JPH06202472A - Image forming device - Google Patents

Abstract

PURPOSE:To provide an image forming device keeping the proper mixing ratio of a developer and attaining the replenishment of a proper quantity. CONSTITUTION:The block of 4X4 pixels is segmented from picture data with line memories 1501-1503 and the average density is detected by a block 1504 and binarized by a block 1506 basing on the value of the detection as a reference. The binarized data of 16 pixels is inputted into a ROM 1507 as an address and a spatial frequency corresponding to the value of the input and the kind of a pattern are outputted as the data. The toner consumption of 4X4 block unit is read from a RAM 1508 basing on these outputted values and the average density and integrated on the whole of an image, to estimate the toner consumption and replenish according to the value of the estimate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a digital copying machine which forms an image with a developer based on image data.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus for forming an image by using a developer such as a copying machine, proper replenishment of the developer has been a necessary function for maintaining good image output. . In particular, in a color image forming apparatus, a two-component developer containing a magnetic powder called a carrier is used in addition to the toner as a coloring agent because of the problem of color reproducibility. In the case of the system using the two-component developer, it is essential to keep the mixing ratio of the toner and the carrier constant to maintain good image quality, and the developer replenishment control is an important technical issue. ing.

A method of replenishing the developer in a copying machine using a two-component developer which has been conventionally devised or put into practical use will be described below.

A sensor detects the reflected light when the developer is irradiated with near-infrared light on the developing sleeve, which is the portion where the developing is actually carried out in the apparatus, and the amount of light reflected from the toner and the carrier. A light detection method (shown in FIG. 28) in which the ratio of the absorption amount is calculated and the developer is replenished according to the difference between the detected value and the reference value.

A certain image is actually toner-developed on the photosensitive member, and the density of that portion is detected by the optical sensor from the reflection amount of light to detect the mixture ratio of toner and carrier in the developer, and the standard A patch detection method in which the developer is replenished according to the difference from the value (shown in FIG. 29).

In particular, an apparatus for handling digital image data,
For example, in a digital copying machine, an image data integration method in which an image is read as a digital amount and a developer is supplied in an amount proportional to the cumulative value of all or part of the image data.

The above three methods have been proposed.

[0008]

As described above, in the image forming apparatus, proper supply of the developer is indispensable for maintaining a good image, and the method as described in the preceding paragraph is used. Conventionally, the control has been performed.

However, in the above-described photodetection method, the black toner using carbon has a light absorption region extending to the near infrared region. Therefore, the toner and the carrier component cannot be discriminated from each other, and the measurement by this method is impossible. Therefore, it is theoretically impossible to control the developer replenishment.

Further, in the patch detection method by measurement using light reflection from the developer developed on the photosensitive member, the light emitting surface of the light emitting element and the light receiving surface of the light receiving element by the developer scattered in the copying machine are shown. Contamination can be a direct measurement error. Further, the transfer medium is contaminated by the actual toner development, and the accuracy of the replenishment control is deteriorated due to the measurement error.

Further, the developer replenishing method proportional to the cumulative value of the image data as described above exhibits good characteristics in a flat image, but not particularly in an image including an edge portion, and is not limited to a simple image data. It has been confirmed by experiments that the error is accumulated only by estimating the toner consumption amount that depends only on the accumulated value.

FIG. 30 shows the experimentally measured ratio α of the toner consumption amount to the estimated toner consumption amount based on the cumulative value of the image data in the type of image pattern (vertical edge, horizontal edge, vertical / horizontal edge) and its spatial frequency. Indicates. As shown in FIG. 30, characteristics according to the spatial frequency of the image, the pattern type of the image (vertical edge, horizontal edge, vertical / horizontal edge), etc. have been confirmed by experiments. It is considered that the characteristics shown in FIG. 30 are brought about by factors such as an effect of emphasizing an end portion of a portion to be developed in an electrophotographic process and deterioration of following a small dot pattern.

Further, in an apparatus that handles digital image data, such as a digital copying machine, the original image is not only a natural image such as a photograph read by a scanner, but also an image that does not exist naturally on a computer. Can also be output. This image (CG image) created on a computer can form an image that does not exist in a natural image such as a painting or a photographic image, and therefore, the edge of the image signal is extremely sharp or a color tone that does not exist naturally is generated. You can create
For example, as shown in FIG. 34, it is known that the characteristic curve showing the relationship between the ratio α and the spatial frequency is different from the natural image. Further, when developing digital image data, an image signal is temporarily modulated and an image is formed by the modulated signal, but the characteristic curve shown in FIG. 30 or FIG. 34 is different depending on the modulation condition. .

The present invention has been made in view of the above conventional example, and an object of the present invention is to provide an image forming apparatus which can always supply an appropriate amount of developer and can control the developer concentration with high accuracy.

[0015]

In order to achieve the above object, the image forming apparatus of the present invention has the following constitution.

An image forming apparatus for visualizing digital image data with a developer, setting means for setting an estimation condition according to the type of digital image data, and characteristic detecting means for detecting characteristics of the digital image data. The estimating means for estimating the consumption amount of the developer under the estimation condition set by the setting means according to the characteristic detected by the detecting means, and the usage amount of the developer estimated by the estimating means. And a developer replenishing means for replenishing the developer.

[0017]

With this configuration, the amount of developer consumed is estimated according to the type of image data and the characteristics of the detected image data, and the developer is replenished according to the estimated amount.

[0018]

【Example】

(First Embodiment) A full-color copying machine will be described in detail below as a preferred embodiment. Needless to say, the present invention is not limited to this embodiment.

[Description of Apparatus Outline] FIG. 3 shows an external view of a copying machine in this embodiment. A document 202 to be read is placed on the platen glass 201. The original 202 is illuminated by the illumination 203 and is reflected by the mirrors 204, 205, 20.
After 6, the image is formed on the CCD 208 by the optical system 207. Further, the mirror unit 210 including the mirror 204 and the illumination 203 is mechanically driven at a speed V by the motor 209, and the second mirror unit 211 including the mirrors 205 and 206 is driven at a speed 1 / 2V, so that the entire surface of the original 202 is covered. Is scanned at a resolution of 400 dpi (dot / inch).

The image processing circuit section 212 is a section for processing the read image information as an electric signal and outputting it as a print signal.

