JPS6318776A - Picture processor - Google Patents

Abstract

PURPOSE:To remove noise, to eliminate the shading of a picture due to the removal of the noise and to obtain a clear picture by deciding the sequence of a density of picture information by a comparison selection means for the picture information in an unit area and taking out the picture information corresponding to the set sequence of the density. CONSTITUTION:The picture information in the unit area read by a CCD 10 is stored in the RAMs 77-80 of a median filter circuit 14 and the reading and the writing of the RAMS 77-80 are controlled by a delay line 71, a D flip-flop 72, a JK flip-flop 73, AND circuits 74, 75, an address counter 76 or the like. The picture is selected by three state buffers 84, 85, multiplexers 86, 87, 92, 93, 95, 96, 98, 99, 105, 109, 111, 113. Further, by comparing in comparison circuits 94, 99, 100, 103, 106, 110, 112, 114, the sequence of the density of the picture information is decided by the multiplexer and the picture information corresponding to the set sequence of the density is taken out. Thereby, the noise is removed, the picture has no shading and is clear.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an image processing device, and more particularly, the present invention relates to an image processing device that projects an image onto a plurality of photoelectric conversion elements and obtains image information read by the photoelectric conversion elements. Copier, filing system input device, CAD (Compute)
r-Aided-Design) This invention relates to an image processing device that can be applied to human-powered devices and the like.

(Prior Art) An image processing device in a conventional document reading device will be described with reference to FIGS. 9 and 10.

FIG. 9 is a schematic explanatory diagram of the document reading device, where 1 is the document, 2 is
, 3.4.5 is a conveying roller, 6 is a reflective plate, 7 is a contact glass, 8 is a fluorescent lamp, 9 is an optical lens, and 10 is L
It is a CD (a charge-coupling device).

In such an apparatus, a document l is conveyed by conveyance rollers 2 to 5, and is illuminated by a fluorescent lamp 8. The original image is captured by the optical lens 9 at C(''.

The image is formed on DIO.

FIG. 10 is a block diagram showing the circuit of the document reading device shown in FIG.
1 is an amplifier circuit, 12 is an A/D conversion circuit, and 13 is a clock driver. In Figure 6, the vertical arrow indicates the main scanning direction, and the horizontal arrow indicates the sub-scanning direction. In Figures 9 and 10, The original image formed on the CCD 10 is output as an analog signal, but since it is a very small signal, it is amplified by the amplifier circuit 11. The A/D conversion circuit 12 converts the amplified analog image signal into a multivalued digital image signal representing each pixel. In the digital image signal after A/D conversion, noise appears in the regular image data due to noise in the original image, uneven light intensity, dirt on the contact glass 7, uneven sensitivity of the CCD 10, and the like.

Conventionally, measures against this noise include performing shading correction before the A/D conversion circuit 12, and
After that, it has been proposed to output the average value of surrounding pixels or to recognize isolated points in the image. However, shading correction does not correct noise in the original image.
Averaging the density in a small region and the entire image reduces noise in the image, but the image loses its sharpness and the image as a whole becomes blurry.

In addition, when noise is removed by isolated point recognition, if the noise is regular or an isolated point with a large temperature difference from the surrounding area, the power spectrum of the periodic noise component is concentrated at a certain position in the power spectrum space. Therefore, when Fourier transform is applied to remove this, and when only a few pixels in a small region have large density changes without having connected components that are connected with the same density as neighboring pixels, it is considered as noise. However, in order to remove the power spectrum by referring to it, the condition is that the power spectrum component of the normal text or photograph is not the same as the power spectrum component seen as noise, and if it is not the same, it is necessary to remove it by referring to the power spectrum. Misrecognition occurs.Furthermore, when recognizing isolated points in small areas, the problem is the number of pixels that are considered as isolated points. , especially in the case of halftone images.

These erroneous recognitions result in missing halftone images, small dots, and the like. Furthermore, this nozzle removal requires an algorithm and hardware configuration based on isolated point recognition, making real-time hardware configuration difficult.

(Objective) The present invention has been made in order to overcome the drawbacks of the above-mentioned conventional devices, and an object of the present invention is to provide an image processing device that can remove noise from an image and remove blur from the image due to the noise removal.

