JP2010004445A - Image reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reader capable of reading an image quickly as far as possible without reducing image quality. <P>SOLUTION: The image reader includes: an initial adjustment unit 35 for adjusting the charge accumulation time of a CCD linear sensor 26 so that light quantity on a reference white board becomes a target light quantity when the rate of change in the light quantity on the reference white board, which is read by the CCD linear sensor 26 after turning on a light source 21, is converged to a fixed range; and a document reading control unit 30 for allowing document reading operation after completing adjustment by the initial adjustment unit 35. When the document reading control unit 30 starts the document reading operation, the initial adjustment unit 35 reads the light quantity on the reference white board, and when a deviation from an average light quantity or a maximum light quantity after initial adjustment executed just before is a predetermined value or greater, readjusts the charge accumulation time of the CCD linear sensor 26 so that the light quantity on the reference white board becomes the target light quantity. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention includes a light source composed of a cold cathode tube that irradiates light on a document, a linear sensor that photoelectrically converts reflected light from the document, an amplification unit that amplifies an analog signal output from the linear sensor, and the amplification The present invention relates to an image reading apparatus including an A / D conversion unit that converts an analog signal amplified by a unit into a digital signal.

  The cold-cathode tube used as the light source of the image reading apparatus has a longer time to reach a stable light amount than other light sources such as halogen lamps, and the reading operation of the document is delayed when waiting until the stable light amount is reached. The problem is inherent.

  When such an image reading apparatus is incorporated in an image forming apparatus such as a copying machine, the first copy is delayed, so that the performance is lowered.

  Therefore, Patent Document 1 discloses a cold cathode tube, which is a light irradiation means, as an image reading apparatus capable of shortening the time for starting reading of an original document in a situation where the light source immediately after the apparatus is turned on is not sufficiently raised. Calculated by the time measuring means for measuring the elapsed time since the start-up, the light quantity calculating means for calculating the light quantity of the light irradiated on the document by the light irradiating means based on the measured elapsed time, and the light quantity calculating means A correction value calculating means for calculating a correction value of the digital signal based on the light quantity and the A / D converted digital signal, and the digital signal is corrected by the correction value calculated by the correction value calculating means. An image reading apparatus provided with γ correction means has been proposed.

JP 2007-214829 A

  In the image forming apparatus described in Patent Document 1 described above, an image reading operation can be performed immediately after the cold cathode tube is started up, but the amount of light is extremely low immediately after the cold cathode tube is started up. The image signal read by the linear sensor has an extremely poor S / N ratio, and even if the digital signal is corrected by the γ correction means, there is a possibility that appropriate image data cannot be obtained.

  In view of the above-described problems, an object of the present invention is to provide an image reading apparatus capable of reading an image as early as possible without causing deterioration in image quality.

  In order to achieve the above-described object, a first characteristic configuration of an image reading apparatus according to the present invention includes a light source formed of a cold cathode tube for irradiating a document with light as described in claim 1 of the claims. A linear sensor that photoelectrically converts reflected light from the original, an amplification unit that amplifies an analog signal output from the linear sensor, and an A / D conversion that converts the analog signal amplified by the amplification unit into a digital signal The image reading apparatus is configured to include a light source, and when the change rate of the light amount with respect to the reference white plate read by the linear sensor after the light source is turned on converges to a certain range, the light amount with respect to the reference white plate is An initial adjustment unit that adjusts the charge accumulation time of the linear sensor so as to obtain a target light amount, and a document reading control unit that allows a document reading operation after the adjustment by the initial adjustment unit is completed. The initial adjustment unit reads the light amount with respect to the reference white plate at the start of the document reading operation by the document reading control unit, and the deviation from the average light amount or the maximum light amount after the initial adjustment performed immediately before is greater than or equal to a predetermined value. The charge accumulation time of the linear sensor is adjusted again so that the amount of light with respect to the reference white plate becomes the target amount of light.

  According to the above-described configuration, the change rate of the light amount is constant even when the light amount of the reference white plate read by the linear sensor does not converge to a constant light amount in a situation where the light source of the image reading apparatus is not sufficiently raised. By adjusting the charge accumulation time of the linear sensor by the initial adjustment unit when it converges to the range so that the light amount with respect to the reference white plate read by the linear sensor becomes the target light amount, The time until the first copy is permitted by the document reading control unit can be shortened without causing a decrease. Further, the initial adjustment unit has a light amount with respect to the reference white plate read at the start of the document reading operation by the document reading control unit, even when the light amount is larger than the light amount when the initial adjustment is performed as the light source is turned on. The charge accumulation time of the linear sensor is again set so that the light amount with respect to the reference white plate becomes the target light amount when the deviation is a predetermined value or more compared with the average light amount or the maximum light amount with respect to the reference white plate executed immediately before. By adjusting, appropriate image data can be obtained without degrading the image quality.

