converted. For this reason, if the lighting time of the light source is constant, fluctuations in the period of the main scanning synchronization signal (MSYNC) with respect to the read image can be almost ignored.

  However, when extremely high S / N is required, such as when reading a transparent document such as a negative film, the dark current component fluctuations of the LIS caused by fluctuations in the period of the main scanning synchronization signal (MSYNC) should be made as small as possible. Is required. In that case, it is necessary to suppress fluctuations in the period of the main scanning synchronization signal (MSYNC) as much as possible. As described above, since the fluctuation range of the period of the main scanning synchronization signal (MSYNC) is from t1 to t1 + t, the fluctuation range is substantially t.

  Basically, it is effective to make the period of the main scanning synchronization signal as small as possible. For this purpose, first, the period (T = t) of the main scanning synchronization signal (MSYNC) in the non-reading operation section is preferably made shorter than the lighting time (t1) of the reading light source lighting signal (LEDR) during the image reading operation (t1). <T1). On the other hand, in order to perform the reading operation normally in the reading operation section, the period of the main scanning synchronization signal (MSYNC) is set longer than the lighting time (t1) of the reading light source lighting signal (LEDR).

  Further, focusing on the period of the output pulse of the encoder, since the reading operation is normally performed, the time interval (tr) of the output pulse (REPLS) of the encoder and the lighting time of the reading light source lighting signal (LEDR) ( t1) satisfies the relationship t1 <tr. For this purpose, the resolution of the slit of the encoder and the moving speed of the line sensor are determined.

  Furthermore, since the analog image signal for one line of the LIS 106 is read even in the non-reading operation period, it is necessary to secure a time required for that purpose. That is, the condition of t ≧ t2 must be satisfied.

  FIG. 7 is a diagram for explaining a case where the period of the main scanning synchronization signal (MSYNC) is smaller than the period of the pulse signal (REPLS) from the rotary encoder sensor 107. FIG. 7 shows a case where there is a non-reading period between two reading periods. That is, based on the pulse signal (REPLS) 571, a reading light source lighting signal (LEDR) 572 is output, and further an analog image signal (AIMG) 574 is output. Thereafter, based on the pulse signal (REPLS) 579, a reading light source lighting signal (LEDR) 580 is output, and further an analog image signal (AIMG) 582 is output. Between these two signal processing sequences, the main scanning synchronization signal (MSYNC) is output twice (575, 577) at the period t. An analog image signal (AIMG) 576 is output based on the main scanning synchronization signal (MSYNC) 575, and an analog image signal (AIMG) 578 is output based on the main scanning synchronization signal (MSYNC) 577. In this manner, during the output processing of the analog image signals (AIMG) 574 and 582 read by turning on the light source, the read analog image signals (AIMG) 576 and 578 are output without turning on the light source.

  As an example of the sequence, FIG. 7 shows the timing of the movement of the LIS 106 in the constant velocity control region. In the case of FIG. 5, the moving speed of the LIS 106 is slower in the case of FIG. 7 than the moving speed of the LIS 106. For this reason, the time interval at which the reading process is executed by the LIS 106 is large. Therefore, during the period when the pulse signal (REPLS) is not input, the main scanning synchronization signal (MSYNC) is output without depending on the pulse signal (REPLS). Such signal output control is performed by the timing signal generation circuit 413. For example, when the timing signal generation circuit 413 detects the input of the pulse signal (REPLS) 571, it outputs MSYNC 573 after time t1. Further, control is performed so that MSYNC 575 is output after time t (t2 ≦ t), and MSYNC577 is output after time t. When the input of REPLS 579 is detected again, signal output is performed in the same order as described above. As described above, the timing signal generation circuit 413 can output signals having a plurality of cycles. If the timing signal generation circuit 413 detects the input of the REPLS 579 before outputting the MSYNC 577, the timing signal generation circuit 413 outputs the MSYNC 581 after t1 from the input of the REPLS 579. That is, the output of MSYNC based on REPLS is prioritized over the output of MSYNC in the period of time t. That is, if REPLS 579 is input before MSYNC 577 is output, MSYNC 577 is cancelled.

