JPH0291634A - Exposure controller for copying machine - Google Patents

Abstract

PURPOSE:To extremely easily control exposure with high accuracy by changing the duty cycle of pulses impressed on an electronic shutter so that exposure may be adjusted. CONSTITUTION:At the time of exposing a photosensitive material 11 through a slit, a PLZT 17 is arranged as the electronic shutter at the position of a pupil and light transmitting state and a light shielding state are repeated in the specified duty cycle, so that the reflected light from a reflecting original 1 is converted into light by pulse. The light by pulse which passes through the PLZT 17 is made incident on the photosensitive material 11 which moves along the image-formation surface of a lens, so that the image recorded on the reflecting original 1 is recorded on the photosensitive material 11. Since the duty cycle of intermittent exposure is adjusted at the time of copying thus, the change of gradation based on the intermittent exposure is not caused and the exposure of the photosensitive material 11 is adjusted according to the recording density of the reflecting original 1.

Description

[Detailed description of the invention] [Industrial application field] It is something that

[Prior Art] In a silver halide photocopying machine, it is necessary to adjust the amount of exposure of a photosensitive material depending on the density of the original and the copying magnification. As a conventional exposure amount control device, for example, the Japanese Patent Publication No. 44-254
As described in Publication No. 2, a variable diaphragm consisting of two diaphragm plates that move in opposite directions is placed between the front group lens and the rear group lens, and the exposure amount is controlled by this variable diaphragm. Devices for controlling are known. In addition, devices that control the amount of exposure by adjusting the moving speed of the lamp and photosensitive material,
The amount of exposure is adjusted by changing the aperture width of a slit mask placed in front of the photosensitive material, the amount of exposure is adjusted by the amount of light from a lamp illuminating the original, and the amount of exposure is adjusted by appropriately inserting an ND filter into the printing optical path. There are also known devices that adjust the.

[Problem to be solved by the invention]

However, these exposure control devices have various problems. For example, devices that vary the feeding speed of lamps and photosensitive materials require motor speed control, which complicates the transmission system, and devices that adjust the slit width have complicated mechanisms and lack reliability. There was a drawback. Furthermore, devices that adjust a variable aperture or adjust the amount of light from a lamp have the disadvantage that the depth of focus and color balance change. Furthermore, in a device that inserts an ND filter, it is difficult to finely adjust the amount of insertion of the ND filter, and the device becomes large.

Therefore, in both the method of adjusting the exposure time and the method of adjusting the amount of light, in order to accurately control the amount of exposure, the mechanism of the apparatus and its control must become quite complex.

The present invention has been made to solve these problems, and an object of the present invention is to provide an exposure amount control device that can perform highly accurate exposure control.

[Means to solve the problem]

In order to achieve the above object, the present invention disposes an electronic shutter whose light transmittance changes in response to voltage application at approximately the pupil position of the copying optical system, and adjusts the duty cycle of the pulse applied to the electronic shutter. By changing the exposure amount of the photosensitive material, the amount of exposure of the photosensitive material can be controlled.

PLZT can be used as the electronic shutter.

[Effect]

The electronic shutter repeats a light transmitting state and a light blocking state in response to pulses, and intermittently exposes the image of the document onto the photosensitive material. In this intermittent exposure, the amount of exposure of the photosensitive material is adjusted by changing the duty cycle of the pulse applied to the electronic shutter.

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

〔Example〕

In FIG. 1 schematically showing a silver halide photocopying machine, a reflective original 1 is set on a transparent stage 10 during copying, and is illuminated with slit light from a lamp unit 2. The lamp unit 2 is composed of a lamp 3, a reflector 4, and a mirror 5, and moves at a constant speed in the arrow direction from the position shown in FIG. 1 when copying the reflective original 1.

The image of the reflective original 1 reflected by the mirror 5 is reflected by the mirrors 8 and 9 of the mirror unit 7. The mirror unit 7 moves at half the speed of the lamp unit 2 in synchronization with the lamp unit 2 to keep the object distance of the lens unit 14 constant.

As shown in detail in FIGS. 2 and 3, a lens unit 14 is disposed between the mirror 9 and the photosensitive material 11, and forms an image of the reflective original 1 on the photosensitive material 11.

This lens unit 14 includes a front group lens 15 and a rear group lens 16, and has a PL as an electronic shutter at the pupil position.
ZT17 is placed. This PLZT 17 includes a PLZT element 17a made of a lanthanum-doped lead zirconium titanate ceramic material, and polarizers 18a and 18b arranged on both sides of the PLZT element 17a so that their alignment axes are perpendicular to each other.
It is composed of. This PLZT element 17a has transparent electrodes 17b formed on both sides thereof, and when an electric field is applied to these, the deflection direction of the incident light is rotated, so the transmittance of the incident light is changed by the deflection action with the polarizers 18a and 18b. is adjusted. Note that if the deflection axes of the deflectors 18a and 18b are made to coincide with each other, a normally open type is obtained. Also, PLZT
17 and the rear group lens 16, a dimming filter divided into three circular or rectangular sections including a yellow filter, a magenta filter, and a cyan filter may be provided to control exposure for each color. In this case, since the light control filter is placed close to the pupil position of the lens, the slit light will not be partially colored.

