JPS62188465A - Image reader - Google Patents

Abstract

PURPOSE:To surely read out a prescribed color component other than a white and black components by forming a color correcting means for correcting picture elements discriminated as the 1st color to white picture elements when a prescribed number or more of the picture elements discriminated as the 1st color are arranged on the periphery of picture elements decided as black elements by a color separating means. CONSTITUTION:A color operating circuit 20 separates the ratio K of inputted signals R, C, and when the ratio K exceeds a prescribed value alpha(0, 4), discriminates whether the signal R is larger than a prescribed value beta(0, 4) or not, When the signal R is larger than the value beta, the picture element is regarded as a red picture element, so that the circuit 20 sets up logical levels '1' and '0' on a read picture signal R1 and a white and black picture signal B1 corresponding to the picture element respectively and outputs both the signals R1, B1. When the signal R is equal or less to/than the value, the picture element is a white or black picture element, so that the circuit 20 sets up logical level '0' on the red picture signal R1 and a logical level obtained by binary-coding the signal C by a prescribed threshold level on the signal B1 and outputs both the signals. Consequently, a prescribed color component other than white and black components can be surely read out with high quality.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an image reading device that reads color information of images other than black and white.

[Prior Art] When inputting an image to a facsimile device, an image processing device, etc., it is often convenient if the color information of the image can also be determined.

For example, if a document to be sent using a facsimile machine is
．． In the case of a stamp or a red underline, if this red information can be output, more effective image information transmission will be possible.

By the way, many methods have been proposed for distinguishing colors in this way, but most of them involve color separation of one color using one filter or the like.

However, in such a conventional method, for example, in order to discriminate red color, consider the case where the light is separated by a red filter and an image is formed on a line image sensor.

When reading an image of a color that contains more than a certain amount of red components, for example magenta, the output level of the line image sensor may exceed a predetermined threshold level and be determined as red, so it may be visually identified as red. There is an inconvenience that colors other than the displayed color are also recognized as red.

Further, the background color of a typical document is white, so the output level of the line image sensor is the highest when reading the background. For this reason, when a red image signal is formed from only the red component light reception signal as described above, the output level of the line image sensor when reading the red part is close to the level of the white part, so the red color of the image is There has also been an inconvenience in that areas where the color is unclear or faint are not determined to be red but are determined to be white.

Furthermore, the color area that is visually recognized as red is wide;
This visual characteristic is different from the spectral characteristic when spectrally analyzed using a single filter, and as a result, a color that is visually recognized as red may not be recognized as red by some devices, resulting in the inconvenience that an appropriate red image signal cannot be output. There was also.

[Objective] The present invention has been made in order to solve the above-mentioned disadvantages of the conventional technology, and it uses a predetermined color component other than black and white components.
An object of the present invention is to provide an image reading device that can read images reliably.

[Configuration] In order to achieve this object, the present invention separates an image into a discrimination color and its complementary color, photoelectrically converts them using a line image sensor, and compares the output signals of these line image sensors pixel by pixel to determine the relevant color. It is determined whether a pixel is of a discrimination color or not, and for pixels for which discrimination has been made, a color image corresponding to the discrimination color is generated by performing a predetermined calculation on both signals of the discrimination color and the image signal of the complementary color. form a signal.

Other pixels are determined to be black and white pixels, and both complementary color signals are output as black and white image signals. Furthermore, the image quality is improved by correcting the pixels of the discrimination color that appear pseudo-in the monochrome image part due to the reading error of the optical system into white pixels or black pixels.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows an optical system of an image reading device according to an embodiment of the present invention, and in this embodiment, red is used as the discrimination color.

In the figure, the image on the reading line of an original document 1 to be read is illuminated by a light source 2, and the image light reflected from the reading line is reflected by a mirror 3 and guided to a lens 4. The beam is split into two by a beam splitting device 5 such as a prism.

The image light thus branched is separated through a red filter 6 that transmits a red component and a cyan filter 7 that transmits a cyan component, and then images are formed on line image sensors 8 and 9.

Note that the red filter 6 has a transmission limit wavelength of, for example, 580 nm and has a characteristic of transmitting light with a wavelength of 4 or more, and the cyan filter 7 has a transmission limit wavelength of, for example, 620 nm, and has a characteristic of transmitting light with a wavelength of 4 or more. It has the property of transmitting light.

Now, when an image is divided into a red component and its complementary cyan component in this way, all colors are divided into these two components and appear as a predetermined level in the output signal of the line image sensor 8゜9. .

