JPS62133866A - Picture reader - Google Patents

Abstract

PURPOSE:To improve picture quality by dividing picture elements into picture signals of discriminant color and complementary color, forming color picture signals corresponding to discriminant color by operation, and outputting picture signals of complementary color as monochromatic picture signals. CONSTITUTION:The picture image of a read original is divided into discriminant color, for instance, red and its complementary color, and photoelectric converted by line image sensors 8, 9. The output signals P1, P2 are shading corrected SD1, SD2 and sent to a color arithmetic circuit 20, and discriminated whether the picture element belongs to discriminant color or not by comparing each picture element of the signal. A picture element discriminated as red forms a color picture signal corresponding to the discriminant color and other picture elements are outputted as monochromatic picture signals. When a part of discriminant color is positioned independently in the white part of background, black picture elements that appear falsely in the periphery of the discriminant color are corrected to white picture elements using NAND circuits 22, 24. Thus, picture quality is heightened.

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 transmission document to be transmitted by a facsimile machine has red writing, 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, consider, for example, a case where the light is separated by a red filter and an image is formed on a line image sensor in order to discriminate red color.

For this reason, when reading an image of a color containing more than a certain amount of red components, such as magenta, the output level of the line image sensor may exceed a predetermined threshold level and be determined as red.

There has been an inconvenience that colors other than colors that are visually identified as red are also identified 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.

[composition] The present invention achieves this objective by using images.

The light is separated into a discrimination color and its complementary color and photoelectrically converted by a line image sensor, and by comparing the output signals of these line image sensors pixel by pixel, it is determined whether the pixel is of the discrimination color or not. For the pixels that have been discriminated, a color image signal corresponding to one discrimination color is formed by performing a predetermined calculation on the discrimination color image signal and the complementary color image signal, and the other pixels are discriminated as black and white pixels and used as complementary colors. image signal is output as a black and white image signal, and furthermore, due to optical characteristics, when the discrimination color part is located alone in the white part of the background, the black that appears pseudo-appears around the discrimination color. Pixels are corrected to white pixels to improve image quality.

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, an original to be read l is illuminated with an image on its reading line by a light source 2, and the image light reflected from the reading line is reflected by m3 and guided to a lens 4. luminous flux splitting device 5
It is divided into two parts.

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 of a wavelength longer than 580 nm.
Further, the cyan filter 7 has a transmission limit wavelength of, for example, 620 nm, and has a characteristic of transmitting light having a wavelength shorter than 620 nm.

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 measured the levels of the red component and cyan component of commercially available color samples such as red writing utensils, 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.

Kc/to r〈α, Kr>β where C is the normalized cyan component level (i.e., the output level of the line image sensor 9), and Kr is the normalized red component level (i.e., the line image sensor 8 output level). level). 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, if the red part is located alone on a white background,
As shown in FIG. 3, in the portions where the image changes from white to red and from red to white, the light reception level of the line image sensor 9 receiving the cyan component changes smoothly.

Therefore, for example, when three red pixels are located between white pixels, the output levels (normalized) of the line image sensors 8 and 9 at this time are as shown in FIG. 4(a).
It changes as shown in (b).

That is, the output level of the line image sensor 8 is such that the level of the red pixel is slightly smaller than the level of the white pixel, and the output level of the line image sensor 9 is such that the level of the red pixel is the same as that of the black pixel. , the level of the white pixel adjacent thereto is lower than the level of other white pixels, and further lower than the threshold level SL for identifying black and white.

In this case, the discrimination state of the red pixel based on the above-mentioned criteria is as shown in FIG. 2(b), so the red pixel signal RD representing red and non-light becomes as shown in FIG. 4(d). Also,
The black and white image signal B111, which produces black and white images, is as shown in FIG. 4(e).

As a result, one black pixel, that is, a pseudo black pixel that does not exist in the actual image, is output as a read image signal adjacent to the red image.

Therefore, when a read image is recorded, the recorded image deteriorates.

In order to solve this problem, if there is one pixel that is determined as a black pixel adjacent to a pixel that is determined as a red pixel, that black pixel is determined as a pseudo black pixel, and this pseudo black pixel is What is necessary is to perform a correction process to correct the pixel to a white pixel.