(Structure) In order to achieve the above object, the present invention projects an image onto a plurality of photoelectric conversion elements and stores image information of a read unit area in an image processing apparatus that obtains read image information of the photoelectric conversion elements. comprising a storage means, a read/write control means for controlling reading and writing of the storage means, and a comparison and selection means for comparing and selecting the image information, and the comparison and selection means determines the density order of the image information in the unit area. The present invention is characterized in that image information corresponding to this density order is extracted.

Hereinafter, a detailed explanation will be given based on one embodiment of the present invention.

FIG. 1 is a circuit block diagram showing an example of a document reading device using the present invention, and like the conventional example shown in FIG. 10, 1 is a document, 9 is an optical lens, and 10 is a CCD (charge coupled device).
, 11 is an amplifier circuit, 12 is an A/D (analog/digital) converter, 13 is a clock driver, and further A
After the /D converter 12, a median filter circuit 14,
It is composed of a control circuit 15 and an operation section 16 for the median filter circuit 14. In the figure, the vertical arrows in the document 10 indicate the main scanning direction, and the horizontal arrows indicate the sub-scanning direction.

A method of reading a document using the document reading device described above will be explained. Reading of the original 1 is performed by scanning in two directions: the main scanning direction in which C0DIO is electrically scanned (main scanning), and the sub-scanning direction in which the scanning position is moved on the original 1 (sub-scanning). The sub-scanning may be performed by moving the original 1 for scanning, or by fixing the original 1 and scanning by moving the optical system.The original image formed on the CCD 10 is sent as an analog image signal. Although it is output, since it is an extremely small signal, it is amplified by the amplifier circuit 11. This amplifier circuit 11
The analog image signal amplified by the A/D conversion circuit 12 is converted into a multi-value (for example, 64th floor!J) digital image signal indicated for each pixel.The digital image signal after this A/D conversion is As explained in the apparatus, noise appears in the regular image data due to noise in the original image, uneven light intensity, dirt on the contact glass (see FIG. 9), uneven sensitivity of the CCD 10, etc. This noise is corrected by the median filter circuit 14. This median filter circuit 14 simultaneously removes image noise, removes image blur due to noise removal, and maintains image sharpness.

Next, the algorithms of the median filter circuit 14 and the averaging circuit will be explained, and specific image data will be shown.

The median filter is, for example, 3 filters as shown in Figure 2.
In the small area of the ×3 matrix, the pixel of interest is ×5, the surrounding pixels are ×2. ×4. ×6. When xB is x2. ×4
．． ×5. ×6. ×8 are compared in order of density, and the third density value is set as the output density of the median filter (corresponding to the pixel of interest). In this case, the noise is represented by white or black peak values, and small? (2) Since the number of pixels in the area is about 1 or 2 pixels, noise can be removed. At the same time, it is also possible to preserve the edges.

The averaging circuit means, for example, when obtaining x5 pixel data in a small area of 3 x 3 matrix 2 as shown in FIG. x4. x5. The sum with x3 is calculated and the average value is used as the output of x5. The following formula (11, (2)
respectively indicate the algorithm of the averaging circuit, and Equation (2)
is a weighted pixel of interest.

(1)D (×5)= (X2+X4+X5+X6+X
8)+5 +2)D (×5)-(x2+x4+x6+x8+2・
×5)+smile, where D(×5) is the output data of the averaging circuit corresponding to the pixel of interest×5.

If FIG. 3 is the image data of the original image, FIG. 4 is the output of the median filter, and FIG. 5 is the output of the averaging circuit (formula 1 above). Although noise is reduced in the output of this averaging circuit, it affects surrounding pixels and edges are also blurred.

On the other hand, with the median filter, noise is completely removed, and at the same time edges are clear.

Sixth regarding the median filter circuit 14 according to the present invention
This will be explained using an example of the image data shown in the figure.

The development data is read from the original document 1 by the CCD 10. First, the line 1 in FIG. ×3. Read the pixel data of ×4--. Next, move from line 1 to line 2 by moving in the sub-scanning direction indicated by the vertical arrow, and move line 2 in the main scanning direction by ×5. Read the pixel data of x (3° x 7.
Read the pixel data. Here, the pixel to be corrected with the median filter (the pixel of interest) is x6, and this pixel of interest x6
In order to correct the 1t4 pixels (peripheral pixels) x 2
．． ×5, ×7. It shall be XIO.

