JPS62100747A - Copying device - Google Patents

Abstract

PURPOSE:To prevent a copying device from miscopying by providing the device with an exposing means, a photoelectric conversion element, a sampling means, a ground density discriminating means, and an automatic exposure control means. CONSTITUTION:Prior to original scanning for exposing an image to the surface of a photosensitive body, an original is scanned and exposed at the fixed quantity of light and the obtained original image is measured by the photoelectric conversion element 12 and sampled every fixed period to obtain output data. The output data are made to correspond to divided blocks for density levels and the density level corresponding to the block including the most data out of the plural blocks is referred as the original ground density to control exposure on the basis of the original ground density. Even if a flaw or dirt exists on the original, the contents of the block corresponding to the flaw or dirt are little, so that miscopying can be suppressed without influence due to the flaw or dirt.

Description

DETAILED DESCRIPTION OF THE INVENTION A field of industrial application relates to copying machines with automatic exposure control.

Conventional technology In automatic exposure control of copying machines, multiple sensors are used to detect the original density, and the lamp voltage during printing is controlled based on the maximum value, minimum value, or average value of these detected data. is disclosed in Japanese Patent Application Laid-Open No. 57-20170.

Problems to be Solved by the Invention However, in the automatic exposure control described above, when the maximum value or minimum value of the density data is used as the background density of the original, if there are scratches or dirt on the original or the optical system, the sensor may may be loaded. Particularly in the case of league printers, dirt on the film or carrier is magnified through the projection lens, so the probability of detecting the dirt is high (it is thought that the data on scratches and dirt will be the maximum or minimum value). This is easy to do, and if it is directly reflected in automatic exposure control, it will cause a copy error.
When the average value of the density data is used, since it is the average value of the background part and image part of the document, it is inconvenient to detect the background density, and it is difficult to perform appropriate exposure control.

An object of the present invention is to perform appropriate exposure control and prevent copy errors by detecting the density that occupies the widest area in a document and using this density as the background density.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides an illumination means for illuminating the document, and an exposure means for scanning and exposing the document image obtained by the illumination means onto a photoreceptor. , a photoelectric conversion element disposed at a position to receive light from the exposure means and photometering the original image; and a photoelectric conversion element that samples the output of the photoelectric conversion element at regular time intervals during scanning of the original prior to image exposure to the photoreceptor. a sampling means, and the output sampled by the sampling means is made to correspond to blocks of concentration levels divided into a plurality of blocks according to the levels;
A background density determination means that determines the density level corresponding to the block with the largest number of data among the blocks as the original background density; and automatic exposure control that controls the illumination means in accordance with the original background density obtained by the background density determination means. It is characterized by having the means.

Operation In automatic exposure control, the original is scanned and exposed with a constant light amount prior to scanning the original to expose an image onto the photoreceptor. The original image thus obtained is photometered by a photoelectric conversion element and sampled at regular intervals to obtain output data. This output data is divided into multiple density level blocks,
The density level corresponding to the block with the largest number of data among the blocks is set as the original background density, and exposure control is performed based on this density level.

Example Embodiments of the present invention will be described below with reference to the accompanying drawings.

Figure 1 shows a reader printer to which the present invention is applied, and this reader printer obtains positive prints from negative or positive microfilm.◇The light from the exposure lamp (2) installed at the bottom of the device is , condenser lens (
3), the film held by the carrier glass (1) is irradiated from below, and the image is transmitted to the projection lens (
4) will be enlarged. The image magnified by the projection lens (4) is projected onto the screen (
The force is transmitted to the photosensitive drum (10) by the scanning first and second mirrors (8) (91).

The first reader mirror (5) is placed directly above the projection lens (4) and reflects light to the second reader mirror (6).

This reader second mirror (6) is rotatably held in the main body, and can be moved by means not shown to a position 6a where the image is projected onto the screen (forced) on the front of the device and a position 6b where it is retracted during printing. be.

Scan first mirror (8) and scan second mirror (9)
is held in one piece, and the retracted position Ba at the time of leader
, ga, exposure start position Bb during printing, 9b
, and exposure start positions BC and gc in the direction of the arrow in the figure.

