JP2958981B2 - Document detection device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to an image processing apparatus for processing image information obtained by optically scanning a document placed on a platen, such as a copying machine and a facsimile. And a document detection device for detecting a document area to be subjected to image processing.

2. Description of the Related Art An image processing apparatus that optically scans a document placed on a platen and processes image information to be read, for example,
For copiers, the automatic paper selection function (APS function), automatic magnification selection function (AMS function), etc. Required. In addition, in order to realize a so-called free registration function, a position of an original to be subjected to image processing is detected on the platen so that a normal image can always be reproduced even if the original is placed at an arbitrary position on the platen. Is required. Conventionally, the following document detecting devices detect the size and position of a document to be subjected to image processing.

For example, as disclosed in Japanese Patent Publication No. Sho 62-47026, a means for giving black information to the background portion of a document is provided, and a difference in optical reflectance between the document and the background portion, that is, based on a density difference, is provided. The document edge is detected, and the size of the document is recognized from the detected document edge. Also, as disclosed in Japanese Patent Application Laid-Open No. 62-220946, the original pressing surface of the original cover is colored with a special color, and the original edge is detected based on the color difference between the original and the original cover. The document size is recognized by the document edge.

[Problems to be Solved by the Invention] In the above-mentioned conventional document detection apparatus, which detects a document based on a density difference from a background portion, when an image is read with a document cover (platen cover) closed, the document is not read. Since the pressing surface is colored black, if the original to be subjected to image processing is thin, the background black is transparent through the original, so that the original background is not processed in a faithful state.

Also, if the original cover is colored with a special color and the original is detected based on the color difference between the original and the original cover,
For example, if the target document to be subjected to image processing is thick like a book, the document cover will float up, so that accurate color difference detection cannot be performed. Further, if an image is to be read while the original cover is open, the function cannot be exhibited at all.

SUMMARY OF THE INVENTION It is an object of the present invention to enable accurate document detection regardless of the open / close state of a document cover (platen cover) while minimizing the influence on the background of the document.

[Means for Solving the Problems] As shown in FIG. 1, the present invention relates to an image processing apparatus for optically scanning a document 2 placed on a platen 1 and processing image information read. In this case, it is assumed that a document detecting apparatus detects two areas of a document to be subjected to image information. In the document detecting apparatus, technical means for solving the above-described problem is as shown in FIG. Then, the original pressing surface 3a of the platen cover 3 that can be opened and closed on the platen 1 is colored with a color different from the color of the target original 1, and the platen cover 3 is opened (OP) and closed (CL). Platen open / close determining means 4 for determining whether the document 2 is open or not (OP) when the platen open / close determining means 4 determines the open state (OP) of the platen cover 3 based on the density difference between the document 2 and its background. One document edge detecting means 5 A second document edge detecting means 6 for detecting a document edge based on a color difference between the document 2 and the document pressing surface 3a of the platen cover 3 when the platen open / close determining means 4 determines the closed state of the platen cover; Second document edge detecting means 5, 6
And a document area specifying means 7 for specifying a predetermined area including the document edge portion detected in step 2 as a document 2 area.

The color of the document pressing surface 3a of the platen cover 3 is determined based on a balance between the effect on the document background when a thin paper document is targeted and the ability to discriminate the color difference from the document. It is preferable to make the color as light as possible within the range in which the color difference can be determined, since the influence on the background of the original is small even when the original is a thin paper.

The density difference, which is the basis for document edge detection by the first document edge detecting means 5, corresponds to the difference in optical reflectance.

The respective components such as the first document edge detecting means 5 and the second document edge detecting means 6 can be provided independently of the image information reading system. In the image processing apparatus provided with the image reading means 8 for reading the image data in a predetermined pixel unit separately into density information (D) and color information (C), the density information (D) read by the image reading means 8 is used. ) And the color information (C), the configuration is simplified as shown in FIG. 1B from the viewpoint of simplifying the configuration. That is, the first document edge detecting means 5 converts the density information (D) obtained in the course of scanning of the document by the image reading means 8 into a predetermined reference between the document 2 and each reading density of its background. Density information binarization means 5a for binarizing based on density, and density change position detection means for detecting a change position of the binarization information obtained by density information binarization means 5a
5b, and a document edge discriminating means 5c for discriminating the document edge position based on the position detected by the density change position detecting means 5b.

In this case, the reference density in the density information binarizing means 5a is determined to be a density between the target document and each reading density of the background portion thereof, but the density is closer to the target document density side (white density side). If it is close to the original document, it may cause erroneous detection of the original edge due to density variation or smudge of the target document. Also, if it is close to the reading density side (black density side) of the background portion, external light may enter (open the platen cover 3). State) may cause an erroneous detection. In general, the density is determined to be so high that it cannot be assumed for a document to be usually targeted.

Furthermore, from the viewpoint of sharing the components of the second document edge detecting means 6 and the components of the first document edge detecting means 5 to simplify the configuration, the first document edge detecting means 5 is used. Assuming the configuration, the second document edge detecting hand 6 has a platen cover 3 as shown in FIG.
Color detection means 6a for detecting the color of the original pressing surface 3a, and density information (D) corresponding to the pixel for which the color detection has been performed by the color detection means 6a.
a) a density conversion means 6b for converting the density information into binary information 5a in the first document edge detection means 5 to detect a document edge based on the density information obtained by the density conversion means 6b. And the density change position detecting means 5b
And the document edge discriminating means 5c.

The mode of specifying the document area in the document area specifying means 7 is as follows.
It may specify the region itself defined by the document edge portion, or may specify a region having a certain extent including the document edge portion. In general, an area is specified in a mode suitable for image processing to be performed. From the viewpoint of easiness of specifying the document area, an XY coordinate system is set on the platen 1 so that the direction along the main scanning direction is the Y direction and the direction along the sub-scanning direction is the X direction. Means 7
X-direction area specifying means for specifying the X-direction area at the maximum and minimum document edge positions in the X direction, and Y-direction area specifying the Y-direction area at the maximum and minimum document edge positions in the Y direction And a specifying means.

[Operation] The platen open / close determining means 4 determines the open state of the platen cover 3 before reading the image information and performing the processing on the thick original 2 such as a book while the platen cover 3 is open / closed. Since there is no optical reflection in the background portion of the document 2 on the first document 1, the first document edge detecting means 5 detects the document edge portion based on the density difference between the document 2 and the background portion. Then, the document area specifying means 7 specifies a predetermined area including the detected document edge as a document area.

On the other hand, before the platen cover 3 is closed and the platen open / close determining means 4 detects the closed state of the platen cover 3 before the image information is read and the processing is performed with the platen cover 3 closed, the second The document edge detecting means 6 detects a document edge based on the color difference between the document 2 and the document pressing surface 3a of the platen cover 3. Then, the document area specifying means 7 specifies a predetermined area including the detected document edge as a document area.

In each of the above cases, image information obtained for each specified document area in the process of optical scanning is to be processed.

Examples Examples of the present invention will be described below in the order of the table of contents.

Table of contents I. Basic configuration II. Image input unit III. Color image information generation unit IV. Original detection unit V. Processing unit VI. Image formation unit VII. Summary I. Basic configuration The basic structure of the scanning system is, for example, It is as shown in FIG.

An openable / closable platen cover 14 is provided above a platen 12 on which a document 13 is placed, and a light guide member 16 including a light source 15 and a selfoc lens and a CCD are provided below the platen cover 14.
And the like, and a one-dimensional image sensor 10 is arranged, and these constitute an integral scanning unit. When the scanning unit performs a parallel movement (in the direction of the arrow in the figure) and optically scans the document 13, the scanning of the document 13 is performed based on a detection signal in cell units corresponding to the amount of received light output from the image sensor 10. , Image information of a predetermined pixel unit corresponding to the grayscale image, the diagram, the character, and the like drawn in FIG.

An open / close detector 18 for detecting the open state and the closed state of the openable / closable platen cover 14 is provided. The open / close detector 18 is configured by, for example, a reed switch, and performs an on / off operation according to the position of the magnet provided on the platen cover 14 in the open state and the closed state. For example, the open / close detector (reed switch) 18 is turned on when the platen cover 14 is open, and the open / close detector 18 is turned on when the platen cover 14 is closed.
Is turned off. A specific configuration of a platen open / close determination circuit for determining the open state and the closed state of the platen cover 14 based on the on / off state of the open / close detector 18 constituted by the reed switch is shown in FIG. 3, for example. It has become. This is because the capacitor C1 is charged via the resistors R1 and R2 by turning on and off the reed switch 18, and the resistor R2
And discharges through the device. Reed switch 18
Is on, the capacitor C1 is discharged and the output of the inverter 19 is at the H level. When the reed switch 18 is off, the capacitor C1 is charged and the output of the inverter 19 is at the L level. The output is a determination output (PLTINT) of the open / closed state of the platen cover 14. That is, when the platen cover 14 is open, the output of the inverter 19 becomes H level, and when the platen cover 14 is closed, the output of the inverter 19 becomes L level.

The original pressing surface of the platen cover 14 is colored with a relatively light color different from the assumed original color (the image color of the target original, a color not used for the marker, for example,
Yellow, etc.).

Next, the basic configuration of the entire image processing apparatus is, for example,
As shown in FIG.

This example is an image processing apparatus on the premise of two-color image processing, for example, image reproduction of black (main color) and red (sub-color).

In FIG. 4, reference numeral 10 denotes a full-color sensor for optically scanning an original image (corresponding to the image sensor in FIG. 2);
Numeral 20 converts read signals sequentially output from the full-color sensor 10 in cell units in a time division manner into color component data (green: G, blue: B, red: R) in predetermined pixel units and outputs them in parallel. The full-color sensor 10 and the sensor interface circuit 20 constitute an original image input unit. Reference numeral 50 denotes a color image information generating circuit which generates density information and color information on a pixel basis from each color component data (GBR) from the sensor interface circuit 20. The color image information generating circuit 50 has density information D of 256 gradations. And sub color flag SCF corresponding to sub color "red" as color information
And main color flag MC corresponding to main color "black"
F is being generated. 70 is a correction / filter circuit for performing various corrections and filter processing on the density information D and the color information (SCF, MCF) from the color image information generation circuit 50, and 100 is density information D and Color information (SCF, MC
An editing / processing circuit for performing processing such as editing, processing such as enlargement, reduction, and color inversion on F).

