JPS60247263A - Original density reader - Google Patents

Abstract

PURPOSE:To read exactly the density of an original with simple constitution by constituting integrally a light emitting means, photodetecting means and control means and making these means manually movable. CONSTITUTION:A light source 51 lights up when an operator directs the tip 21' of a light pen toward the bright part of the original 23 and pushes a read switch 58 for the image density of the bright part. The light thereof irradiates the original 23 through a condenser lens 52, a half mirror 53 and a lens system 54. The reflected light is reflected by the mirror 53 and is made incident through a mirror 55 and an aperture 56 to a photodetector 56. The output thereof is inputted via an amplifier, multiplexer and analog-to-digital converter to a processing circuit (control means), by which the original density is read. The image density in the dark part is similarly read when the operator directs similarly the pen 21 toward the dark part of the original and lights the light source 51 by pushing a read switch 59 for the image in the dark part.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus capable of reading the density of a document.

The purpose of conventional electronic copying devices has been to make copies that are faithful to original images. However, if a diazo original or an original whose background is painted in color is copied using a conventional copying device for the purpose of faithful reproduction, the background of the copied image will be foggy and unreadable. It becomes difficult.

In order to eliminate this, some devices perform a preliminary scan prior to scanning for exposure of the original, detect the density of the original, and then optimize the amount of charge, amount of exposure, developing bias voltage, etc. based on this detected density. Ta.

However, with this method, not only is the configuration and its control complicated, but if the original is not set accurately at the exposure position, the density of the original cannot be read accurately and a proper copied image may not be obtained. Ada.

The present invention has been made in view of the above points, and an object of the present invention is to provide a document density reading device that can accurately read the density of a document with a simple configuration.

That is, the present invention includes a light emitting means for irradiating the original, a light receiving means for receiving light from the original irradiated by the light emitting means, and a control means for controlling the output of the original density signal read by the light receiving means. comprising the light emitting means, the light receiving means,
This device is characterized in that the control means is integrally configured and can be moved manually.

Hereinafter, the present invention will be explained in detail with reference to Examples.

FIG. 1 shows an example of an electronic copying device to which the present invention can be applied;
The figure shows the temporal change in the surface potential Vp on the photosensitive drum l, which will be described later. The solid line shows the change in the surface potential Vp of the dark part of the original (the part that reflects less light), and the broken line shows the change of the surface potential Vp of the dark part of the original (the part that reflects less light). It shows the change in the surface potential Vp of the area (the part where there is a lot of reflection). 1 and 2, first, the charger 2 and light source 3 erase the electrostatic memory on the photosensitive drum 1, which is made up of three layers: an insulating layer 101, a photoconductive layer 102, and a conductive substrate 103. Therefore, as shown in FIG. 2, the surface potential Vp on the photosensitive drum l is O at any part of the photosensitive drum. Next, the drum 1 is uniformly primary charged using a primary charging corona discharger. At the time when the primary charging ends, the surface potential Vp on the drum l is in the state shown in FIG. 2.

Following the primary charging, a light image from the original is exposed through the lens system 7, and at the same time, the weight-removing corona discharger 5 is discharged. Along with this, the surface potential Vp on the drum 1 changes as shown in FIG. 2 according to the amount of exposure light, and reaches the state (2) when the static electricity removal is finished. Next, the entire surface is exposed with a lamp 6 to increase the contrast of the surface potential Vp according to the amount of light. By exposing the whole surface to light, the surface potential Vp reaches the state at time O in FIG. 2, which is necessary for the final electrostatic latent image. The electrostatic latent image on the drum L is transferred to the developing device 8.
to form a visible image, and if necessary, expose the entire surface to light with a lamp 6 to increase the contrast of the latent image, form a visible image with a developing device 8, and then feed paper from a cassette L-10 with a paper feed roller 9. The visible image is transferred onto the transferred transfer paper 11 by the transfer charger 12, the transfer paper 11 is separated from the photosensitive drum 1 by the separation roller 13, and further sent to the fixing device 14 consisting of a fixing roller where it is fixed. It is discharged to

Note that reference numeral 16 indicates an original placing table on which an original is placed, and the reflected light obtained by irradiating the original with a lamp 17 is reflected onto a mirror 18.
The light image that has passed through the lens system 7 is further reflected by a mirror 19 and irradiated onto the photosensitive drum 1 by moving the document table 16 in the direction of arrow F.

