JP2004112705A - Image reading device - Google Patents

Abstract

Provided is an image reading apparatus that can realize high quality of an output image using a reading sensor without increasing a memory between lines.
Data is output from four output buffers each having two lines of light-receiving element columns and two lines of analog shift registers. The two data output from one read light receiving element row can be converted into continuous read data by combining the data as needed, such as when forming an image. By outputting data alternately when outputting from the shift register of one read light receiving element row, continuous output data can be supplied. The image resolution in the main scanning direction of the data output from one reading element row is determined by the pitch of the light receiving elements of the reading element row and the magnification between the element row and the read image. On the other hand, the image resolution in the sub-scanning direction is determined by the light incident period of the light receiving element and the speed at which the read image scans.
[Selection] Fig. 9

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image reading device such as a scanner device, a digital copying device, a digital color copying device, a facsimile device, a color facsimile device, etc., provided with a line sensor in which light receiving elements for image reading are arranged in a line.
[0002]
[Prior art]
In recent years, technology has been developed to optically read images such as pictures and photographs with a contact line image sensor or CCD (charge coupled device) image sensor, and to convert the read electrical signals into digital information. A facsimile apparatus, an electronic copying apparatus, a multifunction apparatus, and the like using a scanner device equipped with a scanner have been widely used.
Along with this, technical development of a reading optical system in an image reading apparatus is also being performed. Various techniques of a reading optical system including the following patent documents are disclosed.
[Patent Document 1]
Japanese Patent No. 2985959 [0003]
Patent Literature 1 discloses an image sensor group in which a plurality of image sensor rows in which a plurality of image sensors are linearly arranged are arranged in parallel with each other, and each image sensor row is another image sensor row in the image sensor group. In the arrangement direction of the imaging elements, the imaging elements are arranged so as to be shifted from each other by a width smaller than the width of each imaging element, and further, the plurality of imaging element rows are individually arranged in a direction perpendicular to the arrangement direction of the imaging elements. There is disclosed a color imaging apparatus in which reading processing is speeded up by arranging at a pitch of an integer multiple of two times or more of the height of a color image.
[0004]
By the way, distribution of instruction information in monochrome paper information, such as drawings and maps, using a highlight color such as red in a scanner or a reading device of a copying machine is generally used as a means of transmitting smooth business instructions. It is being done.
In order to easily perform such a task, an apparatus has been developed which takes in color information in addition to taking in image information using a color reading sensor or a monochrome reading sensor.
[0005]
More specifically, in a color reading sensor, by using the color characteristics of a filter on a three-line CCD (charge coupled device), output is performed as R (red), G (green), and B (blue) video signals. It is carried out. By scanning three times using a one-line CCD and exchanging filters for each scan, R, G, and B can be sequentially output as video signals.
Then, monochrome image information and color information are extracted from the R, G, and B video signals, a plurality of scans are performed by the monochrome reading sensor, and the wavelength of the light source is changed for each scan. Color information other than information can be captured.
[0006]
It is necessary to improve the performance of the reading sensor in order to improve the productivity and achieve higher image quality of the output image.
Specifically, to improve productivity, it is required to increase the data transfer speed, and to achieve higher image quality of the output image, to improve the sensitivity of the sensor, and It is required to increase the number of pixels.
Here, a CCD used as a reading sensor will be described. In order to increase the transfer speed of the CCD, it can be realized by downsizing the pixel size.
[0007]
[Problems to be solved by the invention]
However, if the pixel size is reduced and the sensitivity is increased by decreasing the amount of incident light on the light receiving element, or the amount of incident light is increased, the S / N (signal to noise ratio) must be increased. ) The ratio is reduced, resulting in a reduced image quality.
Also, by increasing the number of CCD lines, a reading distance between lines (physical distance between lines) occurs, and a gap occurs between the image of the preceding reading line and the image of the following reading line. I do. A storage device is required to correct this deviation.
In addition, higher image quality can be realized by increasing the number of pixels of the reading sensor, but increasing the number of pixels increases the size of the semiconductor die and avoids cost reduction due to reduction in the number of silicon wafers and increase in yield. I can't.
SUMMARY OF THE INVENTION It is an object of the present invention to provide an inter-line memory of a reading sensor and an image reading apparatus capable of realizing high image quality without increasing the number of pixels.
