JP2009239632A - Image reading apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reading apparatus capable of carrying out stable readout with keeping a corrected uniform light volume even when the light volume changes from an initial light volume of a light source. <P>SOLUTION: An image reading apparatus has: a light source that illuminates light to an original document; a lens body that collects the light from the light source reflected on a surface of the original document; a light receptor that carries out photoelectric conversion of the light focused by the lens body; a signal processor that carries out a signal processing to a signal obtained by photoelectric conversion at the light receptor by every line; a light source driving circuit having a variable voltage control terminal which changes a voltage and supplies power to the light source by a light source driving signal from the signal processor; and a counter that counts a signal by every line of the signal processor, and transmits a signal which gradually increases a voltage until when the count becomes a predetermined number of count, to the voltage variable control terminal. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image reading apparatus used for image reading and image identification, such as a copying machine and a financial terminal device.

  As a light source control of an image reading apparatus or the like that reads image information, for example, in FIG. 1 (see Patent Document 1) of Japanese Patent Laid-Open No. 8-70369, the maximum level of one line of the output signal of the linear image sensor 3 is clamped. 11 and the selection unit 12, the maximum output detection unit 14 recognizes the magnitude relationship between the maximum level and the predetermined value, and the maximum level and the predetermined value of the output signal of the linear image sensor 3 are determined based on the identified magnitude relationship. A contact image sensor that controls the light emission amount of the LED array 1 to be equal is disclosed.

  Further, in FIG. 1 of Japanese Patent Laid-Open No. 11-187200 (see Patent Document 2), the light source unit 11 is used to perform an appropriate reading operation promptly at the edge portion that changes from black to white immediately after activation of the light source. The first light amount larger than the normal second light amount is obtained during a predetermined period from the start of light emission or after a predetermined number or more of black lines continue until a predetermined period after the white line is read. An image reading apparatus is disclosed in which the light amount control means 8b controls the light source driving unit 12 so that the light source unit 11 emits light.

JP-A-8-70369 (FIG. 1)

Japanese Patent Laid-Open No. 11-187200 (FIG. 1)

  However, the one described in Patent Document 1 uses the maximum level read from the white original or the back plate as a white reference signal, and therefore, if the white original or the back plate is contaminated, the image reading is troubled. There was a problem.

  According to the method described in Patent Document 2, the current that flows through the light-emitting diode D is increased immediately after the start of reading, and then the current that flows through the light-emitting diode D is decreased and line control is performed. Since the current increases and decreases, there is a problem that it is difficult to ensure the image quality at the singular point where the current decreases.

  The present invention has been made to solve the above-described problems, and can perform stable reading while maintaining a uniform light amount corrected for light amount even when there is a change from the initial light amount of the light source. An object is to provide an apparatus.

  An image reading apparatus according to a first aspect of the present invention photoelectrically converts a light source that irradiates a document with light, a lens body that collects light from the light source reflected by the document surface, and light converged by the lens body. A light receiving unit, a signal processing unit that performs signal processing for each line on a signal photoelectrically converted by the light receiving unit, and a variable voltage control that supplies power by varying a voltage to the light source by a light source driving signal from the signal processing unit. A light source driving circuit having a terminal, and a counter that counts a signal for each line of the signal processing unit and sends a signal for gradually increasing the voltage to the voltage variable control terminal until a predetermined count number is reached. .

  According to a second aspect of the present invention, there is provided the image reading apparatus according to the first aspect, wherein the signal for each line inputted to the counter is a start signal.

  According to the image reading apparatus of the first aspect of the invention, the light quantity gradually decreases from the initial light quantity when the light source is initially turned on until the light quantity gradually decreases from the initial light quantity to a certain period, thereby causing the counter to hold the timer function, thereby gradually increasing the light quantity decrease in the predetermined period. It is possible to realize an image reading apparatus with high reading quality by making a uniform light quantity by compensating for the change in the variable potential.

  According to the image reading apparatus of the second aspect of the present invention, the start signal sent for each line is input to the counter and the count number is measured. Therefore, even when there are a plurality of types of light sources, the drive timing condition of the light source drive signal There is an effect that the number of counters can be set without depending on.

