JPH0683337B2 - Image reader - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanner, a digital copying machine, a document file device, and an image reading device for reading a color original used in a facsimile.

2. Description of the Related Art In recent years, there has been a demand for high-speed color image input and multifunctional functions.

A conventional color image reading device is an image reading device using a color image sensor in which a light source and a color filter of the light source are switched, or three-color color filters are sequentially arranged in a light receiving portion of a one-line image sensor.

An example of the conventional image reading apparatus described above will be described below with reference to the drawings.

FIG. 6 is a diagram of a light receiving portion of a 1-line color image sensor used in a conventional image reading apparatus. Red (R), green (G), and blue (B) color filters are sequentially arranged for each pixel on the light receiving unit.

FIG. 8 is a block diagram of a conventional image reading apparatus.
41 is a 1-line color image sensor, 42 is an inversion circuit for converting the RGB color signals output from the image sensor into CMY (cyan, magenta, yellow), 43 is the undercolor that extracts the black component from the CMY color signals The removing circuit 44 is a color correcting circuit for masking the color signals. The operation of the conventional image reading apparatus configured as described above will be described below.

1-line color image sensor 41 as shown in FIG.
The RGB signal is subjected to shading correction and A conversion, and then converted into a CMY color signal by the inverting circuit 42 which outputs the complement of the input data. The output of the inverting circuit 42 is subjected to undercolor removal and black extraction by an undercolor removal circuit 43 which extracts a black component (K) from the CMY color signal. The CMY color signal from which the undercolor has been removed, which is output from the undercolor removal circuit 43, is color-corrected by the color correction circuit 44. (For example, IEICE technical report IE83-61 P4
3) Problems to be Solved by the Invention Compared to a 1-line monochromatic image sensor, the 1-line color image sensor used in the conventional image reading apparatus has a smaller light-receiving area at the same resolution, so that high-speed reading is possible. Is difficult. The black component should be extracted from the color signal obtained by reading the same position on the original.
Since the positions of the respective RGB light receiving parts are different, the RGB color signal does not read the same position on the document, so that there is a problem that an accurate black component cannot be extracted.

In view of the above problems, the present invention provides an image reading apparatus capable of high-speed image reading and accurate black component extraction.

Means for Solving the Problems In order to solve the above problems, an image reading apparatus of the present invention has a document table, an illuminating device for illuminating a document, and a plurality of line image sensors arranged in parallel at a predetermined interval. An image sensor in which a color filter is arranged on the light receiving portion of each line image sensor, an optical system for converging light reflected or transmitted from a document on the image sensor, a sub-scanning unit including at least a lighting unit, and the image A line buffer memory for delaying the image signal from the sensor by a predetermined line and a black detection circuit for detecting the black component of the document using the signal from the line buffer memory are provided, and the image is enlarged or reduced. In this case, the frequency ratio between the drive clock of the image sensor and the operating clock of the processing circuit that processes the output signal of the image sensor is set. A clock generation circuit that can be set, and a line buffer memory circuit that changes the number of delay lines of the line buffer memory according to the enlargement ratio, and enlarges the read image by using the drive clock of the image sensor and the output signal of the image sensor. This is performed by changing the ratio of the operation clock frequency of the processing circuit to be processed, the number of delay lines of the line buffer memory circuit, and the relative moving speed of the sub-scanning unit with respect to the original.

Effect The present invention has the above-described configuration, and accurately extracts the black component by eliminating the deviation of the read position of the color signal from the image sensor by the line buffer memory circuit.
By using an image sensor composed of a plurality of lines, high-speed image reading can be performed, and the line buffer memory circuit can be used to enlarge or reduce the image.

Embodiment An image reading apparatus according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 is a schematic configuration diagram of an embodiment of the image reading apparatus of the present invention.

Reference numeral 11 is a document, 12 is a document table, 13 is a fluorescent lamp, 14 is a rod lens array, 15 is an image sensor, 16 is a fluorescent lamp 13, a sub-scanning unit including a rod lens array 14 and an image sensor 15, and 17 is a casing. is there. The light from the fluorescent lamp 13 is reflected by the original 11 and focused on the image sensor 15 by the rod lens array 14. The sub-scanning unit 16 moves in parallel with the document table 12 in the direction of the arrow in the figure to sub-scan the document.