These mirrors +5+, +61, (81, (9+
To explain the operation, during league, the first leader
Mirror (5) and leader second mirror (6) in position 6a
The light is bent to form a reader optical path (dotted chain line in the figure), and an enlarged image is projected onto the screen (7) on the front of the main body.

On the other hand, when printing, the settings can be switched as follows.

First, the leader second mirror (6) rotates and retreats to position 6b, that is, a substantially horizontal state. Next, the first scan mirror (8) and the second scan mirror (9) move from positions 8a and 9a to positions Bb and gb, respectively, to position 8. c l
9 Move to the left in the figure to c. Then the mirror (8
1 and +91 move to the right in the opposite path and expose the image through the slit (11) on the photosensitive drum (10) rotating in the direction of the arrow by the optical path indicated by the two-dot chain line in the figure to form an electrostatic latent image. do. This electrostatic latent image is developed by a developing device (13), and the toner image thus formed on the photosensitive drum (10) is transferred onto a sheet fed from a paper feed section (14) and then transferred by a fixing device (15). It will be established. The sheet after fixing is then discharged from the paper discharge port (16) at the lower front of the apparatus.

In a league printer having such a configuration, a photoelectric conversion element (12) is provided on the slotted throat (11) in order to perform full automatic exposure control during printing. A plurality of photoelectric conversion elements (12) or only one photoelectric conversion element (12) are provided in a direction orthogonal to the scanning direction.

In addition, a mirror position detection switch (not shown) is arranged in order to detect the positions of the first and second scan mirrors (8) and (91).
9) is in the ON state while moving between positions Bb, gb and positions BC, 9C. As will be described later, photometry starts when the switch state changes from OFF to ON (at the rising edge), and ends when the switch state changes from ON to OFF (at the falling edge).

When the print switch is pressed, the scan 1st and 2nd mirrors +81 and (91) are moved to the retracted position B.
a.

The mirror position detection switch is ON while starting the movement from 9a and moving from position 8b and 9b to position 80°9C.
While in this state, the exposure lamp (2) is turned on at a certain level. During this time, the film image is transferred to the photoelectric conversion element (1
2) is projected and shadowed and photometered.

FIG. 2 is a diagram showing a configuration for automatic exposure control, including a photoelectric conversion element (12) and an A/D converter (17).

Microcomputer CPU (18), ROM (
21).

The exposure lamp (2) is controlled by a RAM (22), a D/A converter (19), and a phase angle control circuit (20). The image density is obtained as the output voltage of the photoelectric conversion element (step 2), and is digitized by the A/D converter (17). This data is sent to CPU (18) when it detects the rising edge of the mirror position detection switch output.
8) is sampled and input at intervals of several m5eC. The CPtJ (18) processes the sampled data and stores it in the RAM (22).

Thereafter, at the fall of the switch output, the CPU (18) calculates a digital signal to provide optimal image exposure according to the content of the data, and outputs it to the D/A converter (19). This signal operates the phase angle control circuit (20) to control the exposure lamp (2) to an optimum level during image exposure to the photosensitive drum (10).

FIG. 3 shows a flowchart for performing arithmetic processing for automatic exposure control within the CPU (18), and routines (al to (d) indicate the state of automatic exposure control, respectively.゛0'' to ``3°'
Indicates the case where This flowchart is a part of the main routine that controls the overall control or the scanning optical system in the league printer of this embodiment, and ='5TA
TE" is determined in this main routine, and each "TE"
5TATE" is selected.

When printing, "5TATE" and the first scan
・The relationship with the position of the second mirror (8), +9) is '5TATE=Q' at mirror positions Ba and ga, and when the mirror (8), +9) moves to position Bb and gb, the mirror position is detected. The switch is turned on.The rising edge of this switch output is detected and the process shown in the routine (al) is performed and '5TATE' is set to "1".The mirror (8) is moved from the mirror position Bb, gb to the position Bc, gc. While [9) is moving, "5"
When TATE=f', sample link photometry shown in routine fbl is performed. Mirror [8), (9] or position 8a
.

The switch turns OFF, detects the fall of the switch output, and sets "5TATE" to "2". ”5TATE=2
'', the process shown in routine (C) is performed, and after determining the optimum lamp voltage, ``5TATE'' is set to ``3''.

Mirrors +8+ and +9+ are from position Bc, gc to position B
While moving to b, 9b, “5TATE=3”
and transmits an image onto the photosensitive drum (10).