  Here, for the main scanning synchronization signal (MSYNC), the interval between MSYNC 573 and MSYNC 575 and the interval between MSYNC 575 and MSYNC 577 may be determined based on the period of the pulse signal (REPLS) (interval between 571 and 579) and the value of t2. . For example, it may be determined based on the moving speed of the LIS 106 and t2. With such a control configuration, even when the LIS 106 is moved at a low speed, an appropriate reading operation can be performed in synchronization with the position signal from the encoder. In addition, as an example of the sequence in FIG. 7, the constant speed control has been described for the movement of the LIS 106, but the present invention can also be applied to the acceleration control region and the deceleration control region. For example, the period of the pulse signal (REPLS) can be predicted by using the number of times the pulse signal (REPLS) is input and the speed information. For this reason, the output of the main scanning synchronization signal (MSYNC) may be controlled in accordance with the predicted cycle. Further, as an example of the sequence in FIG. 7, the number of outputs of the main scanning synchronization signal (MSYNC) with the period t is not limited to two.

  Therefore, according to the embodiment described above, in image reading, an image signal read by the LIS can be obtained in synchronization with each output of the pulse signal from the rotary encoder used for position detection of the LIS. Thereby, even if the speed fluctuation occurs in the movement of the optical unit incorporating the LIS, the image original can be read accurately reflecting the reading position.

  In the embodiment described above, when the image reading operation is not performed, the main scanning synchronization signal (MSYNC) is output at a constant period (t). However, the present invention is not limited to this. For example, as shown in FIG. 8, the LIS main scanning synchronization signal (MSYNC) may be output in accordance with the output of the pulse signal from the rotary encoder sensor even in the non-reading operation section. That is, in FIG. 8, the main scanning synchronization signal (MSYNC) is output at timings 921 and 922 in response to the pulse signal (REPLS) at timings 901 and 902 output in the non-reading operation section. At this time, a dummy analog image signal (AIMG) is output in synchronization with this signal. Note that the period after the pulse signal (REPLS) output at the timing 903 is a reading operation section, and as described above, the reading light source lighting signal (LEDR) is output at the timing 913 according to the pulse signal (REPLS). Subsequently, a main scanning synchronization signal (MSYNC) is output, and an analog image signal (AIMG) is output in synchronization with the signal.

  Alternatively, in the case of using an LIS in which it is not an indispensable condition to input the main scanning synchronization signal steadily according to the specifications of the apparatus, as shown in FIG. 9, the LIS main scanning synchronization signal (MSYNC) is used in the non-reading operation period. ) May not be output at all. That is, FIG. 9 shows that the main scanning synchronization signal is not output according to the pulse signal (REPLS) at the timings 901 and 902 output in the non-reading operation section.

  In the embodiment described above, the LED is turned on for a certain period in synchronization with the pulse signal from the rotary encoder, and then the main scanning synchronization signal is output and the analog image signal is output to execute the image reading operation. The present invention can be applied to an apparatus using a light source that cannot respond at high speed. In this case, the LIS exposure period control may be performed using the LIS electronic shutter function. Specifically, in the time charts of FIGS. 5 to 10, the reading light source lighting signal (LEDR) may be replaced with the LIS electronic shutter enable (shutter open) signal (SHUTEN). At the timing of reading, the SHUTEN signal is enabled (permitted).

  This embodiment will be described below.

  The operation principle of the linear image sensor is that the charge generated in the photodiode portion, which is a photoelectric conversion element, is accumulated in the charge accumulation portion for the period of the main scanning synchronization signal period, and the accumulated charge is transferred to the CCD portion and shifted pixel by pixel. Output. Some image sensors have a function of discharging charges generated in the photodiode portion without accumulating them in the charge accumulation portion. For this purpose, the linear image sensor includes a gate circuit that permits / inhibits charge accumulation. The amount of accumulated charge can be controlled by controlling the length of time for which the gate circuit is allowed. This control is performed by a SHUTEN signal described later.