[0008]
[Means for Solving the Problems]
According to the first aspect of the present invention, in the image reading apparatus, the reading optical system includes a plurality of two-dimensional light receiving sensor elements arranged two-dimensionally using one-dimensional light receiving sensor elements arranged one-dimensionally. The one-dimensional light receiving sensor element row is located at a distance x in the one-dimensional direction that satisfies the following conditional expression 1, and conditional expression 1 x = p × h ÷ i (where p: pixel interval based on a predetermined image resolution, h: The magnification on the light receiving sensor, i is an integer) The two-dimensional light receiving sensor element is located at an integral multiple of the interval y in the two-dimensional direction satisfying the following conditional expression 2, and conditional expression 2 y = q × h ÷ j (where q is a pixel interval based on a predetermined image resolution, h is a magnification on a light receiving sensor, and j is an integer) at least one of the two-dimensional light receiving sensor element rows is different from a two-dimensional light receiving sensor element row. What is different from the one-dimensional row position The above object is further achieved.
[0009]
According to a second aspect of the present invention, in the first aspect, the elements of the two-dimensional light receiving sensor element row or the filters of the two-dimensional light receiving sensor element row correspond to different wavelengths of light to achieve the object. To achieve.
According to a third aspect of the present invention, in the first or second aspect of the present invention, the two-dimensional light receiving sensor element array is one-dimensionally spaced at an interval obtained by equally dividing the one-dimensional direction interval x by the number n of element arrays. The above-mentioned object is achieved by being arranged in the direction.
According to a fourth aspect of the present invention, in the first, second, or third aspect, the two-dimensional light receiving sensor element row is any two colors of red, green, and blue, or The object is achieved by supporting all colors.
[0010]
According to a fifth aspect of the present invention, in the first, second, or third aspect, the light source for illuminating the original and the read area of the image of the original illuminated by the light source are provided. An optical element for guiding the two-dimensional light receiving sensor element row; and signal processing means for encoding an output signal of the two-dimensional light receiving sensor element row, wherein the optical element converts the image of the read area into the two-dimensional image. Scanning is performed using a light receiving sensor element row, and the signal processing means achieves the object by combining the two-dimensional light receiving sensor element row and an output signal from a different two-dimensional light receiving sensor element row.
[0011]
In the invention according to claim 6, in the invention according to claim 1, claim 2, claim 3, claim 4, or claim 5, when output information of the two-dimensional light receiving sensor element row is not required, The object is achieved by providing a state adjusting means for setting at least one of the two-dimensional light receiving sensor element rows to a stop state, a standby state, or a low speed state.
According to a seventh aspect of the present invention, in the invention of the sixth aspect, the state adjusting means stops a reference operation clock used in an image reading process, or lowers a frequency of the reference operation clock. The above-mentioned object is achieved by adjusting the state by using.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the image reading apparatus of the present invention will be described in detail with reference to FIGS.
FIG. 1 is a diagram illustrating a configuration of a line sensor according to the present embodiment in which light receiving elements are arranged in a line. Light receiving elements having filters of R (red), G (green), and B (blue), which are three primary colors of light, are linearly arranged in three rows and parallel to the main scanning direction. The columns are defined so as to be equally spaced depending on the pixel size.
By moving the image at a constant speed in the vertical direction (hereinafter, referred to as the sub-scanning direction) with respect to this column, it is possible to read a planar image with uniform resolution.
The movement of the normal image includes a movement of the read image and a movement of the light receiving element. Further, the pixel size and the column interval of the light receiving element generally correspond to the reduction optical system and the equal-magnification optical system.
In one line of the light receiving element row corresponding to the RGB filter or RGB, the light receiving elements are arranged between the elements of the other two light receiving element rows.
[0013]
FIG. 2 is a diagram showing a configuration of a line sensor according to the present embodiment in which the rows of light receiving elements are arranged differently.
The light receiving elements shown in FIG. 2 are arranged such that the intervals between the light receiving elements are equal. With this arrangement, it is possible to suppress the occurrence of streak-like image unevenness in the sub-scanning direction of the read data due to an error in the arrangement of the light receiving elements.
[0014]
Next, an image reading process in the image reading apparatus according to the present embodiment from when the light receiving element receives a signal to when data is output will be described. .
The reduction type image sensor (reading element) used in the image reading apparatus can be classified into a CCD type, a MOS (metal oxide semiconductor) type, and a bipolar type. It will be described using FIG.
FIG. 3 is a diagram showing the arrangement of the light receiving elements of the CCD.