As described above, the correction / filter circuit 70 and the editing /
The density information D and the color information (SCF, MCF) that have been subjected to various processes in the processing circuit 100 are provided to specific image forming equipment via the interface circuit 140. The image forming apparatus includes a laser printer 15 for performing two-color reproduction.
0, an image transceiver 170, etc., and further, density information D and color information are provided to a computer 180,
A system form in which the information is stored in an auxiliary storage device (such as a magnetic disk device) and various terminals use the information is also possible. When the above laser printer 150 is connected, a two-color copying machine is configured as a whole,
When 170 is connected, a facsimile is configured as a whole.

II. Image Input Unit This image input unit and the color image information generation unit described in the following section III are integrated to realize an image reading unit as a specific component of the present invention.

The full-color sensor 10 includes, for example, five CCDs each having a predetermined dot density (15.748 dots / mm) as shown in FIG.
The sensor chips 10 (1) to 10 (5) are arranged alternately back and forth with respect to the document scanning direction S, and are arranged in a so-called zigzag pattern and integrated. Each CCD sensor chip 10
As shown in FIG. 6, (1) to (5) show green G, blue B, and red R filters (gelatin filters) for each light receiving surface of each diagonally partitioned cell (photoelectric conversion element). Etc.) are provided in order. The adjacent green filter cell 11g, blue filter cell 11b, and red filter cell 11r form a set and receive light from each cell (corresponding to the document reflectance).
Is processed as a signal for one pixel P.

The sensor interface circuit 20 basically arranges the color component signals (G, B, R) based on the output signals from the staggered CCD sensor chips 10 (1) to 10 (5) into one line. Correction function, each color component signal (G, B, R) processed serially as a signal from each cell of the CCD sensor chip
Is converted into a parallel signal for each pixel P, and a correction function for a shift in the detection position of each color component signal (G, B, R) in one pixel P is provided.

The circuit shown in FIG. 7 is a circuit for realizing the function of aligning the outputs from the staggered CCD sensor chips into one line.

In the figure, each CCD sensor chip 10 (1) to 10
Signals serially output from (5) in units of cells are sequentially transmitted to the A / D conversion circuit 22 via the amplification circuits 21 (1) to 21 (5).
(1) to (22) are input. Each A / D conversion circuit 22
In (1) to (5), the sensor output signal in each cell according to the light receiving amount is output as, for example, 8-bit data. At the subsequent stage of each of the A / D conversion circuits 22 (1) to 22 (5), latch circuits 23 (1) to 23 (5) for timing adjustment are provided, and particularly, in the original scanning direction S (see FIG. 5). ), The CCD sensor chips 10 (2) and 10 (4) arranged ahead of the other CCD sensor chips are provided with a first-in first-out system after the latch circuits 23 (2) and 23 (4). FIFO memories 24 and 25 are provided. This FIFO memory 2
Reference numerals 4 and 25 denote output timings of color component signals for the CCD sensor chips 10 (2) and 10 (4) to delay the other CCD sensor chips 10 (1), 10 (3) and 10 (5). This is for adjusting the output timing of the same line signal for the system of FIG. Therefore, while the write timing is determined to be a predetermined timing, the read timing (delay amount) is the distance between the scan lines of the CCD sensor chips 10 (2) and 10 (4) and the scan lines of the other CCD sensor chips. (For example, 62.5 μm) and the document scanning speed of the full-color sensor 10. For example, when the scanning speed is different according to the magnification of the image to be formed, the readout timing is controlled according to the magnification. As described above, when the read timing is made variable by the magnification or the like, the FI is assumed to be the slowest in the read timing.
The capacity of the FO memories 24 and 25 is determined (the memory capacity corresponds to the allowable delay amount). Latch circuits 26 (2) and 26 (4) are provided at the subsequent stage of each of the FIFO memories 24 and 25, while the CCD sensor chips 10 (1), 10 (3) and 10 (5) The next latch circuit 26 (1), 26 (3), 26 (5) is directly connected to the subsequent stage of 23 (1), 23 (3), 23 (5), and the preceding CCD via FIFO 24, 25 is connected. Sensor chip
The latches 26 (1) to 26 (1) to 26 (1) to 26 (1) to 26 (1)
In (6), they are aligned as those of the same scanning line, and transferred to the subsequent stage at a predetermined timing. Each latch 26 (1)
26 (6), the color component signals are serially transferred in the order of G → B → R → G → B → R →... Corresponding to the cell arrangement of each CCD sensor chip.

The circuit shown in FIG. 8 is a circuit for realizing the function of converting each color component signal serially transferred in the system of each CCD sensor chip into a parallel signal for each pixel as described above.

In the figure, each of the above CCD sensor chips 10 (1) to 10 (1) to 10
Serial-to-parallel conversion circuit 30 (1) to (5)
30 (5) are provided. Each of the serial / parallel conversion circuits 30 (i) (i = 1,..., 5) is a latch circuit 31g to which the color component signals (G, B, R) serially transferred as described above are input in parallel. Each of the latch circuits includes a clock signal (in synchronization with the G clock) in which 31g is activated when the color component signal G (green) is transmitted, and 31b which is activated when the color component signal B (blue) is transmitted. In synchronization with the clock signal (B clock).
Each color component signal is latched in synchronization with a clock (R clock) that becomes active at the time of transfer of (red). Further, at the subsequent stage of each of the latch circuits 31g, 31b, 31r, there is provided a tri-state latch circuit 32g, 32b, 32r for latching again for each pixel in order to adjust the transfer timing, and each tri-state latch 32g, 32b , 32r, the latch data (color component signal) of the preceding stage is simultaneously re-latched at the falling timing of the R clock. Further, the tri-state latch circuits 32g and 32g
The b / 32r has its enable / non-drive controlled by an enable signal (i) (i = 1,..., 5).

A memory circuit 34 and a timing control circuit for controlling writing and reading of the memory circuit 34 are provided at the subsequent stage of the serial / parallel conversion circuits 30 (1) to 30 (5). The memory circuit 34 has a dedicated memory for each color component (G, B, R). When writing each color component to the memory, the enable signal is converted from (1) → (2) → (3) →
The active state is switched in the order of (4) → (5),
In addition, by controlling the write address according to a predetermined rule, one line of data is sequentially arranged in the memory for each color component (G, B, R). Then, by reading the data of each color component from each dedicated memory sequentially in parallel, the color component data of each pixel is sequentially transferred from the end of one line to the subsequent stage.

It should be noted that the resolution is converted at the boundary of the memory circuit 34 by the difference between the write timing and the read timing in the timing control circuit 36. For example, a timing control circuit so that the resolution in the system after the memory circuit 34 is 400 SPI
Reference numeral 36 controls the read timing.

The circuit diagram shown in FIG. 9 shows each color component (G, B,
R) is a circuit that implements a correction function for the displacement of the detection position.

As shown in FIG.
Since the reading position of each color component G, B, R is spatially shifted within the pixel, if the signal from each cell is processed as it is as a color component signal, other color pixels will occur at the boundary of the black image. This causes a problem such as ghosting. In order to prevent such a ghost or the like, the correction circuit makes the reading positions of the respective color components seemingly coincide with each other. Specifically, in the arrangement of each cell shown in FIG. 10, when the pixel Pn is focused on, the reading position of each color component is corrected to be virtually the position of the cell Gn. The method of the correction is that the adjacent pixel P _n-1
In consideration of the above, weighted averaging is performed so that the reading position of each color component becomes the position of the cell Gn. That is, Gn = Gn ... (1) Bn = (Bn _-1 + 2Bn) / 3 ... (2) Rn = (2Rn _-1 + Rn) / 3 ... (3) Each color component data (Gn, Bn, Rn).

As a circuit for realizing the above-mentioned operation, for example, there is a circuit shown in FIG.

The color component data output for each pixel in the circuit shown in FIG. 8 is input to the correction circuit in parallel. Then, for the G component system, the latch circuit 38g
For the system of the B component, a subsequent latch circuit 41 and a shifter 42 for shifting the data latched by the latch circuit 38b by one bit are provided at the subsequent stage of the latch circuit 38b, and the latch data of the latch circuit 41 and the shifter An adder 43 for adding the shift data at 42 and a look-up table (ROM) 44 for taking the result of addition at the adder 43 as an address input and outputting 1/3 thereof are provided. As for the system of the R component, a next latch circuit 45 and a shifter 46 for shifting the data latched by the latch circuit 45 by one bit are provided at the subsequent stage of the rally circuit 38r.
There is provided an adder 47 for adding the latch data of r and the shift data in the shifter 46, and a look-up table (ROM) 48 for using the addition result of the adder 47 as an address input and outputting 1/3 thereof as described above. . With such a configuration, the above-described equation (1) is realized in the G component system, and shifting by one bit means a double operation. Therefore, in the B component system, the above equation (2) and the R component In the system, the above equation (3) is realized.

The above is the basic configuration of the original image input section composed of the full-color sensor 10 and the sensor interface circuit 20. When scanning the original document as the original image with the full-color sensor 10, each color is provided in a predetermined pixel unit for each line. The component data (G, B, R) is sequentially output.

Each color component signal that has been processed by the original image input unit as described above is transferred to a color image information generation unit described below through a process such as shading correction that is generally performed.

III. Color Image Information Generating Unit In this color image generating unit, an image reading means for reading the density information and the color information separately is embodied, and a part of the second document edge detecting means which is a constituent element of the present invention. And the density conversion means are embodied.

11 and 12 show the color image information generating circuit in FIG.
50 specific structures are shown.

In FIG. 11, a subtraction circuit 51 for inputting G component data and R component data of the color component data transferred from the sensor interface circuit 20 in pixel units and calculating a difference (R−G) between them, and a B component A subtraction circuit 52 is provided for inputting data and R component data and calculating the difference (R−B). The result of the subtraction by each of the subtraction circuits 51 and 52 is input to the address end of the look-up table 53 in parallel. The look-up table 53 outputs the product (H × C) of the saturation C and the hue H of the pixel and the color discrimination based on each of the subtraction results. The reading is performed in units of 8 bits. , The upper 5 bits are (H × C), and the lower 3
Bits are assigned to the color judgment output.

The contents of the lookup table 53 are determined, for example, as follows.