FIG. 3 is a graph showing the relationship between the simultaneous exposure light amount E to the photosensitive drum l and the surface potential Vp at the zero point, the so-called E-7 curve. In the figure, the horizontal axis is the light amount E (lux@5e
e) - The vertical axis represents the surface potential Vp (V). Here, the exposure light amount O to E3 is called a dark saturation region, and the exposure light amount E9 to ω is called a bright saturation region.In this range, even if the light amount E changes, the surface potential Vp does not change. The amount of light E3 to E9 is called a dynamic range, and in this range, the surface potential Vp changes almost linearly with respect to the amount of light E. When the exposure light amount E from the original has a large dynamic range, that is, when the photosensitive drum is irradiated with a light amount from E3 to E9, a copied image with the best gradation is formed. Furthermore, as shown in Figure 4, if the surface potential of the dark area is at point 0 and the surface potential of the bright area is at point [F], increasing the output voltage of the AC static elimination high-voltage transformer will bring it to point [0]. F] points change from point to point. Similarly, as shown in Figure 5, if the output voltage of the primary charging high voltage transformer is increased, 0
Point [F] The points each change from 0 to 0. That is, changes in both the primary charging high-voltage transformer 36 and the AC static eliminating high-voltage transformer 37, which will be described later, change the surface potential of the bright and dark areas on the photosensitive drum.

As described above, the surface potential Vp of the photoreceptor changes depending on the amount of exposure light, the output voltage of the primary charging high voltage transformer, and the output voltage of the AC static elimination high voltage transformer. Therefore, the surface potential Vp can be adjusted by adjusting the exposure light amount and adjusting the output.
It is possible to control using a secondary charging high-voltage transformer and an AC static elimination high-voltage transformer whose output can be varied.

The present invention provides an electronic copying apparatus capable of forming an image with high contrast by organically linking the above three adjusting means.

Hereinafter, a method for controlling the surface potential Vp of an electronic copying apparatus, which is the gist of the present invention, will be explained with reference to the drawings.

FIG. 6 is an electrical system diagram of an embodiment of the present invention, and its configuration and operation are as follows. Note that members assigned the same numbers as in FIG. 1 indicate the same functions as in FIG. 1. Note that a blank exposure light source 34 was further provided here. The original function of the blank exposure light source 34 is to irradiate light onto a portion of the photosensitive drum l that is not irradiated with the light image from the document 23 during a copying operation to prevent toner from adhering to the portion that is not irradiated. It is also used to irradiate the photosensitive drum l with reference light, the amount of which is varied, in order to control the surface potential Vp before a copying operation. 20 is a processing device using a microprocessor, 21 is a light pen for detecting the original image density, 22 is an amplifier for the signal from the light pen 21, 23 is the original, 24 is a multiplexer, and 25 is an analog/digital converter ( (hereinafter referred to as A/D converter), 26 is a document bright area image density read signal input line, 27 is a document dark area image density read signal input line, 28 is a copy start switch,
29 is a copy stop switch, 30°, 31.33 are primary charging high voltage transformer 36, AC static elimination high voltage transformer 3, respectively.
7. A digital/analog converter (hereinafter referred to as a D/A converter) that converts the digital signal from the processing device 20 into an analog signal in order to control the output of the blank exposure light source 34; 32 is the aperture value of the aperture device 38; 40 is a potentiometer that indicates the aperture value; 35 is a surface potential detector for the photosensitive drum l; 41 is a rotating disk having a hole 41' that rotates together with the photosensitive drum 1; Reference numeral 42 denotes a drum clock generator which generates a so-called drum clock signal, which is composed of a light emitting element and a light receiving element, and generates a signal synchronized with the rotation of the rotating disk 41, that is, the rotation of the drum.

The processing device 20 decodes the information inputted from the input capo) It to I 10, performs logical operations, and processes the result.
Or output the stored data to port 01~01
0 to control the equipment connected to the output port. The processing device has a ROM (read only memory) 201, in which a procedure for carrying out the present invention (details shown in FIGS. 8 to 12) is stored. Further, the processing device 20 has a RAM (read/write memory) 203, and this RAM 203 is a writable memory that temporarily stores data during execution of the procedure. The other components of the processing device 20 include a buffer memory that temporarily stores input data and output data, and a CPU (central processing unit) that issues calculation instructions.
205, a clock generator 206 that generates a clock signal for operating the CPU 205, a memory interface 204 for coupling the CPU 205 with the ROM 201 and buffer memory 202, a control bus 207, an address bus 208, and an input data bus 2.
09, an output data bus 210, etc., but since their detailed mechanisms and configurations are already well known, a detailed explanation will be omitted here. Output ports Ot and 02 each store and hold 4-bit data sent by the output data bus 210, and output terminals 01-a to 01-d and 02-a
It outputs discretely from ~02d.