Therefore, when we calculated the levels of the red component and cyan component of commercially available color samples of red writing utensils, etc., we found that these color samples were located in the shaded area in FIG. In addition, in FIG. 2, the output level of the line image sensors 8 and 9 when reading the white part of the background of the document where the light receiving level is the highest is 1, and the output level of the line image sensor 8 when reading the actual image is assumed to be 1. The output level of .9 is normalized and displayed.

That is, the red color appearing in the original image satisfies the relationship expressed by the following equation.

c/K (-<α, Kr>β where Kc is the normalized level of the cyan component (i.e., the output level of the line image sensor 9).

Kr represents the normalized level of the red component (ie, the level of the line image sensor 8). Also, according to actual measurements, α=0.4. β=0.4. Note that this value is based on the case where the red filter 6 and cyan filter 7 having the characteristics as described above are used, and this value may change when filters with different characteristics are used.

From the above, for each pixel, the line image sensor 8,
It is possible to determine whether or not the 9 output levels (each normalized) satisfy the above relationship, and to determine that a pixel that satisfies that relationship is a red pixel (that is, a red pixel).

Further, as the black and white image signal for determining black and white pixels other than red pixels, the output signal from the line image sensor 9 may be used as is.

By the way, when red is determined using this method, if the color at the boundary between red and another color is read, the color may be partially distorted due to variations in the density of that color. The color is determined to be red, and the rest of the image is determined to be black, so when the read image is recorded, that color is recorded in a dark, dull color. This state is shown in Figure 3 (a
) as an example. Note that in the figure, diagonal lines indicate red pixels, and intersecting diagonal lines indicate black pixels.

In order to eliminate this inconvenience, when there are many pixels determined to be red pixels around pixels determined to be black pixels, it is necessary to perform a correction process to correct the black pixels to white pixels. Bye.

That is, for example, when the red image signal RD and the black and white image signal 8v are distributed in the main scanning direction and the sub-scanning direction in the pattern shown in Table 1, the center pixel may be corrected to a white pixel. In this example, an area of 3 pixels each in the main scanning direction and sub-scanning direction is considered as one judgment unit, and if there are 4 or more red pixels around the center pixel of that area, the center pixel is considered as a white pixel. It is determined. Note that there are many patterns that satisfy this condition, and Table 1 shows four representative ones among them. (The following margins are blank) ■ ■ ■ ■However, the main scanning direction is A→B-)C, and the sub-scanning direction is A+D-
The direction is +G. Therefore, pixels A, n, c (A'
, s', c') are pixels one line before the center pixel E (E'), and pixels G, II, I (G', II', I
') is the pixel one line after the center pixel E (IE'), one pixel D (D') is the pixel one line before the center pixel E (E'), and pixel F (F') is the center pixel E (E')
This is the pixel after .

In addition, in this example, the combination of the logical states of the red image signal RD and both black and white signals oty, and the red pixel.

Table 2 shows the relationship between the discrimination results for white pixels and black pixels. (
4 shows an image reading device according to an embodiment of the present invention, which realizes the principle of the present invention described above. In addition, in the figure, a line image sensor 8 which is not directly related to the present invention is shown.
, 9 and control systems such as the sub-scanning mechanism are omitted.

In the figure, image signals Pi and P2 output from line image sensors 8 and 9 are switched by switchers 11 and 12.

White waveform memory 13.14 or normalization circuit 15.16
can be added to either.

The switch 11.12 is switched by a control means (not shown) to select the white waveform memory 13.14 when reading a reference white image (for example, a white original). As a result, at this time, the line image sensors 8, 9
The image signals PL and P2 output from the white waveform memory 13.
14.

Moreover, the switching devices 11 and 12 are controlled by the above-mentioned control means.
When reading the image of the original document l, the normalization circuit 15.
16 can be selected.

The normalization circuits 15 and 16 convert the image signals PL and P2 obtained when reading the original document 1 into image signals PI and I'.
It has a function of converting the level of the signal 1 applied from the white waveform memory 13.14 in synchronization with the white waveform memory 13.2 and converting it into a corresponding digital signal. The difference in transmittance between the cyan filter and the cyan filter is absorbed.

That is, the switch 11. A shading correction circuit SDI that performs shading correction on the image signal P1 outputted by the line image sensor 8 by the white waveform memory 13 and the normalization circuit 15 is connected to the line image sensor 9 by the switch 12, the white waveform memory 14, and the normalization circuit 16. A shading correction circuit SD2 that performs shading correction on the image signal P2 outputted by the shading correction circuit SD2 is formed respectively.

