JPS6295554A - Image forming device - Google Patents

Abstract

PURPOSE:To obtain a proper image even with variable power by providing a setting means which sets the density of a formed image during image formation on the basis of data on the density and magnification of an original in a specified area. CONSTITUTION:Coordinate data and variable power data are inputted and a prescan for AE value setting is made; and original density is read by a CCD line sensor 2 and an analog signal is converted by a A/D converting circuit 3 into a digital signal with a level corresponding to the density. Then, histograms are formed on the basis of the brightest value and darkest value among digital data on original density of respective lines of an input specified area and an exposure voltage is determined with a coefficient value based upon the maximum value of the histogram of the brightest value and the variable magnification data. Then, counter values for determining on-off states of blank counters n1-n3 and blank lamps L0-Ln are set according to the specified area and a counter value is determined on the basis of the specified area data and variable power data. Thus, an invariably proper image is obtained even with the power variation of the specified area.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an image forming apparatus having an area specifying function.

[Prior art]

Conventionally, in this type of device, for example, a copying machine, prior to scanning a document for copying, A is used for an automatic density adjustment (hereinafter referred to as AE) operation that automatically optimizes the copy density.
The general method used was to perform E-scan once to detect the image density of the document, but
Since E is applied, if you specify an area, AE
There was a problem that made it inappropriate. In particular, this tendency is large when the area specified for the original has a different image ratio (black area per unit area) than the area outside the specified area, and may even result in miscopying.For example, in a text document For example, when specifying an area as a photograph part. At this time, AE is performed in a direction that makes the text portion, which occupies most of the document, appropriate, so the photographic portion for which the area has been designated becomes too dark, resulting in a blurred image.

AE methods include those that detect light reflected from the document by placing a photosensor in the optical system for image exposure or in an optical system separate from the image exposure optical system, and those that detect the reflected light from the original, and those that detect the reflected light from the original. There are some configurations that detect the latent image potential, and a common method is to change the input voltage to the document illumination lamp or the developing bias voltage depending on the detected amount.

Furthermore, there is a drawback that an appropriate copy cannot be obtained especially when changing the size of a designated area.

〔the purpose〕

The purpose of the present invention is to eliminate the drawbacks of the above-mentioned conventional examples, and
An object of the present invention is to provide an image forming apparatus that can obtain an appropriate image even when changing the magnification of a specified area.

〔Example〕

An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a copying machine according to this embodiment.

In FIG. 1, reference numeral 1 denotes a control section that controls the entire copying machine, and controls the copying sequence, exposure lamp, blank lamp, motor, etc.

The control unit 1 is a microcomputer and ROM.

It is composed of microcomputer peripherals such as RAM, and controls the entire copying machine based on programs stored in ROM.

2 is a CCD line sensor, and 3 is an A/D conversion circuit that converts analog signals sequentially sent from the CCD line sensor 2 into digital signals.

4 is a shading correction circuit, and A/D conversion circuit 3
The level of the digital signal from the exposure balance 6 is corrected according to variations in the light amount distribution of the exposure balance 6, variations in the sensitivity of the light receiving section of the CCD line sensor 2, and the like.

A line memory 5 temporarily stores the digital signal from the shading correction circuit and outputs the digital signal to the control section 1 based on the read clock from the control circuit 1.

6 is an exposure lamp that exposes the original, 7 is a blank lamp,
8 is a motor.

Reference numeral 9 denotes an operation section for operating the copying machine, which is composed of a key manual switch.

FIG. 2 is a schematic diagram of the document exposure optical system of the copying machine of this embodiment.

In FIG. 2, 10 is a document, 11 is a photosensitive drum, and 12 is a projection lens for projecting an image of the document 10 onto the photosensitive drum 11.

Reference numeral 3 is a projection lens for projecting an original image onto the CCD line sensor 2. The copying machine of this embodiment uses a slit scanning type optical system. Here, the lens 12 plays the same role as a projection lens used in a normal copying machine, and although Fig. 2 shows the image at the same magnification, the lens 12 is moved as appropriate when reducing or enlarging the image. , lens 13
is for projecting a slit image of the document 1 onto the CCD 2, and its position is fixed.

FIG. 3 is a diagram showing the blank lamp 7 and the photosensitive drum 11, where the blank lamp 7 is the lamp L.

~Ln.

FIG. 4(a) is a diagram showing an example of area specification. 10
is the original, and the shaded area of lO' indicates the area to be specified.When specifying the shaded area 10',

Enter the optical scanning direction and the coordinates perpendicular to it. In the case of FIG. 4(a), x,,x2,y,.