Description will be made below with reference to a detailed block circuit diagram of the median filter circuit 14 in FIG. 7 and a timing chart in FIG. 8.

As shown in the timing chart of FIG. 8, the delay C is the random access memory (RAM) in the block circuit diagram of FIG. This is for creating chip selects of 7, 78, 79.80.

The L gate d indicates effective image data of the image data read from one line of photoelectric conversion elements, and is generated by the COD drive circuit.

This L gate d is latched by the D flip-flop 72 and is used as the load signal e of the address counter 76. J
The toggle mode of the K flip-flop 73 enables write enable (WEI, WB2) at the falling edge of the L gate d.
)f, g, and other control signals.

The address counter 76 is set to an initial value when the load signal e is sLa, and is incremented by the rising edge of the clock (CLK) b when the load signal e is H#. This is input to the addresses of RAMs 77-80.

After passing through the JK flip-flop 73, the L gate d passes through the delay line 71 and the AND circuit 74.75 to the RAM.
Passed 77-80 chip select.

Read/write control of RAMs 77 to 80 is performed using the write enable signal f8g and chip select signals (C3I, C
32) Determined by h and i, write enable #H" during reading, chip select "■,", and write enable "L" during writing, chip select "II"
It is. In this way, delay line 71, D flip-flop 72, JK flip-flop 73, AND circuit? 4, 75, address counter 76, RAM 77
~80 inputs and outputs have been determined.

Here, the symbols in the timing chart of FIG. 8 will be explained. a and b are clocks (CLK), C is delay, and d is! , gate, 0 is Rotoy No. 8, f, g are write enable (WE 1 , WE 2 ), h,
i indicates chip select (CS1.C52), j indicates address, kw x indicates image input data, and y indicates image output data. These symbols are the same in FIG. 7 as well.

In FIG. 7, consider the case where x13 (data value 58) is input as image input data k.

The output of the flip-flop 81 is ×12 (data I direct 52
), the output of the flip-flop 82 is ×11 (data value 56), and the output of the flip-flop 83 is ×10 (data value 5). At that time, flip-flop 8
1, 82.83, 88, 89°90.91 are output in synchronization with the inverted output of the clock. RAM77.78
, and RA Fvl 79.80, when one reads, the other writes.

Data input to RAM77-80 is selected by three-state buffer 84.85,
Outputs 7-80 are selected by multiplexer 86.87. The three-state buffers 84 and 85 output at "L", and the multiplexers 86 and 87 output at #L and output B at "H".

In FIG. 7, X12 in the flip-flop 81
is output, and the 3-state buffer 84 selects the output data of 1L# via the 3-state buffer 84.

This is because the selection is made when the write enable signal (WE2) g of the JK flip-flop 73 is "L#". Here, the 3-state buffer 84 is connected to IG, 1, 2G
and 2 correspond, and when 1G or 2G is #L",
Data is output from the corresponding line ■ or 2. This also applies to the 3-state buffer 85.

RAM7B is write mode (write mode), RAM?
? is in read mode (8th
(See the timing chart in the figure), since the selection signal of the multiplexer 86 is #L#, x8 is output. Furthermore, the flip-flop 88 outputs x7.

In this case, since RAM 79, 80 and 3-state buffer 85 are also similar to the read recycle and write cycle described above, x3 is read and x7 (data value 53) is written from RAM 80. The multiplexer 87 outputs x3 and the flip-flop 89
x2 is output from. The flip-flop 90 outputs ×6 (data value 2), and the flip-flop 9
From 1, x5 (data value 6) is output.

The output from the comparison circuit 94 is A input x 10 (data value 5)
and the B input x 5 (data value 6), and when the A input is larger than the B input, the ``H# signal is output.At that time, the multiplexer 93 inputs the A input x 10 (data value 5). , ×5 (data value 6) is input to the B input, and to the multiplexer 92, ×5 is input to the A input, and ×10 is input to the B input.

