JPS6259302B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to an exposure apparatus.

Even if a copying machine can successfully adjust the density of originals with standard patterns, it may not be possible to obtain good copies due to differences in the originals. For this reason, the person making the copy manually adjusts the darkness, contrast, etc. of the copy while making the copy, but this often relies on the operator's intuition and increases the probability of failure.

The present invention has been made in view of the above points, and it is an object of the present invention to enable optimal image formation on a document without bothering the operator. That is, the present invention provides means for inputting a command to start a copying operation, a document table 4 on which a document to be exposed is placed, and a standard density member provided outside the document table on the document table.
SP, a light source 5 for exposing the original and the standard density member, light detection means PD1 to PD3, and a first means for generating a second density signal (FIG. 3); and means for generating a second density signal by detecting reflected light from the document image irradiated by the light source with the light detection means (FIG. 3); , a recording member 1 for forming an image of an exposed original document, means 3 and 8 for charging the recording member, and in response to a command from the input means, the standard density member is charged by the light source. irradiate,
A maximum value and a minimum value of first data based on the density signal from the first density signal generating means are stored, and the document is subsequently irradiated with the light source, and the density signal is based on the density signal from the second density signal generating means. Second
A maximum value and a minimum value of the data are stored, and the exposure amount of the light source is controlled based on the minimum value of the first data and the second data, so that the contrast of the copied image of the original image is appropriate. data and second
The present invention provides a copying apparatus having a control means (μ-com) for controlling the charging means based on the maximum value and minimum value of data.

Other objects of the present invention will become clear from the description of the embodiments given below in conjunction with the drawings.

FIG. 1 is a side view of a copying machine to which an exposure apparatus according to the present invention is applied.

In the figure, 1 is a photosensitive drum, and this drum has three layers: an insulating layer on its surface, a photoconductive layer below it, and a base (for example, aluminum) below it. When the photosensitive drum 1 is rotated by means not shown, a cleaner blade 2 removes toner and the like from the surface thereof.

The surface of the cleaned photosensitive drum 1 is uniformly and positively charged by positive corona discharge from the charger 3. Next, as the document placed on the document table 4 (hereinafter referred to as the original) is moved (in the direction of arrow P) by means not shown, the document is exposed to the document at a location illuminated by the document exposure lamp 5. The image is formed on the photosensitive drum 1 via the reflection mirror 6 and the in-mirror lens 7, and at the same time
The AC corona discharge by the AC charger 8 removes the positive charge on the exposed area.

Next, the photosensitive drum 1 is irradiated with light from the entire surface exposure lamp 9 to remove the charge on the base of the photosensitive drum 1.

The electrostatic latent image formed on the photosensitive drum 1 as described above becomes a visible image due to the adhesion of toner in the developer spilled onto the developing plate 10.

The photosensitive drum 1 to which the toner is adhered is mechanically squeezed by an electrode roller 11 to mechanically squeeze the liquid layer on the drum surface, and a bias voltage (+V) is applied to the electrode roller.
As a result, excess toner is absorbed by the electrode roller 11.

The developer toner etc. on the photosensitive drum 1 is charged by a charger 12.
This will be further narrowed down due to the negative corona virus.

Next, a positive corona from the charger 13 is applied from the back side of the copy paper (not shown), and the toner on the photosensitive drum 1 is attracted and transferred to the front side of the copy paper. The toner transferred to the copy paper is fixed on the copy paper by the fixing device 14, and the copy process is completed.

In the above-mentioned copying machine, in order to obtain clear copies, it is necessary to consider the following matters.

That is, the fine pattern of the original is detected by a photodetector so as to be identified, converted into an electrical signal, and the electrical signals corresponding to the brightest and darkest parts of the original are sampled and polled. The lightest part generally corresponds to the original background color, and the darkest part corresponds to the darkest part of the pattern such as text or photographs. Contrast can be obtained as the difference between the brightest and darkest areas. For copying machines to be effective, it is best if the background color of the copy corresponds to the brightest part of the original. To do this, the brightest part of the original is detected during the scanning period for reading the original, and the illumination or aperture is simply set so that the level of the brightest part remains constant just before starting the actual copying cycle. For this purpose, it is necessary to always maintain the illumination and aperture during the original reading period as values for a certain sampling. However, since it may be difficult to keep the measurement system operating during the sampling period under certain constant conditions in this way, it is desirable to take the following method.