  By using this function, charge can be accumulated only during a part of the main scanning synchronization signal period. By using this function, the exposure period of the linear image sensor can be controlled even in a reading apparatus using a light source that cannot respond at high speed, and the same effects as those in the above-described embodiment can be obtained.

  This will be specifically described with reference to the timing chart of FIG. The same reference symbols are used for the same signals as shown in FIG. 5, and the same reference numbers are used for the same timing.

  First, the CPU 414 maintains the reading light source lighting signal (LEDR) in a lighting state (high level) in advance and keeps the light output of the reading light source in a stable state (the light source is turned on while the linear sensor scans the reading range). ) When the reading operation is not performed, a main scanning synchronization signal (MSYNC) having a predetermined period is output to the linear image sensor 106 at a predetermined period t. The linear image sensor 106 accumulates and converts the optical signal exposed during this main scanning synchronization signal period into an analog electric signal, and outputs it as an analog image signal for one main scanning during the next main scanning synchronization signal period. However, when the reading operation is not performed, the SHUTEN signal for transferring the charge to the charge storage unit is disabled (prohibited). For this reason, the analog image signal output from the linear image sensor is zero (all black data) (AIMG0 indicated by halftone dots).

  The CPU 414 controls the driving of the DC motor 105 and moves the linear image sensor 106 and the read document relative to each other. At that time, counting of the sensor output signal of the rotary encoder 107 is started when the output signal of the home position sensor 109 is detected prior to the reading operation. Then, when the count value of the sensor output signal of the rotary encoder 107 that has started counting when the output of the home position sensor 109 is detected reaches a predetermined numerical value (when it reaches a predetermined reading start position), the reading operation is started.

  FIG. 13 is a time chart showing the rotary encoder sensor output (REPLS). When the count value of the output signal (REPLS) reaches a predetermined count value, reading is started at timing 501. Charges are accumulated for a predetermined period (t1) at timing 502 of a signal (SHUTEN) for accumulating charges in synchronization with timing 501. Thereafter, the main scanning synchronization signal (MSYNC) is output at timing 503, and then the analog image signal (AIMG) is output at timing 504. Similarly, the reading operation of each line is continuously performed according to the output of REPLS at timings 505 and 506.

  The above-described control is also applied to a case where three LEDs are provided as a reading light source as shown in FIGS. 3 to 4, and lighting of these LEDs is sequentially switched and time-division control is performed to read a color image. Can do.

  FIG. 10 is a time chart of various signals used when reading a color image original. As shown in FIG. 10, the red LED 202, the green LED 203, and the blue LED 204 are sequentially turned on in synchronization with the output of one pulse signal (REPLS) from the rotary encoder sensor. After these lighting operations are completed, the LIS main scanning synchronization signal (MSYNC) is sequentially output, and analog image signals of the respective color components are output in synchronization with this signal. Such an operation is performed continuously. Also in this case, as described above, the period fluctuation of the main scanning synchronization signal can be reduced by setting (t2 <) t <t1 in the non-reading operation section.

  In the non-reading section of the color image original, either of the following two controls may be executed.

  FIG. 11 is a time chart of various signals used when reading a color image original in a non-reading section. As shown in FIG. 11, according to this control, the output of the main scanning synchronization signal (MSYNC) is suppressed in the non-reading section.

  FIG. 12 is a time chart of various signals used when reading a color image original in a non-reading section. As shown in FIG. 12, according to this control, the main scanning synchronization signal (MSYNC) is output in synchronization with the output of the pulse signal (REPLS) from the rotary encoder sensor in the non-reading section.

  In the embodiment described above, a DC motor is used as a drive source for moving the optical unit, but the present invention is not limited to this. For example, a stepping motor may be used as the driving source, and a driving circuit for the stepping motor may be used as the motor driver.

  In the embodiment described above, the LIS image reading position is detected using the rotary encoder attached to the rotating shaft of the DC motor. However, the present invention is not limited to this. For example, a linear encoder that detects the position of the LIS itself may be used for the position detection, or an encoder that is attached to any one of a mechanism system that moves an optical unit incorporating the LIS may be used. Furthermore, in the case of an apparatus configured to read an image by moving an image original, a linear encoder or a rotary encoder attached to any of the moving mechanisms may be used. Thereby, the relative position of the image original and the image sensor can be detected.