Semiconductor lasers 213, 214, 215, 2
16 is driven by the print signal output from the image processing circuit unit 212, and the laser light emitted by each semiconductor laser is polygon mirrors 217 and 21.
8, 219 and 220, the photosensitive drums 225 and 22
A latent image is formed on 6, 227 and 228. Developing device 22
1, 222, 223, and 224 are black (B
k), yellow (Y), cyan (C), magenta (M)
Is a developing device for developing the latent image with the toner of (1), and the developed toner of each color is transferred to the paper, and full-color printout is performed.

The paper fed from any of the paper cassettes 229, 230, 231 and the manual feed tray 232 is adsorbed on the transfer belt 234 via the registration roller 223 and conveyed. The photosensitive drums 228, 227, 226, 22 are synchronized in advance with the timing of paper feeding.
Toners 5 of the respective colors have been developed, and the toners are transferred onto the paper as the paper is conveyed.

The sheet on which the toner of each color is transferred is separated / conveyed, the toner is fixed on the sheet by the fixing device 235, and the sheet is discharged to the sheet discharge tray 236.

Reference numerals 237, 238, 239 and 240 denote developing units 221, 222, 223 and 22 for respectively corresponding color toners.
4 is a hopper for replenishing, and black (Bk), yellow (Y), cyan (C), and magenta (M) toners to be replenished are stored inside.

Reference numerals 241, 242, 243, and 244 denote replenishing screws for replenishing the respective color toners in the hopper to the respective developing devices, and each time a rotation is given by a motor (not shown), a fixed amount of toner is generated. It is replenished in the developing device.

Reference numerals 245, 246, 247 and 248 are developing sleeves for developing the toner in the developing device on the respective photosensitive drums. (Supplementally, the light detection method described in the description of the prior art is performed by measuring the reflectance of infrared rays on this developing sleeve.) [Flow of image signal] FIGS. 1 and 2. Image processing means 212
The signal flow in is shown. 101, 102, and 103 are red (R), green (G), and blue (B), respectively.
CCD sensor of the analog amplifier 104, 10
5, 106 are respectively output as digital signals. Reference numerals 110 and 111 denote delay memories, respectively, for correcting a spatial shift between the three CCD sensors 101, 102 and 103.

151, 152, 153, 154, 15
Reference numerals 5 and 156 denote tri-state gate circuits, which are signals OE1 and O set by the CPU (not shown) according to the contents of the scaling process as shown in Table 1.
Only when E2, OE3, OE4, OE5, OE6 are "0", the input signal is output.

[0028]

[Table 1] Reference numerals 157, 158, 159, and 160 denote scaling circuits, which scale the image signal in the main scanning direction and
In the case of reduction / magnification, the character area signal K ₂ which will be described later is also magnified.

Reference numeral 112 denotes a color space converter, which is R, G, B.
Signal, brightness signal L^* And chromaticity signal a ^* And b^* Conversion to
To do. Where L^* , A^* , B^* Signal is CI
E as an international standard L^* , A^* , B^* Stipulated as space
Is a signal representing the chromaticity component^* , A^* , B^* signal
Is calculated by the following formula.

[0030]

[Equation 1] However, α _ij , X ₀ , Y ₀ , and Z ₀ are constants indicating standard white.

Here, X, Y and Z are also values representing the color space defined by CIE, which are signals generated by being calculated by the R, G and B signals, according to the following equation.

[0032]

[Equation 2] However, β _ij is a constant.

Reference numeral 113 is a luminosity signal encoder, which is L ^*.
The signal is encoded in 4 × 4 pixel block units, and the code L-code signal is output. The structure of the encoder 113 is shown in FIG.

Reference numeral 114 denotes a chromaticity signal encoder, which is a
^* , B ^* signals are encoded in 4 × 4 pixel block units,
The code ab-code is output. The structure of the encoder 113 is shown in FIG.

On the other hand, 115 is a feature extraction circuit,
A determination signal K for determining whether the pixel is a black pixel₁ 'Generates a signal
Black pixel detection circuit 115-1 and the K₁ ’Enter the signal
The 4x4 pixel block is a black pixel area.
4 × 4 area processing circuit 115-11 for determining whether or not
And a determination signal K indicating whether or not the pixel is in the character area
₂ A character area detection circuit 115-2 for generating a signal
Note K₂ 'Signal is input, and the 4x4 pixel block contains characters
4 × 4 area processing circuit 1 for determining whether or not it is an area
15-21.

Reference numeral 116 denotes an image memory, which is an L-code signal which is a code of lightness information and a which is a code of chromaticity information.
b-code signal and determination signal K that is the result of feature extraction
_{The 1} and K ₂ signals are stored.

Reference numerals 141, 142, 143, and 144 denote magenta (M), cyan (C), yellow (Y), and
It is a density signal generation unit for black (Bk) and has almost the same configuration.

117 (similarly to 117 ', 11
7 ″, 117 ″ ′) is a lightness information decoder for decoding the L ^* signal by the L-code signal read from the image memory 116. 118 (similarly 118 ',
Denoted by 118 ″ and 118 ″ ′) are chromaticity information decoders which decode a ^* and b ^* signals by the ab-code signals read from the image memory 116.

119 (similarly to 119 ', 11
9 ″, 119 ″ ′) are color space converters for converting the decoded L ^* , a ^* , b ^* signals to magenta (M), cyan (C), and yellow (toner developing colors). Y) and black (Bk).

120 (similarly 120 ', 12
0 ″, 120 ′ ″) is a density conversion means, and is a ROM
Alternatively, it is composed of a lookup table of RAM.

121 (similarly to 121 ', 12
1 ″, 121 ″ ′) are spatial filters, which correct the spatial frequency of the output image.

122 (similarly to 122 ', 12
2 ″, 122 ′ ″) is a pixel correction means, which corrects the decoded image data.

Further, the pixel-corrected image signal of magenta (similarly cyan, yellow, black) and the character region signal K ₂ are supplied to a PWM (pulse width modulation) circuit 167 (similarly to 167 ', 167'', 167). '''), Modulated and sent to the laser driver for image formation. Along with that, the toner consumption amount estimating means 168 (similarly to 168 ′, 168 ″, 168 ′ ″) is sent to estimate the toner consumption amount of each color, and the estimated toner consumption amount of each color is not shown. It is sequentially input to the CPU. When the consumption amount exceeds a certain value, the CPU causes the supply screws 241 and 24 corresponding to the respective toner colors.
2, 243 or 244 is driven to replenish the toner.