The output signals R and C of the normalization circuits 15 and 16 are applied to the color calculation circuit 20.

The color calculation circuit 20 executes the processing shown in FIG. 5 to determine the color of each pixel, and forms a red image signal R1 and a black and white image signal old.

That is, first, the ratio K of the input signals R and C is calculated (step 101), and it is determined whether the ratio K is larger than a predetermined value α (determination 102).

If the result of this judgment 102 is YES, then the signal R
is larger than a predetermined value β (determination 103
). Note that the predetermined values α and β in this case are both 0.4 as described above.

When the result of this judgment 103 is YES, since the pixel in question is a red pixel, the one-color calculation circuit 20 outputs the red pixel signal R.
1 to the logic level "1" (process 104), and set the logic level "0" to the black and white image signal old corresponding to this pixel (process 105), and set the red image signal R1 and the black and white image signal old to Output.

When the result of decision 102 is NO, and
If the result of step 3 is No, the pixel in question is other than a red pixel,
In other words, since it is either a white pixel or a black pixel, the red pixel signal R1 has a logic level "0" indicating that it is not red.
106), and the logic level of the result of binarizing the signal C at a predetermined threshold level is set for the black and white image signal at (binarization processing 107), and these are output.

In this way, the red component and the black and white component of the image on the read original 1 are converted into a red image signal R1 and a black and white image signal Bl, respectively, and are output.

The red image signal R1 output from the color calculation circuit 20 is sent to the shift register 31 and! It is added to a line buffer 32 having a capacity capable of storing a line's worth of red image signals R1.

The output of line buffer 32 is applied to shift register 33 and line buffer 34, and the output of line buffer 34 is applied to shift register 35.

Furthermore, the black and white image signal old output from the one-color calculation circuit 20 is applied to a shift register 36 and a line buffer 37, and the output of the line buffer 37 is applied to a shift register 38 and a line buffer 39,
The output of is applied to a shift register 40.

Addresses to these line buffers 32, 34, 37, and 39 are specified by address data DA output from the address counter 41, and writing/reading is controlled by a control signal R11l output from the write/read controller 42. Ru. Also, shift register 3
The shift clock CP output from the address counter 41 is added to 1, 33, 35, 36, 38, and 40.

Address counter 41 and write/read controller 4
2 is a clock signal C output from a control section (not shown)
Its operation is controlled by Kl, CK2 and control signal CL.

In this way, the red image signal old one line before the line being added to the shift register 31 is transferred from the line buffer 32 to the shift register '933, and the old red image signal two lines before the line added to the shift register 31 is transferred from the line buffer 34 to the shift register 35.
In addition, the white and black image signals old one line before the line added to the shift register 36 are transferred from the line buffer 37 to the shift register 38, and the black and white image signal B1 two lines before is transferred from the line buffer 39 to the line buffer 39. is added to the shift register 40 from.

Therefore, from the shift register 31, the pixel G, 1
1.

A red image signal R1 corresponding to pixels A, B, and C is sent from the shift register 33, a red image signal R1 corresponding to pixels E and F is sent from the shift register 35, and a red image signal R1 corresponding to pixels A, B, and C is sent from the shift register 35. From the shift register 36, pixels G', II
'.

■The black and white image signal B1 corresponding to 2 is sent to the shift register 38.
From shift 1 register 40, black and white image signals corresponding to pixels D', E', and F' are output, and from shift 1 register 40, pixels A' and B' are output.
, C' are respectively output.

Then, the pixels ^,B,C,D,[E,F,G,+(,I
A red pixel signal R1 corresponding to the pixel E' and both black and white signals B1 corresponding to the pixel E' are stored in a ROM (read only memory) 44.
has been added to.

Further, the black and white image signals B1 corresponding to pixels D' and E' are applied to an exclusive OR circuit 45, and the black and white image signals B1 corresponding to pixels B' and H' are applied to an exclusive OR circuit 46, respectively. , the outputs of these exclusive OR circuits 46 and 47 are added to the ROM 44. Note that the pixels A-I and A' to ■' here correspond to each pixel in Table 2.

The ROM 44 stores the center pixel E based on the relationship shown in Table 2.
Based on the combination of the logical state of the red pixel signal R1 corresponding to the center pixel E' and the logical state of the black and white pixel signal B1 corresponding to the center pixel E', it is determined whether the pixel is a red pixel, a white pixel, or a black pixel. At the same time, when a relationship partially exemplified in Table 1 is detected, a logical operation is performed to determine the pixel as a white pixel, and the result is output as a red side (No. 4 RD and black and white image signal BW).

