JP2006237802A - Document reader - Google Patents

Abstract

A plurality of (white) reference plates are provided, and appropriate (white) reference plate reading data is obtained by considering a plurality of (white) reference plate reading data for the same pixel.
Reflected light from a document is guided to a photoelectric conversion element array 11 through an optical system, and corresponds to the alignment direction of the photoelectric conversion element array 11 reading the document on a contact glass 2 (for shading correction). A reference plate 3, 3 'having a uniform density is installed on a part of the original surface, and image data of each element obtained by reading the reference plate is stored, and read data of the original is stored in a storage element. The calculation is performed for each corresponding pixel according to the image data of the reference plate. Having a plurality of reference plates of uniform density 3, 3 ', taking into account the plurality of reference plate data for the same pixel obtained from them, and calculating the reading data of the document using the data obtained by the consideration as the reference plate data To do.
[Selection] Figure 1

Description

  The present invention relates to a document reading apparatus using an image sensor such as a CCD.

  A second white member is provided on the first carriage and moved together with the first carriage. On the other hand, the second white member is always read by effective pixels other than the original reading of the image sensor, and the entire original image data at that time is sequentially calculated using the read value, thereby correcting the light amount fluctuation of the light source.

  FIG. 4 is a diagram showing an example of the configuration of a general document reading apparatus. In the figure, 1 is a pressure plate, 2 is a contact glass, 3 is a white reference plate, 4 is a first carriage, 5 is a second carriage, Is a light source lamp, 7 is a first mirror, 8 is a second mirror, 9 is a third mirror, 10 is a lens, 11 is a CCD, and photoelectrically converts an optical system such as the lens 10 and optical imaging as shown in the figure. There is a CCD 11 for reading a document on the contact glass 2. Further, the first carriage 4 having the light source lamp 6 and the first mirror 7, the second mirror 8, and the second carriage 5 having the third mirror 9 are moved to the right in the drawing by a motor (not shown). The entire original surface is scanned. Further, a white reference plate 3 for shading correction is provided at the right end (that is, the reading start side) on the document surface.

  FIG. 5 is a block circuit diagram of the document reading apparatus, which includes a CCD 11, a signal processing circuit 12, an A / D converter 13, a memory 14 for storing read data of the white reference plate 3, and a shading correction calculator 15. Yes.

  FIG. 6 is a diagram showing a state in which reflected light from the original is irradiated onto the light receiving surface of the CCD as the carriage moves. When the carriage is at the left end (that is, at the reading start side), light is emitted. Even if the axis center just overlaps (or is adjusted to overlap) with the CCD line sensor, if the carriage moves to the right to read the document, the center of the optical axis is relative to the CCD line sensor. It will shift. This is because the right angle accuracy of the second mirror 8 and the third mirror 9 is insufficient. The second and third mirrors are called roof mirrors and are designed to have an attachment angle of 90 degrees, but there is of course some tolerance. Also, the angle may vary depending on the location of the mirror surface, and the flatness may not be achieved. This also means that when viewed from the CCD, the reading position on the document surface is shifted as the carriage moves.

  FIG. 7 is a diagram showing the illuminance distribution LΦ in the carriage movement direction on the document surface. It has a peak value around a certain position LP, and decreases with increasing distance. That is, in addition to the light amount fluctuation of the lamp, the amount of light applied to the CCD changes depending on the movement of the carriage (that is, in the sub-scanning direction).

FIG. 8 is a graph showing the unevenness of the read value for the entire document surface when a document with a uniform density is read by a certain document reader. In this example, it can be seen that the reading value at the lower right of the document has decreased.
JP-A-6-225137

  In the above-described conventional technology, the white reference data at the end of the light source lamp is referred to detect the light amount fluctuation of the light source. However, the light amount at the end is not representative of the light amount of the entire light source. It is the same for both halogen lamps and fluorescent lamps (both hot and cold cathodes). The light intensity at the end is lower than that at the center, but the filament at the end is first heated immediately after lighting. The ratio is high. On the other hand, when a sufficient time has elapsed after lighting, the center portion also becomes high temperature, so the ratio of the end portions becomes low. Therefore, it is often unsuccessful to correct the total light amount with the information on the light amount at the edge.

  Further, in the above-described conventional technology, it is impossible to correct even reading unevenness in the sub-scanning direction other than the light amount fluctuation. This is because reading unevenness in the main scanning direction is corrected by shading correction by the white reference plate at the leading edge of the document surface, but it depends on the position of the document surface due to insufficient accuracy of the optical system, dirt on the mirror, white reference plate, etc. Unevenness cannot be corrected.

The present invention has been made in view of the above situation,
According to the first aspect of the present invention, a plurality of (white) reference plates are provided and appropriate (white) reference plate reading data can be obtained in consideration of a plurality of (white) reference plate reading data for the same pixel. The object is to enable more appropriate shading correction.