Although the coordinates of Y2 are entered using a dedicated key manual switch for specifying an area provided on the operation unit 9 in FIG. 1, the coordinates may be entered using a numeric keypad for setting the number of sheets. Moreover, in FIG. 4, it is of course possible to set the area 10' to be blank and copy the portion other than the area 10' instead of copying the area 10'.

FIG. 4(b) is an example in which the specified area is actually scaled and outputted, and Y, ~Y2, and X in FIG. 4(a).

``'X2(7) designated area is Figure 4(b)(7)Y',
~Y'2.

It is scaled to K1-X2 and output.

FIGS. 5(a) and 5(b) are flowcharts showing the operation of the control section 1 in the case of area-specified variable-reduction copying in this embodiment.

This embodiment will be described in detail below based on FIGS. 5(a) and 5(b).

In step SL, 32, the coordinate data and scaling data of the specified area are input from the operation unit 9, and in step S3, when it is confirmed that the copy start key of the operation unit 9 is turned on,
Proceeding to step S4, a prescan for setting the AE value is performed. Through this pre-scanning, the original density is read by the CCD line sensor 2, and an analog signal corresponding to the original density is converted into a digital signal at a level corresponding to the density by the A/D conversion circuit 3. The digital signal from the A/D conversion circuit 3 is corrected by the shading correction circuit 4,
It is temporarily stocked in the line memory 5.

In step S5, to line memory 5! The output clock is output and the digital data of the document density stored in the line memory 5 is input, but in this case only the digital signal of the designated area is input.

When the end of the prescan is confirmed in step S6, the process advances to step S7.

In step S7, the AE value is determined and the exposure amount is set (or the developing bias is set).

Here, a method for determining the AE value will be explained. The brightest value of the digital data of the document density in each line of the specified area input in step S5.

Each histogram is created based on the dark value, and when the histogram for the specified area is created by the end of prescanning, the exposure voltage (or development bias) is determined based on the maximum value of the histogram of the brightest value and a coefficient value based on the variable magnification data.
Determine.

In step S8, counter values for determining lighting of the blank counter n1+n2+n3 and the blank lamps L0 to Ln are set according to the designated area. When setting the counter value, the counter value is determined based on the designated area data and the scaling data so that a scaled copy of the designated area is obtained.

Step S9. A copy operation is performed in S10.

FIG. 5(b) is a flowchart showing blank lamp control by the control unit 1 during copy scanning.

First, when a copy scan is started, the lamps L0 to Ln are turned on in step N1, and it is checked in step N2 whether the blank counter nl has counted up. The blank counter nl is o- according to FIG. 4(b).
This is a counter that counts .

When the blank counter n1 counts up in step N2, the process proceeds to step N3, where the lamps Ln1 to Ln
Turn off 2. The lamps Lnl to Ln2 are the lamps Y' to Y2 in FIG. 4(b).

When the blank counter n2 counts up in step N4, the lamp Lnl=Ln2, which was turned off, is turned on again in step N5. The blank counter n2 is a counter that counts 2 from 0 to 2 in FIG. 4(b).

When the blank counter n3 counts up in step N6, the lamps L0 to Ln are turned off in step N7. Here, the count value of the blank counter n3 is determined by the recording paper size.

By the above operations, a resized copy of the specified area can be obtained.

In this embodiment, since the AE value is determined based on the document density data of the specified area and the variable magnification data, an appropriate copy can always be obtained even when variable magnification copying is performed with a specified area.

Further, in this example, the AE value is determined using a histogram, but the method is not limited to this, and can be applied to all commonly known methods, such as a method using integration of concentration data. Of course.

〔effect〕

As explained above, according to the present invention, an appropriate image can always be obtained even when changing the magnification of a specified area.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of this embodiment. FIG. 2 is a schematic diagram of the optical system. FIG. 3 is a diagram showing the blank lamp 7 and the photosensitive drum 11. FIG. 4(a) is a diagram showing a designated area of a document. FIG. 4(b) is a diagram showing a variable size copy of the specified area. FIGS. 5(a) and 5(b) are flowcharts showing the operation of the control section 1 of this embodiment. 1 is a control unit, 2 is a CCD, 3 is an A/D conversion circuit, 4 is a shading correction circuit, 5 is a line memo, 6 is an exposure lamp, 7 is a blank lamp, 8 is a motor, and 9 is an operation unit. . Figure 1

Claims (1)

[Scope of Claims] Area specifying means for specifying an area of a document; scaling specifying means for specifying a scaling ratio of an image; scaling means for scaling an image; the above area specifying means and the above scaling specifying means An image forming apparatus comprising: an image forming means for forming an image based on the above; and a setting means for setting a formed image density at the time of image formation based on the document density data in the specified area and the above magnification ratio.