Embodiment 1 FIG.
Hereinafter, an image reading apparatus according to Embodiment 1 of the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional configuration diagram of the image reading apparatus according to the first embodiment. In FIG. 1, reference numeral 1 denotes an object to be irradiated (also referred to as an original) such as a document or a medium, 2 denotes a top plate that conveys and supports the object to be irradiated 1, 3 denotes a light guide that propagates light, and 3 a denotes a light guide 3. A light emitting unit (emission unit), 4 is a transmission body that allows light to pass through, 5 is a light irradiation unit for the irradiated object 1, 6 is a first mirror that reflects scattered light from the irradiation unit 5 in the sub-scanning direction, and 7 Is a concave first lens mirror (first lens) that receives reflected light from the first mirror 6, 8 is an aperture mirror that receives parallel light from the first lens 7, and 9 is reflected light from the aperture mirror 8. A concave second lens mirror (second lens) 10 for receiving light is shielded from the periphery, an opening provided on the surface of the aperture mirror 8, and a second mirror 11 for receiving and reflecting light from the second lens 9. It is.

  Reference numeral 12 denotes a photoelectric conversion circuit that receives reflected light from the second mirror 11 and performs photoelectric conversion, and a sensor IC (light receiving unit) having a MOS semiconductor configuration including its driving unit. Reference numeral 13 denotes a sensor substrate on which the sensor IC 12 is mounted. A signal processing unit (ASIC) that processes a signal photoelectrically converted by the sensor IC 12, 15 is an electronic component such as a capacitor / resistor mounted on the sensor substrate 13, and 16 is an object to be irradiated via the light guide 3. 1 is a light source for irradiating light to the irradiating unit 5, 17 is a minibus (bus bar) covered with a metal lead installed in the vicinity of the light source, 18 is a light source unit, and is a general term for an illuminating body including the light source 16 and the minibus 17, 19 It is a metal plate (heat radiating plate) that supports the light source unit 18. Reference numeral 20 denotes a housing that houses or holds the light guide 3, an optical system such as a lens or a mirror (also referred to as a lens body), the sensor substrate 13, and the light source unit 18. Reference numeral 21 denotes a transport pulley for transporting the irradiated object 1. The top plate 2 and the transport pulley 21 are usually installed outside the image reading device (also called CIS). In the drawings, the same reference numerals indicate the same or corresponding parts.

  FIG. 2 is an end cross-sectional configuration diagram of the image reading apparatus according to Embodiment 1 of the present invention. In FIG. 2, 22 is a burring hole for fixing the image reading apparatus and the system main body (not shown), 23 is a lens body composed of optical system parts, 23a is a first mirror 6, an aperture mirror 8 and a second mirror. A mirror system integrated unit 23b is formed by integrating and integrating the mirror 11, and a lens system integrated unit 23b is formed by integrating the first lens 7 and the second lens 9. The casing 20 stores or holds the lens body 23, the sensor substrate 13, and the optical unit 18 separately except for the ends.

  Except for the light source unit 18, the light guide 3, the sensor substrate 13, and the lens body 23 are configured to be inserted from the end of the CIS housing 20 in the main scanning direction. The lens body 23 is described as a telecentric optical system lens or mirror in the first embodiment, but may be replaced with a commercially available rod lens array or the like.

  FIG. 3 is an overall side view of the image reading apparatus according to Embodiment 1 of the present invention. In FIG. 3, 24 is a side plate for protecting the end of the CIS, and 25 is an input / output connector including a power supply system for driving the CIS.

  The light source unit 18 and the heat radiating plate 19 extend in the main scanning direction and are inserted from the side surfaces in the sub scanning direction. In the figure, the same reference numerals as those in FIG. 1 denote the same or corresponding parts.

  4 is an overall plan view of the image reading apparatus according to Embodiment 1 of the present invention. FIG. 5 is a plan view for explaining the internal structure of the light source unit 18 in which the light transmitting body 4 shown in FIG. 4 is removed and the light guide 3 and the lens body 23 are seen through, and 26 is the light source unit 18 and the sensor substrate 13. Is a light source terminal connection part that connects the two with a metal wire. In FIG. 5, 72 light sources 16 per unit (group) to be mounted on the unit 18 are mounted on one side in an array with a pitch of 4 or 2 mm. Further, the light source unit 18 is irradiated from both sides to the irradiation unit 5 via the light guide 3.