That is, by providing a standard pattern and normalizing the information from the original by reading the standard pattern together with the original during the sampling period, it is possible to avoid fluctuations in the measurement system.

As an alternative method for establishing a correspondence between the brightest part of the original and the copied background color, the illumination or aperture may be kept constant and controlled by the developing bias. This method reads the brightest part of the original, predicts the corresponding latent image potential of the copier, and
This is a method in which the developing bias is set in advance to prevent toner from adhering to the latent image.

However, the development bias must be controlled in consideration of the difference between the original content and the character pattern, which is halftone like a photograph.

Original with only regular characters (called a line)
Since there is no need to produce intermediate tones, a deep developing bias can be applied so that the latent image for the brightest area completely corresponds to the background of the copy.

However, in the case of originals with many intermediate tones (called solids) such as photographs, it is necessary to obtain continuous gradation from the brightest part of the original, so the developing bias must be applied shallowly.

Furthermore, when the contrast is weak (S/N is low), the primary charging voltage can be increased to strengthen the contrast. In that case, if the AC charging and simultaneous exposure is kept constant, the potential of the latent image will shift (toward the higher side), so the intensity of AC charging will always be at the same potential at the brightest part depending on the intensity of the primary charging voltage. It is also necessary to control AC charging and simultaneous exposure.
However, in order to increase the contrast, only the primary charging voltage may be increased and the developing bias may be adjusted by the amount of latent image potential shift.

FIG. 2 is a diagram showing the detection area of the standard pattern and the original by the means for detecting the contents of the original. In the figure, PD1, PD2, and PD3 are photodetectors, SP is a standard pattern, and ORG is an original. The standard pattern SP is provided beside the original placing portion of the document table 4 shown in FIG.
This standard pattern is used to normalize the measured values to eliminate fluctuations in the sampling measurement system as described above. The standard pattern SP is placed along the y-axis as shown, and one of the photodetectors e.g.
PD1 may be used for standard pattern detection.

In addition, the standard pattern SP may be installed and detected within the original storage area only during the sampling period to determine the content of the original, but in that case, of course, when regular copy control is entered, the standard pattern SP may be placed outside the copy area. It is necessary to produce a standard pattern.

FIG. 3 is a block diagram of exposure control. In the same figure, PD1, PD2, and PD3 are photodetectors, and the scanning area related to scanning the original is measured using three photodetectors. are arranged so that the range in the X direction can be detected at appropriate intervals. The original is scanned in the y direction by moving the document table 4. In this example, there are three photodetectors, but any number may be used. Note that the photodetectors PD1 to PD3 are optically designed to allow light to enter them finely to the extent that the fine patterns of the original and standard patterns can be identified. For example, when the light-receiving area of a photodetector is large, it is necessary to make the light-receiving area equivalently smaller by enlarging the original image and making it incident thereon, or by masking with a suitable slit or the like. In addition, CCD (charge coupled
In the case of photodetection such as a derice array, a single photodetector is miniaturized, so an optical system is provided that does not magnify but instead directs or conversely reduces the amount of light that it enters. With the photodetectors PD1 to PD3 arranged appropriately in the X direction as in this embodiment, the pattern in the Y direction can be read by moving the document table, but electronic scanning such as a CCD linear sensor is also possible. With this arrangement, mechanical scanning for original identification is no longer necessary, and the pattern of the original can be read just before the copier's copy cycle. Furthermore
In a mechanism such as a CCD area sensor in which photodetectors are arranged in a matrix, almost all areas of the original can be sampled instantly.

The outputs of photodetectors PD1 to PD3 are each powered by an amplifier.
Multiplexer MPX1 via Amp1 to Amp3
Sample and hold SH with the circuits shown in a and b in Figure 4
It has a circuit that applies signals to SH-1 and SH-2 and shifts the level of the detected value by the same amount again.

The outputs of sample and hold SH-1 and SH-2 are applied to multiplexer MPX2. Such a multiplexer can be the same as the multiplexer described above. Furthermore, such a multiplexer
MPX-2 also selects sample hold under control from the microcomputer.