When a digital "1" signal is derived on the output terminal OHa, the A/D converter 25 operating signal is output, and when a digital "1" signal is derived on the output terminal 01-b, the multiplexer is output. When the light pen selection signal is output and the digital "lo" signal is derived on terminal 01-a, the multiplexer/surface electrometer selection signal is output, and the digital "lo" signal is output on terminal o1-d.
When the “lo” signal is derived, the multiplexer
A potentiometer selection signal is output. When a digital "1" signal is derived on the output terminal 02-a, the D/A converter 30 is activated and the 8-bit parallel digital signal derived from the output port 04.05, which will be described later, is converted into an analog signal. The DC high-voltage transformer 36, which is the power source for the primary charger 4, is driven by converting it into The DC high voltage transformer 29 is a known transformer that derives a DC high voltage according to the applied analog signal. -Digital “on power output terminal 02-a”
When a signal of O"' is being derived, the D/A converter 30 is deactivated and a predetermined specific voltage (for example, O(V)) is applied to the DC high voltage transformer 36, and the D/A converter 30 is deactivated.
Control so as not to derive high voltage from the C high voltage transformer.

Also, when a digital signal of "°1" is derived on the output terminal 02-b, the D/A converter 31 is activated, and the 8-bit parallel digital signal derived from the output ports o6 and o7, which will be described later, is output. Convert to analog signal and use AC
The AC high voltage transformer 37, which is the power source for the static eliminator 5, is driven. This AC high voltage transformer 37 is a known transformer that derives an AC high voltage according to an applied analog signal. - When a digital "0" signal is derived from the power output terminal 02-b, the D/A converter 31 is inoperative and a predetermined specific voltage (for example, 0
(V) ) is applied to the AC high voltage transformer 37, and the A
Control is performed so that high voltage is not derived from the C voltage transformer.

Also, when a digital "1" signal is derived on the output terminal 02-c, the D/A converter 33 is activated, and an 8-bit parallel digital signal derived from the output port 09.010, which will be described later, is output. The signal is converted into an analog signal, turns on the blank exposure light source 34, and adjusts the amount of light.

On the other hand, when the digital "°O" signal is output on the output terminal 02-c, the blank exposure light source 34 is controlled so as not to light up.

When a digital "lo" signal is derived on the output terminals 0B-c, the pulse motor 39 is driven via the driver circuit 32, and the aperture value of the aperture device 38 is opened by one step. .

Further, when a digital "lpa" signal is derived from the output terminal 08d, the pulse motor 39 is driven via the driver circuit 32 to reduce the aperture value of the aperture device 38 by one step.

Output bus lines 21 are indicated by output bus lines 04 and 05.
Each of the 4 bits of data above 0 is stored and held at the output terminal 0.
4-a to 04-d and 05-a to 05-d, and is converted into an analog signal by the D/A converter 30.

The output terminals 06-a and 07 store and hold the 4-bit data on the pass line 24, respectively, and output the output terminals 06-a and 07.
-d and 07-a-07-d,
It is converted into an analog signal by the D/A converter 31.

The output terminals 209-a to 09-d and 01(1-a to 010-) store and hold the 4-bit data on the pass line 24, respectively.
d, and is converted into an analog signal by the D/A converter 33.

Output terminals other than those described above are used for controlling other parts of the copying machine or displaying the status of the copying machine, and therefore their explanation will be omitted here.

Next, the input boat will be explained. Input ports ■1 and ■2 receive a signal indicating the surface potential from a surface potentiometer 35 which is input to the multiplexer 24, and a potentiometer 4.
A signal indicating the aperture value from 0 and a signal indicating the density of bright and dark areas of the image from the light pen 21 are distributed to the multiplexer and inputted via the A/D converter 25.

The copy start signal from the copy start button 28 is input to the input terminal l3-a, the copy stop signal from the copy stop button 29 is input to the input terminal I3b, and the drum clock generator 4 is input to the input terminal l3-c.
The drum clock pulse from the drum clock generator 42 from 2 is input.