Behind the lens unit 14 is a mirror shutter 2.
2 is provided, and is set at the position shown by the solid line during photometry, and reflects the reflected light from the reflective original 1 toward the measuring section 24 via the mirror 23, and when copying, from the optical path 12 as shown by the dotted line. evacuate.

At the exposure position, a pressure plate 26 for holding the photosensitive material 11 flat and a slit mask 27 are arranged, and two sets of exposure conveyance rollers 28 and 29 are arranged on both sides of these. A photosensitive material 11 in the form of a roll is stored in the magazine 30, pulled out to a certain length by a pull-out roller 31, and then cut by a cutter 32. After the leading edge of the cut photosensitive material 11 is detected by the sensor 33, it is conveyed a certain distance and is temporarily stopped at a position where the leading edge is nipped by the exposure conveying roller 28.

When scanning of the original 1 is started in response to an exposure start signal, the exposure transport rollers 28 and 29 rotate in synchronization with this to transport the photosensitive material 11. This photosensitive material 11 is subjected to slit exposure during transportation, and then sent to a photographic development processing section 34, where it is developed and then discharged onto a tray 35.

The measurement unit 24 measures reflected light during pre-scanning of the reflective original 1. This photometric signal is amplified by an amplifier 36 and then converted into a digital signal by an A/D converter 37. This digital signal is logarithmically converted using a logarithm converter, and then sent to the controller 39 and written into the first memory 40 .

The controller 39 reads the first memory 40 after the pre-scan.
The photometric data is read from , and the exposure amount for intermittent exposure is calculated. The second memory 41 stores data indicating the relationship between the exposure amount and the duty cycle (ratio of pulse period to pulse width) as shown in FIG. controller 39
refers to the second memory 41, reads out the duty cycle value corresponding to the calculated exposure amount, sends it to the duty cycle adjustment circuit 42, and outputs it to the pulse oscillation circuit 43.
Adjust the duty cycle of the pulses output from.

This duty cycle adjustment circuit 42 is composed of, for example, a one-shot multivibrator with a variable pulse width, or a delay circuit with a variable delay time, and an AND circuit that calculates the logical product of this output and a pulse that is not delayed. ing. Note that the reference numeral 44 is a keyboard.

The driver 46 is supplied with power from a constant voltage power supply 47,
After power amplifying the pulse signal of the duty cycle adjustment circuit 42 to a predetermined level, an electric field is intermittently applied to the transparent electrode 17b of the PLZT element 17a.

Next, the intermittent exposure effect will be explained. When intermittent exposure is performed using the same light (same wavelength, same intensity) as continuous exposure, even if the exposure time is kept at the same value, the sensitization effect may be smaller or larger than that of continuous exposure. Such a phenomenon is called an intermittent exposure effect.

Figure 5 shows the relationship between reciprocity law failure and the intermittent exposure effect, and the relationship between the frequency f of intermittent exposure and the exposure effect is shown as the relationship between the exposure amount and frequency to obtain a constant image density. be.

If the intensity of light in intermittent exposure is E, the total time during which the light acts is Σtkf=tl, and the time from the start to the end of intermittent exposure is t2, then the amount of exposure due to continuous exposure with tz waiting time is Let H be the intensity of light that is equal to the exposure amount (E・Σtki), then the photosensitive effect of intermittent exposure is E
The photosensitive effect is intermediate between -t+ continuous exposure and H-t,z continuous exposure.

If E is in the region of low-light reciprocity failure, that is, EL
In this case, increasing the frequency f will decrease the photosensitivity.

- As the continuous exposure at t2 approaches, the photosensitive efficiency decreases. For light Eu in the region of high-intensity reciprocity law failure, when the frequency of intermittent exposure is increased, the photosensitivity approaches that of continuous exposure of EH-t2, and the photosensitivity improves. Note that the photosensitivity does not change below the critical frequency f9 and above rc.