[In Case of Enlargement Processing] Image scaling processing will be described below. FIG. 4 shows an image that has been subjected to a scaling process. (A) is an image before scaling, (b) is a reduced image, and (c) is an enlarged image.

In the first mode in which the enlargement process is performed, the scaling process is performed before the encoding (compression) process. Therefore, as shown in Table 1 above, “0” is set to each of the three signals OE1, OE3, OE6, and OE2, OE4,
"1" is set to each of the three signals of OE5,
Of the tristate gates, 151, 153, 156
Only valid, 152, 154, 155 invalid.

As a result, the R / G / B input image signals synchronized by the delay elements 110 and 111 first pass through the tri-state gate 151, and the scaling circuits 157 and 158.
Enlargement processing is performed at 159. Here, since the detailed operation of the scaling processing circuit is publicly known, detailed description will be omitted.

Next, the enlarged R / G / B image signal is sent to the color space converter 112 and the feature extraction circuit 115 via the tri-state gate 153. Image code L-co coded through the encoder 113/114
de signal, ab-code signal, and feature extraction circuit 1
The characteristic signals K ₁ and K ₂ extracted in 15 are stored in the memory 11
6 and held.

The code read from the memory is decoded (expanded) as a density image signal by the density information decoders for magenta (M), cyan (C), yellow (Y), and black (Bk), respectively. Then, it is sent to the laser driver together with the character area signal K ₂ via the tri-state gate 156 and the magenta (M), cyan (C), yellow (Y) and black (Bk) PWM circuits. [For reduction processing] In the second mode for performing reduction processing,
The scaling process is performed before the encoding (compression) process. Therefore, as shown in Table 1 above, "0" is set to each of the three signals OE2, OE4, OE5, and OE1,
"1" is set to each of the three signals OE3 and OE6.
Only 4,155 are valid, 151,153,156
Is invalid.

As a result, the R / G / B input image signals synchronized by the delay elements 110 and 111 are first sent to the color space converter 112 and the feature extraction circuit 115 via the tristate gate 152. Encoder 113/1
Image code L-code signal coded via 14
The b-code signal and the characteristic signals K ₁ and K ₂ extracted by the characteristic extraction circuit 115 are sent to the memory 116 and held therein.

The code read from the memory is decoded (expanded) as a density image signal by the density information decoders for magenta (M), cyan (C), yellow (Y), and black (Bk), respectively. Then, through the tri-state gate 155, the scaling circuits 157, 158, 159,
Reduction processing is performed at 160. Also here, the detailed operation of the scaling processing circuit is publicly known, and thus detailed description thereof will be omitted.

The signal subjected to the reduction processing is tristate
Character area signal K ₂ With that
Magenta (M), cyan (C), yellow (Y), black
Send to laser driver via PWM circuit of rack (Bk)
To be

[Image control timing chart] FIG.
An image control timing chart in this embodiment is shown in FIG. The START signal is a signal indicating the start of the document reading operation in this embodiment. The WPE signal is a section in which the image scanner reads a document and performs coding processing and memory writing. The ITOP signal is a signal indicating the start of the printing operation, the MPE signal is a section signal for driving the magenta semiconductor laser 216 in FIG. 3, and C
The PE signal is a section signal for driving the cyan semiconductor laser 215 in FIG. 3, the YPE signal is a section signal for driving the yellow semiconductor laser 214 in FIG. 3, and the BPE signal is for the black semiconductor laser 213 in FIG. This is a section signal to be driven.

As shown in FIG. 20, the CPE signal, the YPE signal, and the BPE signal are respectively t ₁ and t with respect to the MPE signal.
₂ , t ₃ , which is the distance d _{1 in} FIG.
For d ₂ and d ₃ , t ₁ = d ₁ / v, t ₂ = d ₂ / v,
It is controlled to have a relationship of t ₃ = d ₃ / v (v is the paper feed speed).

In FIG. 20B, the HSYNC signal is the main scanning synchronizing signal and the CLK signal is the pixel synchronizing signal. The YPHS signal is the count value of the 2-bit sub-scan counter, and the XPHS signal is the count value of the 2-bit main scan counter. As shown in FIG. 19, the inverter 1001, the 2-bit counters 1002 and 1003.
Generated by the circuit.

The BLK signal is a synchronizing signal in units of 4 × 4 pixel blocks, and is 4 × at the timing indicated by BDATA.
Processing is performed in units of 4 blocks.

[Area Processing] FIG. 18 shows a block diagram of 4 × 4 area processing. In the figure, CLK is a pixel synchronization signal, H
SYNC is a main scanning synchronization signal. 901,902,9
Reference numeral 03 is a line memory that gives a delay of one line, and X
_The signals ₁ , X ₂ , X ₃ are delayed by 1 line, 2 lines, 3 lines in the sub-scanning direction with respect to the input signal X, respectively. An adder 904 counts the number of “1” among X, X ₁ , X ₂ and X ₃ for the four pixels of the binary signal X in the sub-scanning direction as a result.

Reference numeral 910 is a "2to1" selector, and 911.
Is a NOR gate, 912 is a flip-flop, and X is
The number of pixels C ₁ of X = “1” counted in 4 × 4 block units is calculated in synchronization with the BLK signals generated by the upper and lower bits of PHS, that is, XPHS (0) and XPHS (1). Is compared with the comparison value C ₂ preset in the register 913, and the output Y becomes “1” only when C ₁ > C ₂ ; otherwise,
It becomes "0" and is output at the timing shown by BDATA in FIG.

Here, what is characteristic is that the image code L-code and ab-code signals obtained by the encoding,
This means that the characteristic signals K ₁ and K ₂ extracted by the characteristic extraction circuit have a one-to-one correspondence in 4 × 4 block units shown in FIG.

That is, the image code and the characteristic signal are extracted for each 4 × 4 pixel block unit, stored at the same address in the memory or at an address calculated from the same address, and read out correspondingly even when reading out. be able to.