As shown in FIG. 13, the vertical axis represents the difference (RG) between the red (R) color component and the green (G) color component, and the red (R) color component and the blue (B) color component. When the color space is set with the difference (R−B) as the horizontal axis, an arbitrary color is specified by the distance r from the origin O and the rotation angle θ. The distance r is a factor mainly determining the saturation C, and the closer to the origin O in the color space, the closer to the achromatic color. The rotation angle θ is a factor mainly determining the hue H. For example, "red""magenta"
“Blue”, “cyan”, “green”, and “yellow” are distributed at positions surrounded by broken lines in FIG. 13 in the color space.

From the relationship described above, (RG) data and (R-
B) The distance r from the origin obtained from the data in accordance with r = {(RG) ² + (RB) ² } ^1/2 and the same as (RG)
A color determination is made at a position in the color space specified by the rotation angle θ obtained from the data and the (RB) data in accordance with θ = tan ^-1 {(RG) / (RB)}. You.

The saturation C is calculated from the relationship between the distance r from the origin determined from the (RG) data and the (RB) data by the above equation and the saturation C, for example, as shown in FIG. It is determined according to the relationship shown. In FIG. 14, when the distance r becomes smaller than the predetermined value r ₀ , the color becomes achromatic and the saturation C becomes “0”.
Becomes

Further, the hue H is a relationship between the rotation angle θ and the hue H determined by the above equation from the (RG) data and the (RB) data, for example, a relationship as shown in FIG. Is required in accordance with In FIG. 15, the rotation angle θ is a predetermined value θ.
When it is smaller than ₀ , the hue H is forcibly set to "0".

As described above, since the color discrimination result, the saturation C and the hue H are both obtained based on the (RG) data and the (RB) data, the (RG) from each of the subtraction circuits 51 and 52 is obtained. And a lookup table 53 having (RB) as an address input realizes the above-described operations such as calculation and determination, and outputs the color determination and the product (C × H) of the saturation C and the hue H. It is configured. Then, as described above, (C × H)
Is represented by 5 bits, and the color discrimination result is represented by 3 bits. It is expressed as shown in Table 1 above.

14 and FIG. 14 which determine the saturation C and the hue H.
The relationship shown in FIG. 15 is determined variously depending on the ability related to color separation required for the system.

In FIG. 11, each of the color component data input in parallel on a pixel-by-pixel basis has a
And the B component data is input to the multiplying circuit 55 of 0.1 times,
The R component data is input to a multiplication circuit 56 of 0.3 times. The multiplication results of the multiplication circuits 54, 55 and 56 are respectively input to an addition circuit 57, and the addition result VV = 0.6G + 0.3R + 0.1B of the addition circuit 57 is transferred to the subsequent stage as brightness data of the pixel. .

The brightness data V is generated based on the G component data of the color component data GBR, taking into account the values of the B component data and the R component data. This is because the spectral sensitivity curve of the G component signal in the image sensor (full color sensor 10) has characteristics close to the human luminous efficiency curve. Each coefficient (multiplied value in each multiplication circuit) in the expression for determining the brightness V is finally determined by the spectral sensitivity characteristics of the image sensor, the spectral distribution of the exposure lamp, and the like.

Since the spectral sensitivity characteristic of the G component signal is close to the human relative luminous efficiency characteristic as described above, it is also possible to use only the G component data as the brightness data V according to the capability required for the system. It is.

The output (H × C) relating to saturation and hue from the look-up table 53, the color discrimination data and the brightness data V from the adder circuit 57 become the address input of the next look-up table 58, and the look-up table 58 It has a function of outputting color density data Dc corresponding to the input. Specifically, it outputs color density data Dc determined according to Dc = K × C × H × V with respect to each of the above inputs. Where K
Is a coefficient that varies depending on the color determination data. The coefficient K is used to match the lightness level between the chromatic color and the achromatic color because the chromatic color and the achromatic color seem brighter, and is determined experimentally in advance in accordance with each discrimination color. Is set to a value within a range of, for example, about 1.1 to 1.3.

The color discrimination output (3 bits) from the lookup table 53 and the color selection data set in the latch circuit 60 are input to the matching circuit 59, and the matching circuit is used when the color discrimination output matches the color selection data. The output of 59 rises to H level. The color selection data is set in the latch circuit 60 based on an operation input by an operator or a setting input by a dip switch or the like, and includes 3-bit data (see Table 1) corresponding to a color to be reproduced as a sub color. Become. The output of the matching circuit 59 is a sub color flag SCF (color information) indicating whether or not the color is a sub color (for example, red) set by the color selection.

The color density data Dc, lightness data V, and sub-color flag SCF generated as described above are further transferred to the subsequent circuit shown in FIG.

In FIG. 12, the color of the original pressing surface (platen color) of the platen cover 14 is set (A input), and a matching circuit 61 for determining a match with the color determination data (B input) is provided. A matching circuit 62 for setting a marker color (area recognition color) for designation (A input) and performing a match determination with the color determination data (B input) is provided. The coincidence signal from each of the coincidence circuits 61 and 62 becomes an output selection signal (SEL) of the selection circuit 64 via the OR gate 63 together with the sub-color flag SCF from the previous stage. An output selection signal (SEL) of the selection circuit 65 via an AND gate 69 that is gate-controlled by an inverted signal of. The selection circuit 64 has a function of switching between brightness data V and “0” data from the preceding stage according to the state of the selection signal, and outputs “0” data when the selection signal is at the H level. Is output at a low level. Selection circuit 65
Has a function of switching between the color density data Dc from the preceding stage and the data from the selection circuit 64 in accordance with the state of the selection signal. When the selection signal is at the H level, the color density data Dc is
When the selection signal is at the L level, data from the selection circuit 64 is output. The output bit of the selection circuit 64 is directly input to the OR circuit 66, and the output of the OR circuit 66 becomes a main color flag MCF (color information) indicating whether or not the output is a main color (for example, black). .

In the above configuration, the main color (black) on the original
In the area, the output of the matching circuit 59 (sub color flag) and the outputs of the matching circuits 61 and 62 (platen color and area recognition color) all become L level, and the brightness data V from the adding circuit 57 is directly selected. It is output via circuits 64 and 65.
At this time, since the brightness data V is not "0", the main color flag MCF becomes H level, and since the output of the matching circuit 59 is L level, the sub color flag SCF becomes L level (the main color flag in FIG. 16). See area Em).
In a sub-color area (for example, red) on the original, the output (SCF) of the matching circuit 59 becomes H level, and the color density data Dc from the lookup table 58 is selected by the selection circuit.
Output from 65. At this time, the output of the selection circuit 64 is “0”
, The main color flag MCF goes low, and the output of the matching circuit 59 is high, so that the sub color flag SCF goes high (see the sub-color area Es in FIG. 16). In the background area of the original image (density “0”), the outputs of all of the coincidence circuits 59, 61, and 62 are at L level. The data is output as "0" data, and both the main color flag MCF and the sub color flag SCF are at the L level (see the background area En in FIG. 16). Further, on the document pressing surface area (for example, yellow) of the platen cover 14 or on the mark for specifying the area, one of the coincidence circuits 61 and 62 becomes H level, and the output of the selection circuit 64 maintains “0”. This "0" data is further output via the selection circuit 65. That is, the density is deleted in these areas.

In FIG. 12, reference numeral 68 denotes a document / area detection control circuit, which is a matching circuit 61, 62 for the platen color and the area recognition color.
In addition to the input of the judgment output of (BSC), as will be described later, an anti-sub-scanning signal (BSC) output from a CPU (not shown) when the scanning unit scans in the reverse direction before starting the normal reading operation.
AN) and the open / close determination signal (PL
TINT) and a mode switching signal for selecting any one of a document detection function and an area detection function to be described later. In the original / area detection control circuit 68, in the original detection function (mode switching signal L level), the platen cover 14 is in the closed state, and the scanning unit performs anti-sub scanning (BSCA).
In performing N), the document / area flag which becomes H level when the determination output of the matching circuit 61 is output is output, while the area detection mode flag (mode switching signal H level) is used to set the area detection mode flag. Start up and gate 63
As a selection signal (SEL) of the selection circuit 64 via the scanning circuit.
The document / area flag is raised when the judgment output of 62 is made. And a document / area detection control circuit
The document / area flag output from 68 becomes the selection signal (SEL) of the selection circuit 65. The selection circuit 67 has a function of switching between the maximum value (+ V: FFH) and the output density data from the selection circuit 65 at the preceding stage. When the selection signal is at the H level, the maximum value is selected. When the level is at the level, the output density data from the selection circuit 65 at the preceding stage is output as it is. Then, the output of the selection circuit 67 is transferred to the subsequent stage as final density data D.

The maximum value (+ V: FFH) input to the selection circuit 67 is the maximum density (FFH = 255 gradations), and is the density (reflection “0”) of the background portion other than the original when the platen cover 14 is open. The corresponding concentration is obtained. That is, the functions of the original / area flag creating circuit 68 and the selecting circuit 67 realize the density converting means which is a specific component of the present invention.

Each of the arithmetic circuits is driven synchronously on a pixel-by-pixel basis under the control of a timing control circuit (not shown), and the density data D and the color flags (MSF, SMF) are data of the same pixel pair. Is transferred to the subsequent stage.

IV. Original Document Detecting Unit In this original document detecting unit, a first original document edge detecting unit, a second original document edge detecting unit, and an original region specifying unit which are constituent elements of the present invention are embodied. In particular, a portion shared with the first document edge detecting means is embodied.

FIG. 17 shows a basic configuration of a document detection circuit. The document detection circuit is configured in the editing / processing circuit 100 in FIG. 4, and is supplied with various signals from a CPU or the like. The density data D from the color image information generation circuit 50 described above is supplied via a correction / filter circuit 70.

In FIG. 17, reference numeral 71 denotes a data control circuit. The data control circuit 71 includes a line memory, and writes density data D supplied to each pixel into the line memory in synchronization with a read timing in the main scanning direction. Similarly, for the next line, the density data D in the line memory is read for each pixel in synchronization with the reading timing in the main scanning direction. When the density data D is written, the write data (Write Data) and the write address (Write ADD) are output from the data control circuit 71. When the density data D is read, the read data (Read Data) is read.
And a read address (Read ADD).