  As described in claim 2, in the second feature configuration, in addition to the first feature configuration described above, after the initial adjustment by the initial adjustment unit is completed, the light source is turned off for a moment to perform shading correction. A shading correction unit for acquiring black data is provided.

  According to the above configuration, after completion of the initial adjustment by the initial adjustment unit and before reading the document, the black data for shading correction is obtained, and the light quantity variation in the main scanning direction of the light source and the linear sensor in the main scanning direction are acquired. Since sensitivity variation can be corrected, more appropriate image data can be obtained.

  As described above, according to the present invention, it is possible to provide an image reading apparatus capable of reading an image as early as possible without degrading image quality.

  The image reading apparatus according to the present invention will be described below.

  As shown in FIG. 1, a copying machine 100 includes an image reading apparatus 100, which is a so-called color scanner, and an image forming apparatus 200, which is a so-called monochrome printer, and an operation unit 90 provided with various operation keys and a liquid crystal display unit. It has.

  As shown in FIG. 2, the image reading apparatus 100 includes a document placing unit 10 that sets a document G, an image reading unit 20 that converts image information from the document G into electronic data and reads the image information, and an image reading unit 20. The document reading control unit 30 controls reading of the document G.

  The image forming apparatus 200 heats the toner image formed on the paper and the image forming unit 40 that forms and outputs a toner image on the paper based on the image data converted into electronic data by the image reading unit 20. A fixing unit 50 for fixing the paper to the paper, a transport unit 60 for transporting the paper, a plurality of paper feed cassettes 70 (70a, 70b) each containing a different size or type of paper, and a series of image forming processes. The image forming control unit 80 is configured.

First, the image reading apparatus 100 will be described in detail.
The document placing unit 10 is configured to set the document G between a contact glass 11 on which the document G is placed and a document cover 12 which is disposed on the upper surface of the contact glass 11 so as to be freely opened and closed.

  The image reading unit 20 includes a light source 21 formed of a cold cathode tube that irradiates light on the document G set on the image placement unit 10, a first mirror 22 that captures reflected light from the document G, and a second mirror 23. An optical system unit comprising a third mirror 24, a lens 25 for focusing the light beam from the third mirror 24, a CCD linear sensor 26 for reading the light beam focused by the lens 25, and the optical system. An optical system drive unit (not shown) is provided for reciprocally moving the unit between a position indicated by a solid line and a position indicated by a broken line. By the optical system unit drive unit, the optical system unit is configured to scan (sub-scan) the original G and read image information while keeping the optical path length from the original G to the CCD linear sensor 26 constant. .

  The CCD linear sensor 26 is a three-line CCD linear sensor including a light receiving portion in which color filters of R (RED), G (GREEN), and B (BLUE) are arranged, and a drive circuit 27 is connected to the CCD linear sensor 26. The drive circuit 27 photoelectrically converts the reflected light read by the CCD linear sensor 26 into an analog signal and transfers the analog signal to the document reading control unit 30.

  A reference white plate 28 is disposed along the main scanning direction of the light source 21 outside the document reading range of the contact glass 11.

  As shown in FIG. 3, the document reading control unit 30 is a control device such as a CPU 31, a ROM 32 storing a control program executed by the CPU 31, a RAM 33 used as a working area, and an image processing unit 34. Each is electrically connected via a bus such as an address bus, a data bus, and a control signal line.

  The CPU 31 controls the light emission of the light source 21 based on the control program and data stored in the ROM 32 and the RAM 33, the data stored in the initial adjustment unit 35 and the shading correction unit 36 mounted on the CPU 31, and the setting value of the control device. Each operation of the image reading apparatus 100 such as image processing in the image processing unit 34 is comprehensively controlled to read the original G.

  The CPU 31 is configured to be able to switch the reading mode of the CCD linear sensor 26 between a color mode and a monochrome mode by switching control of a transfer clock for transferring an analog signal from the drive circuit 27 to the image processing unit 34. In the color mode, the accumulated charge of each RGB component is transferred, and in the monochrome mode, the accumulated charge of only the G component is transferred.