That is, the image information and the characteristic (attribute) information are made to correspond to each other and stored at the same address of the memory or at an address calculated from the same address. It is possible to simplify, and also when performing editing processing such as scaling and rotation on the memory, it is possible to perform with simple processing, and it is possible to optimize the system (it will be described later,
The toner amount is also estimated in the same 4 × 4 block unit).

FIG. 21 shows an example of specific area processing for character pixel detection. For example, with respect to the document shown in 1201, in the portion shown in 1201-1, the determination result as to whether each pixel is a character pixel or not is K ₂ '= 1 at a pixel indicated by "○", such as 1202, and other than that. It is assumed that it is determined that K ₂ '= 0 at the pixel of. Area processing circuit 115
In -11 a process as shown in FIG. 18, for example, C ₂ =
Set 4 and do. This makes it possible to obtain a noise-reduced signal K ₂ as indicated by 1203 in units of 4 × 4 blocks. In FIG. 21, a unit of 4 × 4 blocks in which numbers 0 to 3 are assigned in the main scanning direction and the sub scanning direction is used.

Similarly, the determination result K of the black pixel detection circuit
By treatment with a similar circuit (115-21 in FIG. 2) also ₁ ', the signal K ₁ corresponding to the 4 × 4 blocks
Can be obtained. [Color space converter 119 (119 ′, 119 ″, 11
9 ″ ′)] FIG. 11 shows a block diagram of the color space converter 119 (similarly to 119 ′, 119 ″, 119 ′ ″). 501 designates L ^* , a ^* , b ^* signals as R, G,
It is a means for converting into a B signal, and is converted by the following equation.

[0063]

[Equation 3] However,

[0064]

[Equation 4]

[0065]

[Equation 5] [Α _ij '] _{ij = 1,2,3} is the inverse matrix of [α _ij ] _{ij = 1,2,3 in} the formula ₁ [β _ij '] _{ij = 1,2,3} is the formula 2 Inverse matrices 502, 503, and 504 of [β _ij ] _{ij = 1,2,3} are luminance / density converters, respectively, which perform conversion as shown in Formula 6.

[0066]

[Equation 6] 523 is a black extraction circuit,

[0067]

[Equation 7] Bk₁ = Min (M₁ , C₁ , Y₁ ) ... Black signal Bk as in (7)₁ Is generated. 524, 525, 5
26 and 527 are multipliers, respectively, and C₁ , M₁ , Y
₁ , Bk₁ A predetermined coefficient a for each signal of₁ , A₂ , A ₃ , A
_Four After being multiplied by, the sum is added in the adder 508,
The sum product operation shown in Expression 8 is performed.

[0068]

(Output C, M, Y, or Bk) = a ₁ M ₁ + a ₂ C ₁ + a ₃ Y ₁ + a ₄ Bk ₁ (8) 509, 510, 511, 512, 513 are registers, respectively. 119, a ₁₁ , a ₂₁ , a ₃₁ ,
a ₄₁ and 0 are set, and 119 'contains a
₁₂ , a ₂₂ , a ₃₂ , a ₄₂ , and 0 are set,
In 119 ″, a ₁₃ , a ₂₃ , a ₃₃ , a ₄₃ , and 0 are set, and in 119 ′ ″, a ₁₄ , a ₂₄ , a.
₃₄ , a ₄₄ and a ₁₄ 'are set.

Reference numerals 531, 532 and 533 are gate circuits, 5
30 is a selector circuit of "2to1", 520 is a NAND circuit
A gate circuit, as a result, the logical product of the black pixel determination signal K ₁ and a character area determination signal K _2, by determining the pixel is whether a black character area, a ₁ to as is shown in FIG. 12 , A ₂ , a ₃ , and a ₄ are selected, the processing of Equation 9 is performed when the area is not a black character area, and the processing of Equation 10 is performed when the value is a black character area.

[0070]

[Equation 9]

[0071]

[Equation 10] That is, in the black character area, as shown in Expression 10, by outputting with black (Bk) single color, it is possible to obtain an output without color shift. On the other hand, in areas other than the black character area, M,
C, Y, but will output four colors of Bk, R read by the CCD sensor by the operation of Equation 9, G, and _{M 1, C 1, Y 1} , Bk 1 signal based on B signal toner The M, C, Y, and Bk signals are corrected based on the spectral distribution characteristic of and output.

[Spatial Filter] FIG. 16 shows a spatial filter 121 (similarly to 121 ', 121'',121''').
The block diagram of is shown. In the figure, reference numerals 801 and 802 denote line memories, which give a delay of 1 line,
Reference numerals 805, 806, 807, 808, and 809 are flip-flops which give a delay of 1 pixel. Reference numerals 810 and 811 denote adders, and reference numerals 812, 813 and 814 denote multipliers, which are multiplied by coefficients b ₁ , b ₀ and b ₂ and an adder 815 performs a sum product operation.

On the other hand, 816, 817, 818, 819,
Reference numerals 820 and 821 denote registers, which hold values b ₁₁ , b ₁₂ , b ₀₁ , b ₀₂ , b ₂₁ , and b ₂₂ in advance, and selectors 822, 823, and 824 follow the character determination signal K _2. Values are set in b ₁ , b ₀ and b ₂ .

FIG. 17 shows the relationship between K ₂ and the values of b ₀ , b ₁ and b ₂ . For example, b ₀₁ = _4/8 , b ₁₁ = 1/8,
b ₂₁ = 1/8, b ₀₂ = _12/8 , b ₁₂ = -1 / 8, b ₂₂
= -1 / 8, the registers 816, 817, 8
When set to 18, 819, 820, 821, as shown in FIG. 17, in K ₂ = 0, that is, in the non-character portion, a smoothing filter can be formed to remove noise of high frequency components in the image. On the other hand, at K ₂ = 1 or the character portion, the edge emphasis can be formed to correct the sharpness of the character portion.

[Pixel Correction Means] FIGS. 5 and 6 show block diagrams of the pixel correction means. As will be described later, in the figure, CLK is a pixel synchronizing signal and HSYNC is a horizontal synchronizing signal.
Line memories 401 and 402 give a delay of one line. 403, 404, 405, 406, 407,
Flip-flops 408, 409, 410 and 411 each give a delay of one pixel. As a result,
As shown by 0, peripheral pixels X ₁₁ , X ₁₂ , X ₁₃ , X ₂₁ , X ₂₃ , X ₃₁ , X ₃₁ in the vicinity of the pixel of interest X ₂₂ in the vicinity of 8 are centered.
₃₂ and X ₃₃ are output.