FIG. 2 is a block diagram of the image reading device in the embodiment of the present invention shown in FIG. 1. Reference numeral 1 denotes a 3-line image sensor, and color filters are arranged on the light receiving portions of the respective lines. 2 is a signal processing circuit for the signal from the image sensor which performs AD conversion and shading correction, 3 and 3'is a line delay memory, 4 is an address generating circuit for generating the address of the line delay memory 3, 3 ', and 9 is a black component detection Circuit, 10
Is a color correction circuit for masking CMY signals, 12 is an inversion circuit for converting RGB color signals into CMY color signals, 8 is a lower color removal circuit for removing black components from color signals, 7 is a clock generation circuit, 5 Is an operation clock of the image sensor and the processing circuit 2, and 6 is an operation clock of the circuits after the inverting circuit 12.

The RGB color signal output from the image sensor 1 is subjected to AD conversion and shading correction in the processing circuit 2. R and G
The color signal of is delayed by a predetermined line by the line delay memories 3, 3 '. The inverting circuit of 12 outputs the complement of the RGB color signal delayed by a predetermined delay and converts it into a CMY color signal. The black component detecting circuit 9 extracts the black component from the CMY color signal. The undercolor removal circuit 8 outputs the difference between the black components extracted by the black component detection circuit 9 from the CMY color signal to remove the undercolor. The color signal correction circuit 10 is a CM with a lower color removal circuit.
Correct the color signal by masking the Y signal.

FIG. 2 is a diagram of the line delay memory section in the embodiment of the image reading apparatus of the present invention. 21, 22, 23, and 24 are dual port RAMs, 26 is an address generation circuit, and 25 is a selector. The SCLK input to the address generating circuit 26 is a clock synchronized with the color signal and has the same frequency as the drive clock of the image sensor, and LENBL is a one-line synchronization signal. The same value is input to two addresses of the dual port RAM, and the input image signal is delayed by one line. The selector 25 selects how many line-delayed image signals to output according to a signal input from the outside.

FIG. 4 is a diagram of an embodiment of the black component detecting circuit of the image reading apparatus of the present invention. 31,33 is a comparator, 32,34,36
Is a selector and 35 is an adder. The Y and M color signals are input to the comparator 31 and the selector 32, respectively. The output of the comparator 31 controls the selector 32, and the selector 32
Outputs the smaller one of the Y and M color signals.
Similarly, the output of the selector 32 and the color signal of C are comparators.
33 and selector 34, respectively. comparator
The output of 33 controls the selector 34, and the smaller of the output of the selector 32 and the color signal of C is output from the selector 34. 37 controls the level of black extraction with a negative value input from the outside. The output of the selector 34 and the black extraction level signal 37 are input to the adder 35. The carry of the adder 35 controls the selector 36, and when the carry is not standing, the selector
36 outputs the output of the adder 35. Adder for selector 36
35 outputs and "0" are input.

FIG. 5 is a diagram of an embodiment of the light receiving portion of the image sensor used in the image reading apparatus of the present invention. There is a row of light receiving sections of three lines, and RGB color filters are arranged on the respective rows of light receiving sections. The pitch L of the light receiving section array of the image sensor is equal to the pitch of the light receiving sections. The sub-scanning direction of the image sensor is the arrow direction. The same signal is used to drive the image sensors of these three lines. That is, main scanning of three lines is simultaneously performed.

FIG. 7 shows the distance traveled by the image sensor during one line of main scanning when the relative speed between the sub-scanning unit and the original is changed and the enlargement / reduction in the sub-scanning direction is performed, that is, 1 of the original in the embodiment of the present invention. It is a figure which shows the distance of a subscan.

Reference numerals 37, 38 and 39 respectively indicate the positions of the B, G and R image sensor light receiving unit rows on the original at the start of one sub-scanning. The tips of the solid line arrows indicate the positions of the B, G, and R image sensor light receiving unit rows on the original at the start of the next sub-scan.

A is the enlargement ratio of 100%, that is, the relative movement distance between the image sensor and the original from the start of one sub-scan to the start of the next sub-scan is equal to the line pitch of the image sensor. At this time, a line delay memory as shown in FIG. 2 is used to delay the R color signal by two lines and the G color signal to 1
By delaying by the line, the RGB of the same position on the original
A color signal can be obtained.

B is when the enlargement ratio is 200%, that is, when the relative movement distance between the image sensor and the original from the start of one sub-scan to the start of the next sub-scan is half the line pitch of the image sensor. Also in this case, the R color signal can be delayed by 4 lines and the G color signal can be delayed by 2 lines using the same line delay memory to obtain RGB color signals at the same position of the original.

C is when the enlargement ratio is 50%, that is, when the relative movement distance between the image sensor and the original from the start of one sub-scan to the start of the next sub-scan is twice the line pitch of the image sensor. At this time as well, a similar line delay memory is used to delay the R color signal by one line and the G color signal without delay, so that the R and B color signals at the same position on the document and the image sensor A G color signal at a position shifted by 1/2 of the line pitch is obtained.

