JPH0513422B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an image recording apparatus that records a color image by reading an original image and repeating image signal processing and image forming processes for each color.

(Prior art) In conventional image recording devices, no effective measures have been taken to output and express the density of each color image in a well-balanced manner. In order to be able to copy colors such as these with sufficient density, the bias voltage of the developing section is adjusted. For example, the developing bias voltage is lowered for documents with similar reflection densities, such as orange and light blue.
On the other hand, for blue writing instruments (for example, ballpoint pens), in order to obtain sufficient copy density, writing instrument manufacturers use measures such as adding a small amount of carbon black. In addition, in the case of manuscripts containing a mixture of characters written in black, blue, and red writing instruments, black,
Even if blue characters are copied with sufficient density, red characters may not be copied with sufficient density, although there is a problem with the spectral sensitivity characteristics of the photoreceptor. The reason for this is that the reflection density differs depending on the color. Furthermore, this type of conventional image recording apparatus is configured to repeat the image forming process a number of times corresponding to the number (types) of colors to be recorded.

(Problems to be Solved by the Invention) Therefore, the emergence of an image recording apparatus that can output and express the density of each color image in a well-balanced manner is awaited. Further, in the conventional apparatus described above, the entire image forming process is repeated regardless of the number of colors on the original image, so there is a problem that the recording time cannot be shortened.

The present invention has been made in view of these problems, and its purpose is to provide an image recording apparatus that can shorten recording time according to the number of colors in an original image.
An object of the present invention is to realize an image recording device capable of recording images of each color with well-balanced density.

(Means for Solving the Problems) The present invention solves the above problems in an image recording apparatus that records a color image by reading an original image and repeating an image signal processing and an image forming process for each color. An image reading means that separates and reads reflected light or transmitted light from a document into at least two colors; and a color separation map that classifies each pixel of the document image into one of a plurality of predetermined colors. color information storage means in which a color separation map with density data set is stored in the memory at each address; and an address signal for the memory storing the color separation map is created from the output signal of the image reading means. color separation information generation means for outputting the color separation information to the color information storage means; threshold generation means for generating a threshold value determined for each of the plurality of predetermined colors; a comparison means for comparing the density data read out from the color information storage means in response to an address signal and a threshold value output from the threshold value generation means; a determining unit that performs reading to determine the color of the original image; and a control unit that, based on the determination result of the determining unit, omits execution of an image forming process for a color that is deemed not to exist in the original image in a subsequent image forming process; It is characterized by consisting of.

(Function) In the image recording apparatus according to the present invention, reflected light or transmitted light from a color document is separated into at least two colors and read, and from this signal, the color separation information creation means is used to create a color separation map in a memory in which a color separation map is stored. Create and output an address signal to. The comparison means performs multi-value conversion by comparing the density data read from the color information storage means in response to this address signal with a threshold value determined for each of a plurality of predetermined colors. or,
In the image recording apparatus according to the present invention, the color of the original image is also determined by first reading the original image. As a result of this determination, if there is a color that can be considered not to exist in the original image, execution of the image forming process for the color that can be considered not to exist in the original image is omitted in the subsequent image forming process.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIGS. 1 and 2 are configuration diagrams showing one embodiment of the configuration of an image reading and image processing section in an image recording apparatus of the present invention. FIG. 1 shows an optical system that decomposes optical information, and FIG. 2 shows an electrical system that processes image signals converted into electrical signals. 1st
In the figure, 31 is a lens, 32 and 33 are prisms whose one surfaces are in contact with each other, and this contact surface forms a dichroic mirror 34. 35,3
6 is a CCD that converts optical information into electrical signals.
It is an image sensor (hereinafter simply referred to as CCD).

Optical information from a color original (not shown) enters a lens 31 and is focused, and then enters a prism 32 . The wavelength range of the light passing through the prism 32 is divided into two by a dichroic mirror 34, and the red light passes through the dichroic mirror 34 and enters the red CCD 35 via the prism 33. On the other hand, the cyan light is reflected by the dichroic mirror 34, travels through the prism 32 in the opposite direction, is reflected once more within the prism 32, and then is used for cyan light.
The light enters the CCD36. Conventional method R, G, B 3
Compared to imaging using primary colors, the device configuration is simpler and cheaper.