FIG. 5 shows an image reading device according to an embodiment of the present invention, which implements 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 same figure, image signals PI and P2 output from line image sensors 8 and 9 are switched by switching devices 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 PI 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 1, 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 P2.
This normalization circuit 1 has a function of converting the level of the signal applied from the white waveform memory 13 and 14 as a reference and converting it into a corresponding digital signal in synchronization with the normalization circuit 1.
5.16, the difference in transmittance between the red filter 6 and the cyan filter 7 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. 6 to determine the color of each pixel, and forms a red image signal R1 and a black and white image signal B.

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, the pixel in question is a red pixel, so the color calculation circuit 20 calculates the red image signal old based on the following equation (processing 104).

R1=a-R+b- Here, R and C are equal to signals R and C, respectively, and.

a and b are constants with different signs. Note that the constants a and b are set in consideration of white balance and image enhancement. In this way, since the color calculation circuit 20 calculates the red image signal R1 by multiplying it by an appropriate coefficient, it is possible to expand the level of the red image signal R1, and as a result, it is possible to reliably output various red colors. can.

Furthermore, the black and white image signal Bl corresponding to this pixel is as follows.

A value DIi for white is set (processing 105), and the red image signal R1 and black and white image signal Bl calculated at this time are
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,
That is, since it is either a white pixel or a black pixel, a value NR indicating non-light is set for the red pixel signal R1 (process 106), and a signal C is set for the black and white pixel signal Bl (process 107). ), and output them respectively as follows.
The red component and black and white component of the image in the read document l are
The signals are respectively converted into a red image signal R1 and a black and white image signal B1 and output.

The red image signal R1 output from the color calculation circuit 20 is applied to one input terminal of the latch circuit 21 and the NAND circuit 22,
The black and white image signal Bl is sent to the latch circuit 23 and the NAND circuit 24.
is applied to one input terminal of the .

The output R2 of the latch circuit 21 is outputted to the outside as a red image signal RD and applied to the latch circuit 25, and is also inverted to a signal R3 by an inverter 26 and then input to one input terminal of a NAND circuit 22 and 24, respectively. has been added.

The output B2 of the latch circuit 23 is applied to the latch circuit 27 and one input terminal of the OR circuit 28, and is also inverted to the signal B3 via the inverter 29, and then one input terminal of the NAND circuit 22.24. has been added to.

The output R4 of the launch circuit 25 is connected to one input terminal of the NAND circuit 24, and the output B4 of the latch circuit 27 is connected to the NAND circuit 22.
are applied to one input terminal of each.

The NAND circuit 22 detects and corrects pseudo-black pixels in the portion that changes from white to red, and its output S2 is applied to one input terminal of the NAND circuit 30.

Further, the number one circuit 24 detects and corrects pseudo-black pixels in the portion where red changes to white, and its output S1
is applied to the other input terminal of the NAND circuit 30.

The output C1 of this NAND circuit 30 is applied to the other input terminal of an OR circuit 28, and the output of this OR circuit 28 is outputted to the outside as a black and white image signal B111.

Now, as shown in Figures 7(a) and (b), there are two white pixels, one black pixel, three red pixels, one black pixel, and four white pixels in succession. Consider that the signals R and C are affected by this. In this case, as described above, the black pixel sandwiched between the white pixel and the red pixel is a pseudo black pixel.

Therefore, the output R1 of the latch circuit 22, the inverter 2
The output R3 of the launch circuit 23 and the output R4 of the latch circuit 25 change as shown in FIG.
3. The output B4 of the latch circuit 27 is shown in FIG. 4(f).
, (g) and (h).

The signal added to the NAND circuit 22, B3. r13.
Observing the state change of B-'1, since the signal R1 is at the logic level L up to the third pixel, its output signal S2 is at the fourth pixel.
As shown in Figure (j), the logic level becomes 1 (and all the inputs become logic level 11 at the fourth pixel, so the output signal S2 falls to logic level L, which causes the output of the NAND circuit 30 to Since CI (see Figure 4 (k)) rises to logic level 11, the third black pixel (logic level L) of the old signal is converted to a white pixel (logic level H), changing from white to red. Pseudo-black pixels occurring in the portion where the image is displayed are removed (see signal BW in FIG. 4 (1)).