Reference numerals 400, 412, 413, and 414 are pixel edge detection circuits, and as shown in FIG.
The value of | A-2B + C | / 2 is output with respect to the three inputs of C. The target pixel X ₂₂ is input to all B inputs of the four pixel edge detection circuits.

X ₁₂ and X ₃₂ are input to the A input and C input of the edge detection circuit 400, respectively, and the result is | X
₁₂ −2X ₂₂ + X ₃₂ | / 2 is output, which is shown in FIG.
The edge strength in the sub-scanning direction indicated by 0 is output.

X ₁₁ and X ₃₃ are input to the A input and C input of the edge detection circuit 412, respectively, and the result is | X
₁₁ −2X ₂₂ + X ₃₃ | / 2 is output, which is shown in FIG.
It becomes the absolute value of the second derivative amount in the diagonally downward right direction indicated by 0, and the strength of the edge in the diagonally downward right direction shown in FIG. 10 is output.

X ₂₁ and X ₂₃ are input to the A and C inputs of the edge detection circuit 413, respectively, and the result is | X
₂₁ −2X ₂₂ + X ₂₃ | / 2 is output, which is shown in FIG.
It becomes the absolute value of the secondary differential amount in the main scanning direction shown in 0,
The strength of the edge in the main scanning direction shown in is output.

X ₃₁ and X ₂₃ are input to the A and C inputs of the edge detection circuit 414, respectively, and the result is | X
₃₁ −2X ₂₂ + X ₁₃ | / 2 is output, which is shown in FIG.
It becomes the absolute value of the second derivative amount in the diagonally downward right direction indicated by 0, and the strength of the edge in the diagonally downward right direction shown in FIG. 10 is output.

Reference numeral 415 in FIG. 6 is a maximum value detection circuit,
With respect to the four input signals a, b, c and d, it is determined which input signal has the maximum value, and the 2-bit determination result y is output.

FIG. 7 shows details of the maximum value detection circuit 415. Reference numeral 421 is a comparator, which outputs "1" only when a> b as the comparison result of a and b. 422 is
It is a selector of 2 to 1, and a and b are applied to two input signals A and B.
Is input and the comparison result of the comparator 421 is input to the select signal S, resulting in the maximum value ma of a and b.
x (a, b) is output.

Similarly, the comparator 423 and the selector 424 output the comparison result of c and d and the maximum value ma of c and d.
x (c, d) is output.

Further, the maximum values max (a, b) of a and b and the maximum values max (c, d) of c and d are respectively compared by the comparator 425, and the y ₁ signal is output. As a result, the y ₁ signal has a maximum value max of a, b, c and d.
When the value of (a, b, c, d) is a or b, it becomes "1", and the maximum value max (a, b, c, d of a, b, c, d
It becomes “0” when the value of d) is c or d.

Reference numeral 428 is an inverter, and 426, 427, 4
Reference numeral 29 is a 2-input NAND gate, and as a result, the y ₀ signal has the maximum value max (a, a, b, c, d).
b, c, d) is "1" when the value is a or c,
When the maximum value max (a, b, c, d) of a, b, c, d is b or d, it becomes "0".

That is, the maximum value max of a, b, c, d
Depending on the value of (a, b, c, d), 2 of the maximum value detection circuit
The bit outputs y ₀ and y ₁ are as follows.

When max (a, b, c, d) = a
When y ₀ = 1 y ₁ = 1 max (a, b, c, d) = b y ₀ = 0 y
_{When 1} = 1 max (a, b, c, d) = c, y ₀ = 1 y
_{When 1} = 0 max (a, b, c, d) = d y ₀ = 0 y
₁ = 0 Smoothing circuits 416, 417, 418 and 419 in FIG. 6 respectively output a value (A + 2B + C) / 4 for three inputs A, B and C as shown in FIG. To do.
The B pixels of the four smoothing circuits all have the target pixel X _22.
Has been entered.

X ₁₂ and X ₃₂ are input to the A and C inputs of the smoothing circuit 416, respectively, and the result is (X ₁₂ +
2X ₂₂ + X ₃₂ ) / 4 is output, which is subjected to smoothing processing in the sub-scanning direction shown in FIG. 10 and output.

X ₁₁ and X ₃₃ are input to the A and C inputs of the smoothing circuit 417, respectively, and the result is (X ₁₁ +
2X ₂₂ + X ₃₃ ) / 4 is output, which is subjected to smoothing processing in the diagonally lower right direction shown in FIG. 10 and output.

X ₂₁ and X ₂₃ are input to the A input and C input of the smoothing circuit 418, respectively, and the result is (X ₂₁ +
2X ₂₂ + X ₂₃ ) / 4 is output, which is subjected to smoothing processing in the main scanning direction shown in FIG. 10 and output.

X ₃₁ and X ₁₃ are input to the A and C inputs of the smoothing circuit 419, respectively, and the result is (X ₃₁ +
2X ₂₂ + X ₁₃ ) / 4 is output, which is subjected to the smoothing processing in the diagonally upper right direction shown in FIG. 10 and output.

Reference numeral 420 denotes a 4to1 selector,
For the four input signals A, B, C and D and the 2-bit select signal S, the following logic is used.

When S = 00, B input is output (Y ←
B) When S = 01, A input is output (Y ← A) When S = 10, D input is output (Y ← D) When S = 11, C input is output (Y ← C) Therefore, the pixel correction circuit The final output is as follows. That is, in FIG. 10, when the edge amount in the direction is the maximum, the direction is smoothed.

When the edge amount in the direction is the maximum, the direction is smoothed.

When the edge amount in the direction is the maximum, the direction is smoothed.

When the edge amount in the direction is the maximum, the direction is smoothed.

