JP2003189068A - Color image reader - Google Patents

Abstract

(57) [Problem] To provide a color image reading device capable of increasing a reading speed without deteriorating image quality. SOLUTION: A color light source driving circuit 113 controls a light source unit 112 such that a combination pattern of a plurality of color reading lines for each image line L is different for adjacent pixel lines and the combination pattern is periodic for each image line. Drive. Then, the scaling processing unit 14 (color line interpolating unit) applies the color (for example, red) on the reading line of a color not included in the image line L.
Is interpolated by a read line having the same color as the adjacent color.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image reading apparatus capable of increasing reading speed without degrading image quality.

[0002]

2. Description of the Related Art In general, an image reading apparatus irradiates an original moving relative to a one-dimensional line sensor with light from a color light source and detects reflected light from the original with the one-dimensional line sensor. Target. Normally, in this type of color image reading device, three light sources of red (R), green (G), and blue (B) are sequentially switched to read an original image, and R, G, and B reading lines are set. They are combined to create one image line. In this case, assuming that the reading speed depends on the light-emission time of the image sensor, the color reading is 3 times as much as the monochrome reading.
It takes twice as long, and the reading speed for color is 1/3 that for monochrome.

[0003]

In the color image reading apparatus, the reading speed can be increased by shortening the light accumulation time of the image sensor element (photo sensor). In order to shorten the light storage time, it is possible to use a light emitting element having a strong light emission intensity or a line sensor having a high light storing efficiency, but since these light emitting elements and line sensors are expensive, the reading device itself Manufacturing costs are also increased.

Further, in order to increase the reading speed, the reading width for each line is increased (the resolution in the sub-scanning direction is lowered). However, if the resolution is lowered, the image quality is inevitably deteriorated. .

An object of the present invention is to provide a color image reading apparatus which can increase the reading speed without degrading the image quality.

[0006]

The inventor has found that the same resolution is not required for the read lines of all colors when forming one image line from the image data read by the read lines of a plurality of colors. In view of the above, the present invention has been accomplished by finding that the reading speed can be increased by thinning the reading lines of a specific color according to the resolution required for the reading lines.

That is, the color image reading apparatus according to the first aspect of the present invention sequentially irradiates the original moving relative to the one-dimensional line sensor with light from a plurality of color light sources having different emission colors. Then, a color image is read by detecting the reflected light from the original document by the one-dimensional line sensor, and the combination pattern of read lines of a plurality of colors for each image line is different in adjacent pixel lines, and the combination pattern is And a color light source driving means for driving a color light source so as to be periodic with respect to an image line, and a color corresponding to a read line of a color not included in the image line is interpolated by a read line of the same color as the adjacent color. And a color line interpolating means for controlling the color line.

In the color image reading apparatus of the first aspect of the present invention, the plurality of color light sources are a red light source, a green light source,
The combination pattern of the reading line for each image line at the time of reading can be a combination of two lines of the red line, the green line, and the blue line.

In the color image reading apparatus according to the second aspect of the present invention, a document moving relatively to the one-dimensional line sensor is irradiated with light from a non-monochromatic light source through a color filter which is switched for each reading line. A color image is read by detecting reflected light from the original by the one-dimensional line sensor, and a combination pattern of filters used for reading a read line for each image line is different between adjacent pixel lines, and A filter driving unit that drives the filter so that the combination pattern is periodic for each image line, and a color that interpolates a line of a color not included in the image line by a read line of the same color as the adjacent color. And a line interpolating means.

In the color image reading apparatus of the second aspect, the plurality of filters include a red transmission filter, a green transmission filter, and a blue transmission filter, and a combination pattern of read lines for each image line is a red line, a green line, It can be a combination of two of the blue lines. Further, in the color image reading apparatus of the second aspect, the filter may be a rotary disc type filter provided in the light emitting section of the non-monochromatic light source.

The color image reading apparatus of the first and second aspects can be provided with a color space conversion means for converting the RGB color space data obtained by the line sensor into Y, Cr, Cb color space data. . In this case, the color light source driving means or the monochromatic light source driving means drives the combination pattern of the read color lines for each image line as a red line / green line, a blue line / green line, and the color line interpolating means, Red line /
RGB pixel lines are generated by performing blue interpolation for a combination pattern of green lines and red interpolation for a combination pattern of blue lines / green lines,
The color space conversion means can generate a YCrCb pixel line from the RGB pixel line after the interpolation.

[0012]

FIG. 1 is a block diagram showing an embodiment of a color image reading apparatus of the present invention. In FIG. 1, a color image reading device 1 includes a document image reading means 11
And A / D conversion means 12, γ conversion means 13, scaling processing means (corresponding to “color line interpolation means” in the present invention) 14, color coordinate conversion means 15, and storage means 16. . The color original reading device 1 can be applied to either a reduction optical system or a unity magnification optical system (contact image sensor).

