JP2008131171A - Image reading apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reading apparatus that prevents an image from becoming uneven in luminance owing to strains etc., of a frame and a glass of the reader and can read the image as a stable image. <P>SOLUTION: The apparatus has a luminance value storage means for storing luminance values of an area of a reference document read by an image reading means in the form of luminance values of respective divided areas obtained by dividing the area by a predetermined number. Then an average luminance value is calculated from the luminance values of the respective divided areas stored in the luminance value storage means, and differences between the average luminance value and the luminance values of the respective divided areas are used as correction values to correct luminance values read by the respective divided areas in subsequent image read processing with the correction values. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image reading apparatus using an image sensor.

  In general, it is known that an image processing apparatus reads a document with an image input apparatus, converts it into an electrical signal, performs image processing on the signal, and then records it as an image with an output apparatus such as a laser printer. .

  An image signal obtained by a photoelectric conversion element such as a solid-state image pickup element used in such an image input device produces an image with a constant density due to non-uniformity of lamp illuminance, sensitivity variation between pixels of the photoelectric conversion element, and the like. Even if read, the signal levels are not the same.

  For such a phenomenon, conventionally, a white reference plate is provided near the original glass, and the obtained image signal is stored in a storage element such as SRAM, and the image signal is corrected based on this data.

  When storing in the storage element, data of a plurality of lines is added to each pixel and stored, and then an averaging process is performed to reduce data variation.

JP-A-7-28981

  However, this type of conventional method is effective for non-uniformity when the white reference plate is read, but when reading the document by moving the image sensor, the frame of the reading device or the platen glass is distorted For example, even if a document having a uniform density is read, the luminance of the read image data may not be uniform, and there is a possibility that the luminance varies greatly depending on the location.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image reading apparatus that can prevent a luminance of an image from becoming uneven due to distortion of a frame or glass of the reading apparatus and can read a stable image.

  According to a first aspect of the present invention, in the image reading apparatus having an image reading unit for reading an image, the luminance value of the area read from the reference original by the image reading unit is stored as the luminance value of each area divided into a predetermined number. A brightness value storage means for calculating an average brightness value from the brightness value of each divided area stored in the brightness value storage means, and correcting a difference between the average brightness value and the brightness value of each divided area; An image reading apparatus characterized in that a luminance value read for each area divided during the subsequent image reading process is corrected with the correction value.

  According to a second aspect of the present invention, in the image reading apparatus according to the first aspect, the reference document has a larger image density than the area read from the image reading means and a uniform image density in the entire area.

  As described above, a density reference object having a uniform density larger than the effective reading area of the platen glass of the reading apparatus is read in advance, and the read image data is stored in the storage device, and the average luminance of the data The difference between the value and the luminance value for each area is set as a correction value.

  Thereafter, when the image is read, a correction process is applied to each area of the image using the correction value, so that a stable image from which physical factors such as distortion of the platen glass are removed can be provided.

  Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a sectional view showing the structure of an image processing apparatus according to a first embodiment of the present invention.
Reference numeral 1 denotes a document feeding device as document feeding means, which feeds placed documents one by one or two consecutively to a predetermined position on the platen glass surface 2.

  Reference numeral 3 denotes a scanner including a lamp, a scanning mirror 5 and the like. When the scanner 3 is placed on the document table glass surface 2 by the document feeder 1, the scanner body is reciprocated in a predetermined direction. The original reflected light passes through the lens 8 via the scanning mirrors 5 to 7 and forms an image on the image sensor unit 9. The input reflected light is color-separated and converted into an electric signal, and various image processing is performed on the original reading signal.

  Reference numeral 10 denotes an exposure control unit constituted by a laser scanner, and a light beam modulated based on image data output from an image signal control unit 43 (see FIG. 3) of the controller unit CONT is a photosensitive drum 11 which is an image carrier. Irradiate.

  Reference numerals 12 and 13 denote developing units that visualize the electrostatic latent image formed on the photosensitive drum 11 with a developer (toner) of a predetermined color. Reference numerals 14 and 15 denote recording material stacking units, in which recording materials of a fixed size are stacked and stored, and are fed to a registration position by driving a feed roller, and the leading edge alignment timing with the image formed on the photosensitive drum 11 is adjusted. The paper is fed again in the picked state.