On the other hand, as shown in FIG. 18, the direction along the main scanning is the Y direction on the platen 12, the direction along the sub-scanning, and particularly the direction Sb (the reverse direction,
An XY coordinate system in which the X direction is the BS direction) is set. The XY coordinate system can be arbitrarily set on the platen 12. For example, the X direction is the same as the direction S when reading a regular original, even in the direction along the sub-scanning, contrary to the above. The direction may be set, and the Y direction may be set in a direction along the main scanning, which is opposite to the direction at the time of reading a normal document.

Further, in FIG. 17, reference numeral 72 denotes a Y detection circuit.
The detection circuit 72 has a function of calculating the minimum value Ymin and the maximum value Ymax of the document edge position in the Y direction of the document 13 placed on the platen 12 as shown in FIG. And a Ymin detection circuit 72a and a Ymax detection circuit 72b. The Ymin detection circuit 72a detects that the document is an original edge based on the write density data D (Write Data) supplied from the data control circuit 71, and writes the write address (Write ADD) of the density data D corresponding to the edge. Indicates the edge position. The Ymax detection circuit 72b outputs the read density data D (Read Dat
The edge of the document is detected based on a), and the edge of the document is specified based on the read address (Read ADD) of the density data D corresponding to the edge.
74 is an X detection circuit.
It has a function of calculating the minimum value Xmin and the maximum value Xmax of the document edge position in the X direction of the document 13 placed on the document 12. The X detection circuit 74 determines that the first document edge detection by the Y detection circuit 74 is the minimum document edge position in the X direction and that the last document edge is the maximum document edge position in the X direction. Each of them is detected, and the minimum and maximum values of the document edge position are specified based on the number of drive pulses (Motor Clock) of the pulse motor for driving the scanning unit corresponding to the edge portion.

76 is a signal control circuit.
And the like, for example, a video clock signal (V.Clock) that specifies a pixel-unit read timing, and a video valid signal (V.Clock) that specifies an effective main scanning timing.
VAD), a registration position signal (Regi Sens) based on the detection signal from the registration sensor that detects that the scanning unit has reached the document registration position, a driving pulse signal (Motor CLOCK) of a pulse motor for driving the scanning unit, A mode switching signal or the like for designating a mode of a document detection function and an area detection function (to be described later as an additional function to the original document detection function) is input. It is distributed to the X detection circuit 74.

In this document detection circuit, as shown in FIG. 18, the position of the document 13 on the platen 12 is specified by the minimum value Ymin and the maximum value Ymax of the document edge position in the Y direction, and the position of the document edge position in the X direction is specified. Since the document area is specified by the minimum value Xmin and the maximum value Xmax, the document processing target document area actually recognized in the image processing apparatus is a rectangular area E circumscribing the document 13.
(Two-dot chain line in FIG. 18).

The specific configuration of the Ymin detection circuit 72 is, for example, as shown in FIG.

In the figure, reference numeral 81 denotes a reference value setting device. The reference value setting device 81 has a predetermined density between the document density and the background density, for example, in the case of expressing 256 gradations (8 bits) at the maximum, for example, an intermediate floor. The key “128” is set as the reference value. This reference value is a density value larger than the assumed document density. A comparison circuit 82 compares the reference value (Q input) from the reference value setting device 81 with the write density data D (P input) from the data control circuit 71 described above. When the relationship is P> Q, the judgment output becomes L level, and when the relationship is P ≦ Q, the judgment output becomes H level. 83 is a 1/4 frequency divider for dividing the video clock signal (V.Clock) by 1/4, and 85 is, for example, a three-stage shift register. The shift register 85 is gate-controlled by a mode switching signal. The determination output result of the comparison circuit 82 via an exclusive OR (EOR) gate 84 is sequentially shifted in synchronization with a signal from the 1/4 frequency divider 83. The mode switching signal is at "L level" when the document detection function is selected, and at "H level" when the area detection function is selected. The output of each stage of the shift register 85 is input to a NAND circuit 86, and the output of the NAND circuit 68 is a document detection signal Xdata, which will be described in detail later.
The output of the NAND circuit 86, that is, the document detection signal Xdata, is when the D input of the shift register 85 is at the H level for three consecutive clocks of 1/4 clock from the 1/4 frequency divider 83 (document detection mode When the input of the comparison circuit 82 satisfies P ≦ Q, the input becomes P> Q in the area detection mode), and becomes active (L level).

Reference numeral 88 denotes a multiplexer for selectively outputting preset initial data Yin (Do input) and the write address (D1 input) from the data control circuit 71 described above. The original detection signal Xdata from the NAND circuit 86 is connected to an inverter. A selection signal S for the multiplex 88 is provided via the signal 87. The multiplexer 88 selectively outputs Do when the selection signal is at the L level and D1 when the selection signal is at the H level. Reference numeral 89 denotes a latch circuit for latching data via the multiplexer 88, and reference numeral 90 denotes latch data (P input) of the latch circuit 89 and data (Q
), And outputs a determination output that becomes H level when P> Q. The determination output from the comparison circuit 90 is a latch signal (T) of the latch circuit 89. Reference numeral 91 denotes a latch circuit. The latch circuit 91 transmits data sequentially latched by the latch circuit 89 to a registration position signal (Re).
gi Sens) is finally latched, and the latched data becomes the minimum document edge position Ymin in the Y direction.

Reference numeral 92 denotes a counter that counts up a video valid signal (V.VAD) and outputs, for example, a carry signal at the 15th count. Reference numeral 93 denotes a flip-flop that is set when the carry signal from the counter 92 rises. The outputs Q of the two systems of the flip-flop 93 are timing signals for anti-sub-scanning (back scan), respectively (Q: BSCAN1
H,: BSCAN2L) The multiplexer 88, the latch circuits 89, 91, and the comparison circuit 90 are each enabled when the anti-sub-scanning timing signal becomes active. This is because, for example, 15 lines of read data are ignored in the original detection process due to various correction processes after the start of the anti-sub-scan (back scan).

The specific configuration of the Ymax detection circuit is, for example, as shown in FIG.

This circuit configuration includes a reference value setting unit 81, a comparison circuit 82, a 1/4 frequency divider 83, and an EOR gate 8 similarly to the above-described Ymin detection circuit.
4, equipped with a shift register 85, a NAND circuit 86,
An inverter 87, a multiplexer 88 which is effective when an anti-sub-scanning timing signal becomes active, latch circuits 89 and 91, and a comparison circuit 90 are provided. However, the comparison circuit 82 reads out the read data (Read D) instead of the write data (Write Data) from the data control circuit 71.
ata) is compared with the reference value, and the multiplexer 88 outputs the write address (Write ADD) from the data control circuit 71.
Instead of the read address (Read ADD) and the initial data Yin
Is switched. Also, the comparison circuit 90
The input relationship is reversed with the case of the above Ymin detection circuit,
The data from the multiplexer 88 is P input, and the latch circuit 89
Becomes the Q input, and the comparison determination output rises when P> Q. Then, the latch data of the last-stage latch circuit 91 is set to the maximum document edge position.
It becomes Ymax.

Further, a specific configuration of the X detection circuit is, for example, as shown in FIG.

In the figure, reference numeral 101 denotes a counter for counting a driving pulse (Motor Clock) of a pulse motor for driving a scanning unit;
02 is a flip-flop that is set at the rising edge of the document detection signal Xdata from the Y detection circuit, 103 is a latch circuit that latches the count value of the counter 101 by setting the flip-flop 102, and 104 is the document detection signal Xdata
Is a latch circuit that latches the count value of the counter 101 every time the signal rises. A latch circuit 105 latches the count value latched by the latch circuit 103 again at the rise of the registration position signal (Regi Sens), and a latch circuit 106 stores the count value latched by the latch circuit 104 in the same registration position signal (Regi Sens). R
The count value finally latched by the latch circuit 105 is the minimum document edge position Xmin in the X direction and the latch circuit 10
The count value finally latched at 6 becomes the maximum document edge position Xmax in the X direction.

Next, the operation of detecting the document edge position will be specifically described.

 The conditions of the scanning system and the like are assumed as follows, for example.

Maximum scanning area: 296.7 × 434 (mm) Anti-sub-scanning speed (back scan speed): k times (for example, 4 times) the normal sub-scanning speed Scan density: 15.748 dots / mm First, turn on the power of the image processing apparatus. Then, light source 1
5. The scanning unit composed of the image sensor 10 and various optical components moves from a standby position (home position) before the start of regular document scanning to a predetermined position at the opposite end of the platen 12 (back scan standby position). And wait at that position.
At this time, the drive control system of the scanning unit recognizes the position of the scanning unit by the number of clock pulses of the driving pulse to the driving pulse motor from the time of output of the registration sensor, and moves to a predetermined standby position (back scan standby position). Movement control is performed up to the corresponding clock number.

When the operator sets the document 13 at an arbitrary position on the platen 12 with the scanning unit waiting at the back scan standby position as described above, and performs a start operation with the platen cover 14 closed, the scanning unit Moves from the back scan standby position in the direction opposite to the normal scanning (direction Sb in FIG. 18: anti-sub-scanning direction) to start document scanning. At this time, the platen open / close determination circuit shown in FIG. 2 determines the closed state of the platen cover 14 and outputs its output (PLTIN
T) is at the L level, and the anti-sub-scanning signal (BSCAN) rises in this state. In the process of scanning the document from the opposite direction, the density data D is output for each pixel from the color image information generation circuit 50 having a specific configuration shown in FIGS. 11 and 12. Regarding the pixel of the color of the original pressing surface (platen color) of the platen cover 14, the original / area flag from the original / area detection control circuit 68 in FIG. The density data D having a value of 255 is output.

Color image information generation circuit in the process of scanning one line (main scanning)
The density data D output from 50 is sequentially input to a data control circuit 71 and sequentially stored in a line memory. When writing the density data D into this line memory, the write data (Writ
e Data) and its corresponding address (Write ADD) are Y
It is supplied to the min detection circuit 72a. Where the data control circuit
The line memory in 71 is the scanning area width 296.7 (m
m), and has a capacity for pixels corresponding to
In this embodiment of 5.748 dots / mm, one main scanning line has 296.
7 × 15.748 = 4672 dots, and the corresponding address counter counts up from 0 to 4672. Then, each address value becomes Y coordinate data in the XY coordinate system as it is.