The original image reading means 11 is, as shown in FIG. 2A, a line sensor (image sensor) 111.
A light source unit 112 and a color light source drive circuit 113
And a lens system 114, and the light source unit 112 includes a red (R) light source 1121 and a green (G) light source 1122.
And a blue (B) light source 1123 are incorporated.

The analog RGB outputs A (R), A (G), A (B) of the line sensor 111 are converted into digital RGB signals D (R), D (G), D by the A / D conversion means 12.
Is converted to (B). Digital RBG signal D (R), D
(G), D (B) are digital signals S (R '), S suitable for display on the display by the γ conversion means 13.
(G '), S (B'). Line sensor 11
Digital signals D (R), D sequentially extracted from one cell
(G), D (B) columns are read lines RL, GL, B
It is L. These reading lines RL, GL, BL are subjected to γ conversion or the like to create RGB image lines L.

In the conventional color image reading device, one image line L is read lines RL, G of three colors R, G, B.
It is created by combining the read signals of L and BL.
In the color image reading device 1 of the present embodiment, the color light source drive circuit 113 includes the three color reading lines RL, GL, and B.
The light source unit 112 is controlled so as not to drive one reading line number of L.

FIG. 3 shows an R light source lighting signal R_ON and a G light source lighting signal G_O output from the color light source driving circuit 113.
The relationship between the N and B light source signals B_ON, the line synchronization signal SY which is a drive timing signal for these signals, and the output signal LS of the line sensor 111 is shown. FIG. 3 also shows the time width LW corresponding to one image line width. In the present embodiment, the odd-numbered image lines are set to the green read line GL.
And the actual detection data of the blue read line BL and the interpolation calculation value of the red read line RL. Further, even-numbered image lines are created from the actual detection data of the green read line GL and the red read line RL and the interpolation calculation value of the blue read line BL.

Originally, the image lines are read lines RL, GL, B of three colors for each one image line.
Although it is created by synthesizing the data of L, in the present embodiment, the red read line RL does not exist for the odd-numbered image line and the blue read line BL exists for the even-numbered image line at the time of image reading. I haven't. The scaling processing unit 14 reads the red read line R for the odd-numbered image lines that does not exist at the time of reading.
L is interpolated using the actual detected read lines RL before and after (but not necessarily adjacent). Further, regarding the even-numbered image lines L, the blue read line BL that does not exist at the time of reading is interpolated by using the read lines BL actually detected before and after, as in the case of the red read line RL.

As an interpolation method (variable-magnification method), the closest method that simply enlarges (pads) or reduces (decimates) the original image,
Averaging method that performs linear interpolation from neighboring pixels, surrounding (eg, 8
It is possible to employ a bicubic method or the like, in which each pixel is multiplied by a specific coefficient to determine a pixel value. In this embodiment, one of the plurality of processing methods can be selected according to the original. For example, in the case of a manuscript image in which characters are emphasized, the process by the closest method or the process by the averaging method can be selected, and in the case of a manuscript image containing many photographs and paintings, the process can be selected by the bicubic method. .

The scaling processing means 14 has the digital signals D (R '), D (G'), D (B ') from the γ conversion means 13.
Are sequentially accumulated in the storage means 16, and when the data necessary for the scaling processing is fetched, the scaling processing is sequentially performed,
The image line signal L (R ′, G ′, B ′) is output to the color coordinate conversion means 15.

FIG. 4A shows the relationship between the image line L and the reading lines RL, GL and BL. For comparison, FIG. 4B shows the relationship between one image line L and the reading lines RL, GL, BL in the conventional color image reading device. FIGS. 5A and 5B are explanatory views of the case where the scaling processing unit 14 performs bicubic interpolation processing.

In FIG. 5A, the scaling processing means 14 is an odd-numbered (here, (2n-3) th) image line L.
When generating (R ', G', B ': 2n-3) data, the read line data input from the γ conversion means 13, the read line data temporarily stored in the storage means 16, and the storage means 16 The relationship with the read line data to be read is shown.

At this time, the data inputted from the γ conversion means 13 are the data S (R ': 2n) for the 2nth red reading line RL and the data S (G': 2n) for the green reading line GL. Yes, these signals are temporarily stored in the storage means 16.

Next, the storage means 16 is used for interpolation processing.
To (2n-6), (2n-4), (2n-2), (2
Data S (R ': 2) of the (n) th red read line RL
n-6), S (R ': 2n-4), S (R': 2n-
2), S (R ': 2n) is read. Magnification processing means 14
Performs the following interpolation calculation to produce the data S (R ': 2n-3) of the read line RL.