  In the invention of claim 2, the (white) reference plate is installed on both the start side and the end side of the document surface, and the (white) reference plate reading data on the start side and the end side are used between them. The purpose of this is to correct the reading unevenness in the sub-scanning direction of the original reading data.

  According to the invention of claim 3, by taking the average value of the same pixel for the (white) reference plate reading data on the start side and the end side, the reading unevenness in the sub-scanning direction is also corrected for the original reading data between them. It is intended to do.

  The invention according to claim 4 is a calculated value obtained in accordance with the reading position of the original for the white reference plate reading data on the start side and the end side, so that further sub-scanning is performed for the original reading data in between. The purpose is to correct the reading unevenness in the direction.

  Since the invention of claim 5 is adapted to the color image sensors of R, G, and B, it is an object to correct reading unevenness in the sub-scanning direction for each color.

  According to a first aspect of the present invention, there is provided a light source that irradiates a document surface, an optical system that guides reflected light from the document to a predetermined position, a photoelectric conversion element array disposed at a predetermined position, and each of the photoelectric conversion element arrays. An A / D converter that converts the analog image output of the pixel into a digital signal and a reference plate having a uniform density (for shading correction) corresponding to the arrangement direction of the photoelectric conversion element arrays are installed on a part of the document surface. The image data of each element obtained by reading the reference plate is stored, and the calculation is performed for each corresponding pixel by the image data of the reference plate stored in the storage element and the read data of the original. A plurality of uniform density reference plates, a function for taking into account a plurality of reference plate data for the same pixel obtained therefrom, and data obtained by such consideration as reference plate data Characterized by calculating the read data of the document to.

  According to a second aspect of the present invention, in the first aspect of the present invention, the plurality of reference plates are provided at least on both the start side and the end side of the document surface.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the function of considering a plurality of reference plate data for the same pixel is an average value of the corresponding pixels.

  According to a fourth aspect of the present invention, in the first or second aspect of the present invention, the function that takes into account a plurality of reference plate data for the same pixel is a calculated value obtained in accordance with the position corresponding to the read data of the document. It is characterized by that.

  A fifth aspect of the present invention is the color image sensor according to any one of the first to fourth aspects, wherein the photoelectric conversion element array is a color image sensor in which R, G, and B sensors are arranged at a certain interval. And

  According to the first aspect of the present invention, a plurality of (white) reference plates are provided, and appropriate (white) reference plate reading data can be obtained by considering a plurality of (white) reference plate reading data for the same pixel. More appropriate shading correction can be performed.

  According to the second aspect of the present invention, the (white) reference plate is provided on both the start side and the end side of the document surface, and the (white) reference plate reading data on the start side and the end side are used. However, uneven reading in the sub-scanning direction can be corrected for the original reading data.

  According to the invention of claim 3, by taking the average value of the same pixels for the (white) reference plate reading data on the start side and the end side, the reading unevenness in the sub-scanning direction is also obtained for the original reading data between them. It can be corrected.

  According to the fourth aspect of the present invention, since the calculated values obtained in accordance with the reading position of the document for the (white) reference plate reading data on the start side and the end side, the further reading is performed on the document reading data between them. Reading unevenness in the scanning direction can also be corrected.

  According to the invention of claim 5, since it is adapted to the color image sensors of R, G, B, it is possible to correct the reading unevenness in the sub-scanning direction for each color.

  FIG. 1 is a mechanism diagram for explaining an example of a document reading apparatus according to the present invention. In contrast to the conventional example shown in FIG. 4, a white reference plate 3 at the front end is also installed at the rear end 3 '. . FIG. 2 is a diagram showing an example of a circuit block diagram of the document reading apparatus according to the present invention. Compared with the conventional example of FIG. 5, a memory 14 'for storing read data of the rear white reference plate 3' and front and rear A calculator 16 is provided for calculating using the data 14, 14 'of the two white reference plates 3, 3'.

  Below, it demonstrates based on these figures. First, as in the conventional example, the white reference plate 3 at the front end is read prior to document reading, and the data after A / D conversion is stored in the front end memory 14. Next, the read data at the time of document reading is stored in a separately prepared memory for holding image data, but this is not particularly necessary as will be described later. When the document reading is completed, the white reference plate 3 'at the rear end is read and stored in the rear end memory 14'.

  Here, the optimum white reference data is calculated by the calculator 16 which calculates using the data of the two front and rear white reference plates 3 and 3 '. The optimum white reference data is, for example, an average value between the same pixels. According to the average value, for example, the unevenness of the read value in FIG. However, unevenness is created on the part where there is no unevenness at the tip.