[Result of Pixel Correction] FIG. 22 shows the result of the pixel correction. When an image having a density pattern as shown in FIG. 22A is subjected to encoding / decoding processing by block encoding, as shown in FIG. 22B, 4 × 4 due to an encoding error. Roughness in the unit may appear. Therefore, by performing the above-mentioned smoothing process on (b), the roughness is reduced as shown in (c). For example, the pixel shown in A of FIG. 10B is decoded to have a higher density than the pixel corresponding to A of FIG. In the pixel A of FIG. 10B, the amount of edge (density gradient) in the direction shown in FIG. 10 is larger than the amount of edge in the other direction, and thus smoothed in the direction orthogonal to
The density is corrected to a lower level. Similar corrections are made for other pixels as well, and as shown in FIG. 7C, the overall roughness is reduced. Further, since the smoothing process is performed in the direction orthogonal to the density gradient, the sharpness of the character portion is not impaired.

[PWM Circuit (Pulse Width Modulation Circuit)] FIG.
3 to the PWM circuit 167 (similarly to 167 ', 16
7 ″, 167 ′ ″) and a timing chart thereof is shown in FIG.

This circuit is an already known analog PWM circuit that uses a sawtooth wave with a constant period as a reference signal.

In FIG. 23, CLK is a pixel synchronizing signal, 1401 is a 400-line (400-dpi period) saw-tooth generator, and 1402 is a 200-line (200-dpi period) saw-tooth generator, each 1 inch. Per 40
Zero cycle sawtooth SC4 signal and 200 per inch
As shown in FIG. 24, the sawtooth wave SC2 signal having a period is generated in synchronization with the rising edge of the CLK signal, the SC4 signal is a sawtooth wave having a period of one CLK signal period, and the SC2 signal is the CLK signal. It is a sawtooth wave having a period of two signal periods.

In FIG. 23, reference numeral 1403 denotes an analog switch, which is the character area signal K input to the switching control signal s.
_{From 2} , from the two analog input signals A and B,
One of them is selectively analog-outputted as a reference signal REF. Here, the switching selection signal s =
In the case of 1, the A input is output, and in the case of the switching selection signal s = 0, the B input is output. That is, as shown in FIG. 24, K ₂
= 1, that is, if the image data is a character area, SC4 is output as a REF signal, and if K ₂ = 0, that is, if the image data is not a character area, SC2 is output as a REF signal.

On the other hand, reference numeral 1404 in FIG. 23 is a DA converter, which converts an 8-bit digital input signal DATA into an analog output signal ADATA. Reference numeral 1405 denotes an analog comparator (comparator), which compares the magnitudes of the two-input analog signals A and B, and when A ≧ B, “1”
If A <B, "0" is output. The output is sent to the laser driver of each color as a laser ON signal LON, and the laser is emitted only at the portion "1" to form an image. The timing is as shown in FIG.

Here, as shown in Table 2, the reason why two sawtooth waves having different periods are used for the character area signal K ₂ is as follows.
The 400-line sawtooth wave PWM is excellent in resolution, but is difficult in terms of gradation and color reproducibility, and the 200-line sawtooth wave PWM is excellent in gradation and color reproducibility. However, because the resolution is difficult, PWM with a 400-line sawtooth wave is used to reproduce the character part, which emphasizes the resolution rather than the gradation and color reproducibility. This is because PWM with a 200-line sawtooth wave is performed to reproduce the important halftone portion (that is, other than the character portion).

[0104]

[Table 2] [Toner Consumption Estimating Means] To estimate the toner consumption, refer to FIG.
This is performed in units of 4 × 4 pixel blocks shown in FIG. Toner consumption is (1) average density of output image, that is, integrated value of image data, (2) spatial frequency of output image, (3) image pattern type of output image (flat, vertical edge,
Experiments have confirmed that it depends on the horizontal edge and the vertical / horizontal edge. Furthermore, (4) it is known that the characteristics differ depending on the image type (natural image, CG image, PS image). Therefore, in this embodiment, the toner consumption amount is estimated based on the above four items (1) to (4).

That is, as the first step, as shown in (1), the toner consumption amount estimated by integrating the image data for each 4 × 4 pixel block is set as the standard consumption amount T0. This corresponds to the toner consumption amount in the case of a flat image. Further, as a second step, the coefficient α shown in FIG. 30 is obtained under the conditions (2) and (3). At this time, .alpha..multidot.T0 becomes the toner consumption amount estimation value in this 4.times.4 pixel block, and when this is added for the entire output image, it becomes the toner consumption amount estimation value of the output image.

FIG. 25 shows the toner consumption amount estimating means 168 (similarly to 168, 168 ', 168'', 16).
8 ″ ′) is a block diagram. 1501,1502
Reference numeral 1503 denotes a line memory equivalent to 401 and 402 in FIG. 5, respectively, which is controlled by the pixel synchronization signal CLK and the main scanning synchronization signal HYSNC, and delays one line of the input signal to provide an image of four lines in the sub scanning direction. Data is output from each line memory at the same time, and in the subsequent stage, synchronous control is performed by the XPH and YPHS signals shown in FIG. 15, so that the image signal in 4 × 4 block units shown in FIG. 15 can be extracted. it can.

Reference numeral 1504 denotes an average density extraction means, which is a part for calculating the average density of the output image shown in (1) above.
The average density in the 4 × 4 block is detected. 1505
Is means for determining the spatial frequency shown in (2) and the image pattern type shown in (3).

Reference numeral 1506 denotes an intra-block binarizing means,
In the output image as shown by 1601 in FIG. 26, for example, the 4 × 4 multivalued pixel block shown at 1602 is compared with the density calculated at 1504 to determine 16
A total of 16 bits of 4 × 4 binary patterns as shown in 03 are obtained.

Reference numeral 1507 in FIG. 25 is a portion for detecting the spatial frequency in the block and determining the type of pattern in the block, which is composed of a read-only memory (ROM) and is determined by the procedure shown below. But ROM beforehand
It is written in 1507.

First, the number of all changing points (0 → 1 and 1 → 0) in the main scanning direction in the 4 × 4 binary pattern 1603 is counted, and this is designated as E1. Similarly, 4x4
The number of all change points (0 → 1 and 1 → 0) in the sub-scanning direction in the binary pattern 1603
And (For example, in the example shown in FIG. 16, E1 =
8, E2 = 0. ) Next, the type of pattern in the 4 × 4 block is determined by the values of E1 and E2. That is, as shown in FIG. 27, when the value of E1 + E2 is less than the constant value A, the 4 × 4 pixel block is determined to be flat, and when E1> 2 × E2, it is determined to be a vertical edge, If E2> 2 × E1, it is determined to be a horizontal edge, and if E1 ≦ 2 × E2 and E2 ≦ 2 × E1, it is determined to be a vertical / horizontal edge.