Next, FIG. 2 will be explained. In the figure,
300 is a document, 301 is a reading unit mainly composed of a light source 302, and 303 is a mirror that guides a light image to an optical system 304 shown in FIG.
The reading unit 301 and the mirror 303 perform so-called slit scanning on the original in the direction of the arrow to convert the optical image into a first image.
CCD41 (corresponding to 35 in Figure 1), second CCD4
2 (corresponding to 36 in FIG. 1). 51 is a first CCD 41 that amplifies the photoelectric conversion output of the first CCD 41;
The amplifier 52 is a second amplifier that amplifies the photoelectric conversion output of the second CCD 42. 1st and 2nd
A photoelectric conversion means 40 is composed of CCDs 41 and 42,
Amplifying section 50 with first and second amplifiers 51 and 52
Configure. 61 is a first A/D converter that converts the output of the first amplifier 51 into digital data;
A second A/D converter 62 converts the output of the second amplifier 52, and the first and second A/D converters 61 and 62 constitute an A/D converter 60. The number of bits used for the A/D converters 61 and 62 is, for example, about 6 bits.

Reference numeral 72 denotes a first cell for storing luminance signal data V _R +V _C.
memory 73 is the color difference signal data V _C /(V _R +
A _second memory 81 stores the first and second memories 72 and 73 and outputs chromatic color (red, cyan) data.
memory 82 is also the first and second memory 7
This is the fourth memory which receives the outputs of 2 and 73 as addresses and outputs achromatic color (black, gray, white) data. The first and second memories 72 and 73 constitute color separation information creation means 70, and the third and fourth memories 81 and 82 constitute color information storage means 80.

43 is a first buffer that temporarily stores the output of the third memory 81, and 44 is a second buffer that temporarily stores the output of the fourth memory 82.
45 is a color selection circuit that receives B (black), B (blue), R (red) selection signals and the output of the second memory 73; the output is sent to the first and second buffers 43 and 44; is being applied.

46 is a color determination unit which receives the outputs of the first and second buffers 43 and 44 and counts data of each color to obtain the color of the original and the density information of the color, and obtains the number of times the original is scanned and multi-value threshold information. (Details will be described later), 47 receives the output of the color determination section 46 as threshold information, and converts the output (density data) of the buffers 43 and 44 into multi-values (including 2
This is a threshold circuit that converts into values. The first and second buffers 43 and 44, the color selection circuit 45, and the color determination section 46 constitute a color control means 90 that controls the output of the color information storage means 80. The output of the threshold circuit 47 becomes the output of the configuration of the image processing section.
The operation of the above-mentioned components will be explained as follows.

When a color document is scanned, this optical information enters the optical means shown in FIG. 1 and is separated into red and cyan, for example, for each wavelength range. The decomposed red and cyan optical information are each stored on CCD4.
1 and 42 and is converted into an electrical signal. The converted image signals enter amplifiers 51 and 52, respectively, and are linearly amplified to a predetermined level.
Subsequent A/D converters 61 and 62 convert the data into digital data at equal intervals. At this time, the red and cyan image data converted into digital data by a circuit (not shown) is normalized by the output value of the reference color (white). In other words, the image data of the reference color
Let the values obtained by normalizing the red and cyan image data to 1.0 be V _R and V _C , respectively.

Next, a coordinate system is created using the digital image data V _R and V _C , and color separation is performed based on the created color separation map. To determine this coordinate axis, consider the following points.

In order to be able to express halftones, information on the reflectance (reflection density) of the document, which corresponds to the brightness signal of the television, is taken in.

Incorporates information on color differences (including hue and saturation) of red, cyan, etc.

From the above, it is preferable to use the following luminance signal information and color difference signal information.