FIG. 6 shows the relationship between the intermittent exposure amount and the continuous exposure amount necessary to achieve the same density, and the vertical axis represents the exposure amount and the horizontal axis represents the illuminance. As shown by the solid line, when the exposure time 1+ is 100 m5, the illuminance for obtaining D=0.15 is in the high illuminance reciprocity law failure region. The illuminance to obtain D=2.0 is in the low illuminance reciprocity failure region. Here, each exposure amount marked with a triangle mark is shown in Figures 8 to 13.
It is shown in the figure. This figure 8 shows that the low-density area of the original is irradiated with a constant light amount (original surface illuminance 300,000 lx), and the exposed surface illuminance E
,=100/! This shows a state in which continuous exposure is performed at x, t+ = 100 ms. Also, in FIG. 9, E+=1004! x, duty cycle is “1:IJ Ctk==1
/2T), tz =200ms.

A case is shown in which intermittent exposure of Σjkt=100 ms is performed and the same exposure amount as in FIG. 8 is given. Figure 10 shows the exposure surface illuminance F
: o , tz = 200 ms intermittent exposure is shown. In addition,
11 to 13 show continuous exposure and intermittent exposure of the high-intensity reciprocity failure region of E.

As shown in Figure 6, in the region of low-light reciprocity law failure, H
L is smaller than EL, and the low-light failure is larger, and the effect of intermittent exposure (EL ・Σt,k,) in between is lower than that of continuous exposure (EL-t,), and the low-light failure is larger. . Also, when the time during which light acts once in intermittent exposure is equal to the time during which no light acts (the duty cycle is 1
), intermittent exposure is the effect of continuous exposure of EL-t+,
The effect is intermediate between continuous exposure of 1/2E and 2t. When performing intermittent exposure at frequency f by shortening one exposure time, if frequency f becomes larger than critical frequency fc, 1
The photosensitive effect is the same as continuous exposure of /2E/2tz. Therefore, the frequency f is changed from the critical frequency f to the critical frequency feO
By changing between them, the gradation of a part of the shadow changes.

On the other hand, at high illuminance En, E)I is thicker than H11, so high illuminance failure is smaller than continuous exposure (Eu-t+), and intermittent exposure (EH・Σtk,) is better than continuous exposure EH・mu. The photosensitivity becomes high. Therefore, by changing the frequency f between the critical frequency fp and the critical frequency f, the gradation of the highlighted portion changes.

FIG. 7 shows characteristic curves when a reversal photosensitive material is used as the photosensitive material and the frequency of intermittent exposure is varied. As is clear from this figure, by changing the frequency f of intermittent exposure between the critical frequency f and the critical frequency f,
The gradation of the highlight part and the shadow part changes. That is, at the critical frequency f, the highlight portion and a portion of the shadow become soft-toned, and at the critical frequency fc, the highlight portion and a portion of the shadow become hard-toned.

According to experiments, fp=100Hz, T=10ms, tk
! =5ms, tz =200ms, intermittent exposure with pulse number n=20, fe-500Hz, T=10ms,
tkl = 1ms, tz = 200ms.

The same density was achieved with intermittent exposure with the number of pulses n=100.

As is clear from FIG. 7, in the present invention, since the duty cycle is changed while keeping the frequency constant, only the exposure amount can be adjusted without changing the gradation.

Next, the operation of the above embodiment will be explained. When the previous copying is completed, the pull-out roller 31 rotates and the magazine 3
The photosensitive material 11 inside 0 is pulled out.

When this photosensitive material 11 is pulled out for a certain length, the cutter 3
2 is activated to cut into sheets. After the tip of the cut photosensitive material 11 is detected by the sensor 33,
It is conveyed a certain distance and stops at the position where the leading end is crossed by the exposure conveyance roller 28.

When copying, when the reflective original 1 is set on the stage 10 and a copy start key provided on the keyboard 44 is operated, prescanning is started prior to the start of copying.

During this pre-scan, the controller 39 sends a 50% duty cycle command to the duty cycle adjustment circuit 42, so a pulse with a 50% duty cycle is output. The driver 46 amplifies the power of this pulse to a predetermined value and sends it to the transparent electrode 17b of the PLZT element 17a, so the lens unit 14 alternately transmits and blocks the incident light.

During pre-scanning, the lamp unit 2 moves at a constant speed in the arrow direction, and the mirror unit 7 starts moving at 1/2 the speed relative to the lamp unit 2 to illuminate the reflective original 1 with a slit. The reflected light from the reflective original 1 is reflected by the mirror 5
．． After being reflected by 8 and 9 and transmitted through the lens unit 14, it is reflected downward by a mirror shutter 22 inserted in the optical path, and then reflected by a mirror 23 and enters a measuring section 24, where measurement is performed. The output signal of the measuring section 24 is amplified, digitally converted, and logarithmically converted before being written into the first memory 40 .