In the process of completing the scanning of one line and scanning the next line (actually after k = 4 lines since the scanning is at k = 4 times the normal scanning speed), the data control circuit Reference numeral 71 does not input the density data D from the color image information generating circuit 50, reads the density data D written in the line memory in the previous line scan, and reads the read data (Read Data).
a) and its companion address (Read ADD) are sequentially Y
It is supplied to the max detection circuit 72b. At this time, reading from the line memory is performed in the direction opposite to the writing (in the opposite main scanning direction), and the corresponding address counter performs down-counting from 4672 to 072. Thereafter, similarly, for one line, the write data and its address are sequentially supplied to the Ymin detection circuit 72a in the main scanning direction, and the read data and its address are sequentially supplied to the Ymax detection circuit 72b in the anti-main scanning direction. That is,
Minimum original edge position Ym from main scanning direction for one line
The detection of in and the detection of the maximum document edge position Ymax from the anti-main scanning direction are performed, and the same processing is performed every other reading line.

As described above, the write data (Wr
ite Data) and its address (Write ADD) are supplied Y
In the min detection circuit 72a, first, the initial value Yin input (Do) to the multiplexer 88 (see FIG. 19) is set to the maximum address value "4672". In this state, if the scanning does not reach the document 13 in the main scanning process from the 0 dot to 4672 dots of each line, that is, while the document pressing surface of the platen cover 14 is being scanned, the data control is performed. The write data from the circuit 71 has a maximum density value of 25.
5, and the output of the comparison circuit 82 maintains the L level (P
> Q). As a result, the multiplexer 88 is provided in the latch circuit 89.
, The initial value Yin = “4672” is latched.
Here, when the scanning reaches the document 13 (document edge),
The write data D becomes a value corresponding to the density of the original 13 (close to white density), becomes less than the reference value 128 (P ≦ Q), and the output of the comparison circuit 82 rises as shown in FIG. NAND circuit 8 when 1/4 clock continues for 3 clocks 8
6 Output falls. That is, a pixel corresponding to a document density equal to or less than the reference value is 0.75 mm (1/4 clock for 3 clocks:
It recognizes that there is a true document edge when continuous (12 pixels). Therefore, even if the output of the comparison circuit 82 rises temporarily due to dust or signal noise having a high reflectance adhered to the original pressing surface of the platen cover 14, the NAND circuit 86 must maintain the H level. Therefore, as shown in FIG. 23, the rising edge of the temporary comparison circuit 82 is not recognized as erroneous data that is a document edge. The output of the NAND circuit 86 is a signal Xdata indicating the original portion.
It is supplied to the X detection circuit 74 as (original portion when L level).

When the document edge is recognized as described above, the selection signal input of the multiplexer 88 rises, and the output is switched to the write address (Write ADD) output at that time. Since the address value at the time of document edge recognition is smaller than the maximum address value "4672", the output of the comparison circuit 90 rises (P>
Q) The address value is newly latched by the latch circuit 89. Thereafter, in the same line, the write address (Write ADD) is incremented and sequentially increased, and when the output of the NAND circuit 86 rises outside the original portion, the output of the multiplexer 88 changes to the maximum address value "46".
72 ", the output of the comparison circuit 90 is maintained at the L level, and the latch circuit 89 is not updated. That is, the latch circuit 89 is provided with the background portion and the document portion as viewed from the main scanning direction of the line. This means that the Y coordinate value (address value) of the document edge that changes to is stored.

Next, in the line targeted by the Ymin detection circuit 72a, with the address value corresponding to the previous document edge latched by the latch circuit 89, the multiplexer 88 outputs until the main scan reaches the document edge of the line. Is all bits “1”
And the contents of the latch circuit 89 are stored as they are. When the main scanning reaches the document edge portion of the line, the output of the NAND circuit 86 falls in the same manner as described above, and the address value at that time is output from the multiplexer 88. Here, if this address value is smaller than the address value already latched by the latch circuit 89 (the one of the previous read line), the discrimination output of the comparison circuit 90 rises (P> Q) and this new address The value is latched by the latch circuit 89 and the contents are updated. Thereafter, the smaller one of the address values corresponding to the document edge for each target line is latched by the latch circuit 89, and the scanning of the entire scanning range is completed and the registration position signal (Regi Sens) rises. At this point, the address value held in the latch circuit 89 is latched by the next-stage latch circuit 91, and the address data is transferred to the subsequent stage as minimum document edge position Ymin data.

The Ymax detection circuit 7 alternates with the processing in the Ymin detection circuit 72a.
The processing in 2b is executed. In this Ymax detection circuit 72b,
First, the initial values for multiplexer 88 (see FIG. 20)
The Yin input (Do) is set to the minimum address value “0”.
In this state, the density data D written in the line memory in the data control circuit 71 during the processing in the Ymin detection circuit 72a is in the order of the final addresses "4672" to "0", that is, in the anti-main scanning direction. , And supplied. In this process,
For pixels in an area that does not reach the portion of the document 13, the read data (Read Data) from the data control circuit 71 becomes the maximum density value 255, and the output of the comparison circuit 82 maintains the L level (P> Q). As a result, the latch circuit 89 is in a state where the initial value Yin = "0" from the multiplexer 88 is latched. Here, when the target pixel reaches the document 13 portion (document edge), the read data D (read Data) becomes a value corresponding to the document 13 density (used for white density) and becomes a reference value 128 or less. (P ≦ Q) The output of the comparison circuit 82 rises (see FIG. 22), and this state is 1 as in the case of Yin detection.
When ク ロ ッ ク clocks continue for three clocks, the output of the NAND circuit 86 falls to recognize the document edge.

When the document edge changing from the background portion to the document portion in the anti-main scanning direction is recognized, the selection input of the multiplexer 88 rises, and the output is switched to the read address (Read ADD) output at that time. . Since the address value at the time of this document edge recognition is larger than the minimum address value “0”,
When the output of the comparison circuit 90 rises (P> Q), the address value is newly latched by the latch circuit 89. And after that,
In the same line, the read address (Read ADD) is decremented and sequentially decreased, and when the output of the NAND circuit 86 rises outside the original portion, the output of the multiplexer 88 switches again to the minimum address value "0". Therefore, the output of the comparison circuit 90 is maintained at L level and the latch circuit
89 updates will not be made. That is, the latch circuit 89 stores the Y coordinate value (address value) of the document edge that changes from the background portion to the document portion as viewed from the anti-main scanning direction of the line.

Next, in the line targeted by the Ymax detection circuit 72b, in the state where the address value corresponding to the previous document edge is latched by the latch circuit 89, the memory read in the anti-main scanning direction reaches the document edge of the line. Until then, the output of the multiplexer 88 becomes the minimum address value “0” and the contents of the latch circuit 89 are held as it is. When the read reaches the document edge portion of the line, the output of the NAND circuit 86 falls in the same manner as described above, and the read address (Read ADD) at that time is output from the multiplexer 88. here,
If this address value is larger than the address value already latched in the latch circuit 89, the judgment output of the comparison circuit 90 rises (P> Q) and this new address value is stored in the latch circuit 89.
And the contents are updated. Thereafter, the larger address value corresponding to the document edge for each target line is latched by the latch circuit 89, and scanning of the entire scanning range is completed, and the registration position signal (Regi Sens)
When the signal rises, the address value held by the latch circuit 89 is latched by the next-stage latch circuit 91, and this address data is transferred to the subsequent stage as the maximum document edge position Ymax data.

As described above, the minimum document edge position Ymin and the maximum document edge position Ymax are determined before the scanning in the reverse direction from the back scan standby position ends (see FIG. 18). In parallel with the processing relating to the document edge position in the Y direction, the X detection circuit 74 performs processing relating to the document edge position in the X direction.

The drive pulse (Mo
tor Clock) is input to the X detection circuit 74, the scanning unit starts moving from the back scan standby position, and when the anti-sub-scanning timing signal (BSCAN1H) rises, the counter 101
(See FIG. 21). In the Ymin detection circuit 72a, the output of the NAND circuit 86, that is, the document detection signal Xdata is at the H level while the background portion is being scanned for each scanning line, while scanning the document 13 portion. During this time, the state falls to the L level. In such a state, the flip-flop 102 is set as shown in FIG. 24 at the timing when the scanning line first reaches the document portion and the document detection signal Xdata first rises from the H level to the L level (H Rise to the level). By the set signal of the flip-flop 102, the latch circuit 103 causes the current counter 1
Latch the count value at 01 while flip-flop
The count value is latched by the latch circuit 104 at the rise of the document detection signal Xdata which has become the set signal of 102.
After the scanning line reaches the document portion for the first time, the flip-flop 102 maintains the set state, so that the data of the latch circuit 103 is not updated.
Each time the document detection signal Xdata rises in each scanning line of the main scanning performed every k lines, the latch circuit 104 newly latches the count value at that time and updates the content. By repeating such processing, when the scanning of the entire scanning range is completed and the registration position signal (Regi Sens) rises, the data stored in the latch circuit 103 is set in the next-stage latch circuit 105 and Then, the data stored in the latch circuit 104 is set in the next-stage latch circuit 106. Here, the data held in the latch circuit 105 is the first original detection signal Xda
The count value at the rising timing of ta, that is, the minimum document edge position Xmin in the X direction, and the data stored in the latch circuit 106 is the count value at the rising timing of the last document detection signal Xdata, that is, the value in the X direction. This is the maximum document edge position Xmax (see FIG. 24). Then, the minimum document edge position Xmin data stored in the latch circuit 105 and the maximum document edge position Xmax data stored in the latch circuit 106 are paired and transferred to the subsequent stage.

As described above, the minimum document edge position Ymin, Xmin and the maximum document edge position Ymax, Xmax in the XY coordinate system set on the platen of the document 13 by scanning in the reverse direction from the back scan standby position are detected. As shown in FIG. 18, the image processing device performs the rectangular area E specified at each edge position.
Is recognized as the document area. Then, in the normal reading scanning started after the scanning in the reverse direction, only the image information of the document area E is to be processed (specifically, described later).