Here, when A = 4, for example, in the example shown in FIG. 26, it is determined to be a vertical edge.

On the other hand, the spatial frequency is estimated by "0" in the case of flatness and by an amount proportional to E1 in the case of vertical edges (E1
/ 32 [pixel- ¹ ]), in the case of a horizontal edge, an amount proportional to E2 (E2 / 32 [pixel- ¹ ], and in the case of a vertical / horizontal edge, an amount proportional to E1 + E2 ((E1 / 2 + E2 / 2)
/ 32 [pixel- ¹ ]).

In the ROM 1507, when 16 bits of 4 × 4 binary pixel patterns are input as an address, they are written in advance so as to obtain the result estimated by the above-mentioned criterion, and the 8-bit data D7 ... Of D0, pattern types (00 for flat, 01 for vertical edge, 10 for horizontal edge, 11 for vertical / horizontal edge ... Binary numbers) correspond to D1 to D0, and spatial frequencies correspond to D6 to D2. Corresponds to the estimated value of 5 bits.

Reference numeral 1508 in FIG. 25 is a toner consumption amount estimating unit in a block, which is composed of a look-up table RAM, and is a 4 × 4 average density within a block calculated by 1504, a spatial frequency estimated by 1505, and The pattern type and the character area signal K ₂ are input to the address, and T0 estimated from the image data integrated value (average value) is added to the pattern type and the spatial frequency as shown in FIG.
The quantity α · T0 multiplied by the coefficient α estimated by the characteristic of 0
The value calculated in advance is written so that is output as data. Further, the characteristics shown in FIG. 30 are different in the influence of the frequency of the PWM reference signal.
It has been empirically found that there is a difference in the characteristics between the PWM of 400 lines and the PWM of 400 lines. In order to consider the difference, the character area signal K ₂ signal, which is the switching control signal of the PWM reference signal, is also input to the address of the lookup table RAM 1508,
It can be adapted to the case of PWM of both 200 lines and 400 lines.

Further, the characteristics shown in FIG. 30 are different depending on the image processing, for example, a general image such as a photograph and a CG image or PS image created by a computer. In addition, the lookup table RA stores different data depending on a predetermined image type.
Write to M1508.

The sequence of writing different data depending on the image type into the lookup table RAM 1508 is shown in the flowchart of FIG.

First, the user determines the image type and selects the image type from the image type selection screen of the operation unit (not shown) (S2101).

If the user determines that the image is a PS image,
If the PS image is selected on the image type selection screen (S2
102) and write the data for the PS image in the lookup table RAM 1508 (S2103).

If the user determines that the CG image is not the PS image and the CG image is selected (S210).
4) Look up table RA for CG image data
Write to M1508 (S2105).

If no particular selection is made, it is determined that the image is a natural image such as a photograph and the data for the natural image is written in the look-up table RAM 1508 (S2106).

The data to be written in the RAM 1508 is a ROM
It is only necessary that the value is held in advance in.

As described above, according to the characteristics of the image,
By estimating the toner consumption amount that is closer to the actual value, it is possible to replenish the toner according to the toner consumption amount.

[0123]

[Other Examples]

(Second Embodiment) In the first embodiment described above, the user selects an image type, and based on the image type, weighting data of image data suitable for the selected image type is looked up in a look-up table. Although written in the RAM 1508, the present invention is not limited to this.

FIG. 32 shows the second embodiment.

FIG. 32 shows a toner consumption amount estimating means 168 (similarly to 168, 16 in FIG. 1) in the first embodiment.
8 ', 168'''), and those common to FIG. 25 are designated by the same reference numerals.

The image information storage memory 2201 stores the average density information from the above-mentioned average density detection circuit 1504 for each block, the spatial frequency information from the ROM 1507, and the pattern type information for each block.

The stored information is read by the CPU (not shown) after the image formation is completed, and the CPU reads the information based on the information.
Estimates the image type. The CPU obtains different data according to the image type based on this estimation from the lookup table RA.
Write to M1508.

FIG. 33 shows a sequence flowchart of the above processing.

First, the document is pre-scanned (S230).
1). At this time, the image is not developed, only the image data is read by scanning, and the information about the density, spatial frequency, and pattern relating to the read image is stored in the RAM 2201 shown in FIG.

When the prescan is completed, the CPU (not shown) reads the image information from the RAM 2201 (S2302). Next, the CPU determines the type of image based on the read image information (S2303).

When the image type is judged by the CPU, the image type is P
If it is determined to be an S image (S2304-Y), PS data is written in the lookup table RAM 1508 (S2305).

When it is determined that the image is not the PS image but the CG image (S2306-Y), the data for the CG image is written in the lookup table RAM 1508 (S2).
307). In other cases, it is determined that the image is a natural image such as a photograph, and the data for the natural image is looked up in the lookup table R.
Write to the AM 1508 (S2308).

After storing the weighting data corresponding to the image type in the look-up table RAM 1508 in this way, the main scan is started and the image output is started (S23).
09).

The above procedure is realized by the CPU executing the program stored in the ROM or the like.

(Third Embodiment) In the first and second embodiments, the CPU executes the program to determine the image type based on the image information input and stored from each detecting section. However, this determination may be performed by a hardware circuit.

FIG. 34 shows the third embodiment.

FIG. 34 shows the toner consumption amount estimating means 168 (similarly to 168 ', 168'',
168 '''), and those common to FIG. 25 are designated by the same reference numerals.

Reference numeral 1510 denotes an orthogonal transform (frequency transform) means, which performs Fourier transform or Hadamard transform for each 4 × 4 pixel block. The output of the orthogonal transform means 1510 makes the spatial frequency distribution in the vertical / horizontal direction of the input block clear. Reference numeral 1511 denotes a feature extraction means, which extracts the feature of the image by the spatial frequency distribution in the vertical direction / horizontal direction, and the fundamental spatial frequency of the input image (spatial frequency with the strongest power) as in the first embodiment. Is output in 5 bits, and a 2-bit pattern type (00 for flat, 01 for vertical edge, 10 for vertical edge, 11 for vertical / vertical edge) is output.

