JPH0678152A - Image processor - Google Patents

Abstract

PURPOSE:To obtain the image processor small in memory capacity and fast in processing speed by compressing original image data and then storing the compressed data in a memory without directly storing them. CONSTITUTION:An input compensating circuit 1 A/D-converts input data obtained from a CCD and applies various compensation. An error diffusing circuit 2 reduction-converts multilevel data of 8-bit pixel obtained from the circuit 1 into 1- or 2-bit pixel. By this conversion, the using capacity of a memory can be limited to 1/4 in a 2 bits and 1/8 in 1 bit. Image data stored in an image memory can be restored to the original multilevel data. Data variously processed by an image processing part 5 are compressed from 8 bits to 1 or 2 bits by the processing of error diffusing circuit 6 and stored again in the memory 3. The stored image data are restored to mutilevel 8-bit data by a smoothing filter, subjected to pulse width conversion by a laser diode circuit 8, and a laser diode is driven to print out the data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing device.

[0002]

2. Description of the Related Art In the conventional image scaling processing, (1) information is stored in a memory as it is without compression of image data, and the scaling processing is performed after storage. (2) If the scaling value is unknown when reading the image, the scaling factor is calculated in the first scan, 2
There has been proposed a method of performing actual scaling processing in the second scan.

[0003]

However, in the above (1), when the image data amount becomes large, there are many cost and technical problems in order to realize a memory satisfying the function. In the case of (2), it is necessary to scan one document twice, which causes a problem that the document processing speed is halved. Further, the histogram data is created in the first scan, and thereafter, the processing such as high contrast is performed in the second scan, so that the scanning requires twice the time. There were problems such as complicated control that required a long time for manuscript processing.

An object of the present invention is to provide an image processing apparatus which eliminates these problems.

[0005]

An image processing apparatus of the present invention comprises means for compressing image data, means for storing compressed image data, and means for restoring compressed image data output from this storage means. And a means for scaling the restored image data.

[0006]

The image processing apparatus of the present invention does not store the original image data as it is, but stores the compressed image data in the memory. The image data stored in the memory is reproduced as necessary, and the reproduced compressed image data is restored. Moreover, the desired image is obtained by performing the scaling process on the restored image data.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 3 is a side view showing an overall configuration of a digital copying machine, which is an embodiment of an image forming apparatus equipped with a document conveying apparatus according to the present invention.

As shown in the figure, the digital copying machine 30 of this embodiment includes a scanner section 31 and a laser printer section 3.
2. A multi-stage paper feeding unit 33 and a sorter 34 are provided.

The scanner unit 31 includes a document placing table 35 made of transparent glass and a double-sided automatic document feeder (RDF) 36.
And a scanner unit 40.

The multi-stage sheet feeding unit 33 includes the first cassette 5
It has the 1st, 2nd cassette 52, the 3rd cassette 53, and the 4th cassette 55 which can be added by selection.

In the multi-stage sheet feeding unit 33, the sheets are fed out one by one from the sheets stored in the cassettes of the respective stages and are conveyed toward the laser printer section 32.

The RDF 36 sets a plurality of originals at one time, automatically feeds the originals one by one to the scanner unit 40, and one side or both sides of the original is scanned by the scanner unit 40 according to an operator's selection. It is configured to be read by.

The scanner unit 40 includes a lamp reflector assembly 41 for exposing a document, a plurality of reflection mirrors 43 for guiding a reflected light image from the document to a photoelectric conversion element (CCD) 42, and a reflected light image from the document on the CCD 42. It includes a lens 44 for imaging.

When scanning a document placed on the document table 35, the scanner section 31 is configured to read the document image while the scanner unit 40 moves along the lower surface of the document table 35. When the RDF 36 is used, the document image is read while the document is being conveyed while the scanner unit 40 is stopped at a predetermined position below the RDF 36.

The image data obtained by reading the original image with the scanner unit 40 is sent to an image processing unit (not shown), which will be described later, and undergoes various processing, and then temporarily stored in the memory of the image processing unit. In response to the output instruction, the image data in the memory is given to the laser printer unit 32 to form an image on the paper.

The laser printer unit 32 includes a manual document tray 45, a laser writing unit 46, and an electrophotographic process unit 47 for forming an image.

The laser writing unit 46 is a semiconductor laser which emits a laser beam according to the image data from the above-mentioned memory, a polygon mirror which deflects the laser beam at a constant angular velocity, and an electrostatic photography process section which converts the laser beam deflected at a constant angular velocity. It has an f-θ lens and the like for correcting so as to deflect at a constant velocity on the photosensitive drum 48 of 47.

The electrophotographic process section 47 comprises a charging device, a developing device, a transfer device, a peeling device, a cleaning device, a static eliminator and a fixing device 49 arranged around the photosensitive drum 48 according to a well-known mode. .