The above processing is performed when the platen cover 14 is in the closed state. For example, when the platen cover 14 is in the open state, such as when a thick document such as a book is to be processed, the output of the platen open / close determination circuit shown in FIG. (PLTINT) goes to the H level state, and when scanning in the reverse direction from the back scan standby position similar to the above (BSCAN), the color image information generation circuit 50
The document / area flag from the document / area detection control circuit 68 in (1) maintains the falling state (L level) (see FIG. 12). For this reason, since the selection circuit 67 selects the B input, the color image information generation circuit 50 outputs the same as in the normal case.
In the main color (black) area, the brightness data V is output as the density data D as it is, and in the sub-color area, the color density data Dc obtained by correcting the brightness data V is output as the density data D. The background portion of the original 13 does not have the platen 14, and the light from the light source 15 passes through the platen 12 as it is and the light incident on the image sensor 10 is blocked, so that the color image information generation circuit 50 outputs The density data D obtained has a maximum value of 255.

Thus, the density data D obtained from the background portion of the original 13
Always has a maximum value of 255, the Y detection circuit 72 and X
The detection circuit 74 calculates the difference between the density (255) of the background portion and the density (close to white density) of the document 13 as in the case described above.
That is, the document edge is detected based on the output change (from the L level to the H level) of the comparison circuit 82 (see FIGS. 19 and 20), and the minimum document edge position Ymin, Xmin and the maximum document edge position Ymax, Xmax are determined. Transferred to the subsequent stage.

As described above, when the platen cover 14 is in the closed state, the color of the document pressing surface of the platen cover 14 is converted into density information, and a document detection process is performed based on the difference between the density and the document density. That is, the document area on the platen is specified by the difference between the color of the document pressing surface of the platen cover 14 and the color of the document. On the other hand, when the platen cover 14 is open, the document area on the platen is specified based on the difference between the density information corresponding to the background portion of the document and the density information corresponding to the document portion.

In the image processing apparatus, an area detection function can be realized in addition to the document detection function. This area detection function is a function of specifying a surrounding area when a predetermined area is surrounded by a marker of a specific color (area recognition color) on a document. The specified area is processed separately from the other areas.

This area detection is to detect the edge of the closed loop C drawn by the area recognition color marker in the document 13 placed on the platen 12 as shown in FIG. Similarly, in the XY coordinate system set on the platen 12, the minimum edge positions Ymin, Xmin
Then, the recognition area Ec is specified by the maximum edge positions Ymax and Xmax. The specific processing is as follows.

The document 13 on which the closed loop C is drawn by the marker of the specific color (area recognition color) is placed on the platen 12, and the selection operation of the area detection function is performed. Then, the mode switching signal is switched to the H level, and the area detection flag from the original / area detection control circuit 68 in the color image information generation circuit 50 rises to select the circuit.
The output 64 is fixed to "0" (see FIG. 12), and the EOR gate 84 in the Y detection circuit 72 becomes an inverting gate (see FIGS. 19 and 20). In this state, in the process of scanning in the reverse direction from the back scan standby position as in the case of document detection, for the read pixels located in the closed loop C of the area recognition color, the matching circuit 62 in the color image information generation circuit 50.
The output of (see FIG. 12) rises, the document / flag from the document / area detection control circuit 68 rises, and the density data D from the selection circuit 67 becomes the maximum density value 255. For the read pixels other than the closed loop, the output of the selection circuit 64 fixed to “0” is output as it is via the selection circuits 65 and 67. Accordingly, in the process of scanning from the opposite direction, in each scanning line, for example, as shown in FIG. Has a maximum value of 255 for the pixels in the closed loop C portion, and is "0" for the other pixels. When the density data D in such a state is input to the Y detection circuit 72 via the data control control circuit 71, the output of the comparison circuit 82 is output in the same manner as in the case of the original detection function. (The input to the shift register 85 is in an inverted state), and the minimum and maximum closed-loop edge positions Ymin and Ymax (address values) in the Y direction are obtained based on the signal change. In the X detection circuit 74, as in the case of the original detection function, the minimum and maximum closed loop edge positions Xm in the X direction based on the Xdata signal from the Y detection circuit 72.
in and Xmax are determined.

In this manner, the minimum edge position Ymin, Xmin and the maximum edge position Ymax, Xmax of the closed loop C are detected by scanning in the reverse direction from the back scan standby position, and when the recognition area Ec is specified by the detected data, the reverse is performed. In the normal reading scan started after the scanning from the direction, the recognition area Ec is processed while being distinguished from other areas.

V. Processing section Minimum document edge position Ymin, Xmi output as described above
When a document area is specified by n and the maximum document edge positions Ymax and Xmax, specific processing based on these data is performed. For example, assuming a copier, a function that always reproduces the image in accordance with the positional relationship with the paper regardless of the position of the document on the platen (free registration). The function of reproducing an image at the center of a sheet (area centering) is realized as follows.

FIG. 27 is a block diagram showing an example of the overall configuration of a processing circuit for realizing the functions of the free registration and the area centering.

In the figure, reference numeral 110 denotes a system control circuit. The system control circuit 110 inputs the minimum edge position Xmin and maximum edge position Xmax in the X direction and the minimum edge position Ymin and maximum edge position Ymax in the Y direction as described above. The control information based on the input data is supplied to the data output circuit 120, the scanning drive control circuit 145, and the paper feed drive control circuit 148.

A specific configuration of the data output circuit 120 is, for example, a twenty-eighth
It is as shown in the figure.

This data output circuit 120 is an image forming apparatus 135 for outputting image data (density data D and each color flag data MCF, SCF) from the color image information generation circuit 50 shown in FIGS. 11 and 12.
(The details will be described later).

In FIG. 28, 127 and 128 are memories (SRAM) each having a capacity of one scanning line.
Reference numeral 28 denotes writing and reading of image data (density data D, color flags MCF and SCF) in pixel units. 121 is a register for setting an initial read address, and 122 is a read address counter.
Is the minimum document edge position Ym in the Y direction (main scanning direction).
An address value (output from the system control circuit 110) based on in is stored as an initial read address. The initial read address stored in the register 121 is loaded into the read address counter 122 in synchronization with the fall of the video valid signal (V.VAD) output for each scanning line, and the read address counter 122 reads the initial read address. The address is sequentially incremented in synchronization with a read clock (RD CLK) created based on the video clock from the address. Reference numeral 123 denotes a register for setting an initial write address, and reference numeral 124 denotes a write address counter. The register 123 stores an address value (output from the system control circuit 110) corresponding to the first pixel of the scanning line (effective portion) in the initial write address. Is stored as The initial write address stored in the register 123 is loaded into the write address counter 124 in synchronization with the fall of the video valid signal (V.VAD), and the write address counter 124 is created based on the video clock from the initial write address. The write clock (WR CLK) is sequentially incremented in synchronization with the write clock (WR CLK).

Reference numerals 125 and 126 denote multiplexers for selecting and outputting the A side input when the selection signal input S is at the H level and selecting the B side input when the selection signal S is at the L level, respectively. The count value from the counter 122 and the count value from the write address counter 124 are input to the B side, and the multiplexer 126 inputs the count values of the read address counter 122 and the write address counter 124 in a reverse relationship to the above. . Then, the memory switching signal (ME
M.SW) (output from the system control circuit 110) is input as the selection signal S of each of the multiplexers 125 and 126. The output Y of the multiplexer 125 is the address of the memory 127 (ADDR)
The output Y of the multiplexer 126 is connected to the address (ADDR) bus of the memory 128.
Buffers 129 and 130 are connected to the data (DATA) buses of the memories 127 and 128, respectively.
(See FIGS. 11 and 12)
It is supplied to memories 127 and 128 via 9,130. Also,
The read data from the memory 127 is stored in the A of the multiplexer 131.
The read data from the memory 128 is input to the B-side input terminal of the multiplexer 131 at the side input terminal. This multiplexer 131 is similar to the other multiplexers 125 and 126 described above.
Similarly, when the memory switching signal (MEM SW) is at the H level, the A-side input is applied.
Each side input outputs Y, and further has a control terminal (G) so that when the control terminal (G) is at the L level, the output Y is fixed to “0”. Has become. The effective area signal from the effective area signal generation circuit 132 is input to the control terminal (G) of the multiplexer 131. The effective area signal generation circuit 132 determines, based on each information (output from the system control circuit 110) of the minimum edge position Ymin and the maximum edge position Ymax in the Y direction, that the readout pixel is set to the minimum edge position Ymin and the maximum edge position Ymax. An effective area signal which becomes H level when it becomes a corresponding one is generated.

On the other hand, the scanning system drive control circuit 145 is
Edge position in X direction (sub-scan direction) output from
Based on the position information corresponding to Xmin and the maximum edge position Xmax, the scanning system 146, in particular, the scanning unit (light source, full-color sensor, optical system, etc.) is controlled to reciprocate between the above positions. . Specifically, the number of drive pulses of the pulse motor for driving the scanning unit is counted, and the count value is controlled so as to perform forward / reverse rotation drive between values corresponding to the minimum edge position and the maximum edge position. I have.

Further, a paper feed system drive control circuit 148 is provided in a paper feed system 149 for conveying a recording sheet for image formation in an image forming apparatus described later.
In particular, when realizing the function of "area centering", the paper feed system 149, specifically, the recording paper conveyance timing is set so that the target area is reproduced at the center of the recording sheet conveyance direction. Controlling.

Next, the “free registration” function will be described.

As shown in FIG. 29, in a state where the original is placed at an arbitrary position on the platen 12, the original 13 as described above is scanned in the process (back scan) from the side opposite to the registration position (Regi).
Minimum document edge position Ymin, Xmin and maximum document edge position
Ymax and Xmax are obtained.

When a start scan is performed in this state, first, the system control circuit 110 determines a registration position (Regi) based on the minimum document edge position Xmin and the maximum document edge position Xmax in the X direction.
The document position Smin (front end position) and Smax (rear end position) in the scanning direction based on the position side are calculated. The document position information (Smin, Smax) is supplied to the scanning system drive control circuit 145. Then, the scanning system drive control circuit 145 moves the scanning unit to the leading edge position Smin of the document, and scans from there to the trailing edge position Smax of the document. When performing multiple image reproductions, the scanning unit uses
The reciprocating motion between in and the rear end position Smax is repeated.