Luminance signal information = V _R + V _C (1) Sum of V _R , V _C (0≦V _R ≦1.0, 0≦V _C ≦1.0) V _R +
V _C (0≦V _R +V _C ≦2.0) corresponds to the black level (=0) and the white level (=2.0), and all colors exist in the range from 0 to 2.0.

Color difference signal information = V _R / (V _R + V _C ) or V _C / (V _R + V _C ) (2) In the case of achromatic color, V _R component included in the whole (V _R + V _C ), V _C The proportions of the ingredients are constant. Therefore, V _R /(V _R +V _C )≒0.5 V _C /(V _R +V _C )≒0.5. On the other hand, in the case of chromatic colors, V _R /
The value of (V _R +V _C ) or V _C /(V _R +V _C ) is one measure of the hue and saturation of the original.

That is, (1) Red color 0.5<V _R /(V _R +V _C )≦1.0 0≦V _C /(V _R +V _C )<0.5 (2) Cyan color 0≦V _R /(V _R +V _C ) It can be expressed as <0.5 0.5<V _C /(V _R +V _C )≦1.0. From this, the coordinate axes are V _R + V _C and V _R / (V _R + V _C ) or V _C / (V _R +
By using a coordinate system with two axes of V _C ),
It becomes possible to clearly separate chromatic colors (red, cyan) and achromatic colors.

FIG. 3 is a diagram showing an example of a color separation map that is divided according to the color separation method described above. In the figure, the horizontal axis represents color difference signal information V _C /(V _R +V _C ),
The left vertical axis shows the luminance signal information V _R +V _C , and the right vertical axis shows the reflection density due to achromatic color. Color difference signal information =
There is an achromatic color near 0.5 (shaded area in the figure), areas smaller than 0.5 are reddish, and areas larger than 0.5 are cyanish. Also, reflection density and luminance signal information V _R +
Since there is a correspondence relationship with V _C as shown in the figure, it is easy to connect directly to the output value. In the example shown in the figure,
Although V _C /(V _R +V _C ) is plotted on the horizontal axis as color difference signal information, the same can be said of V _R /(V _R +V _C ).

The operation of the image forming apparatus using this color separation map (table) will be explained. A document is first scanned by a slit exposure optical system used in ordinary copying machines, etc., and the obtained optical image is passed through the color separation means shown in Figure 1, and is received by a photoelectric conversion means such as a CCD to form an image. Obtain the signals V _R , V _C and further calculate V _R +V _C , V _C /(V _R
+V _C ) signal. Addressed by these values, density-corresponding values are output according to the table.

On the other hand, if the recording means that records on the recording medium has a recording section that records in black, blue, and red, for example, black, blue, and red are sequentially recorded in correspondence to each scan.
Blue and red are driven frame by frame, and each color is overwritten. That is, the following operations are performed: document scanning→outputting density corresponding values from the table→black recording→document scanning→density corresponding value output from the table→blue recording→document scanning→density corresponding value output from the table→red recording. For such recording means,
The output signal from the table is processed by means (the above-mentioned BBR color select circuit 45 and buffer 4 shown in FIG.
3, 44), thereby properly recording a predetermined color.

In the actual image processing unit, the color separation map shown in FIG. 3 is created and stored in the ROM table. Specifically, it is stored in the third and fourth memories 81 and 82.

Here, as mentioned above, the color difference signal V _C /(V _R +
Red and blue can be distinguished by whether V _C ) is larger or smaller than 0.5. Therefore, since red and blue can be distinguished by the upper bits of V _C /(V _R +V _C ), chromatic color data can be stored together in memory 81. Color difference signal V _C / from memory 73
The reason why (V _R +V _C ) is input to the color select circuit 45 is to distinguish between red and blue colors.

The luminance signal V _R +V _C is stored in the first memory 72, and the color difference signal V _C /(V _R +V _C ) is stored in the second memory 72.
3. The outputs of these first and second memories 72 and 73 are given to third and fourth memories 81 and 82 as address signals. The third and fourth memories 81 and 82 output density data stored at addresses corresponding to the input addresses, and are held in buffers 43 and 44, respectively. Further, the logical sum of the outputs of the memories 81 and 82 is held in the buffer 92 (described later).