  FIG. 6 is a functional block diagram for explaining CIS driving. In FIG. 6, 40 is an amplifier that amplifies the signal photoelectrically converted by the sensor IC 12, 41 is an analog-to-digital converter (A / D converter) that performs analog-to-digital conversion on the amplified photoelectric conversion output, and 42 is RGB for each color. A signal processing circuit for signal processing of digital output, 43 is a RAM for storing image information of each color and data correction, 44 is a CPU for controlling signals of the signal processing circuit 42 and RAM 43, and 45 is for driving RGB LED power sources A light source driving circuit to be controlled. In the figure, the same reference numerals as those in FIG. 1 denote the same or corresponding parts.

  Next, the operation of CIS will be described. In FIG. 6, based on the system control signal (SYC) and the system clock signal (SCLK) from the system body, the clock signal (CLK) of the signal processing unit (ASIC) 14 and the start signal (SI) synchronized therewith are detected by the sensor IC 12. At this timing, a continuous analog signal (SO) of each pixel (n) is output from the sensor IC 12 for each reading line (m). For example, analog signals for 7200 pixels are sequentially output.

  The analog signal amplified by the amplifier 40 is A / D converted by the A / D converter 41 and converted into a digital signal. After the A / D conversion, the signal output of each pixel (bit) is subjected to shading correction and all bit correction. The signal processing circuit 42 performs processing. In this correction, the correction data is read out from the RAM 43 that stores correction data obtained by uniformizing the data read in advance with a reference test chart such as a white original, and a digital signal corresponding to the A / D converted image information is processed. By doing. Such a series of operations is performed under the control of the CPU 44. This correction data is for correcting the sensitivity variation between the elements of the sensor IC 12 and the non-uniformity of the light sources 16.

  FIG. 7 shows the CIS drive timing according to the first embodiment of the present invention. 6 and 7, the ASIC 14 turns on the light source lighting signal in conjunction with the CPU 44, and in response to this, the light source driving circuit 45 sequentially lights up by supplying power to each RGB light source 16 for a predetermined time. The RGB light source includes a red light source (R light source) having a wavelength of 630 nm, a green light source (G light source) having a wavelength of 525 nm, and a blue light source (B light source) having a wavelength of 475 nm.

  A start signal (SI) is sent for each reading line (one line) in synchronization with a clock signal (CLK) that is continuously driven, and a shift register of each element (pixel) that forms an RGB driving circuit inside the sensor IC 12. Are sequentially turned on, and the SO line to which the corresponding switch group is commonly connected is sequentially opened and closed to obtain RGB image information (image output) synchronized with CLK. This image output is an output of each image read and accumulated in the previous line. BLK (blanking) time is set for each color reading section of one line, and exposure time setting is varied. Therefore, in the BLK section, all SO lines are released.

  Next, analog signals (SO) that are sequentially output will be described with reference to FIGS. Scattered light as image information of the irradiated object 1 enters the first lens 7 arranged in an array via the first mirror 6. The light from each optical system arranged in an array is focused at the openings 10 of the aperture mirrors 8 arranged discretely, and the light emitted from the openings 10 is determined by the second lens 9 installed in the array. The sensor IC 12 at the focal position is incident as an inverted image via the second mirror 11. Analog signals (SO) are simultaneously output in three series for each RGB by a shift register provided in the drive circuit of the sensor IC 12 or a sequential switching signal. The analog signal (SO) processed by the signal processing circuit 42 is finally sent to the system main body as image signal data from the SIG (R, G, B) signal terminal.

  The RGB light source 16 is sequentially lit in RGB in the first embodiment. However, if the light receiving unit pixel (also referred to as a cell) of the sensor IC 12 is loaded with each color RGB filter, the RGB light source 16 is turned on at the same time and is pseudo white. It is good also as a light source.

  Next, light amount correction control of the light source 16 will be described. FIG. 8 is a diagram for explaining a change in the amount of LED light that occurs at the beginning when the light source is activated by a light source on / off signal such as RGB. The LED chip used for the light source 16 generally retains temperature characteristics in luminance characteristics, and the luminance tends to decrease at a higher temperature than at a low temperature. Particularly in the initial stage after LED activation (lighting), since the LED chip generates heat, the PN junction of the LED chip becomes high temperature, and the forward light voltage drop has a negative temperature coefficient, but the amount of light decreases.