The image forming apparatus according to the present embodiment uses a sensor in which windows of R and G light receiving elements are arranged as shown in FIG.
[0015]
Next, an embodiment of the reading optical system will be described.
FIG. 4 is a diagram showing a schematic configuration of the reduction reading optical system.
In this reduced reading optical system, the original 42 on the contact 41 is imaged on the sensor 44 through the lens 43. Here, the image formed on the sensor 44 can be enlarged or reduced by moving the lens 43.
The light source 45 illuminates the original, and uses a fluorescent lamp, a xenon lamp, a halogen lamp, or the like.
[0016]
FIG. 5 is a diagram showing a schematic configuration of the original moving reading optical system.
In this document moving reading optical system, a document 53 is transported between a white roller 51 and a contact 52, and an image illuminated by a light source 54 is formed on a 1 × sensor 56 by a 1 × lens 55.
FIG. 6 is a diagram showing a schematic configuration of the sensor movement reading optical system.
In this sensor movement reading optical system, a moving body 63 on which a 1 × sensor 61 and a light source 62 are mounted is moved to form an image of a document 65 on a contact 64 illuminated by the light source 62 onto the 1 × sensor 61. I have.
[0017]
FIG. 7 is a diagram showing a schematic configuration of an original platen moving reading optical system.
The contact 72 on which the original 71 is mounted is moved, and the image illuminated by the light source 73 is formed on the sensor 75 by the equal-magnification lens 74.
FIG. 8 is a diagram showing a schematic configuration of a mirror movement reading optical system.
In this mirror movement reading optical system, scanning is performed by moving the first traveling body 83 and the second traveling body 84 with the lens 81 and the sensor 82 fixed to the apparatus main body.
[0018]
In the reading optical system as described above, the light receiving element accumulates electric charges according to the received light amount. The accumulated charges are transferred to the analog shift register at one time via the shift gate. The analog shift register shifts the charge in synchronization with the clock and outputs data via the output buffer.
FIG. 9 is a diagram illustrating an example of an output buffer to which data is output.
As shown in FIG. 9, there are four output buffers each having two rows of analog shift registers for the two lines of light receiving element rows, from which data is output.
The two data output from one read light receiving element row can be converted into continuous read data by combining the data as needed, such as when forming an image. In addition, when outputting data from the shift register of one read light receiving element array, continuous output data can be supplied by alternately outputting data. Usually, in order to lower the operating frequency of the transmission circuit, it is often the case that only the necessary parts are combined. The same applies to the case where one line is separated into three or more lines.
[0019]
The image resolution in the main scanning direction of the data output from one read light receiving element row is determined by the pitch of the light receiving elements in the read light receiving element row and the magnification between the element row and the image to be read.
On the other hand, the image resolution in the sub-scanning direction includes a light incident period of the light receiving element (a period during which the light is converted into an electric charge in the light receiving unit, a period from the start of the accumulation to the transfer to the analog shift register), and the scanned image is scanned. Determined from speed.
Therefore, the pixel pitch in the main scanning direction is defined by the element pitch of the sensor, but the pixel pitch in the sub-scanning direction is defined by the light incident period and the scanning speed. A desired image resolution can be achieved by performing any processing of minimizing the length in the sub-scanning direction.
[0020]
The resolution on the read image is usually expressed in dpi (dot per inch) and is defined by the number of pixels in one inch. In addition, since the resolution is distinguished from the apparent resolution in the image processing, the real may be described as a real 1200 prefix using the prefix. Some facsimile machines are defined by the number of lines within 1 mm, such as the number of lines / mm.
When handling the images of the line sensors as shown in FIG. 9, the images of the two line sensors include a shift in the pixel row in the main scanning direction and a shift in the line row in the sub-scanning direction.
Since the shift in the main scanning direction is a shift between the pixel rows of the two line sensors, the shift on the sensor is defined by the pixel rows in the read image space. Accordingly, the deviation in the main scanning direction can be obtained in the same manner as in the case of obtaining the distance between the light receiving sensor elements from the pixel distance in the read image space.
[0021]
For example, if the required resolution is real 600 dpi and the magnification between the sensor and the read image is 0.125, the element spacing in the main scanning direction is
(1 inch @ 600 dpi x 25.4 mm) x 0.125
Gives about 5.29 μm.
Therefore, the deviation in the main scanning direction is about 2.645 on the sensor.
The shift in the sub-scanning direction can be obtained in the same manner.