On the other hand, the color determination unit 46 counts the density data for each color from the first and second buffers 43 and 44 during preliminary scanning, obtains a density histogram based on these counted values, and uses the density histogram information to obtain a density histogram. Set the number of scans and threshold. The color determination unit 46 provides the color selection circuit 45 with a BBR signal during main scanning, and also provides the threshold circuit 47 with threshold data for multi-value conversion (including binary conversion).

FIG. 4 is a diagram showing the relationship between the BBR signal and color designation. That is, the BBR signal is input as 2 bits. The color select circuit 45 controls the first and second buffers 43 and 44 using this BBR signal and the upper bits of V _C /(V _R +V _C ). for example,
If the response shown in Fig. 4 is taken, the first buffer 43 becomes valid when (1 0) is input, and at this time, red and blue are mixed by V _C /(V _R +V _C ). Take action to avoid it and output red data from the buffer 43. The case of selecting a red light has been taken as an example above, but the same applies to the case of selecting a green light, except that (0 1) is input.

When (0 0) is next input, the second buffer 44 becomes valid and only the contents of the black memory are output. Also, when (1 1) is input, the all-black mode is set, and in the all-black mode (a mode in which both the red and blue of the original image are black), the first and second buffers 43,
44 will be valid.

In this way, density data for each color can be output from the apparatus shown in the figure. These density data are converted into multivalued data (including binary data) by a threshold value circuit 47 using a threshold value set for each color gamut. This multivalued data is used as input data to the recording means. The above operations are performed using CCD41,
42 will be repeated each time new optical information is received.

FIG. 5 is a diagram showing a specific example of the configuration of the color control means 90. Components that are the same as those in FIG. 2 are designated by the same reference numerals. In the figure, 91 is a color designation signal B.
The first decoder receiving BR, 92 is the memory 8
This is a third buffer (tri-state buffer) that receives the OR signal of the outputs of 1 and 82. Note that the first and second buffers 43 and 44 are also tristate buffers. The first output of the decoder 91 enters the second buffer 44 as a gate signal E;
The AND signal of the second and third outputs enters the second decoder 93, and the fourth output enters the third buffer 92 as the gate signal G.

In addition to the above signal, the second decoder 93 receives the color difference signal output from the memory 73 and one bit (D ₁ ) of the BBR signal. The AND signal of the first and fourth outputs of the decoder 93 is then
The signal is input to the buffer 43 as the gate signal F. The AND signal of the second and third outputs is input to the buffer 94 in FIG. 4 as a gate signal H. 0/1 is input to the data input of the fourth buffer 94 by turning on/off the switch _SW1 . The outputs of the first to fourth buffers 43, 44, 92, and 94 are connected in common and enter a latch 95.

96 is a threshold in which various threshold data are stored.
In the ROM, the threshold ROM 96 contains a color designation signal BBR, a density regulation signal, and a clock as addresses.
CLK is being input. And threshold ROM96
is designed to output optimal threshold data according to color specification and density. The output of the threshold ROM 96 is sent to a latch 95. A comparison circuit 97 receives density data and threshold data for each color from the latch 95 and performs multi-value processing such as binarization processing on the image signal. As the comparison circuit 97, for example, a digital comparator is used. Multivalued data is then output from the comparison circuit 97. The operation of the circuit configured as described above will be explained as follows.

Now, when the color specification signal BBR is (0 0), the first
Only the gate signal E becomes "0" by the second decoders 91 and 93, and the second buffer 44 is activated. As a result, only the output of the black memory 82 becomes valid, and the contents of the black memory 82 are output and latched into the latch 95.