A conveying path 50 is provided on the downstream side of the fixing device 49 in the conveying direction of the sheet on which the image is to be formed. The conveying path 50 is connected to the conveying path 57 leading to the sorter 34 and the multi-stage paper feeding unit 33. It branches into a communication path 58 which is in communication.

The conveying path 58 is branched in the multi-stage paper feeding unit 33, and the reversing conveying path 50 is formed as a conveying path after branching.
a and a double-sided / composite transport path 50b are provided.

The reverse conveyance path 50a is a conveyance path for reversing the front and back sides of a sheet in the double-sided copy mode for copying both sides of a document. The double-sided / composite conveyance path 50b conveys a sheet from the reverse conveyance path 50a to the image forming position of the photosensitive drum 48 in the double-sided copy mode, or forms an image of a different original or a toner of different colors on one side of the sheet. This is a transport path for transporting the paper to the image forming position of the photoconductor drum 49 without inverting the paper in the single-sided composite copy mode in which composite copying is performed.

The multi-stage sheet feeding unit 33 includes a common conveyance path 56, and the common conveyance path 56 includes the first cassette 51 and the second cassette 51.
The sheets from the cassette 52 and the third cassette 53 are carried out toward the electrophotographic process section 47.

The common conveying path 56 is the electrophotographic process section 47.
On the way to the transport path, it joins the transport path 59 from the fourth cassette 55 and leads to the transport path 60.

The conveying path 60 merges with the conveying path 61 from the double-sided / composite conveying path 50b and the manual document tray 45 at a confluence point 62 to form an image between the photosensitive drum 48 of the electrostatic photography process section 47 and the transfer device. The confluence point 62 of these three conveyance paths is provided at a position close to the image forming position.

Therefore, in the laser writing unit 46 and the electrophotographic process section 47, the image data read from the above-mentioned memory is the laser writing unit 46.
The toner image formed as an electrostatic latent image on the surface of the photoconductor drum 48 by scanning with a laser beam is visualized with toner, and the toner image is statically formed on the surface of the sheet conveyed from the multi-stage sheet feeding unit 33. It is electrotransferred and fixed. The sheet on which the image is thus formed is sent from the fixing device 49 to the sorter 34 via the transport paths 50 and 57, or is transported to the reverse transport path 50a via the transport paths 50 and 58.

FIG. 1 is a block diagram showing the basic functions of the image processing unit included in the digital copying machine 30 shown in FIG.
This processing unit is composed of an input correction circuit 1, an error diffusion 2, an image memory 3, a smoothing filter 4, an image processing 5, an error diffusion 6, a smoothing filter 7 and a laser drive circuit 8.

The input correction circuit 1 is a unit for A / D (analog / digital) converting input data from a so-called CCD and performing various corrections. Image data here is 8 bits /
This is multi-valued data of pixels. The error diffusion 2 is a conversion block that converts multivalued data into 1 bit / pixel or 2 bits / pixel from the standpoint of image processing. By this conversion, the memory usage can be reduced to 1/4 for 2 bits or 1/8 for 1 bit. The image data stored in the image memory 3 is restored to the original multi-value (8 bits / pixel) data by the smoothing filter 4. 4 as the smoothing filter 4
Multi-value data restoration is performed using a window function such as × 3, 7 × 5. The image processing 5 includes high contrast, density conversion for background removal, an arithmetic circuit for scaling, a feature extraction arithmetic function for image size recognition and area recognition, and the like. Further, the data processed by the image processing 5 is compressed from 8 bits to 2 to 1 bit by the error diffusion 2 processing and stored again in the image memory 3. The stored data can be passed through the smoothing filter 4, the image processing 5, and the error diffusion 6 again. The finally processed image data is restored to multi-valued 8 bits by the smoothing filter 7. The restored data is pulse-width converted by the laser drive circuit 8 which is a partial circuit of the LBP (Laser Beam Printer hereafter referred to as “printer”) that inputs multi-valued data, the laser diode is driven, and the data is printed. It

FIG. 2 is a block diagram embodying FIG. 1 in more detail. The input correction circuit 1 shown in FIG. 1 is the same as that shown in FIG.
The correction 14, the r correction 15, the cutout 16 and the histogram 17 are subdivided. The CCD 11 is a line sensor and outputs analog white / black data. A / D conversion 1
2 converts analog data into a digital value of 8 bits / pixel. The black and white correction 13 is a sewing correction circuit in the main scanning direction, and the MTF correction 14 performs blur correction of the lens optical system. The r correction 15 is a circuit for luminosity correction, and the cutout 16 is a circuit for extracting an effective image data area from the drooping image data and cutting it out. Histogram 1
Reference numeral 7 represents a histogram creation block of the image density for the effective area. The histogram 17 handles multi-valued data of 8 bits / pixel.

The data compressed to 1 bit or 2 bits / pixel by the error diffusion 18 is further image-compressed by the compression 19. If a run length method such as FAX is used as a compression method, the compression is usually about 1/10. The compressed image is stored in an image memory 21 composed of a D-RAM via a DMA (developed mass per area) 20.