Further, with respect to a shift in the sub-scanning direction, the pixel interval in the read image space is multiplied by an integer so that when the images of the two line sensors are combined in the read image space, the images are shifted in units of the number of lines. Therefore, there is an advantage that the memory space can be reduced.
For example, when the pixel interval is 42.3 μm and the line interval is 21.15 μm, the read image is doubled in the sub-scanning direction, and the distance between the lines is apparently handled as one line, and the read image is treated as one line. Since the images are synthesized after being shifted, a memory for expanding the sub-scanning direction by a factor of two is required. However, when the distance between the lines is 42.3 μm, it is only necessary to shift and compose the image by one line, so it is only necessary to increase the memory by one line.
[0022]
When each image is output separately, a shift is dealt with according to the output. For example, in the image read by the preceding line sensor and the image read by the subsequent line sensor, the line interval is different by the line interval of the read image space between the line sensors, so in the sub-scanning image tip registration, When the preceding line sensor is used as a reference, it is necessary to shorten the image tip registration of the following line sensor by the line interval.
In addition, regarding the leading edge image of the main scan, it is necessary to correct the deviation of the pixel row in the read image space between the image read by the preceding line sensor and the image read by the subsequent line sensor.
Further, when synthesizing the respective output images, it is necessary to perform the synthesizing process so as to correspond to the deviation of each pixel column.
[0023]
As a method of coping with the main scanning direction, when a half of the pixel pitch in the main scanning direction in the read image space is shifted, the memory space in the main scanning direction is doubled, and the two images are respectively extended in the main scanning direction. At this time, interpolation of the expanded data is performed using a simple increase or a simple decrease, an adjacent pixel averaging method, or the like.
Further, in order to extend the main scanning direction twice, the deviation of half the pixel pitch is also extended in units of one pixel. Here, the physical image resolution in the main scanning direction can be almost doubled by synthesizing the image by the displacement of the line sensor by one pixel. Specific synthesis methods include and synthesis, or synthesis, conditional or synthesis, and the like.
The conversion from the three primary colors of R, G, and B light to the three primary colors of Y (yellow), M (magenta), C (cyan), and K (black) can be similarly performed.
[0024]
On the other hand, as a method of responding in the sub-scanning direction, when the read pixel pitch in the sub-scan direction in the read image space is an integral multiple of the pixel pitch of a desired resolution, it is only necessary to shift and combine the two line sensors. Good. Specific synthesis methods include and synthesis, or synthesis, conditional or synthesis, and the like.
When the read pixel pitch in the sub-scanning direction is an integral multiple of half of the desired pixel pitch, the memory space in the sub-scanning direction is doubled as in the main scanning, and the two images are respectively shifted in the sub-scanning direction. Expand. At this time, interpolation of the expanded data is performed using a simple increase or a simple decrease, an adjacent pixel averaging method, or the like.
Further, in order to double the sub-scanning direction, the deviation of half the pixel pitch is also expanded to one pixel. Here, by synthesizing an image corresponding to the displacement of the two line sensors by the required number of lines, the physical image resolution in the sub-scanning direction can be almost doubled.
Further, at this time, the physical image resolution can be increased by shortening the light incident period or the opening in the sub-scanning direction of the light receiving sensor element to reduce the overlap between the line sensors.
[0025]
When synthesizing the output of the reading device provided with R, G, and B as the filter of the light receiving sensor element, the output level differs depending on each filter. The same applies to the case where the read image is black and white. However, since black is output to all of R, G and B, the output level can be made uniform by performing shading correction for the black level and white level. . Therefore, high-resolution image data can be extracted by using the image after the shading correction.
For example, when the read image data is considered to be simply luminance data, the luminance data after shading of a single color having sensitivity to the light receiving sensor element is uniform regardless of the color sensitivity of the light receiving sensor element. Here, since the color tone differs depending on the color of the read image and the color sensitivity of the light receiving sensor element, the resolution of the halftone by shading also differs. Therefore, at the time of halftone synthesis, smoothing processing for equalizing the resolution is performed.
[0026]
【The invention's effect】
According to the first aspect of the invention, by forming the two-dimensional light receiving sensor element array using the one-dimensionally arranged light receiving sensor elements, the reading resolution in the main scanning direction can be increased.
According to the second aspect of the present invention, the reading resolution in the main scanning direction is increased by making the elements of the two-dimensional light receiving sensor element row or the filters of the two-dimensional light receiving sensor element row correspond to different wavelengths of light. Can be.