On the other hand, in the main scanning direction, the system control circuit
110 is the minimum document edge position Ymin and the maximum document edge position Y
Each information of max is supplied to the data output circuit 120. Then
Address value ADDR (Ym
in) is stored in the register 121, and the address value ADDR (0) corresponding to the first pixel of the scan line is stored in the register 12
Stored in 3. In this state, the positions (Smin and Sma
When scanning in x interval starts, the memory switching signal (MEM S
W) becomes H level and the above address value ADD is added during the scanning process.
The address value from the write address counter 124 that sequentially counts up from R (0) is supplied to the memory 128. Then, the image data output from the color image information generation circuit 50 for the scanning line is sequentially written into the memory 128 for one scanning line. When the scanning unit shifts to the next scanning line, both the read address counter 122 and the write address counter 124 are reset to the initial address value.
In this state, the memory switching signal (MEM SW) switches to the L level, and the write address from the write counter 124 is supplied to the memory 127 in the opposite direction to the previous line, and the read counter 122
Is supplied to the memory 128. Then, while writing the image data in the scan line to the memory 127 in the same manner as described above, the memory 12
Image data written in the pre-scanning line from 8 is read out in pixel units. The image data is read from the memory 128 in order from the address value corresponding to the minimum document edge position Ymin. Then, the read image data is supplied to the image forming apparatus via the multiplexer 131. Here, since the effective area signal generation circuit 132 outputs an effective area signal that is at H level between the minimum document edge position Ymin and the maximum document edge position Ymax in each scanning line, the multiplexer 131 At other times, the output is fixed at “0”, and the image data read from the memory 128 is output only during that time.

Thereafter, similarly, each time the scanning line moves, writing and reading are switched between the memory 127 and the memory 128. In the writing, image data for one scanning line is written. In reading, the image after the minimum document edge position Ymin is read. Data is read. Further, from the multiplexer 131, the image data after the maximum document edge position Ymax among the read image data after the minimum document edge position Ymin is fixed to “0”.

As described above, by particularly controlling the scanning system and the reading of image data, the main scanning direction is set to the minimum document edge position Ym.
between in and the maximum document edge position Ymax, since the image data in the sub-scanning direction between the document head position Smin and the document end position Smax is transferred to the image forming apparatus at the same timing as the normal timing, An image is formed on a recording sheet in the same manner as when a document is set at the registration position (Regi).

Further, the function of “area centering” will be described.

As described above, the minimum edge position Ymin, Xmin and the maximum edge position Ymax, Xmax of the area E drawn on the original in the process of scanning from the opposite side performed before the scanning related to image formation are sent to the system control circuit 110. When supplied, the system control circuit 1
Numeral 10 calculates the center position Dp (with reference to the registration position) of the area E in the recording sheet conveyance direction (sub-scanning direction) based on the data. When a recording sheet on which an image is to be formed is selected (either automatic selection according to the document size or user designation), a center position PDc in the transport direction of the recording sheet is calculated.

Here, if the relationship between the center position DPc of the recording sheet sh and the center position Dp of the area E satisfies, for example, PDc> Dp as shown in FIG. 30 (a), the difference value (PDc−Dp) is supplied. Paper drive control circuit 1
Transferred to 48.

In this state, in the process of scanning the original, the paper feed system drive control circuit 148 controls the paper feed system 149 so that the recording sheet comes ahead of the normal timing by the difference value (PDc-Dp).

On the other hand, with respect to the image data, the image data read in the course of scanning the original is supplied to the data output circuit 120 in a masked state except for the area E (a masking circuit is not shown). Then, the data output circuit 120 performs the same processing as the above-mentioned “free registration” on the area E.

By controlling the transfer timing of the image data in the same manner as in the above-mentioned "free registration" in such a manner that the recording sheet is supplied in advance, the designated area E is relatively positioned at the registration position as shown in FIG. When the position is close to (Regi), the image of the area E is formed at the center of the recording sheet.

When the relationship between the center position DPc of the recording sheet sh and the center position Dp of the area E satisfies, for example, PDc ≦ Dp as shown in FIG. 30 (b), the difference value (Dp−PDc) is used as the scanning system. The data is transferred to the drive circuit 145.

Then, by the start operation, the scanning unit is controlled to move from the registration position (Regi) to a position further preceding by the difference value (Dp-PDc). In this state, scanning of the original corresponding to the selected recording sheet is performed.

At this time, the image data is output in the same manner as described above.

By starting scanning according to the recording sheet from a state where the scanning unit is in a standby state at the preceding position in advance (the output timing of the image data is the same as described above), the 30th
As shown in FIG. 6B, the designated area is relatively located at the registration position (Re
gi), the image of the area E is formed at the center of the recording sheet.

VII. Image Forming Unit Image data (density data, main color flag MCF, sub color flag S
A specific configuration of an image forming apparatus that forms an image based on CF) is, for example, as follows.

There are various image forming apparatuses such as a laser printer 150 and an image transceiver 170 such as a facsimile, and the laser printer 150 will be described below as an example. In this case, a copying machine is configured as a whole as described above.

The basic configuration of the laser printer 150 that forms a two-color image based on the density data D and the color flag is, for example, as shown in FIG. The two-color image forming laser printer shown here uses an electrophotographic system, and realizes main color black image forming and sub-color red image forming in one image forming cycle. This is a one-pass two-color (1P2C) type copying machine.

In FIG. 31, a charger 201, a developing device 202 for a sub-color (red), a developing device 203 for a main color (black), a corotron 208 for transfer, and a cleaning device for executing an image forming process around the photosensitive drum 200. Each of the devices 206 is arranged, and the sub-color exposure position Ps is set immediately before the sub-color developing device 202, and the main color exposure position Pm is set immediately before the main-color developing device 203. Regarding the exposure system, the irradiation light from the image writing laser diode 161 for the main color is
Polygon mirror 164 and f-θ lens 1 rotating at a constant speed
65, it is set to reach the exposure position Pm of the main color through an optical system such as the reflecting mirrors 167 and 168, and the irradiation light from the image writing laser diode 160 for the sub-color is similarly set to the polygon mirror 164 and the f-θ lens 165. And a reflector
The sub-color exposure position Ps is set via an optical system such as 166. Further, a transfer corotron 204 and a recording sheet peeling detack 205 are arranged at a transfer position around the photosensitive drum 200. At this position, the red toner image formed on the photosensitive drum 200 by the developing units 202 and 203 described above. The black toner image and the black toner image are collectively transferred to a recording sheet 210 conveyed from a paper feeding system. Then, the recording sheet 210 on which the image has been transferred is further discharged through, for example, a tray after the image is further fixed by the fixing unit 207.

The recording sheet 210 is transferred from the cassette by the driving of the sheet feeding system 149 based on the control of the above-described sheet feeding system control circuit 148,
The fixing device 207 is further transported to a tray.

On the other hand, the image writing laser diodes 160 and 161
Looking at the control system of

The density data Dm and the color flag CF are supplied for each pixel via the above-described image processing system interface circuit 140, and the main color density data Dm (black density) and the sub color density Ds ( A switching circuit 151 for separating red density) is provided. In the above processing section, the color flag is set to the main color flag MCF.
However, the color flag CF provided to the switching circuit 151 is changed to a 1-bit configuration representing the sub-color and the rest by the interface circuit 140. Specifically, only the sub-color flag SCF is transferred from the interface circuit 140 to a subsequent stage. That is, the pixels in the background area are handled as being included in the main color area, and the color flag CF for controlling the switching circuit 151 is set to the H level in the pixels in the sub color area and to the L level in the pixels in the other areas. I have to.

The specific configuration of the switching circuit 151 is, for example, as shown in FIG. That is, two selection circuits 171 and 172 are provided for selecting the output from two systems of input signals (A and B) according to the state of the color flag, and the density data D is selected by the selection circuit 1.
Data is input to an input terminal B of the selection circuit 171 and an input terminal A of the selection circuit 172, and "0" data is input to an input terminal A on the opposite side of the selection circuit 171 and an input terminal B on the opposite side of the selection circuit 172, respectively. doing. These selection circuits 171 and 172 select an input signal on the A side by an L level control input and an input signal on the B side by an H level control input, and the color flag CF is the control input. The output of one selection circuit 171 is transferred to the subsequent stage as sub-color density data Ds, and the output of the other selection circuit 172 is transferred to the subsequent stage as main color density data Dm in pixel units. In the switching circuit 151 having such a configuration, the corresponding sub-color density data Ds is transferred to the subsequent stage for the pixels in the sub-color area, while the pixels in the other areas (the main color area and the background area) are correspondingly transferred. The main color density data Dm is transferred to the subsequent stage.

The main color density data Dm and the sub color density data Ds separated by the switching circuit 151 are such that the sub color density data Ds is provided to the first screen generator 152, and the main color density data Dm is provided to the second screen generator.
153 has been entered.

Each screen generator 152, 153 has 2
Each of the density data Dm and Ds through the switching circuit 151 expressed in 56 gradations is converted into a laser diode modulation code for each pixel. Specifically, it converts the density data D expressed in 256 gradations into the laser lighting area amount of each pixel. For example, as shown in FIG. The sub-pixels SP1 to SP3 are set, and the laser lighting area is determined by the number of divided pixels according to the density data D. This screen generator 15
The modulation codes output from 2,153 are set, for example, as shown in Table 2.

According to Table 2, for example, as shown in FIGS. 34 (a) to (d), four levels of density expression can be achieved for each pixel.

When the density data D of 256 gradations is converted into a four-step code as described above, the threshold value of each step is determined based on the color reproduction characteristics (development characteristics) of each color. It is set so that it is reproduced. Therefore, different thresholds are set for the first screen generator 152 based on the color reproduction characteristics of the sub color (red), and for the second screen generator 153 based on the color reproduction characteristics of the main color (black).

The sub-color modulation code SC from the first screen generator 152 is transmitted via a one-line FIFO memory (first-in first-out) 154, and the main color modulation code MC from the second screen generator 153 is transmitted via a gap memory 156. The signals are input to the corresponding first ROS control circuit 155 and second ROS control circuit 157, respectively. The above gap memory
156, as described above, the sub-color exposure position Ps and the main color exposure position Pm are separated from each other by the gap Gp on the photosensitive drum 200 due to the arrangement of the developing devices 202 and 203. This is for delaying the transfer timing of the modulation code of the main color by an amount corresponding to the gap Gp in order to match the formation position. Therefore, the timing of writing and reading of the gap memory 156 is determined by the gap Gp of each of the exposure positions Ps and Pm, the rotation speed of the photosensitive drum, and the like.