These outputs are input to the RAM 1508 as addresses, and the toner consumption amount data stored in advance in the RAM 1508 corresponding to the addresses representing the characteristics of the image are read out.

With such a configuration, the spatial frequency is calculated instead of simply counting the number of pixels, and the characteristic of the image is determined based on the calculated spatial frequency. Can be brought close to the frequency indicated by the horizontal axis in FIG. Further, since it is composed of hardware, the processing can be performed quickly.

Although the natural image, the PS image, and the CG image are taken as the image types in the above-described embodiments, the image type may be another image type mode.

Further, although the toner consumption amount is estimated based on the image divided into 4 × 4 pixel blocks, the present invention is not limited to this, and the pixel block of a desired size (m, n is 2 or more) is used. Estimation may be performed for each m × n pixel).

Although the present invention has been described with respect to a color copying machine, the present invention is not limited to this, and it is also possible to use monochrome and general output equipment such as a printer for printing out digital image data using a developer. Applicable.

Furthermore, the present invention may be applied to a system composed of a plurality of devices or an apparatus composed of one device. Further, it goes without saying that the present invention can be applied to the case where it is achieved by supplying a program to a system or an apparatus.

[0145]

As described above, the image forming apparatus according to the present invention can always supply an appropriate amount of the developer and control the developer concentration with high accuracy.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment.

FIG. 2 is a block diagram showing a configuration of an example.

FIG. 3 is a sectional view of a color copying machine according to an embodiment.

FIG. 4 is a diagram illustrating scaling (enlargement / reduction) of an image.

FIG. 5 is a block diagram of pixel conversion means.

FIG. 6 is a block diagram of pixel conversion means.

FIG. 7 is a block diagram of a maximum value detection circuit.

FIG. 8 is a block diagram of a smoothing circuit.

FIG. 9 is a block diagram of an edge detection circuit.

FIG. 10 is a diagram showing pixel blocks and edge directions.

FIG. 11 is a block diagram of a color conversion unit.

FIG. 12 is a diagram illustrating masking coefficients.

FIG. 13 is a block diagram of an encoding (L-code) circuit.

FIG. 14 is a block diagram of an encoding (ab-code) circuit.

FIG. 15 is a diagram showing a 4 × 4 pixel block.

FIG. 16 is a block diagram of a spatial filter.

FIG. 17 is a diagram showing the character of a filter according to an input.

FIG. 18 is a block diagram of 4 × 4 area processing.

FIG. 19 is a block diagram of a circuit for generating XPHS and YPHS signals.

FIG. 20 is an image control timing chart.

FIG. 21 is a diagram illustrating area processing.

FIG. 22 is a diagram illustrating a result of pixel correction.

FIG. 23 is a diagram illustrating PWM.

FIG. 24 is a diagram illustrating PWM.

FIG. 25 is a block diagram of toner consumption amount estimating means.

FIG. 26 is a diagram for explaining the operation of the intra-block binarization circuit.

FIG. 27 is a diagram illustrating image pattern type determination.

FIG. 28 is a diagram illustrating a conventional example.

FIG. 29 is a diagram illustrating a conventional example.

FIG. 30 is a diagram showing toner density consumption characteristics with respect to spatial frequency.

FIG. 31 is a flowchart showing switching of the image data weighting table according to image type.

FIG. 32 is a block diagram of an image type determining unit according to a second embodiment.

FIG. 33 is a sequence flowchart of switching of the image data weighting table according to the second embodiment.

FIG. 34 is a diagram showing a difference in toner density consumption characteristic with respect to spatial frequency depending on image type.

FIG. 35 is a block diagram of image type determination means of the third embodiment.

[Explanation of Codes] 112 Color Space Converter, 113 Lightness Information Encoder, 114 Chromaticity Information Encoder, 116 Memory, 157, 158, 159, 160 ... Magnification / Magnification Circuit, 141, 142, 143, 144 ... Decoding Converter, 151, 152, 153, 154, 155, 156 tri-state gate, 167, 167 ', 167 ", 167"' PWM
Circuits, 168, 168 ', 168 ", 168'" toner consumption estimation circuit, 202 read original, 212 image processing circuit section.

Continuation of front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical indication location G03G 15/01 113 Z (72) Inventor Yoshinori Ikeda 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Michio Kawase 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (11)

[Claims] 1. An image forming apparatus for visualizing digital image data with a developer, comprising setting means for setting an estimation condition according to the type of digital image data, and characteristic detection for detecting characteristics of the digital image data. Means, an estimation means for estimating the consumption amount of the developer under the estimation condition set by the setting means in accordance with the characteristic detected by the detection means, and a use of the developer estimated by the estimation means An image forming apparatus comprising: a developer replenishing unit that replenishes the developer based on the amount. 2. The image forming apparatus according to claim 1, wherein the characteristic detecting unit uses a rectangular pixel block including a plurality of pixels as a unit. 3. The image forming apparatus according to claim 1, wherein the estimating unit uses a rectangular pixel block including a plurality of pixels as a unit. 4. The image forming apparatus according to claim 1, wherein the characteristics of the image data detected by the characteristic detecting unit are image density, spatial frequency, and image edge direction. 5. The image forming apparatus according to claim 4, wherein the characteristic detecting unit includes a unit that orthogonally transforms image data. 6. The image according to claim 1, further comprising input means for inputting the type of digital image data, and the setting means sets the estimation condition based on the type input by the input means. Forming equipment. 7. The image according to claim 1, further comprising a modulation unit that modulates digital image data, and the estimation unit estimates the amount of developer consumed according to a modulation condition of the modulation unit. Forming equipment. 8. The modulation means performs pulse width modulation for comparing image data with a predetermined signal to obtain an output signal, and the modulation condition is a cycle of the predetermined signal. Image forming device. 9. An identification means for identifying a character area and an area other than the character area are further provided, and the estimation means estimates the consumption amount of the developer according to the identification result by the identification means. The image forming apparatus according to item 1. 10. The image forming apparatus according to claim 1, wherein a color image is formed by a plurality of kinds of developers. 11. The image forming apparatus according to claim 1, wherein the image is formed by an electrophotographic method.