A/D converter COV1 is multiplexer MPX2
The applied value is converted into an 8-bit digital value. Such a multiplexer MPX1 is for example
IH5060 (manufactured by Intasil) can be used. The output of multiplexer MPX1 is applied to sample holds SH-1 and SH-2, and is controlled by the microcomputer described later to PD-1 and PD.
-2 and PD-3 are selected one after another. Sample and hold SH-1 samples the maximum value, and sample and hold SH-2 samples the minimum value. A in FIG. 4 is a maximum value detecting section in sample hold SH-1, and b in FIG. 4 is a minimum value detecting section in sample hold SH-2. Note that when detecting the minimum value, the output of the multiplexer MPX-1 is subjected to level shift conversion in the negative direction. For example, AD7570 (manufactured by Analog Devices) can be used as such an A/D converter. Note that this output
8 bits out of 10 bits are used.

The output of the A/D converter CONV-1 is input to the microcomputer μ-com. μ-com includes an input/output circuit I/O, a processing circuit CPU, a memory ROM in which control procedures, etc. are stored, and storage units WR1 and WR2 in which processed data, etc. are temporarily stored for calculation.
Consists of memory RAM with etc.

The processing circuit CPU is μPD8080A (manufactured by Nichiden)
A μPD8255 (manufactured by Nichiden) is used as the input/output circuit, and is connected to peripheral circuits as shown in FIG.

The data processed by the processing circuit CPU is converted into an analog value by the D/A converter CONV-2. For example, AD7530 (manufactured by Analog Devices) can be used as such a D/A converter. Note that the output
8 bits out of 10 bits are used. This output is sent as a control signal to the original exposure lamp control circuit LC, the developing tray 10 bias control circuit BC, the charger 3 control circuit CC-1, and the AC charger control circuit CC-2 via the multiplexer MPX-3. send.

Note that the control circuit uses a storage element EUW-A1C (manufactured by Matsushita) as an analog memory.

TG is a timing generator that generates a signal in response to the rotation of the photosensitive drum 1 of the copying machine.

The microcomputer μ-com performs various controls and processes based on the signals from the timing generator TG.

The operation of the embodiment having the above configuration will be explained with reference to FIGS. 6 and 7.

When a copy button (not shown) of the copying machine is operated, the timing generator TG of the copying machine sends a clock signal to the input/output circuit I/O of the μ-com.
The microcomputer μ-com was initially developed using memory.
The signal from the timing generator TG starts counting according to the control procedure stored in the ROM. The value of this count is stored in the count storage section CNT of the memory RAM, and each time a new signal arrives at the input/output circuit I/O, the contents of the memory RAM are read into the CPU.
It is added up and stored again in the count storage unit CNT in the RAM. When the count reaches a predetermined value, the content detected by the document table 4 or the standard pattern section by the photodetectors PD1 to PD3 is sent to the sample hold circuits SH-1 and SH by the multiplexer MPX-1. -2 begins to be applied. The multiplexer MPX-1 sequentially samples and holds the detection contents such as photodetector PD1, photodetector PD2, etc. according to the procedure stored in the memory ROM.
Send to 2. Sample hold SH-1 samples the maximum value (the darkest part SPMAX of the standard pattern), and sample hold SH-2 holds the minimum value (the brightest part SPMin of the standard pattern). Since the timing generator TG generates a clock in synchronization with the movement of the copying machine, by counting the clocks, it is determined, for example, to what position the document table 4 has moved. Therefore, it is possible to know whether the standard pattern has been read by the photodetectors PD1 to PD3.

When CNT in the memory RAM reaches a predetermined value, the multiplexer MPX-2 is controlled via the input/output circuit I/O according to the control procedure stored in the memory ROM. The data is input to the D converter COV1, converted into 8-bit digital data, and stored in the data storage section SPMAX of the memory RAM. Subsequently,
The contents of the sample hold SH-2 are applied to the A/D converter COV-1 by the multiplexer MPX-2, converted into 8-bit digital data in the same manner as described above, and stored in the storage section SPMin of the memory RAM.

After the above control is performed, sample holds SH-1 and SH-2 are reset and original pattern detection control begins. Similar to the standard pattern SP described above, the procedure stored in the memory ROM is decoded by the processing circuit CPU, and the result of such decoding is set in the input/output circuit I/O, operates the multiplexer MPX-1, and outputs the photodetector. PD1～PD
3 detection output is sequential sample hold SH-1,
The maximum value (the original darkest part ORGMax) is applied to the sample hold SH-2, and the minimum value (the original brightest part ORGMin) is stored in the sample hold SH-2.