The first ROS control circuit 155 generates a laser modulation signal of a corresponding system based on the sub-color modulation code SC, and also generates a control signal for a servo motor 163 for rotating the polygon mirror 164. The second ROS control circuit 157 receives the synchronization signal from the first ROS control circuit 155 and generates a laser modulation signal of a corresponding system based on the main color modulation code MC. A motor driver 162 drives a polygon mirror servo motor 163 at a constant speed based on a control signal from the first ROS control circuit 155, and a laser driver based on a sub-color modulation signal from the first ROS control circuit 155. 158 turns on and off the image writing laser diode 160 for the sub-color,
On the basis of the main color modulation signal from the second ROS control circuit 157, the laser driver 159 turns on and off the image writing laser diode 161 for the main color.

The on / off control of the main-color image writing laser diode 161 and the sub-color image writing laser diode 160 as described above causes the potential state corresponding to each color on the photosensitive drum 200 uniformly charged by the charger 201. , An electrostatic latent image is formed, and for each of the electrostatic latent images, red toner development is performed by the developing device 202 for the sub-color and black toner development is performed by the developing device 203 for the main color. Then, the red and black toner images formed on the photosensitive drum 200 are supplied to the recording sheet 210 supplied from the paper feeding system.
The recording sheet is transferred onto the recording sheet, and after the image is fixed, the recording sheet on which two colors are reproduced is discharged.

In the sub-color image formation, a latent image Z1 having an exposed portion as an image portion is formed as shown in FIG. 35 (a), and this latent image Z1 is developed by a developing device 202 into a first developing bias VB1.
And a sub-color (red) toner image T1 is formed. In the main color image formation, the 35th
A latent image Z2 having an unexposed portion as an image portion as shown in FIG. 2B is formed, and the latent image Z2 is developed by the developing device 203 under a second developing bias VB2 to form a main color (black). Is formed. More specifically, the toner images T1 and T2 are batch-transferred on the recording sheet 210 by the transfer corotron 204 after their polarities are aligned by the pre-transfer corotron 208.

VII. Conclusion In the above embodiment, the document edge position is detected based on image information (color and density) obtained in the process of scanning from the back scan standby position in the direction opposite to the normal scanning direction. In particular, when the platen cover is in the closed state, for pixels of the same color as the color of the original pressing surface (yellow), the density is forcibly corrected to the maximum value of 255, and the density and the original density (close to white density) are compared. While detecting the document edge based on the difference,
When the platen cover is in the open state, there is no reflected light from the background portion. Therefore, the document edge detection is performed based on the difference between the density data and the document temperature at that portion. And
In the XY coordinate system set on the platen, the document area is specified by the minimum document edge position Ymin, Xmin and the maximum document edge position Ymax, Xmax. By forcibly converting the color data on the original holding surface of the platen cover to the maximum density data as described above, the color difference processing is converted to the density difference processing, and the processing system for closing and opening the platen cover is shared You can do it. Further, in the XY coordinate system, the document area is specified only at the four maximum and minimum document edge positions in each direction, and the area specifying process is easier. In addition, since the original is detected in the process of scanning from the opposite direction to the normal scanning, and the specified original region is continuously subjected to image processing in the process of normal scanning, useless movement of the scanning unit is prevented. And efficient processing is realized.

It is also possible to directly determine the difference between the color of the original pressing surface of the platen cover and the original color. In this case, independent processing (density and color) is performed when the platen cover is open and closed. Further, it is of course possible to perform the document detection processing by scanning in the same direction as normal scanning, instead of processing in the scanning process from the reverse direction.

In the above embodiment, the document detection function and the area detection function are individually described. However, both functions can be realized in a series of processes. For example, before the normal image reading scan, scanning from the reverse direction is performed twice, that is, scanning related to the document detection function and scanning related to the area detection function are performed, respectively, and the document specified in the process of the regular scanning is The area is set as an object to be processed, and processing for distinguishing the specified area from other areas, such as area centering processing and color conversion processing, is performed.

[Effects of the Invention] As described above, according to the present invention, when the document cover is open, the document edge is detected based on the density difference between the document and its background, and when the document cover is closed, the document is detected. And the document edge is detected based on the color difference between the document pressing surface of the document cover and the document area is specified based on the detected edge, so that the effect on the document background is minimized even when the document cover is closed. Further, regardless of the open / close state of the document cover, more accurate document detection can be performed.

In particular, in an image processing apparatus provided with an image reading unit that reads image information to be subjected to image processing while discriminating density information and color information in a predetermined pixel unit, the read information from the image reading unit is used. By sharing the constituent elements between the first document edge detecting means and the second document edge detecting means, the structure is further simplified.

An XY direction in which the direction along the main scanning direction on the platen is the Y direction, and the direction along the sub-scanning direction is the X direction.
Since the coordinate system is set and the document area is specified at the maximum and minimum positions of the document edge in the coordinate system, the specification becomes easy because the document edge does not need to be specified finely.

[Brief description of the drawings]

1 (a) and 1 (b) are block diagrams showing the configuration of the present invention, FIG. 2 is a diagram showing an example of the structure of a scanning system, and FIG. 3 is a configuration of a circuit for detecting the open / closed state of a platen cover. FIG. 4 shows an example of the overall configuration of an image processing apparatus to which the document detection device according to the present invention is applied, FIG. 5 shows a structural example of a full-color sensor, and FIG. 6 shows a full-color sensor. FIG. 7 to FIG. 9 are circuit diagrams showing an example of the configuration of a sensor interface circuit, FIG. 10 is a diagram showing an example of a cell configuration in pixel units, and FIG. 11 to FIG. FIG. 13 is a circuit diagram illustrating a configuration example of a color image information generation circuit. FIG. 13 is a diagram illustrating a state of a discrimination color in a color space. FIG. 14 is a diagram illustrating a relationship between a distance r from an origin and a saturation C in a color space. FIG. 15 is a diagram showing the relationship between the angle θ and the hue H in the color space.
FIG. 16 is a diagram showing a correspondence relationship between density data and a color flag, FIG. 17 is a diagram showing a basic configuration example of a document detection circuit, and FIG.
FIG. 19 is a diagram showing a setting state of an original on a platen, FIG. 19 is a circuit diagram showing a specific configuration example of a Ymin detection circuit, FIG. 20 is a circuit diagram showing a specific configuration example of a Ymax detection circuit, FIG. 21 is a circuit diagram showing a specific configuration example of the X detection circuit, FIG. 22 is a diagram showing a relationship between density data and a detected document edge, and FIG. 23 is a diagram showing a process of detecting a document edge position in the Y direction. FIG. 24 is a timing chart showing a process of detecting a document edge position in the X direction, FIG. 25 is a diagram showing a state of a designated area on the document, and FIG. 26 is a area designated on the document. FIG. 27 is a block diagram showing a basic configuration example of a control system based on detected document edge data, and FIG. 28 is a specific configuration example of a data output circuit. Figure 29 shows the minimum document edge position and the maximum document edge position FIG. 30 is a diagram showing a relationship between a document leading position and a document end position, FIG. 30 is a diagram showing position management of a designated area, FIG. 31 is a diagram showing a basic configuration example of an electrophotographic two-color printer, and FIG. FIG. 33 is a diagram showing a configuration example of a circuit for separating density data by a color flag, FIG. 33 is a diagram showing an example of divided pixels forming one pixel, and FIG. 34 is a laser modulation code and laser lighting state corresponding to the density data. FIG. 35 is a diagram showing an example of the development characteristics of the main color and the sub color. [Explanation of Symbols] 1,12 Platen 2,13 Document 3,14 Platen cover 3a Document holding surface 4 Platen open / close determining means 5 First document edge detecting means 5a Density information binarizing means 5b density change position detecting means 5c document edge discriminating means 6 second document edge detecting means 6a color detecting means 6b density converting means 7 document area specifying means 10 Full color sensor 20 Sensor interface circuit 50 Color information generation circuit 70 Correction / filter circuit 100 Editing / processing circuit 140 Interface circuit 150 Laser printer 170 Image transceiver 180 ……Computer

Claims (4)

(57) [Claims] An original (2) placed on a platen (1)
An image processing device that processes image information that is read by optically scanning a document, and that can be opened and closed on a platen (1) in a document detection device that detects the area of the document (2) to be subjected to image processing Na platen cover (3)
The original pressing surface (3a) of the platen cover (3) is colored in a color different from the color of the target original, and the open state (OP) and the closed state (C
Platen open / close determining means (4) for determining L) and the density difference between the document (2) and its background when the platen open / close determining means (4) determines the open state (OP) of the platen cover (3). A first document edge detecting means (5) for detecting a document edge portion based on the document, and a document (2) when the platen open / close determining means (4) determines the closed state (CL) of the platen cover (3). Second document edge detecting means (6) for detecting a document edge portion based on a color difference of the document pressing surface (3a) of the platen cover (3).
And document area specifying means (7) for specifying a predetermined area including the document edge detected by the first or second document edge detecting means (5) (6) as a document area. Document detection device. 2. An image processing apparatus comprising image reading means (8) for reading out image information to be subjected to image processing in a predetermined pixel unit while distinguishing between density information (D) and color information (C). The first document edge detecting means (5) converts the density information (D) obtained in the course of the document scanning by the image reading means (8) between the document (2) and each reading density of the background portion thereof in advance. Density information binarization means (5a) for binarizing based on the determined reference density, and density change position detection means for detecting a change position of the binary information obtained by the density information binarization means (5a) 2. The document detecting apparatus according to claim 1, further comprising: (5b) and document edge determining means (5c) for determining a document edge position based on a position detected by the density change position detecting means (5b). . 3. A second document edge detecting means (6) comprising: a color detecting means (6a) for detecting a color of a document pressing surface (3a) of a platen cover (3); and a color detecting means (6a). Density conversion means (6b) for converting the density information (D) corresponding to the color-detected pixel into a density (Da) corresponding to the read density of the background portion, and the density conversion means (6b) Density information binarization means (5a) in the first document edge detection means (5) for detecting a document edge based on the density information (Da) obtained in
3. The document detecting apparatus according to claim 2, wherein the density change position detecting means (5b) and the document edge discriminating means (5c) are shared. 4. A X direction in which the direction along the main scanning direction is the Y direction and the direction along the sub scanning direction is the X direction on the platen (1).
A Y-coordinate type is set, and a document area specifying means (7) specifies an X-direction area at the maximum and minimum document edge positions in the X direction; 4. The document detecting apparatus according to claim 1, further comprising a Y-direction area specifying unit configured to specify a Y-direction area at a document edge position.