DMA 23, restoration 24, smoothing filter 25
Is a subdivision of the smoothing filter 4 shown in FIG. The DMA 23 corresponds to a control unit that reads data from the image memory 21 of the D-RAM. The decompression 24 is to arithmetically decompress the data compressed by the run length in the compression 19 described above. The restored image data has 2 bits / pixel, and the smoothing filter 25 restores this to 8-bit multi-valued data. The details of the circuit configuration of the smoothing filter 25 in this embodiment are shown in FIG. In the same figure, edge detection 71 is performed in a 3 × 3 area centered on the pixel of interest, and if the edge is the target area is close to a text original, pixel data calculated by the 3 × 3 smoothing filter 72 is used as the edge data. If not, it is a photo manuscript and it is 7 × 5.
The pixel data calculated by the smoothing filter 73 is switched by the selector 74 and output. As a result, multi-valued data of 8 bits / pixel is restored.

1/8 reduction 26, binarization 27, feature extraction 2
8, the density conversion 29, and the scaling 31 are image processing 5 of FIG.
Equivalent to. For example, the density conversion 29 is used for high contrast and background removal, but its internal structure is a LUT (look up table) using a RAM. The image data output from the smoothing filter 25 is connected to the RAM address (for example, 8 bits), and the density conversion data is written in the RAM data, whereby the conversion can be easily performed. For example, the background threshold level is calculated from the histogram data at the time of image reading, and the data below the threshold in the density conversion table is the background, so it is corrected to "0" so that it is not printed as output data. It can be realized by

Similarly, this conversion table can be used for high contrast. Further, another major feature of the present invention is that high scan and background processing can be performed by one scan. According to the present invention, it is possible to perform automatic density conversion such as high contrast with a minimum memory usage and one scan.

The scaling 31 is a block for performing a scaling operation for main scanning / sub scanning. Since the main scanning / sub-scanning operations are separately performed, it is possible to change the magnification in one direction. As a feature of the present invention,
This means that it is possible to determine the magnification and perform the scaling processing with a minimum amount of memory after the scan is completed in one scan. For example, when determining the effective image size of the read image by image processing, the effective size is not known until after the image processing. Therefore, the automatic scaling in which the magnification is automatically set on the designated paper is used in the present invention. Only possible.

The 1/8 reduction 26 is for reducing the document size to 1/8 and shortening the processing time. The binarization 27 is based on the fact that the feature extraction 28 can be executed only with binary data. The feature extraction 28 performs the extraction of the original area, the determination of the shadow of the original, etc., but the feature extraction is performed with the figure contracted to 1/8 by the 1/8 reduction 26, and the blocks not necessary for repeating the feature extraction processing are extracted. The structure is such that the processing loop can be repeated many times while passing through and storing the processed data in the image memory 21. The three switches S1, S2, and S3 are provided to selectively switch the functional blocks according to these processing conditions.

The error diffusion 32 and compression 34 are blocks having the same purpose as the error diffusion 18 and compression 19 of the input system.

An outline of the error diffusion method will be described.
Let the pixel point of interest in the dimensional data be point A in FIG. A
The image data at the point is divided into "result" and "error". The value of "result" is determined by the number of bits of the error diffusion output. Table 1 shows the relationship between the result and the error when the output is 2 bits.

[0037]

[Table 1]

The result at the point A becomes the error diffusion output data. The remaining error is distributed to the peripheral pixels B, C, D and E and added to the original image data at each point. Based on this means, it is possible to finish the processing for the entire target area by performing the same processing at the time of shifting while shifting the pixel of interest in the main scanning direction and the sub scanning direction. As a result, the image data is compressed from 8 bits to 2 bits, the image density is preserved in the entire area of the target area, and gradation can be expressed in halftone.

[0039]

According to the image processing apparatus of the present invention, images can be stored and reproduced with a smaller memory capacity and a faster processing time.

[Brief description of drawings]

FIG. 1 is a schematic functional configuration block diagram of the present invention.

FIG. 2 is a functional block diagram in which FIG. 1 is subdivided.

FIG. 3 is a side view showing the overall configuration of a digital copying machine that is an embodiment of the present invention.

FIG. 4 is a diagram for explaining an error diffusion method.

FIG. 5 is a diagram showing a circuit configuration of a smoothing filter.

[Explanation of symbols]

 1 Input Correction Time 2, 6 Error Diffusion 3 Image Memory 4, 7 Smoothing Filter 5 Image Processing Section 8 Laser Driving Circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H04N 1/411 9070-5C // G06F 15/68 320 A 9191-5L

Claims (2)

[Claims] 1. A unit for compressing image data, a unit for storing compressed image data, a unit for restoring compressed image data output from the storing unit, and a scaling process for the restored image data. And an image processing apparatus. 2. The image processing apparatus according to claim 1, wherein an error diffusion method is used for the compression means, and a smoothing filter is used for the decompression means.