When the contents of the counter CNT in the memory RAM reach a predetermined value, it is determined that the detection of the original ORG has ended, and the contents of the sample hold SH-1 are first processed by the multiplexer MPX-2 according to the control procedure stored in the memory ROM. A/D converter
It is converted into 8-bit digital data by COV-1 and stored in the storage section ORGMax of the memory RAM, and then the contents of sample hold SH-2 are sent to the A/D converter via multiplexer MPX-2.
The signal is applied to COV-1, converted in the same manner as described above, and stored in the storage section ORGMin of the memory RAM.

When the above operations are completed, the data stored in the memory RAM is processed under the control of the memory ROM.

First, data in the storage area ORGMin and storage area SPMin
The processing circuit CPU performs subtraction with the data of
This result is calculated by the processing circuit CPU so that the contents of ORGMin match SPMin according to the calibration curve of illuminance (or aperture) and (ORGMin - SPMin) stored in the memory ROM, and the result is input/output. D/A converter COV- via circuit I/O
2, and the analog converted value is sent to the memory ROM.
The above value is sent to the control circuit LC that performs original illumination or the control circuit IC that performs aperture control in response to a channel designation signal from. The above-mentioned value is stored in the analog memory element EUW-A1C in the control circuit, and a drive signal responsive to this value is output to the controlled object.

Instead of the above control, the developing bias (ORGMin
The output may be sent to a control circuit BC that controls the developing bias based on a calibration curve with -SPMin) so that the original background color does not appear.

Next, (SPMax−SPMin) = SPsub and (ORGMax
−ORGMin)=ORGsub is calculated, the result is stored in the storage parts SPsub and ORGsub of the memory RAM, and further division of ORGsub/SPsub is performed in the processing circuit CPU, and the calibration between ORGsub/SPsub and the primary charging voltage is performed. Due to the curve, ORGsub/SPsub=1
The processing circuit CPU processes the image so that the contrast is the same as that obtained in the above conditions. This value is sent by the memory ROM via the input/output circuit I/O and the multiplexer MPX-3 to the control circuit CC-1 which controls the primary charge voltage. Next, AC charging is corrected almost proportionally according to the amount of correction of the primary charging voltage according to the procedure of the memory ROM. This correction voltage is also calculated from the calibration curve of AC static elimination with respect to the primary charging voltage, and a signal is sent to the control circuit CC-2 of the AC charger.

Controlled as described above, a copy operation is performed on the original during double action.

Although the above example deals with the movement of the document table, exposure can be similarly controlled by movement of the optical system.

As explained above, according to the present invention, the standard density member and the original are exposed with the same light source in response to a copy start command, and the exposure amount for copying is set to the minimum value of the density signal based on the standard density member and the original. Since the charging means is controlled by the maximum and minimum values of the density signals based on the standard density member and the original in order to make the contrast of the copied image appropriate, it is possible to always copy the original with good image quality.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view of a copying machine for explaining an embodiment of the present invention, FIG. 2 is an explanatory diagram for explaining document scanning for explaining an embodiment of the present invention, and FIG. 3 is a side sectional view of a copying machine for explaining an embodiment of the present invention. A block diagram showing an embodiment according to the invention,
4 is a partial detailed diagram of the sample hold shown in FIG. 3, FIG. 5 is a block diagram of the input/output circuit I/O shown in FIG. 3, and FIG. 6 is an explanatory diagram of the operation of an embodiment according to the present invention. , FIG. 7 is an explanatory diagram showing a control procedure of an embodiment according to the present invention. RAM...memory, ROM...memory.

Claims (1)

[Scope of Claims] 1. A means for inputting a command to start a copying operation; a document table on which a document to be exposed is placed; a standard density member provided outside the document table on the document table; and a light source for exposing the standard density member; a light detection means; and means for detecting reflected light of the standard density member irradiated by the light source with the light detection means to generate a first density signal; means for generating a second density signal by detecting reflected light of the document image irradiated by the light source with the light detection means; a recording member for forming an image of the exposed document; and a recording member for forming an image of the exposed document. and means for irradiating the standard density member with the light source in response to a command from the input means to charge the maximum value of the first data based on the density signal from the first density signal generating means, and Memorize the minimum value and continue to illuminate the above document with the above light source.
storing a maximum value and a minimum value of second data based on the density signal from the second density signal generating means; controlling the exposure amount of the light source based on the minimum value of the first data and the second data; A copying apparatus comprising: a control means for controlling the charging means based on the maximum value and minimum value of the first data and the second data in order to make the contrast of the copied image of the original image appropriate.