  FIG. 9 is a diagram illustrating a light source driving circuit 45 that drives the light source 16 of the image reading apparatus according to the first embodiment of the present invention. In FIG. 9, 16R is a red light emitting chip, 16G is a green light emitting chip, 16B is a blue light emitting chip, 160 is a fixed chip-shaped limiting resistor, 160R is a limiting resistor for the red light emitting chip 16R, and 160G is a green light emitting chip. A limiting resistor 160B for the chip 16G is a limiting resistor for the blue light emitting chip 16B.

  Reference numeral 170 denotes a voltage variable unit that changes the voltage by digital control having a voltage variable control terminal (C) function of 10V to 12V, 180 denotes a driver circuit that drives each color light source by an LED drive signal sent from the ASIC 14, 190 denotes 1 A counter composed of a multi-stage D-type flip-flop circuit having a reset (R) and a latch (LA) function, and a start signal (SI) sent out for each line is inputted. The digital output of the counter 190 is converted into an analog voltage. A digital / analog converter (D / A converter) for conversion, 210 is a buffer circuit that is taken out from the higher branch output of the counter output resolution, 220 is a branched system control signal (SYC1), and the output of the buffer circuit 210 Is input and output to the latch (LA) of the counter 190 It is a verification circuit.

  Next, the operation of the light source driving circuit 45 will be described. With an effective reading width of 297 mm in the main scanning direction and an effective reading width of 420 mm in the sub-scanning direction such as an A3 size document, the CIS sensor IC 12 configured with a density of 600 DPI in the main scanning direction shown in the first embodiment has 7200 pixels in the main scanning direction. Are installed, and about 10,000 lines are scanned in the sub-scanning direction per document. When the conveyance speed is set to 0.3 ms / line, the reading time of one original is about 3 seconds. Accordingly, the RGB light sources 16 of the light sources 16 are driven with an average of 0.1 ms. As shown in FIG. 5, the light source 16 is composed of a plurality of groups of 72 LEDs connected in series on one side and supplies a driving current of 20 mA. Therefore, in the example of FIG. 9, there are 6 groups in the red light source (R light source). Yes, 0.12A LED current flows. There are 12 groups in the green light source (G light source) and the blue light source (B light source), and an LED current of 0.24 A flows.

  The counter 190 resets the circuit according to the drive instruction of the system control signal (SYC). When the CIS reading signal is started, one signal is input to the counter 190 for each line as the start signal (SI). Therefore, in the high-speed reading CIS driven at 0.3 ms / line, a counter capable of counting up to 8 bits can count about 0.076 seconds, and a counter capable of counting up to 15 bits can count about 10 seconds. Further, in a relatively low-speed reading CIS driven at 3 ms / line, a counter capable of counting up to 8 bits can count about 0.76 seconds, and a counter capable of counting up to 15 bits can count about 100 seconds.

  The digital signal output from the counter 190 is converted into an analog signal by the digital-analog converter (D / A) 200, and the resistance value of the variable resistor or the like is decreased by the voltage variable unit 170 with respect to the increasing count number, and the light source. The supply current for 16 is increased. In other words, a relatively low voltage is supplied to the light source 16 in the initial stage, and the voltage is gradually increased as time elapses. Alternatively, the output is fixed at the latch (LA) portion of the counter 190 using the buffer circuit 210 or the like as appropriate. The latch unit is also released from the latch state at reset by SYC1, which is a branch circuit of the system control signal (SYC).

  In the first embodiment, the sequential lighting method using the RGB light source 16 has been described. However, for monochrome reading, a monochromatic light source may be used, and similarly, a fluorescent light emitting monochromatic light source is used. A color reading light source may be replaced with an RGB light source, and a closed (loop) circuit configuration of the light source 16 that is simultaneously turned on / off may be used. The light source need not be limited to RGB, and a light source in which a plurality of colors are mixed or a light source having a different optical wavelength may be used in combination.