Place i8b.

When the mirror (8i, +9) reaches 9b, the end of printing is detected and "5TATE" is set to '0' again.

Lucia (al is "5TATE=0" (7) Indicates the case. When the rise of the mirror position detection switch is determined (step 2), a sampling timer for determining the sampling time is set (step 2).

Then, clear the contents of the RAM (22) for storing the concentration data (Step ■), "S T A T E
Set "to '1" and return.

RAM (22) that stores this density data is divided into a plurality of blocks at equal intervals depending on the density level.
A plurality of output data of the photoelectric conversion element (12) obtained by matching RAM addresses one-to-one for each block are processed by determining the correspondence with the blocks of the above-mentioned density according to each level. Then, as will be described later, the density corresponding to the block with the largest number of data is detected as the background density, and optimal exposure is performed.

Next, when it is determined that "5TATE=l" in the main routine, the routine (bl) is entered. When the fall of the mirror position detection switch is detected in the routine (bl) (step ■), photometry is ended and "5TATE=2" However, until the falling edge of the switch is detected, photometry is performed as shown in the figure.In this photometry, when the end of the sampling timer is detected (step ■), the timer is set again (step 0), and the photoelectric conversion element ( The image density data output from step 12) is read (step 0), and the content of the kAM address corresponding to this density data is incremented multiple times (step 2).

= STATE = 2'', the optimum lamp voltage is determined according to the contents of the density data as shown in the routine fcl. First, the contents of each RAM address are compared and step
), select the RAM address with the largest number of data (step @), set the density corresponding to this selected RAM address as the background density (step ■), and determine the optimal lamp voltage (step O). After that, "5TATE= Returns as 3”.

"5TATE=3" is a process during image exposure, and as shown in routine fdl, the end of printing is determined (step O) and "5TATE=0" is set. (Step ■).

In this way, the density corresponding to the block with the largest number of data is determined as the background density and exposure control is performed.

Effects of the Invention As explained above, the present invention includes an illumination means for illuminating a document, an exposure means for scanning and exposing an image of the document obtained by the illumination means onto a photoreceptor, and light from the exposure means. a photoelectric conversion element disposed at a light receiving position to photometer the original image; a sampling means for sampling the output of the photoelectric conversion element at regular time intervals during scanning of the original prior to image exposure to a photoreceptor; A background density determining means that associates the sampled output with blocks of density levels divided into a plurality of blocks according to the levels, and sets the density level corresponding to the block having the largest number of data among the blocks as the original background density. , automatic exposure control means for controlling the illumination means according to the background density of the original obtained by the background density determination means, so that even if there is a scratch or dirt on the original, the corresponding block can be removed. Since the content is small, it is not affected by these and copy mistakes can be prevented. Also,
When the present invention is applied to a league printer, automatic exposure can be performed under the same control regardless of the negative or positive polarity of the film.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a reader printer according to an embodiment of the present invention, and FIG.
This figure is a diagram showing automatic exposure control by a microcomputer, and FIG. 3 is a flowchart showing arithmetic processing within the CPU. (1)...Carrier glass (2)...Exposure lamp f31...Condenser lens +41...Projection lens (5)...League 1st mirror (6)...Leader 2nd mirror (7 )...Screen (8)・
... Scan first mirror (9) ... Scan second mirror (10) ... Photosensitive drum - (11) ... Slit 02) ... Photoelectric conversion element applicant Minolta Camera Co., Ltd. / Figure ( l no carrier or las (q) λ+?shi negative drunkenness 2 mirror 0 () pickpocket (12) t'l support 1 move. Figure Z (α) (b)

Claims (1)

[Claims] 1. An illumination means for illuminating the original; an exposure means for scanning and exposing the original image obtained by the illumination means onto a photoreceptor; and an exposure means disposed at a position to receive light from the exposure means and photometering the original image. a photoelectric conversion element; a sampling means for sampling the output of the photoelectric conversion element at regular time intervals during document scanning prior to image exposure on the photoreceptor; and dividing the output sampled by the sampling means into a plurality of parts according to the level thereof. A background density determining means that sets the density level corresponding to the block with the largest number of data among the blocks as the original background density, and a document background density obtained by this background density determining means. automatic exposure control means for controlling the illumination means according to the invention.