  A transfer separation charger 16 transfers the toner image developed on the photosensitive drum 11 onto a recording material, and then separates from the photosensitive drum 11 and is fixed by a fixing unit 17 via a conveyance belt. A paper discharge roller 18 discharges the recording material on which an image has been formed to a paper discharge tray 20. In 19, the conveyance direction of the recording material on which the image is formed by the direction flapper is switched between the paper discharge port and the internal conveyance path direction to prepare for the multiplex / double-side image formation process.

  FIG. 2 shows the CCD 31. In FIG. 2, 32 is a solid-state image sensor substrate, 33, 34, and 35 are solid-state image sensor arrays corresponding to R, G, and B colors, respectively, and solid-state image sensors 36 are arranged in an array.

  Reference numerals 37 and 38 denote intervals of the three-line array. Three-line sensor intervals corresponding to the three primary colors R (red), G (green), and B (blue) are determined with respect to the angle of view.

  FIG. 3 is a block diagram for explaining the circuit configuration of the controller unit CONT shown in FIG. 1. 45 is a CPU (central processing unit) circuit unit, which includes a ROM (read only memory) 46 and a RAM (random access memory). 47 is built in, and each part is controlled comprehensively based on the control program memorize | stored in ROM46.

  Reference numeral 41 denotes an automatic document feeder control unit that controls, for example, feeding the placed documents one by one or two consecutively to a predetermined position on the surface of the platen glass 2.

  Reference numeral 42 denotes an image reader which outputs an analog image signal which is constituted by the image sensor unit 9 and the like and subjected to color separation and photoelectric conversion to the image control circuit 43.

  A printer 44 drives the exposure control unit 10 based on the video signal output from the image control circuit 43 to irradiate the photosensitive drum 11 with a light beam. An operation panel 48 is provided with an operation panel having keys, a display and the like for setting a mode necessary for image formation.

  The image reading apparatus reads in advance the luminance value of an image having a size equal to or larger than the effective reading area of the reference document on the platen glass and having a uniform density, and temporarily stores the image data of the luminance value in the luminance value storage means. Next, the average brightness value is obtained by dividing the brightness value of the image data stored in the brightness value storage means by the number of areas obtained by dividing the overall brightness value as shown in FIG.

  Next, in order to obtain the correction value of the luminance value, the difference between the average luminance value and the luminance value of each divided area is obtained as shown in FIG.

  Then, the difference is set as a correction value for each area as shown in FIG. 6, and when the image is actually read, the correction value is corrected for each area for each area of the read image data. It is a thing.

  In the above embodiments, the reference document is described in units of regions divided by a predetermined number. However, the correction may be performed by reading the luminance value of each pixel in one pixel unit of the reference document.

  As a result, it is possible to prevent factors such as the luminance of the image becoming unstable due to physical factors such as distortion of the platen glass depending on the location, and provide a stable image.

1 is a cross-sectional view illustrating a structure of an image processing apparatus according to the present invention. The perspective view which showed the structure of CCD. The block diagram which shows the circuit structure of a controller part. The figure which shows the formula which calculates | requires the average luminance value of this invention, and each area | region of a reference original. The figure which shows the luminance value of each area | region at the time of calculating | requiring the correction value of each area | region of this invention. The figure which showed the correction value in each area | region of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Document feeder 2 Document glass surface 3 Lamp 4 Scanner 5, 6, 7 Scanning mirror 8 Lens 9 Image sensor part 10 Exposure control part 11 Photosensitive drum (image carrier)
12, 13 Developers 14, 15 Recording material stacking unit 16 Transfer separation charger 17 Fixing unit 18 Paper discharge roller 19 Direction flapper 20 Paper discharge tray 31 CCD
32 Solid-state imaging device substrate 33 Solid-state imaging array R
34 Solid-state imaging array G
35 Solid-state imaging array B
36 Solid-state image sensor 41 Automatic document feeder control unit 42 Image reader 43 Image signal control unit 44 Printer control unit 45 CPU circuit unit 46 ROM
47 RAM
48 Operation unit

Claims (2)

  An image reading apparatus including an image reading unit that reads an image, the image reading unit including a luminance value storage unit that stores a luminance value of an area read from a reference document by the image reading unit as a luminance value of each area divided into a predetermined number. The average luminance value is calculated from the luminance value of each divided area stored in the luminance value storage means, and the difference between the average luminance value and the luminance value of each divided area is used as a correction value, and the subsequent image reading An image reading apparatus, wherein a luminance value read for each area divided at the time of processing is corrected with the correction value.   The image reading apparatus according to claim 1, wherein the reference document is larger than an area read from the image reading unit and has a uniform image density in the entire area.

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