As shown in FIG. 4, the initial adjustment unit 35 has a change rate ΔI / Δt of the light amount with respect to the reference white plate 28 read by the drive circuit 27 after the light source 21 is turned on, for example, 50 when the light source 21 sufficiently rises. The charge accumulation time T of the drive circuit 27 is adjusted so that the light amount becomes 100% when the change rate of the light amount becomes%. A time t _50% required until the amount of light with respect to the reference white plate 28 read by the driving circuit 27 reaches 50% of the constant amount of light is sufficiently shorter than a time t _100% required for the amount of light to rise 100%. The time until the reading control unit 30 allows the first copy of the original G can be shortened.

  The change rate ΔI / Δt of the light amount is not limited to the change rate at the time of 50% of the constant light amount, and may be any light amount that can obtain a predetermined S / N ratio even if it is less than that. Good. In the present invention, it is possible to make adjustment without depending on the charge accumulation time T of the CCD linear sensor 26 or the like by detecting that the amount of light has been reached based on the change rate of the light amount.

  Further, the initial adjustment unit 35 reads the light amount with respect to the reference white plate 28 at the start of the document reading operation by the document reading control unit 30, and the deviation from the light amount after the initial adjustment performed immediately before being stored in the RAM 33 is predetermined. When the value exceeds the value, the charge accumulation time T of the CCD linear sensor 26 is adjusted again so that the amount of light with respect to the reference white plate 28 becomes the target amount of light.

  The amount of light with respect to the reference white plate 28 read by the drive circuit 27 may be the maximum value or the average value among the output values of each pixel of the CCD linear sensor 26.

  The shading correction unit 36 acquires black data for shading correction when the CPU 31 turns off the light source 21 for a moment after completion of the initial adjustment by the initial adjustment unit 35, and is used as a reference when the operator instructs the reading of the original G. Reference white data is acquired based on the reflected light from the white plate 28, and shading correction is applied to the image data of the original G read based on the black data and the reference white data.

  The image processing unit 34 includes an amplification unit 341 and an A / D conversion unit 342. The amplification unit 341 amplifies an analog signal output from the drive circuit 27, and the A / D conversion unit 342 includes an amplification unit 341. The analog signal amplified by the above is converted into image data as an 8-bit digital signal of 256 gradations and sent to the RAM 33.

  The RAM 33 temporarily stores the reflected light from the reference white plate 28 and the document G, and sends the image data of the document G processed by the image processing unit 34 to the image forming unit 40 of the image forming apparatus 200.

  The document reading control unit 30 is electrically connected to an image forming control unit 80 of the image forming apparatus 200 described later.

Next, the image forming apparatus 200 will be described.
The image forming unit 40 is arranged in order along the rotation direction around the photoconductor 41 and an image carrier formed of a photoconductor 41 having a photoconductive layer formed on the surface of an aluminum tube, and the RAM 33 of the document reading control unit 30. A charging member 42 for charging the photosensitive member 41 based on the image data sent from the image forming unit, an exposure unit 43 for exposing the charged photosensitive member 41 to form an electrostatic latent image, and the formed electrostatic latent image. A developing unit 44 that electrostatically attaches toner to the toner, a transfer unit 45 that transfers the developed toner image onto the paper, and a toner that remains on the photoreceptor 41 after the toner image is transferred to the paper. And a neutralizing lamp 47 for reducing the residual potential on the surface of the photoreceptor 41 and making it uniform.

  The transfer unit 44 applies a high transfer bias voltage to a transfer roller 48 that is arranged so as to be parallel to the axis of the photoconductor 41, so that the transfer unit 44 is conveyed to a site where the photoconductor 41 and the transfer roller 48 are opposed to each other. The toner image formed on the photoconductor 41 is transferred to the paper sheet.

  The fixing unit 50 includes a fixing roller 51 provided with a heater for heating, and a pressure roller 52 disposed in pressure contact with the fixing roller 51, and heats the toner image formed on the sheet to fix it on the sheet. Let

  The transport unit 60 includes a plurality of transport rollers 61 provided in the transport path of the fed paper, a registration sensor 62 that detects the leading edge of the sheet before transfer, and a registration roller 63 for aligning the leading edge of the sheet. .