The lamp unit 2 and the mirror unit 7 are moved a predetermined distance and returned to their initial positions after completing the pre-scan. The controller 39 reads the photometric data from the first memory 40 and calculates the exposure amount. The controller 39 reads out the duty cycle value corresponding to the calculated exposure amount from the table data in the second memory 41 and sends it to the duty cycle adjustment circuit 42 . The duty cycle adjustment circuit 42 adjusts the duty cycle of the pulse signal sent from the pulse oscillation circuit 43 based on a command signal from the controller 39. The pulse signal adjusted by the duty cycle adjustment circuit 42 is sent to the driver 46.

After the pre-scan is completed, the lamp unit 2 and mirror unit 7 are moved again at a constant speed in the arrow direction, and the exposure conveyance rollers 2B and 29 are rotated after a predetermined time delay from the start of this scan to remove the sheet-like photosensitive material. 1
1 is conveyed at a speed synchronized with the lamp unit 2. At the same time, the mirror shutter 22 is moved to the position shown by the dotted line, and slit exposure of the photosensitive material 11 is started.

During slit exposure of the photosensitive material 11, the PLZT17
The light transmitting state and the light blocking state are repeated at a designated duty cycle, and the reflected light from the reflective original 1 is converted into pulsed light. The pulsed light that has passed through the PLZTI 7 is incident on the photosensitive material 11 that moves along the imaging plane of the lens, so the image recorded on the reflective original 1 is recorded on the photosensitive material 11.

During this copying, the duty cycle of the intermittent exposure is adjusted, so the exposure amount of the photosensitive material 11 is adjusted according to the recording density of the reflective original 1 without causing gradation conversion based on the intermittent exposure.

When the reflective original 1 is moved to a predetermined position, the mirror shutter 22 is displaced to the position shown by the solid line to close the optical path.

At the same time, the lamp unit 2 and the mirror unit 7 start returning, and the operation of the PLZT 17 is stopped.

The exposed photosensitive material 11 is sent to a photographic developing section 34, where it is subjected to color development, bleach-fixing, washing, and drying processes, and then discharged onto a tray 35. Through this photographic development process, the copy image of the original 1 is recorded on the photosensitive material 11 as a positive image.

Although the above embodiments have been described with respect to a copying machine using an autopositive photosensitive material, the present invention can also be applied to other silver salt photosensitive materials, such as diffusion transfer photosensitive materials.

Further, in addition to controlling exposure depending on the document, the present invention can also be applied to controlling the amount of exposure depending on the copying magnification.

Furthermore, the above embodiment has a structure in which the reflective original is fixed and the lamp unit 2 and mirror unit 7 are moved.
A structure may also be used in which the reflective original 1 is moved and subjected to slit exposure.

〔Effect of the invention〕

As described in detail above, according to the present invention, the electronic shutter is disposed approximately at the pupil position of the lens, and a pulse signal is applied to the electronic shutter to provide intermittent exposure to the photosensitive material, and the duty cycle of the pulse signal is Since the exposure amount is controlled by changing the exposure amount, highly accurate exposure amount control can be performed extremely easily, and a compact exposure amount control device with a simple structure can be provided.

[Brief explanation of the drawing]

FIG. 1 is a diagram schematically showing a silver salt photographic copying machine embodying the present invention. FIG. 2 is an exploded view showing the configuration of PLZT. FIG. 3 is a perspective view schematically showing the lens unit. FIG. 4 is an explanatory diagram showing the relationship between exposure amount and duty cycle. FIG. 5 is a graph showing the relationship between intermittent exposure and reciprocity law failure. FIG. 6 is a graph showing the relationship between illuminance and exposure amount to obtain the same density. FIG. 7 is a graph showing characteristic curves of the reversal photosensitive material when the frequency is changed. FIG. 8 is a time chart showing continuous exposure at exposure surface illuminance E4. FIG. 9 is a time chart showing intermittent exposure with exposure surface illuminance EH. FIG. 10 is a time chart showing intermittent exposure at an exposure surface illuminance iZ 11. FIGS. 11 to 13 are diagrams similar to FIGS. 8 to 10 showing continuous exposure and intermittent exposure of a high-intensity reciprocity failure region. 1... Reflective original 11... Photosensitive material 15...
Front group 16... Rear group 17... PLZT 17a... PLZT element 17b... Transparent electrode 18a
, 18b... Deflector 22... Mirror shutter 42... Duty cycle adjustment circuit. Figure 4 Figure 5

Claims (2)

[Claims] (1) In a copying machine in which light reflected from a slit-illuminated document is imaged on a photosensitive material through a copying optical system, the light transmittance is adjusted approximately at the pupil position of the copying optical system in response to voltage application. 1. An exposure amount control device, characterized in that a variable electronic shutter is arranged, and the exposure amount is adjusted by changing the duty cycle of a pulse applied to the electronic shutter. (2) The exposure amount control device according to claim 1, wherein the electronic shutter is PLZT.