  In the first embodiment, the start signal (SI) is input to the counter 190 and counted. However, in order to control the light amount of the light source 16, the clock signal (CLK) or the system clock signal (SCLK) is used. You may divide and use. Further, although a multi-stage D-FF circuit is used for the counter, the same effect can be obtained by using another counter circuit or a timer circuit for measuring the number of counts.

  From the above, with respect to the light quantity that gradually decreases from the initial light quantity when the light source 16 is initially turned on to a certain period, it is possible to compensate the change in the variable potential that gradually increases the light quantity decrease for a predetermined period by holding the timer function in the counter 190. Thus, it is possible to realize an image reading apparatus capable of high quality reading with a uniform light quantity over a short period and a long period.

  In addition, by using a start signal (SI) as a signal input to the counter 190, the light amount is automatically corrected in a short time during high-speed reading, and the light amount is corrected in a long time during low-speed reading. There is no need to install a circuit, and a simple image reading apparatus with light amount correction that matches the reading environment can be obtained.

  Further, since the counter 190 counts using the start signal (SI), the light source drive signal and the start signal at the time of starting the light source are driven independently (indicated by td in FIG. 8). The counter 190 counts only the common start signal regardless of whether it is lit or simultaneously lit. Therefore, there is an effect that the counter can be used without changing the counter even if the type of light source or the drive timing is changed.

1 is a cross-sectional configuration diagram of an image reading apparatus according to Embodiment 1 of the present invention. 1 is an end cross-sectional configuration diagram of an image reading apparatus according to Embodiment 1 of the present invention; 1 is a side view of an image reading apparatus according to Embodiment 1 of the present invention. 1 is a plan view of an image reading apparatus according to Embodiment 1 of the present invention. It is internal structure explanatory drawing of the light source unit of the image reading apparatus by Embodiment 1 of this invention. 1 is a block diagram of an image reading apparatus according to Embodiment 1 of the present invention. It is a drive timing of the image reading apparatus by Embodiment 1 of this invention. It is a figure explaining the change of the LED light quantity which generate | occur | produces in the light source lighting initial stage. It is a figure explaining the light source drive circuit which drives the light source of the image reading apparatus by Embodiment 1 of this invention.

Explanation of symbols

1. ・ Irradiated object (original) 2. ・ Top plate 3. ・ Light guide 3a ・ ・ Ejecting part 4 ・ ・ Transmitter 5 ・ ・ Irradiating part 6 ・ ・ First mirror 7 ・ ・ First lens 8 ・ ・Aperture mirror 9 .. Second lens 10 .. Aperture 11 .. Second mirror 12 .. Sensor IC (light receiving portion photoelectric conversion circuit)
13 .... Sensor board 14 .... Signal processing IC (Signal processing part) 15 .... Electronic component 16 .... Light source 16R ... Red light source (R light source) 16G ... Green light source (G light source)
16B ... Blue light source (B light source)
17. ・ Mini bus (bus bar) 18. ・ Light source unit 19. ・ Heat sink (metal plate) 20. ・ Case 21. ・ Transport pulley 22 ・ ・ Burring hole 23 ・ ・ Lens body 23a ・ ・ Mirror system integrated unit 23b ..Lense system integrated unit 24..Side plate 25..Connector 26..Light source terminal connection 40..Amplifier 41..Analog / digital converter (A / D converter)
42..Signal processing circuit 43..RAM (random access memory)
44. ・ CPU (Central processor unit)
45 .. Light source drive circuit
160..Limiting resistor 170..Voltage variable part 180..Driver circuit 190..Counter (timer) 200..Digital analog converter (D / A converter)
210 .. Buffer circuit 220 .. Verification circuit (AND circuit)

Claims (2)

A light source that irradiates light on the document, a lens body that collects light from the light source reflected by the document surface, a light receiving unit that photoelectrically converts light converged by the lens body, and a photoelectric conversion performed by the light receiving unit A signal processing unit that processes a signal for each line, a light source driving circuit having a voltage variable control terminal that supplies power by changing a voltage to the light source by a light source driving signal from the signal processing unit, and the signal processing unit And a counter that sends a signal for gradually increasing the voltage to the voltage variable control terminal until a predetermined count is reached. The image reading apparatus according to claim 1, wherein the signal for each line input to the counter is a start signal.

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