At present, the pixel data of ×10 is 5 and the pixel data of ×5 is 6, so the comparison circuit 94 outputs an “L” signal, the multiplexer 93 outputs ×5 (data value 6), and the multiplexer 92 outputs × 10 (data value 5) is output.

Comparison circuit 97 compares data of x6 (data value 2) and data of x5 (data value 6) in the same way as described above, and multiplexer 96 outputs x5 and multiplexer 95 outputs x6.

Similarly, the comparison circuit 100 compares x6 and XIO, and multiplexer 99 outputs x10 and multiplexer 98 outputs x6.

In the comparison circuit 103, ×5 and ×7 (data value 53
), ×7 is not shown), multiplexer 101
The smaller data x5 is outputted from , and the data x7 is deleted here. This is because ×7 (data value 53) is the largest data among ×5 (data value 6), ×6 (data value 2), and ×10 (data value 5), so This is because it is not necessary.

Next, the comparison circuit 106 compares ×10 and ×5, and the multiplexer 105 outputs ×5, and the multiplexer 10
4 outputs x10.

Similarly, in the comparison circuit 110, the multiplexer 109
The larger data x 10 is output from . Again, the smaller data need not be selected by the algorithm.

Similarly, in the comparison circuit 112, the multiplexer 111
x5 (data value 6) is output from.

Finally, in the comparator circuit 114 as well, the multiplexer 113 outputs the larger data x5.

As above, ×2 (data value 8), ×5 (data value 6)
), ×7 (data value 53), and the third pixel data that is the intermediate value of Xl0 (data value 5) ×5 (data value 6)
is taken out.

According to the above embodiment, the image information of the unit area read by C0DIO is sent to the RA of the median filter circuit 14.
Stored in M77-80, delay line 71, D flip-flop 72, JK flip-flop 73, AND circuit? 4, 75, address counter 76, etc.
77 to 80, 3-state buffer 84°85, multiplexer 86, 87, 92, 93
゜95.96.9B, 99,105,109,111.
An image is selected at 113, and comparison circuits 94,99°100.
By comparing signals 103, 106, 110, 112, and 114, the density order of the image information can be determined by the comparison circuit and the multiplexer, and image information corresponding to the set density order can be extracted.

The circuit configuration of the median filter removes noise, eliminates blurring of the image, and sharpens the image.

Moreover, the peripheral pixels are minimized, and the intermediate value (third)
Since only pixel data is extracted, the hardware is simplified, which is advantageous in terms of cost, and further downsizing is possible.

(Effects) As described above, according to the present invention, the density order of the image information is determined by the comparison and selection means for image information within a unit area, and the image information corresponding to the set density order is extracted. An image processing device that can remove noise from read image information and eliminate image blur due to this noise removal, and can obtain clear images that are free of dirt other than the necessary image information and maintain sharpness at the same time. can be provided.

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram showing an example of a document reading device using the present invention, FIG. 2 is a 3×3 matrix diagram showing the relationship between a pixel of interest and peripheral pixels in a small area, and FIG. 3 is a document image data FIG. 4 is a matrix diagram showing the output of the median filter, FIG. 5 is a matrix diagram showing the output of the averaging circuit, and FIG. 6 is a matrix diagram showing image data used in the embodiment of the present invention. , FIG. 7 is block number 10 explaining the median filter according to the present invention.
...CCD, 12...A/D converter, 14...
median filter circuit, 71... delay line,
72...D flip-flop, 73...JK flip-flop, 74.75...AND circuit, 7G...
Address counter, 77-80...RAM, 84.8
5...3 state buffer, 86.87,92,93
゜95.96.9B, 99,105,109,111
, 113-? JLz Chibrexa, 94,99,100
．． 103, 106, 110, 112, 114... Comparison circuit. Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 9 Fig. 1 O Procedural amendment (voluntary) 19862 as month ρ

Claims (1)

[Claims] In an image processing device that projects an image onto a plurality of photoelectric conversion elements and obtains read image information of the photoelectric conversion elements, the apparatus includes a storage means for storing image information of a read unit area, and controls reading and writing of the storage means. comprising a read/write control means and a comparison selection means for comparing and selecting the image information,
An image processing apparatus characterized in that the comparison and selection means determines the density order of the image information within the unit area, and extracts the image information corresponding to this density order.