  Further, in the embodiment described above, the image reading is performed using the LIS having the LED light source, but the present invention is not limited to this. For example, a CCD linear image sensor having a reading light source and a reduction optical mechanism may be used.

  In the embodiment described above, the pulse signal from the rotary encoder sensor is used as it is for generating the LIS main scanning synchronization signal, but the present invention is not limited to this. For example, a signal obtained by dividing or multiplying the pulse signal of the rotary encoder sensor can be used. As a result, it is possible to improve the accuracy of line density fluctuation in the sub-scanning direction when reading an image document and to read with a reading line density higher than the mechanical line density of the rotary encoder. Furthermore, in an apparatus having a plurality of reading modes, an optimal signal can be selected according to the selected reading mode by generating an original pulse signal or a divided or multiplied signal. The image sensor is not limited to a CCD image sensor, and may be applied to a CMOS image sensor.

1 is an external perspective view of a flat bed type image reading apparatus which is a typical embodiment of the present invention. FIG. 2 is a side sectional view showing an internal configuration of the image reading apparatus shown in FIG. 1. It is a sectional side view which shows the detailed structure of a linear image sensor unit. FIG. 2 is a block diagram illustrating a control configuration of the image reading apparatus illustrated in FIG. 1. It is a time chart of various signals for image reading synchronized with the rotary encoder sensor output during the image reading operation. It is a time chart of the various signals for image reading when the period of a rotary encoder sensor output becomes long. 6 is a timing chart when there is a non-reading section between a reading section and a reading section. It is a time chart which shows the production | generation control of the main scanning synchronizing signal in the non-reading area at the time of image reading operation. It is a time chart which shows another aspect of the production | generation control of the main scanning synchronizing signal in the non-reading area at the time of image reading operation. It is a time chart of various signals for image reading synchronized with the rotary encoder sensor output at the time of color image reading operation. It is a time chart which shows the production | generation control of the main scanning synchronizing signal in the non-reading area at the time of color image reading operation. It is a time chart which shows another aspect of the production | generation control of the main scanning synchronizing signal in the non-reading area at the time of color image reading operation. It is a time chart of various signals in another example for image reading synchronized with the rotary encoder sensor output at the time of image reading operation. It is a time chart explaining the fluctuation range of the period of a main scanning synchronizing signal (MSYNC). It is a block diagram which shows the function structure of a linear image sensor unit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Image reader 101 Optical unit 102 Circuit board 103 Belt (or wire)
104 Document glass 105 DC motor 106 LIS (linear image sensor)
107 Rotary encoder sensor 108 Document 108 Home position sensor 110 LCD
202 Red LED
203 Green LED
204 Blue LED
410 LCD backlight LED
413 Timing signal generation circuit 414 CPU
420 Motor driver for DC motor

Claims (17)