S (R ': 2n-3) = [-S (R': 2
n-6) + 5S (R ': 2n-4) + 5S (R': 2n
-2) -S (R ': 2n)] / 8

The scaling processing means 14, from the storage means 16,
Data S on the (2n-3) th read line BL
(B ': 2n-3) and the data S on the read line GL
(G ′: 2n−3) is read out, and these and S (R ′: 2n−3) obtained by the interpolation processing are used as image line data L (R ′, G ′, B ′: 2n−3). It is output to the color coordinate conversion means 15 described later.

In FIG. 5B, the scaling processing unit 14 is an even-numbered (here, (2n-2) th) image line L.
When the (R ', G', B ': 2n-2) data is generated, the read line input from the γ conversion means 13, the read line temporarily stored in the storage means 16, and the storage means 1
6 shows the relationship with the read line read from No. 6.

At this time, the read line data input from the γ conversion means 13 are the data S (B ': 2n + 1) for the 2n + 1th blue read line BL and the data S (G' for the green read line GL. : 2n +
1), and these signals are temporarily stored in the storage means 16.

Then, the storage means 16 is used for interpolation processing.
From j to (2n-5), (2n-3), (2n-1),
Data S on the (2n + 1) th blue read line BL
(B ': 2n-5), S (B': 2n-3), S
(B ': 2n-1) and S (B': 2n + 1) are read. The scaling processing means 14 performs the following interpolation calculation in order to generate the data S (B ': 2n-2) of the blue reading line BL.

S (B ': 2n-2) = [-S (B': 2
n-5) + 5S (B ': 2n-3) + 5S (B': 2n
-1) -S (B ': 2n + 1)] / 8 The scaling processing means 14 stores (2n-2) in the storage means 16.
Data S (R ': 2n-2) of the th read line RL
And the data S (G ': 2n-2) of the read line GL
And S obtained by interpolation processing
(B ': 2n-2) and the image line signal L (R',
G ', B': 2n-2), which is output to the color coordinate conversion means 15 described below.

The color coordinate conversion means 15 converts the data of the image line signal in the RGB color space into YCrCb.
Convert to image line signal in color space. YCrCb
Y in the color space is a luminance component, and Cr and Cb are color difference components. The contribution of R, G, and B to Y is 0.299 for R, 0.587 for G, and 0.114 for B. Therefore, when compressing an image, the resolution of R and B is not as high as that of G. From this, in the present embodiment, the color coordinate conversion means 1
In No. 5, reading is performed by alternately thinning R and B at the time of image reading, interpolation processing is performed on thinned lines, and then conversion from the RGB color space to the YCrCb color space is performed.

The color image converted into the YCrCb color space by the color coordinate conversion means 15 is converted into data for the printer or plotter. Color image reader 1
In place of the original image reading means 11 of FIG. 3, it is possible to use an original image reading means for generating reading lines of three colors by driving a filter. FIG. 2B shows a non-monochromatic light source 211.
A non-monochromatic light source drive circuit 212 and a filter drive circuit 2
13 shows a filter driving type original image reading means 21 having a number 13.

The filter drive circuit 213 is the micromotor 21 to which the rotary disc filter 2141 is attached.
42 can be driven. The light from the non-monochromatic light source 211 is emitted from the first filter R of the rotary disc filter 2141.
The document is irradiated with light through the F, second filter GF, and third filter BF. In FIG. 2B, the non-monochromatic light source 211
Can be emitted at the timing when the filter passes through RF, GF, BF, GF, ... In this order. In addition,
Non-monochromatic light source 2 when reading according to the invention is not performed
12, the filter is RF, GF, BF, RF, BF, B
Light is emitted at the timing of passing in the cycle of F, ....

Although the rotary disk filter is used in the example of FIG. 2B, the filter may be slid by a piezoelectric drive type micromachine actuator, an electrostatic drive type micromachine actuator or the like. FIG. 6 shows the line synchronization signal SY and the non-monochromatic light source drive circuit 21.
3 drive signal P and line sensor 211 output signal LS
And the time width LW corresponding to one image line width are also shown.

[0034]

According to the color image reading means of the present invention, it is possible to increase the reading speed without degrading the image quality, and particularly when converting from the RGB color space to the Y, Cr, Cb color space. The influence of the thinning process of the read line is extremely small.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a color image reading device of the present invention.

FIG. 2A is a diagram showing an example of a document image reading unit having a plurality of light sources, and FIG. 2B is a diagram showing an example of a document image reading unit having a non-monochromatic light source.

FIG. 3 is a diagram showing a relationship among a light source lighting signal of each color output by a color light source driving circuit, a line synchronization signal, and an output signal of a line sensor when the original image reading unit of FIG. 2A is used. is there.