Note that from then on, any one of the inputs of the NAND circuit 22
Since two or more are at the logic level, the output signal S2 of the NAND circuit 22 maintains the logic level 11 state.

Signal 81 . applied to NAND circuit 24 . R3,111
Considering the state changes of 4 and 83, the signal R4 is at the logic level up to the 5th pixel, and the signal B3 is at the 6th and 7th pixel.
is at the logic level L, so its output signal Sl is as shown in Fig. 4 (
As shown in i), the logic level is ■, and all the inputs at the 8th pixel become logic level 11, so the output signal S
1 falls to the logic level, which causes the output CI of the NAND circuit 30 to rise to the logic level 11.
The black pixels of the 7th pixel of signal 131 are converted to white pixels,
Pseudo-black pixels that occur in areas that change from red to white are removed.

Note that from then on, any one of the inputs of the NAND circuit 24
Since the output signal S1 is at the logic level L, the output signal S1 of the NAND circuit 24 maintains the logic level II state.

In this way, the pseudo-black pixels appearing in the black-and-white image signal B1 are converted to white pixels, and a monochrome image signal Bld from which the pseudo-black pixels are removed is formed, which is output to the outside. That is, latch circuits 21, 23, 25, 27, NAND circuits 22, 24, 30, inverters 26, 29, and
The OR circuit 28 constitutes a pseudo black pixel removal circuit DBS that removes pseudo black pixels.

Therefore, the red image signal RD and the black and white image signal BW from which pseudo black pixels have been removed are outputted to the outside in parallel.

By the way, the one-color calculation circuit 20 discriminates red according to the levels of the signals R and C, and also generates a red image signal R1 and a black and white image signal B1, and the result is unique to the levels of the signals R and C. Therefore, this color calculation circuit 20 is
It can be configured by a ROM (read only memory) that uses signals R and C as input addresses, and in that case, processing speed can be improved.

Further, the color calculation circuit 20 and the pseudo black pixel removal circuit DI3
5 can also be combined into one circuit. Furthermore,
The pseudo black pixel removal circuit DBS is also not limited to the one described above.

Note that in the embodiment described above, the red color of the image is discriminated, but it is also possible to discriminate other colors.

Further, the means for dividing an image into spectra 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, photoelectrically converted by a line image sensor, and the output signals of these line image sensors are compared pixel by pixel. It is determined whether or not the pixel is of the discrimination color, and for pixels for which the determination has been made, a color image corresponding to the discrimination color is created by performing a predetermined calculation on the image signal of the discrimination color and the image signal of the complementary color. form a signal,
Other pixels are distinguished as black and white pixels and a complementary color image signal is output as a black and white image signal.Furthermore, when a discrimination color part is located alone in a white part of the background, a pseudo color is generated around this discrimination color. Since the image quality is improved by correcting black pixels that appear as white pixels, there is an advantage that predetermined color components other than black and white components 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 is a cyan component component. A waveform diagram for explaining the light receiving characteristics of
5 is a block diagram showing an example of a device according to an embodiment of the present invention; FIG. 6 is a flowchart showing an example of processing of a color calculation circuit; FIG. 2 is a waveform diagram for explaining the operation of the pseudo black pixel removal circuit. FIG. 6...Red filter, 7...Cyan filter, 8,9
...Line image sensor, 11.12...Switcher, 13.14...White waveform memory, 15.16...
Normalization circuit, 20... Color calculation circuit, 21, 23, 2
5.27...Latch circuit. 22.24.30... Nan! Circuit, 26.29・
...Inverter, 28...OR circuit, SDI, SD2
...Shading correction circuit, DBS...Pseudo black pixel removal circuit. Agent Patent Attorney Crest 1) Makoto Fig.1 Fig.2 Fig.3 Fig.4

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 color discrimination means, a color image signal corresponding to the first color is calculated from the image signal based on a predetermined calculation, and pixels for which there is no discrimination output from the color discrimination means are treated as black and white pixels. color separation means for discriminating and outputting an image signal corresponding to the second color as a monochrome image signal; and an independent pixel represented as black in the monochrome image signal in an area adjacent to the area of the color image signal. 1. An image reading device comprising a pseudo-black pixel correcting means for correcting a black pixel to a white pixel when the black pixel is located as a white pixel.