An image reading apparatus for reading an image recorded on a document,
Reading means for optically reading an image recorded on the original by irradiating the original with light from a light source;
Moving means for moving the reading means relative to the original;
Position signal generating means for outputting a position signal in accordance with movement of the reading means by the moving means;
Lighting control means for controlling the light source to light for a first period in synchronization with the position signal;
After the light source is turned on for the first period, a control signal for outputting an image signal of an image read by the reading unit is generated, and the image signal is output for a second period in synchronization with the control signal. And an output control means for controlling the image reading apparatus.   The image reading apparatus according to claim 1, wherein the reading unit is a linear image sensor having a plurality of pixels arranged in a direction perpendicular to a moving direction of the moving unit. The moving means is
A DC motor;
A motor driver for controlling the driving of the DC motor,
The image reading apparatus according to claim 1, wherein the position signal generation unit includes an encoder.   The image reading apparatus according to claim 1, wherein a moving speed of the reading unit is determined so that a period of the position signal is longer than the first period.   5. The image reading apparatus according to claim 1, wherein the lighting control unit and the output control unit are controlled so that the first period is longer than the second period. 6. .   The image reading apparatus according to claim 5, wherein a period of the control signal in a period when the original reading operation is not performed is shorter than a lighting time of the light source.   7. The period of the control signal in a period when the original reading operation is not performed is shorter than an output time of the image signal corresponding to one scan from the reading unit. Image reading device.   The image reading apparatus according to claim 1, wherein the light source is an LED.   The image reading apparatus according to claim 8, wherein the LEDs include a red LED, a green LED, and a blue LED.   The image reading apparatus according to claim 9, wherein the lighting control unit controls the red LED, the green LED, and the blue LED to sequentially light for a predetermined time in synchronization with the position signal. An image reading apparatus for reading an image recorded on a document,
A reading unit that includes a photoelectric conversion element array in which photoelectric conversion elements are arranged and a shift register, and optically reads an image recorded on the original by irradiating the original with light from a light source;
Moving means for moving the reading means relative to the original;
Position signal generating means for outputting a position signal in accordance with movement of the reading means by the moving means;
Lighting control means for controlling the light source to light for a first period in synchronization with the position signal;
After the light source is turned on for the first period, a timing signal is generated to transfer the charge accumulated in the photoelectric conversion element to the shift register. After the timing signal is generated, the shift register is turned on for a second period. And an output control means for controlling to output electric charge from the reading means. The output control means includes
The timing signal is generated after the first period has elapsed from the input of the position signal, and the timing signal is generated after the second period has elapsed after the generation of the timing signal. The image reading apparatus according to claim 11. The output control means includes
The timing signal is generated after the first period has elapsed from the input of the previous position signal until the next position signal is input after the input of the previous position signal, and the generation of the timing signal The image reading apparatus according to claim 11, wherein the timing signal is generated every time the second period elapses. The output control means includes
The image reading apparatus according to claim 11, wherein the timing signal is periodically generated at a time interval longer than the second period until lighting of the light source is permitted. An image reading apparatus for reading an image recorded on a document,
A reading unit that includes a photoelectric conversion element array in which photoelectric conversion elements are arranged and a shift register, and optically reads an image recorded on the original by irradiating the original with light from a light source;
Moving means for moving the reading means relative to the original;
Position signal generating means for outputting a position signal in accordance with movement of the reading means by the moving means;
Permission signal control means for generating a permission signal for allowing the photoelectric conversion element to accumulate charges in a first period in synchronization with the position signal in a state where the light source is turned on;
After the permission signal is generated for a first period, a timing signal is generated to transfer the charge accumulated in the photoelectric conversion element to the shift register. After the timing signal is generated, the shift register is turned on for a second period. And an output control means for controlling to output electric charges from the reading means. An image reading method for optically reading an image recorded on an original by irradiating the original with light from a light source using a reading unit including a photoelectric conversion element array in which photoelectric conversion elements are arranged and a shift register. ,
A moving step of moving the reading unit relative to the document;
A position signal generating step for outputting a position signal in accordance with the movement of the reading unit by the moving step;
A lighting control step for controlling the light source to light for a first period in synchronization with the position signal;
After the light source is turned on for the first period, a timing signal for transferring the charge accumulated in the photoelectric conversion element to the shift register is generated, and after the generation of the timing signal, the timing signal is passed through the shift register for a second period. And an output control step for controlling to output electric charges from the reading unit. An image reading method for optically reading an image recorded on an original by irradiating the original with light from a light source using a reading unit including a photoelectric conversion element array in which photoelectric conversion elements are arranged and a shift register. ,
A moving step of moving the reading unit relative to the document;
A position signal generating step for outputting a position signal in accordance with the movement of the reading unit by the moving step;
A permission signal control step for generating a permission signal for allowing the photoelectric conversion element to accumulate charges in a first period in synchronization with the position signal in a state where the light source is turned on;
After the permission signal is generated for the first period, a timing signal for transferring the charge accumulated in the photoelectric conversion element to the shift register is generated, and after the generation of the timing signal, the second period, An image reading method comprising: an output control step of controlling to output charges from the reading unit via a shift register.

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