Next, when the color designation signal BBR is (1 0), the 6th
As shown in the figure, the operation differs depending on whether the most significant bit of the color difference data V _C /(V _R +V _C ) is "0" or "1".
In the case of “0”, the decoder 93 outputs the gate signal F
set to “0”. As a result, the first buffer 4
Only 3 is active. When buffer 43 becomes active, only the red data in memory 81 is output and latched into latch 95. In the case of “1”, the gate signal F also becomes “1” and the buffer 4
All of the outputs 3, 44, and 92 become high impedance, and no concentration data is output. Data is output from the fourth buffer 94 so that it is a black or white output that is not actually printed.

Next, even when the color designation signal BBR is (01), the operation differs depending on whether the most significant bit of the color difference data V _C /(V _R +V _C ) is "0" or "1". In the case of "0", the gate signal E of the buffers 43, 44, 92,
F and G are all set to "1", and no density data is output, which is the same as above. In the case of "1", the second decoder 93 sets only the gate signal F to "0". As a result, only cyan (blue) data in memory 81 is output and latched in latch 95.

Finally, when the color designation signal BBR is (1 1), the first decoder 91 sets only the gate signal G to "0". As a result, only the third buffer 92 becomes active, and the logical sum data (all black, all red, all blue) of all colors (black data, red/cyan data)
is output and latched in latch 95.

Now, consider the case where the color designation signal BBR is (1 0) or (0 1). When it is (1 0), the color difference signal V _C /(V _R +V _C ) is "0", and when it is (red), F is "0" and the red data is output as is. On the other hand, when the color difference signal V _C /(V _R +V _C ) is "1", all of the gate signals E, F, and G become "1", but at this time, only the H signal (the gate signal of the fourth buffer 94) becomes "0", and in this case, only the fourth buffer 94 becomes active. in this case,
When switch SW ₁ is off, data input is “1”
Therefore, white data is output, and when switch _SW1 is on, the data input becomes "0" and black data is output. In this way, in the normal mode, when a signal other than the specified color is received, white data is output, and only the specified color is output. Furthermore, in the inversion mode, an all-black (all-red, all-blue) signal is output as a non-designated signal.

Next, the operation of binarizing using the color designation signal BBR will be explained. As mentioned above, the BBR signal is given to the threshold ROM 96 as an address. Assuming that the threshold data is composed of a 2x2 matrix, for example, the addresses of the threshold ROM 96 are determined as shown in FIG. 7, and predetermined optimal thresholds are stored in the memory addresses corresponding to these addresses. Just leave it there. Figure 7 1st row BB
R, 2, 3, and CLK indicate input terminals of the threshold value ROM 96, and switching of the density of each color between light, medium, and dark is specified from, for example, an operation unit (not shown).

The method of storing threshold value data in the threshold value ROM 96 is shown in FIG. For example, numerical data is stored one by one as shown in C in correspondence to the input address shown in the row of threshold data of a 2×2 matrix as shown in A. Conversely, when reading out the stored threshold data, it will be read out in the order of 0→2→3→1. This procedure is effective not only for binarization but also for multivalue (three to four or more values). Furthermore, color conversion is possible by changing the color correspondence between the color designation signal and the enhancement means. For example, you can replace blue with red.

FIG. 9 is a diagram showing a specific example of the configuration of the color determination section 46 (see FIG. 2). Components that are the same as those in FIGS. 2 and 5 are designated by the same numbers. The density data held in the first to third buffers 43, 44, and 92 are sequentially output onto the data bus DB in response to a select signal from the color select circuit 45, and enter the latch 95. On the other hand, the optimum threshold value corresponding to the color is input from the threshold value ROM 96 to the other input of the latch 95, and the conversion into multivalued data (including binary data) in the subsequent threshold value circuit 47 is the first step. 5
This is as described for the circuit shown in the figure.

The counter 100 receives a dot clock (a clock output for each pixel) and generates a 2-bit pseudo color designating signal BBR', which is applied to the color select circuit ₄₅ via a switch SW11 which is turned on only during preliminary scanning. At the same time, the BBR' signal is constantly applied to the decoder 101. Now, let's not consider all black data here, and counter 1
Select all black data from 00 (1 1)
should not occur.