FIG. 4A is a diagram showing a relationship between image lines and reading lines of respective colors in the embodiment shown in FIGS. 1 to 3, and FIG. 4B is a diagram showing image lines and reading lines of respective colors in a conventional color image reading device. It is a figure which shows the relationship of.

FIG. 5 is a diagram showing read line data input from the γ conversion unit, read line data temporarily stored in the storage unit, and read line data read from the storage unit when the scaling processing unit generates image line data. It is a figure which shows a relationship, (A) is a relationship diagram about odd-numbered image line data generation, (B) is a relationship diagram about even-numbered image line data generation.

FIG. 6 is a diagram showing a relationship between a light source lighting signal of each color output by a color light source drive circuit, a line synchronization signal, and an output signal of a line sensor when the original image reading unit of FIG. 2B is used. is there.

[Explanation of symbols]

1 Color image reader 11 Original image reading means 12 A / D conversion means 13 γ conversion means 14 Magnification processing means 15 Color coordinate conversion means 16 storage means 111 line sensor 112 Light source unit 113 Color light source drive circuit 114 lens system 1121 red light source 1122 green light source 1123 blue light source 211 Non-monochromatic light source 212 Non-monochromatic light source drive circuit 213 Filter drive circuit 21 Original image reading means 2141 rotating disc filter 2142 Micro Motor RF first filter GF second filter BF 3rd filter

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) G06T 5/00 100 H04N 1/04 D H04N 1/48 1/40 D 1/60 1/46 A F term (reference) 5B047 AA01 AB04 BB02 BC11 CA04 CA17 CA19 CB10 DC20 5B057 AA11 BA02 BA15 CA01 CA08 CA11 CA16 CB01 CB08 CB12 CB16 CD06 CE17 5C072 AA01 BA03 CA05 CA07 CA12 PP37H01P24P07P01P24B01B01B04B01B04B01B01B04B01B04B01B04B01B04B01B04B01B04B01B04B01B24B01B04B01P04Q12B07B01B24B01B04B01P24Q4B01B04B01B04B01B04B01B04B01B04B01B04B01B24B01B04B01B04B01B04B01B04B01P04P25Q07B01B04B01B04B01B04B01B04B01B04B01B04B01B04B01B04BA01B04B01B04BA01B04BA01B04 MA03 MA11 NA03 NA09 PA01 PA02

Claims (6)

[Claims] 1. A document moving relative to a one-dimensional line sensor is sequentially switched and irradiated with light from a plurality of color light sources having different emission colors, and reflected light from the document is transferred to the one-dimensional line sensor. In an image reading device that reads a color image by detecting the color image, a combination pattern of read lines of a plurality of colors for each image line is different in adjacent pixel lines, and the combination pattern is cyclic for each image line. A color light source driving unit that drives a light source; and a color line interpolating unit that interpolates the color associated with a read line of a color not included in the image line with a read line of the same color as the adjacent color. Characteristic color image reading device. 2. The plurality of color light sources comprises a red light source, a green light source, and a blue light source, and a combination pattern of read lines for each image line at the time of reading is two lines of a red line, a green line, and a blue line. 2. The color image reading device according to claim 1, wherein the color image reading device is a combination of 3. A document moving relative to a one-dimensional line sensor is irradiated with light from a non-monochromatic light source through a color filter that switches for each reading line, and reflected light from the document is transferred to the one-dimensional line sensor. In an image reading device that reads a color image by detecting with a line sensor, the combination pattern of filters used for reading the color line of each image line is different between adjacent pixel lines, and the combination pattern is periodic for each image line. And a color line interpolating unit that interpolates a color line not included in the image line by a color line of the same color as the color that is adjacent to the color line interpolating unit. Characteristic color image reading device. 4. The plurality of filters are composed of a red transmission filter, a green transmission filter and a blue transmission filter, and a combination pattern of read color lines for each image line is two lines of a red line, a green line and a blue line. 4. The color image reading device according to claim 3, wherein 5. The color image reading apparatus according to claim 3, wherein the filter is a rotary filter provided in a light emitting section of a non-monochromatic light source. 6. A color space conversion means for converting the RGB color space data obtained by the line sensor into Y, Cr, Cb color space data, wherein the light source driving means is a read color line for each image line. Driving the light source with the combination pattern of red line / green line, blue line / green line, and the color line interpolating means interpolating blue for the combination pattern of red line / green line to obtain a blue line / green line. The RGB pixel line is generated by performing red color interpolation for the combination pattern of 1., and the color space conversion means generates Y, Cr, Cb pixel lines from the RGB pixel line after interpolation. 6. The color image reading device according to any one of 1 to 5.