  The paper feed cassette 70 (70a, 70b) includes a paper feed roller 71 (71a, 71b) that feeds the paper stored therein, a transport roller 72 (92a, 72b) that transports the paper to the image forming unit 6, and a paper feed A stepping motor (not shown) for driving the roller 71 and the conveying roller 72 is provided.

  As shown in FIG. 3, the image formation control unit 80 includes a CPU 81, a ROM 82 storing a control program executed by the CPU 81 and control table data, and calculation data and control data for controlling each functional block. Is stored and functions as a storage unit, a battery-backed RAM 83, a control signal for a motor or the like incorporated in each functional block such as the image forming unit 40, an operation control unit (see FIG. An input / output interface (not shown) for inputting signals from the image reading apparatus 100 is provided, and is electrically connected to the document reading control unit 30 provided in the image reading apparatus 100 via a serial interface 84 for data communication.

  The image formation control unit 80 performs a predetermined control calculation based on an instruction input from the operation unit 90, image data of the original G sent from the RAM 33, and an input signal from a sensor incorporated in each functional block. Is executed to output a control signal for a load such as a motor or a heater incorporated in each functional block, thereby performing overall control of the image forming operation.

  The operation unit 90 includes various operation keys such as a power key, a start key, and a stop key, and a liquid crystal display unit that displays operation information, setting information, guidance information, and error information of the document reading apparatus 100 and the image forming apparatus 200. Yes. The document reading control unit 30 and the image formation control unit 80 execute various controls based on inputs from the operation unit 90.

  An image reading control process by the image reading apparatus 100 configured as described above will be described.

  As shown in FIG. 5, when the power of the copying machine 1 is turned on, the document reading control unit 30 turns on the light source 21 of the cold cathode tube (S1) and sets the reading by the CCD linear sensor 26 to the color mode ( S2), the amount of reflected light from the reference white plate 28 is detected (S3).

  Specifically, the reflected light from the reference white plate 28 read by the CCD linear sensor 26 is photoelectrically converted into an analog signal by the drive circuit 27 and output to the image processing unit 34. The analog signal is amplified by the amplification unit 341 of the image processing unit 34, converted to a digital signal by the A / D conversion unit 342, and stored in the RAM 33. Here, the charge accumulation time T of the drive circuit 27 and the gain by the amplification unit 341 are preset default values.

  The document reading control unit 30 determines whether the change rate ΔI / Δt of the amount of light with respect to the reference reflector 28 stored in the RAM 33 is 50% of the amount of light when the light source 21 is sufficiently raised. The light quantity detection by the linear sensor 26 is repeated (S4: NO). When the rate of change ΔI / Δt becomes the rate of change when it is 50% of the amount of light when the light source is sufficiently raised (S4: YES), the CCD linear sensor 26 reflects the reflected light from the reference white plate 28 at that time. The initial adjustment unit 35 adjusts the charge accumulation time T of the drive circuit 27 so that the light amount with respect to the reference white plate 28 becomes the target light amount (S6), and the RAM 33 The amount of light at the completion of the initial adjustment is stored (S8), and the initial adjustment is completed (S9).

  When the initial adjustment by the initial adjustment unit 35 is completed (S9), the CPU 31 turns off the light source 21 for a moment (S10), and the shading correction unit 36 acquires black data for shading correction (S11).

  After the shading correction unit 36 acquires the black data for shading correction, the CPU 31 turns on the light source 21 again (S12), and switches the reading by the CCD linear sensor 26 to the monochrome mode (S13). Thereafter, reading of the original G by the image reading apparatus 100 is permitted (S14).

  When the start switch is pressed by the operation unit 90 by the operator (S15), the CCD linear sensor 26 detects the amount of reflected light from the reference white plate 28 (S16). The initial adjustment unit 35 compares the light amount at the completion of the initial adjustment with the newly read light amount, and if the deviation is equal to or greater than a predetermined value (S17: NO), the light amount with respect to the reference white plate 28 becomes the target light amount. Then, the charge accumulation time T of the CCD linear sensor 26 is adjusted again (S18). If the deviation is less than or equal to a predetermined value (S17: YES), the charge accumulation time T at the completion of the initial adjustment is not adjusted.

  Thereafter, the shading correction unit 36 reads the amount of light with respect to the reference white plate 19 (S19), acquires reference white data for shading correction (S20), and the document reading control unit 30 starts reading the document G (S21).