According to the third aspect of the present invention, by disposing the two-dimensional light receiving sensor element rows at an interval obtained by equally dividing the one-dimensional direction x by the number of element rows n, it is possible to output an image without unevenness in the main scanning direction. Can be.
According to the fourth aspect of the present invention, a high-quality monochrome image can be provided by associating the two-dimensional light receiving sensor element array with the three primary colors of light, red, green, and blue.
[0027]
According to the fifth aspect of the invention, by synthesizing the output signals of the two-dimensional light receiving sensor element array, it is possible to provide a high-quality monochrome image without requiring a complicated configuration.
According to the sixth aspect of the present invention, the provision of the state adjusting means makes it possible to reduce energy consumption when output information of the two-dimensional light receiving sensor element array is not required.
According to the seventh aspect of the invention, the electric field intensity noise can be reduced by stopping the reference operation clock used in the image reading process or decreasing the frequency of the reference operation clock.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a line sensor according to an embodiment in which light receiving elements are arranged in a line.
FIG. 2 is a diagram showing a configuration of a line sensor according to the present embodiment in which light receiving elements are arranged in different rows.
FIG. 3 is a diagram showing an array of light receiving elements of a CCD.
FIG. 4 is a diagram showing a schematic configuration of a reduction reading optical system.
FIG. 5 is a diagram showing a schematic configuration of an original moving reading optical system.
FIG. 6 is a diagram showing a schematic configuration of a sensor movement reading optical system.
FIG. 7 is a diagram showing a schematic configuration of an original platen moving reading optical system.
FIG. 8 is a diagram showing a schematic configuration of a mirror movement reading optical system.
FIG. 9 is a diagram illustrating an example of an output buffer to which data is output.
[Explanation of symbols]
41 contact 42 document 43 lens 44 sensor 45 light source 51 white roller 52 contact 53 document 54 light source 55 1: 1 lens 56 1: 1 sensor

Claims (7)

In an image reading apparatus, the reading optical system includes a plurality of two-dimensionally arranged two-dimensional light receiving sensor element arrays using one-dimensionally arranged one-dimensional light receiving sensor elements.
The one-dimensional light receiving sensor element row is located at an interval x in a one-dimensional direction that satisfies the following conditional expression 1,
Conditional expression 1 x = p × h ÷ i (where p: pixel interval based on a predetermined image resolution, h: magnification on the light receiving sensor, i: integer)
The two-dimensional light receiving sensor element is located at an integral multiple of the interval y in the two-dimensional direction that satisfies the following conditional expression 2:
Conditional expression 2 y = q × h ÷ j (q: pixel interval based on predetermined image resolution, h: magnification on light receiving sensor, j: integer)
An image reading apparatus, wherein at least one of the two-dimensional light receiving sensor element rows is different in a one-dimensional direction from a different two-dimensional light receiving sensor element row. 2. The image reading apparatus according to claim 1, wherein the elements of the two-dimensional light receiving sensor element row or the filters of the two-dimensional light receiving sensor element row correspond to different wavelengths of light. The said two-dimensional light receiving sensor element row | line is arrange | positioned in the one-dimensional direction by the space | interval which divided | segmented the space | interval x of the said one-dimensional direction to the number n of element rows, The Claims 1 or 2 characterized by the above-mentioned. Image reading device. The said two-dimensional light receiving sensor element row respond | corresponds to any two colors among red, green, and blue, or all colors, The Claim 1, Claim 2, or Claim 3 characterized by the above-mentioned. The image reading device according to claim 1. A light source for illuminating the original,
An optical element that guides a read area of the image of the document irradiated by the light source to the two-dimensional light receiving sensor element row;
Signal processing means for encoding an output signal of the two-dimensional light receiving sensor element row,
The optical element scans the image of the read area using the two-dimensional light receiving sensor element row,
4. The signal processing unit according to claim 1, wherein the two-dimensional light receiving sensor element row is combined with an output signal from a different two-dimensional light receiving sensor element row. Image reading device. When output information of the two-dimensional light receiving sensor element row is not required, a state adjusting means for setting at least one of the two-dimensional light receiving sensor element rows to a stop state, a standby state, or a low speed state is provided. The image reading device according to claim 1, 2, 3, 4, or 5, wherein 7. The image according to claim 6, wherein the state adjusting unit adjusts the state by stopping a reference operation clock used in an image reading process or decreasing a frequency of the reference operation clock. Reader.

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