In this way, shift registers 31, 33, 35, 3
6°38.40, line buffer 32, 34, 37, 3
9. Address counter 42. Write/read control unit 4
3. ROM44° and exclusive OR circuit 45.46
Thus, a color determination circuit 30 is formed which determines the color of each pixel from the output of the color calculation circuit 20 and corrects a read image when a color close to red is read.

Therefore, for example, a read image with a dull color as shown in FIG. 3(a) is corrected to an image with a clear tone as shown in FIG. 3(b). However, Fig. 3(a)
, (b) are all white images.

By the way, in this process of correcting the color portion close to red to a clear tone, it is sufficient to refer only to the central pixel E' as the black and white image signal old.

In the embodiment described above, the states of pixels D', F', B', and ■' are excluded so that the ROM 44 can perform image processing that refers to the states of images before and after the center pixel E (E'). It is input via logical OR circuits 45 and 46.

Note that the image processing is a correction process that removes, for example, pseudo black pixels that occur in red and white images and pseudo red pixels that occur in black and white images, and each correction process is performed by switching the upper bit input of the ROM 44. can be switched.

In addition, in the above-mentioned embodiment, correction processing is performed based on the number of red pixels located around the center pixel of the area for areas cut out by three pixels in the main scanning direction and the sub-scanning direction. The number of red pixels that serve as a reference for correcting the area and the center pixel to white pixels is not limited to the above-mentioned number.

Furthermore, in the embodiment described above, the color calculation circuit performs the binarization process, and the occurrence of pseudo red pixels is detected using the binarized red image signal and black and white image signal. This can be done even with the signal intact.

Note that although the above-described embodiment discriminates the red color of an image, the present invention can also be applied to a device that discriminates other colors. Further, the means for dividing an image into color components is not limited to the above-mentioned method.

[Effects] As explained above, according to the present invention, an image is separated into a discrimination color and its complementary color and photoelectrically converted by a line image sensor, and the output signals of these line image sensors are compared pixel by pixel to determine the relevant color. It is determined whether a pixel is of a discrimination color or not, and for pixels for which the discrimination has been made, a color image signal corresponding to the discrimination color is generated by performing a predetermined calculation on the image signal of the discrimination color and the image signal of the complementary color. , other pixels are determined to be black and white pixels, and a complementary color image signal is output as a black and white image signal.Furthermore, pixels determined to be a black pixel are surrounded by a predetermined number or more of pixels determined to be a discrimination color. When the pixel is located, the image quality is improved by correcting this pixel to a white pixel, which provides the advantage that a predetermined color component other than the black and white component can be read reliably and with high quality.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing an example of an optical system of an image reading device according to an embodiment of the present invention, FIG. 2 is a graph diagram for explaining the principle of determining red color, and FIG. 3(a) 4 is a schematic diagram illustrating an example of a read image when a color close to red is read, FIG. FIG. 5 is a block diagram showing an example of the apparatus according to the example, and a flowchart showing an example of processing of the color calculation circuit. 6...Red filter, 7...Cyan filter. 8.9...Line image sensor, 11.12...
Switcher. 13, l/l... White waveform memory, 15.16... Normalization circuit, 20... Color calculation circuit, 30... Color judgment circuit, 31.33, 35, 36, 38.40. ...Shift register. 32.34, 37.39... line buffer, 42.
. . . address counter, 43 . . . write/read control unit. 44...ROM (read only memory), 4
5.46...Exclusive OR circuit. Agent Patent attorney Makoto Hijiri Figure 1 Figure 2 U4 亦闦名] Figure 3 (a) (b)

Claims (1)

[Claims] a spectroscopy means for separating the image light on the reading line into a predetermined first color and a second color complementary to the first color; and receiving the image light of the first color and the second color. two line image sensors that output image signals corresponding to each pixel; a color discrimination means that discriminates the first color based on a comparison of the image signals output from these line image sensors; and this color discrimination means. For pixels for which there is a discrimination output from the above, a color image signal corresponding to the first color is calculated from the above two signals, and pixels for which there is no discrimination output from the color discrimination means are discriminated as black and white pixels, color separation means for outputting an image signal corresponding to the black and white image signal as a black and white image signal; and a predetermined number or more of pixels determined as the first color are located around the pixels determined as black pixels by the color separation means. An image reading device comprising: a color correction means for correcting the pixel to be a white pixel.