  Therefore, a method for completely eliminating unevenness in all places will be described below. That is, since the document surface is between the leading edge and the trailing edge, the reading unevenness on the document surface should be within that range. For example, it has a linear inclination in the sub-scanning direction, or is obtained by a certain calculation formula. For example, the linear value is an average value of the leading edge and the trailing edge at a position exactly in the middle of the document surface, and a value obtained by dividing the leading edge 3 by the trailing edge 1 at a position that is a quarter of the leading edge.

In general, when the leading white data of the i-th pixel in the main scanning is Si, the trailing white data is Ei, and the optimal white data Mi for the Mth line from the leading edge is N, the total number of sub-scanning lines is N. Since it is divided into a front end M and a rear end (NM),
Mi = {M × Si + (N−M) × Ei} / N
It becomes. That is, white data to be used for shading correction is sequentially calculated in correspondence with the position in the sub-scanning direction. Since this calculation is an arithmetic operation, it does not spend much time, and the reading speed does not decrease due to this calculation. Thereby, it is possible to completely correct the reading unevenness of the original surface.

  In the above example, the optimum white data is calculated from the white data 14 and 14 'before and after reading the white reference plate 3' at the rear end. Although the data is stored, the memory has recently become cheaper, so that the original reading device has a frame memory for storing all image data not for the present invention but for image editing and processing. Since there are many, you may use this together. However, it is not particularly necessary in the present invention. For example, the rear end white data 14 'may be used in the most recent reading (especially when reading continuously). Then, as in the conventional example, real-time shading correction can be performed while reading a document.

  FIG. 3 is a configuration diagram of an optical system for reading a color original. In the color CCD 11, image sensors each having R, G, and B filters attached thereto are arranged in three rows, and each color is read. Since each line sensor is configured with an interval, the reading position at the same time is shifted for each color. This deviation of the reading position is corrected by a method called “inter-line correction”. However, as in the case where the line sensors are in a single row (that is, monochrome), unevenness in reading values in the sub-scanning direction due to optical axis deviation occurs. On the contrary, since there is a difference in reading position by the widths of R, G, and B, in FIG. 2, even if G is brought to the peak position by adjustment, for example, R and B are inclined away from the peak. Become. Since it is already inclined at the tip, naturally, if the carriage moves, the amount of change increases and the unevenness of the reading value in the sub-scanning direction also increases. In addition, since the degree of unevenness varies from color to color, white balance and hue are not matched, which significantly affects image quality. If the present invention is adapted to color reading, these can be solved immediately, but rather it can have a great effect in the case of color reading.

It is a mechanism figure of the apparatus of this invention. It is an example of the block diagram of the circuit of the apparatus of this invention. FIG. 3 is a configuration diagram of an optical system for reading a color document. It is a mechanism diagram of a general document reading apparatus. 2 is a block diagram of a circuit of a document reading device. FIG. It is a figure which shows a mode when the reflected light from a document is irradiated to the light-receiving surface of CCD when a carriage moves. It is a figure which shows the illumination intensity distribution of the carriage movement direction on a document surface. 6 is a graph showing unevenness of read values with respect to the entire document surface when a document having a uniform density is read by a document reading apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Pressure plate, 2 ... Contact glass, 3, 3 '... White reference board, 4 ... 1st carriage, 5 ... 2nd carriage, 6 ... Light source lamp, 7 ... 1st mirror, 8 ... 2nd mirror, 9 ... 1st 3 mirrors, 10 lenses, 11 CCDs, 12 signal processing circuits, 13 A / D converters, 14, 14 'memories, 15 shading correction calculators, 16 calculators.

Claims (5)

  A light source that illuminates the document surface, an optical system that guides reflected light from the document to a predetermined position, a photoelectric conversion element array disposed at a predetermined position, and an analog image output of each pixel from the photoelectric conversion element array An A / D converter for converting the signal, and a reference plate having a uniform density (for shading correction) corresponding to the arrangement direction of the photoelectric conversion element arrays, provided on a part of the document surface; A document reading device having a storage element for storing image data of each element obtained by reading a plate, and a function for performing calculation for each corresponding pixel by image data of a reference plate stored in the storage element. And a function for taking into account a plurality of reference plate data for the same pixel obtained from the plurality of uniform density reference plates, and reading data of an original using the data obtained by the consideration as reference plate data. Document reading apparatus characterized by computing the data.   2. The document reading apparatus according to claim 1, wherein a plurality of reference plates are provided at least on both the start side and the end side of the document surface.   3. The document reading apparatus according to claim 1, wherein the function of considering a plurality of reference plate data for the same pixel is an average value of the corresponding pixels.   3. The document reading apparatus according to claim 1, wherein the function of considering a plurality of reference plate data for the same pixel is a calculated value obtained in accordance with the position corresponding to the read data of the document.   5. The document reading apparatus according to claim 1, wherein the photoelectric conversion element array is a color image sensor in which R, G, and B sensors are arranged at a certain interval. 6.