  Reflected light from the original G is read by the CCD linear sensor 26, the reflected light is photoelectrically converted into an analog signal by the drive circuit 27, the analog signal is amplified by the amplifier 341, and the analog signal is amplified by the A / D converter 342. The signal is converted into image data as a digital signal. The shading correction unit 36 performs shading correction on the image data (S22), and the image data subjected to the shading correction is stored in the RAM 33 (S23).

  As described above, reading control of the image data of the original G is performed by the image reading apparatus 100. The image data stored in the RAM 33 is sent to the image forming unit 40 of the image forming apparatus 200, and the image forming apparatus 200 performs an image forming process based on the image data to form an image on a sheet.

  In the above-described embodiment, the configuration for reading the document G placed on the document placement unit 10 has been described. However, an automatic document feeder is provided above the document placement unit 10, and the document G is moved with respect to the light source 21. Alternatively, the reflected light may be read by the CCD linear sensor 26.

  In the above-described embodiment, the case where the image reading apparatus 100 is a color scanner and the image forming apparatus 200 is a monochrome printer has been described. However, the image reading apparatus may be a monochrome scanner, and the image forming apparatus is a color printer. There may be.

  In the above-described embodiment, the configuration in which the image reading apparatus 100 is mounted on the copying machine 1 and the image data of the original G read by the image reading apparatus 100 is printed by the image forming apparatus 200 has been described. The image reading apparatus is not limited to the one mounted on the machine, and the image data of the read document may be sent to a FAX or a personal computer.

  Each of the above-described embodiments is merely an example of the present invention, and the scope of the present invention is not limited by the description. The specific configuration of each part is appropriately selected within the scope of the effects of the present invention. It goes without saying that changes can be designed.

1 is a perspective view of a multi-function peripheral equipped with an image reading apparatus according to the present invention. Schematic diagram of a multifunction machine equipped with an image reading device according to the present invention. Explanatory diagram of main functional blocks Illustration of the light source startup, elapsed time, and light intensity Flow chart of image reading control

Explanation of symbols

1: Copying machine 10: Document placement unit 11: Contact glass 12: Document cover 20: Image reading unit 21: Light source 22: First mirror 23: Second mirror 24: Third mirror 25: Lens 26: CCD linear sensor 27 : Driving circuit 28: Reference white plate 30: Document reading control unit 31: CPU
32: ROM
33: RAM
34: Image processing unit 341: Amplifying unit 342: A / D conversion unit 35: Initial adjustment unit 36: Shading correction unit 40: Image forming unit 41: Photoconductor 42: Charging member 43: Exposure unit 44: Development unit 45: Transfer Unit 46: cleaner unit 47: static elimination lamp 48: transfer roller 50: fixing unit 51: fixing roller 52: pressure roller 60: transport unit 61: transport roller 62: registration sensor 63: registration roller 70a: paper feed cassette 70b: feeding Paper cassette 71a: paper feed roller 71b: paper feed roller 72a: transport roller 72b: transport roller 80: image formation control unit 81: CPU
82: ROM
83: RAM
84: Serial interface 90: Operation unit 100: Image reading apparatus 200: Image forming apparatus G: Document T: Charge accumulation time

Claims (2)

A light source composed of a cold cathode tube that irradiates light on the original, a linear sensor that photoelectrically converts reflected light from the original, an amplifying part that amplifies an analog signal output from the linear sensor, and amplified by the amplifying part An image reading apparatus configured to include an A / D conversion unit that converts an analog signal into a digital signal,
The charge accumulation time of the linear sensor is adjusted so that the amount of light with respect to the reference white plate becomes the target amount of light when the change rate of the amount of light with respect to the reference white plate read by the linear sensor converges within a certain range after the light source is turned on. An initial adjustment unit, and a document reading control unit that allows a document reading operation after the adjustment by the initial adjustment unit is completed,
The initial adjustment unit reads a light amount with respect to the reference white plate at the start of a document reading operation by the document reading control unit, and a deviation from an average light amount or a maximum light amount after the initial adjustment performed immediately before is equal to or greater than a predetermined value. In this case, the image reading apparatus is configured to adjust the charge accumulation time of the linear sensor again so that the amount of light with respect to the reference white plate becomes a target amount of light.   The image reading apparatus according to claim 1, further comprising a shading correction unit that obtains black data for shading correction by turning off the light source for a moment after completion of the initial adjustment by the initial adjustment unit.

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