Generally, at any enlargement ratio, by properly selecting the number of delays in the line delay memory, RGB with a positional deviation within 1/2 of the line pitch of the image sensor in the sub-scanning direction can be obtained.
You can get a signal. There is always no displacement in the main scanning direction.

In a conventional image reading apparatus using a 1-line color image sensor, when the relative speed between the sub-scanning unit and the document is changed to perform enlargement / reduction in the sub-scanning direction, an RGB color signal having no displacement in the sub-scanning direction can be obtained. However, it is possible to obtain only RGB color signals with a positional deviation of 2/3 pixels constantly in the main scanning direction.

Next, a method of enlarging / reducing in the main scanning direction will be described.

In FIG. 1, the frequency of a clock 5 (hereinafter referred to as SCLK) for driving the image sensor 1, the processing circuit 2 and the address generation circuit 4 is F ₁ , and a clock 6 for driving circuits after the inverting circuit 12 (hereinafter referred to as PCLK). When the frequency of the F ₂ magnification in the main scanning direction is F ₂ / F _1.

FIG. 9 is a block diagram of the clock generation circuit 7 in FIG. Reference numeral 51 is an oscillator circuit, 52 is a 1 / N frequency divider, and 53 is an M-fold frequency multiplier circuit. The oscillator circuit 51 outputs a clock of frequency f ₀ . This is used as SCLK. The output of the M-fold frequency multiplication circuit 53 is M / N × f ₀ , and this is used as PCLK. At this time, the enlargement ratio in the main scanning direction is M / N and M
By making N and N programmable, an arbitrary enlargement ratio can be set.

Although one embodiment of the present invention has been described above, the line delay memory unit may have a similar function by using a FIFO or a normal memory.

EFFECTS OF THE INVENTION As described above, in the image reading device of the present invention, the line buffer memory circuit eliminates the displacement of the position of the reading device of the color signal from the image sensor, so that the accurate black component extraction and the image composed of a plurality of lines can be obtained. High-speed image reading can be performed by using the sensor. Moreover, even when the image is scaled up or down, the color separation color is detected by using the line buffer memory circuit so that the reading positional deviation is 1/2 pixel or less in the sub-scanning direction and there is no positional deviation in the main scanning direction. Since a signal can be obtained, accurate black component extraction and image reading can be performed.

[Brief description of drawings]

1 is a block diagram of an image reading apparatus according to an embodiment of the present invention, FIG. 2 is a block diagram of a line delay memory section in an embodiment of the image reading apparatus of the present invention, and FIG. 3 is a block diagram of an image reading apparatus of the present invention. A schematic configuration diagram of one embodiment,
FIG. 4 is a circuit diagram of an embodiment of a black component detecting circuit of the image reading apparatus of the present invention, and FIG. 5 is a schematic view of an embodiment of a light receiving portion of an image sensor used in the image reading apparatus of the present invention.
FIG. 6 is a schematic diagram of a light receiving portion of a one-line color image sensor used in a conventional image reading apparatus, and FIG. 7 is a sub-scanning unit according to an embodiment of the present invention in which a relative speed between a sub-scanning unit and an original is changed. FIG. 8 is a schematic diagram showing the distance of one sub-scan on the original when scaling in the scanning direction, FIG. 8 is a block diagram of a conventional image reading apparatus, and FIG. 9 is a block diagram of the clock generation circuit 7 in FIG. Is. 1 ... Image sensor, 3 ... Line delay memory,
7 ... Clock generation circuit, 9 ... Black component detection circuit, 13 ...
… Fluorescent lamp, 14 …… Rod lens array, 16 …… Sub scanning unit, 21,22,23,34 …… Dual port RAM, 25 …… Selector, 31,33 …… Comparator, 32,34,36 …… Selector, 35 …… Adder, 52 …… Frequency divider, 53 …… Frequency multiplier circuit.

Claims (1)

[Claims] 1. A document table, an illuminating device for illuminating a document, a color image sensor in which a plurality of line image sensors are arranged in parallel at a predetermined interval and a color filter is arranged on a light receiving portion of each line image sensor. An optical system for converging light reflected or transmitted from a document on the color image sensor, a sub-scanning unit including at least the illuminating means for mechanically scanning the document, and a color-separated image signal from the color image sensor. Has a line buffer memory circuit for delaying the line by a predetermined line, and a black detection circuit for detecting a black component in the image signal using a signal from the line buffer memory circuit. It has a line delay number setting means that can set the number of delay lines in the buffer memory, and can read images in the machine scanning direction. Scaling a line delay number of settings and the image reading apparatus, which comprises carrying out by changing the mechanical scanning speed for an original.