During a preliminary scan, a color select signal is sequentially output from the color select circuit 45, and red, blue (cyan), and black data are extracted and output onto the data bus DB. The extracted color data is applied to counters 105-107 via buffers 102-104 for each color. The decoder 101 sequentially provides a select signal to each of the buffers 102 to 104 in accordance with the input signal (00→01→10) at this time. Each counter 105-1
07 counts input data for each color and forms a histogram. And these counters 105 to 10
The count value of 7 is latch 108 when the preliminary scan is completed.
~110 is given. And each latch 108
The outputs of 110 to 110 are applied to the subsequent determination circuit 111.

The determination circuit 111 has counters 105 to 1 for each color.
Upon receiving the output of step 07, the number of scans in the main scan and the multi-value melting threshold are determined from the information of each color and the density histogram. The number of scans during the main scan is determined by the number of colors. For example, if there are three colors, red, blue, and black, the number of scans will be three.
Next, the multivalue threshold is determined as follows. For example, the output of each counter (density histogram)
In the case of a normal color original consisting of an image and a background image, the characteristics are as shown in FIG. 10A. In the case of such characteristics, the threshold value is, for example, the density _K1 at the point that is the valley of the curve in the figure. In the case of a color document in which it is difficult to distinguish between an image and a background image, a valley appears as shown in FIG. 10B. In such a case, it is conceivable to use, for example, the integral value from the highest concentration point K _nax of the power to 0.9M _nax (shaded area in the figure) as the threshold value. Therefore,
Codes 2 and 3 in FIG. 7 are selected based on the threshold values determined in this way.

Once the number of scans and threshold information are determined in this manner, these information are provided from the determination circuit 111 to the main body control section 112. Main body control section 112
Upon receiving this information, gives the threshold ROM 96 an address for outputting the optimal threshold data, and
The scanning number information is given to the BBR signal generation circuit 113. The BBR signal generation circuit 113 is designed so that the number of scans can be set separately from the outside.
The BBR signal generation circuit 113 supplies a color designation signal BBR based on the number of scans to the threshold ROM 96, and
Color selection circuit 45 via switch SW ₁₂
It is also given to In addition, during preliminary scanning, the switch
SW ₁₂ is turned off, and the color selection circuit 45 is given the pseudo color selection signal BBR.

Now, assuming that only black and red are detected by the circuit shown in the figure, and the threshold values for each color are determined to be T _B and _TR , respectively, at the time of main scanning, first the color designation signal indicating red is detected.
BBR is specified as (1 0) and threshold value _TR is specified. Switch SW ₁₁ is off and SW ₁₂ is on. When one scan ends in this state, this time
The BBR signal is designated as black (0 0), and the threshold is designated as T _B. In this case, scanning is completed in two times.

When the color selection signal and the threshold value are specified in this manner, the image data read from the color original is multivalued and output as multivalued data. Note that the method for determining the threshold value is not limited to the method described above, and other methods may be used.
The multivalued data output from the threshold circuit 47 is reproduced as an image by a recording means such as a printer.

FIG. 11 is a diagram showing an example of the configuration of recording means in the image recording apparatus of the present invention. In this configuration, the laser device 120 emits modulated light modulated by red density data. The emitted modulated light exposes the surface of the moving drum 121. This exposed photosensitive drum 121 is then transferred to the developing section 1.
At step 22, red toner is first applied and transferred to the copy paper fed from the paper feed cassette 123. Next, the photosensitive drum 121 rotates once and receives an initial charge in the charge control section 124, and then the laser device 1
At 20, modulated light modulated by the blue density data is output. The emitted modulated light is sent to the photosensitive drum 1
The surface of 21 is exposed. Blue toner is attached to the surface of this photosensitive drum 121 in the subsequent developing section 122. Photosensitive drum 12 with blue toner attached
1 to copy paper. The copy paper onto which the image of a predetermined color has been transferred in this manner is sent to the fixing section 125 and is fixed as a color image.

Next, another embodiment of the main part of the present invention will be described. FIG. 12 and FIG. 13 are diagrams showing other embodiments of the main part of the present invention, respectively. First, the first
The embodiment shown in FIG. 2 will be described. The two types of optical signals are converted into electrical signals V _A and V _B by photoelectric conversion means 161 and 161' such as CCD. After the converted V _A and V _B signals are amplified by amplifiers 162 and 162', an adder 163 performs the calculation (V _A +V _B ). This calculation output is determined by the comparator circuit 164 to be white when V _A +V _B ≧a ₁ , white when a ₂ ≦V _A +V _B < a ₁ , and black when chromatic color V _A +V _B ≦a ₂ . The reason why the output from the comparison circuit 164 is input to the color discrimination circuit 165 is that a ₂ ≦V _A +
This is to notify the color discrimination circuit 165 of the case where V _B <a ₁ (that it is a chromatic color).

On the other hand, the V _A and V _B signals are sent to the logarithmic amplifier 166,
166' for logarithmic amplification. The logarithmically amplified signals logV _A and logV _B are subjected to an operation (logV _A −logV _B ) in a subsequent subtracter 167 . For this value of (logV _A −logV _B ), the following color discrimination circuit calculates 165 when logV _A −logV _B ≧b ₁ Red b ₂ <logV _A −logV _B <b ₁ Green logV _A −logV _B When ≦b ₂ , it is judged as blue.

Here, during the preliminary scan _, the blue, _green ,
By creating a red density histogram, it is possible to know the density of the original color and determine the threshold value for each color, similar to the apparatus of the present invention described above. Comparison circuit 16
4 has a density histogram creation function and a threshold value creation function, the threshold value created for each color from the comparison circuit 164 is given as a reference value to each comparator 168 to 170, and the image data output from the color discrimination circuit 165 is multiplied. Value.

Next, the embodiment shown in FIG. 13 will be described. In the example shown in the figure, color separation is performed based on the condition that optical information can be separated into colors using a color separation map as shown in FIG. Photoelectric conversion means 17
The red signal V _R and the blue signal V _B converted into electric signals by amplifiers 172 and 171' are respectively
After being amplified by 172', A/D converter 173,
At step 173', the data is converted into digital data and given as addresses to red memory 174, blue memory 175, and black memory 176, respectively. memory 17
4 to 176 constitute a ROM table based on a color separation map as shown in FIG. 14, and the image data in each memory is outputted and stored in the corresponding buffer memories 177 to 179. The output data from each buffer selected by the color selection circuit 180 is sent to the comparison circuit 1.
81, it is multi-valued. The threshold value of this comparison circuit 181 is given by its threshold value circuit 182,
The threshold circuit 182 includes a color selection circuit 180.
The threshold circuit 182 generates a threshold according to the color gamut.

Here, in the embodiment shown in the figure, a histogram cannot be simply created because there is no concept of density for the _VR and _VB axes. However, Z=√
A histogram can be created by making the value of V _R ² +V _B ² correspond to the density and counting this Z. If a histogram can be created, a threshold value can be determined based on this histogram.

Therefore, an arithmetic unit 183 that calculates Z by calculating √ _RB + _B ² and an arithmetic unit 184 that calculates V _R −V _B are provided. The outputs of these arithmetic units 183 and 184 are given to each of the memories 174 to 176 as addresses, and the output of the arithmetic unit 183 is given to a threshold circuit 182 as an address for threshold selection. The arithmetic unit 184 is provided because, for example, if V _R is larger than V _B , red color,
This is because if it were the other way around, it would be possible to distinguish the color from blue.

During preliminary scanning, a density histogram for each color is determined and a threshold value is determined, and during main scanning, this threshold value is used to perform multi-value conversion (including binary conversion). Note that YMC full color can be achieved by creating a histogram of the output data of each channel for each red, green, and blue color. The same applies to YMC multicolor.

In the above explanation, V _C /(V _R +V _C ) was used on the horizontal axis of the color separation map shown in FIG. 3, but V _R /
It may be (V _R +V _C ). A similar effect on the horizontal axis can also be obtained by using (V _R −V _C )/(V _R +V _C ) or (V _C −V _R )/(V _R +V _C ) as the horizontal axis. For example, if we use (V _R − V _C )/(V _R + V _C ) on the horizontal axis, (V _R − V _C )/(V _R + V _C ) = 0 Achromatic color in the vicinity > 0 Reddish color < 0 Cyan color.

Furthermore, in the above description, a dichroic mirror with red transmission and cyan reflection type was used as the spectral characteristics, but the present invention is not limited to this. It's okay to be hot. Further, the color separation means is not limited to a dichroic mirror, but may be any device that can separate colors. For example, it may be a spectral filter or the like. Further, the color separation map is not limited to the T-shape shown in FIG. 3, but may be of any shape.

(Effects of the Invention) As explained in detail above, according to the present invention,
Before performing image formation, the original image is read and the color of the original image is determined, and in the subsequent image forming process, the execution of the image forming process for colors that can be considered not to exist in the original image is omitted. The recording time can be shortened according to the number of colors in the original image, and the density data read from the color information storage means can be compared with a threshold value set for each of a plurality of predetermined colors. and
Since the threshold value is changed depending on the color, sufficient copying density can be obtained for all colors without changing the developing bias voltage, so this image recording device can record the image density of each color in a well-balanced manner. can be realized.

[Brief explanation of drawings]

1 and 2 are configuration diagrams showing one embodiment of the configuration of the image reading and image processing parts in the image recording apparatus of the present invention, and FIG. 3 is a diagram showing an example of a color separation map.
4 and 6 are diagrams showing the relationship between the BBR signal and color designation, FIG. 5 is a diagram showing a specific configuration example of the color control means, and FIG. 7 is a diagram showing the address of the threshold ROM,
FIG. 8 is a diagram showing a method of storing threshold data in the threshold ROM, FIG. 9 is a diagram showing a specific configuration example of the color determination section, FIG. 10 is a diagram showing an example of a density histogram,
FIG. 11 is a diagram showing an example of a recording means, FIG. 12,
FIG. 13 is a diagram showing another embodiment of the main part of the present invention, and FIG. 14 is a diagram showing an example of a color separation map. 31... Lens, 32, 33... Prism, 3
4...Dichroic mirror, 35, 36, 4
1, 42...CCD, 40...photoelectric conversion means, 4
3, 44, 92, 94, 102-104...Buffer, 45...Color selection circuit, 46...Color determination section, 50...Amplification section, 51, 52...Amplifier, 60...A/D conversion section , 61, 62...A/
D converter, 70...color separation information creation means, 72,
73, 81, 82, 174-176...memory,
80... Color information storage means, 90... Color control means,
91, 93, 101...decoder, 95, 108
~110...Latch, 96...Threshold ROM, 97
... Comparison circuit, 105 to 107 ... Counter, 1
11... Judgment circuit, 112... Main body control section, 12
1...Photosensitive drum, 122...Developing section, 123...
...Paper feed cassette, _SW1 , _SW11 , _SW12 ...Switch, DB...Device, 301...Reading unit, 302...Light source, 304...Optical system.

Claims (1)

[Claims] 1. An image recording device that records a color image by reading an original image and repeating image signal processing and image forming processes for each color, comprising at least two types of reflected light or transmitted light from a color original. An image reading means that separates and reads the image into colors, and a color separation map that classifies each pixel of a document image into one of a plurality of predetermined colors, and a color separation map in which density data is set for each address. color information storage means in which the map is stored in memory; and color separation information generation for creating an address signal for the memory in which the color separation map is stored from the output signal of the image reading means and outputting it to the color information storage means. means, threshold value generation means for generating a threshold value determined for each of the plurality of predetermined colors, and a density read out from the color information storage means based on an address signal output from the color separation information creation means. a comparison means for comparing the data with a threshold value output by the threshold value generation means; and a discrimination means for reading the original image and determining the color of the original image before forming an image based on the output of the comparison means. An image recording apparatus comprising: a control means for omitting execution of an image forming process for a color that can be considered not to exist in a document image in a subsequent image forming process based on the determination result of the determining means.