Further, a bright area image density reading signal from the light pen 21 is inputted to the input terminal l4-a, and a dark area image density reading signal is inputted to the input terminal l4-b.

Signals indicating the status of the copying machine and other signals are input to input terminals other than those described above, but detailed description thereof will be omitted here. The data input to each input port is input to the buffer memory 202 via the input data bus 209 when the CPU 205 outputs a read command via the control bus 207.

Next, the structure of the light pen 21 will be explained using FIG. 7. In FIG. 7, 51 is a high-intensity light source, and 52 is a condenser lens that condenses the light from the light source 51 and projects it onto the original 23 via a half mirror 53 and a lens system 54, and the reflected light is reflected by a lens system. 54, a half mirror 53, and a total reflection mirror 55, the image is formed on the aperture 56, and after being photoelectrically converted in the light receiving element 57, the output line 6
1 to the aforementioned amplifier circuit 22, multiplexer 24,
The signal is transmitted to the processing circuit 20 via the A/D converter 25. 58 is a light image density reading switch, 59 is a dark image density reading switch, and 60 is the reading switch 58.59.
This is a control circuit that includes a power source for the light source 51 that controls the light source 51 to turn on only when is pressed and to output an image density reading signal to the processing circuit 20.

When the tip 21' of the light pen 21 is directed toward the bright area of the original 23 and the bright area image density reading switch 58 is pressed, the light source 51
lights up, a bright area image density reading signal is input to the processing circuit 20 via the input line 26, and a voltage EL corresponding to the density of the bright area of the document is output from the photoelectric converter 57 and is applied to the amplifier 2.
2. The signal is input as a digital signal to the input port 11 and 2 via the multiplexer 24 and the A/D converter 25. On the other hand, the voltage ED corresponding to the dark area image density 5 is also input to the input board in the same way as EL.
1 and ■2.

Now, in the ROM 201, procedures necessary to carry out the present invention are stored as shown in the flowcharts of FIGS. 8 to 12, and each functional element shown in FIG. 6 is driven according to these procedures. It is something.

First, the l4-a terminal is read (STEPI), the bright image density reading switch 58 is pressed, and the digital "t" is sent to ■4-a.
5TEP 2), if digital ゛l゛' is not standing, return to 5TEPI, and if it is standing, L, X, multiplexer 24 switches to light pen 2
Select the input signal from 1 (STEP 3). Next A/
5TEP to output a signal to operate the D converter 25
4) Read the bright area density signal EL (STEP 5), and store the signal EL in the RAM 203 (STEP 6).
. In the same way, read the second terminal in ■4 (STEP 7), the dark area image 6 density read switch 59 is pressed, and the digital “4-b” is displayed.
I want to judge whether II is standing or not 5TEP8),
If digital "1" is not set, return to 5TEP7,
If it is standing, the multiplexer 24 selects the input signal from the light pen 21 (1TEP9), outputs a signal to operate the A/D converter 25 (5TEP10), reads the dark area density signal ED (STEpH), and transfers the signal ED to the RAM 203. (STEPI2). Next, reset all output ports of the processing circuit 20.5TEPp13
), standard aperture value NEX stored in ROM201
, the initial value E11 of the voltage applied to the charger and the initial value E21 of the voltage applied to the AC static eliminator are stored in the RAM 203 (5TEP14), and the drum clock number CLK is set to zero. Next, the multiplexer 24 selects the signal from the bodyiometer (5TEP16), outputs a signal to operate the A/D converter 25 (5TEP17), reads the aperture value from the potentiometer 40 (STEP18), and the aperture value becomes the standard aperture value NEX. I don't know if it's 5TE
P19) If the aperture value is not NEX, return to 5TEP18, which drives the pulse motor and changes the aperture value, and if the aperture value is NEX, proceed to the next step.

Next, it is determined whether the copy start button 28 has been pressed (5TEP20), and if it has not been pressed, 5TEP2
0 repeatedly and the copy start button 28 is pressed, the standard bright area surface potential VSL (according to measurements, approximately 11
50 volts), and the surface potential VSL of a slightly darker area than the standard bright area (+50 volts as measured), and the difference between the standard dark area surface potential VSD (+450 volts as measured) and the standard bright area surface potential VSL. Differential voltage VS
C and the standard blank exposure lamp applied voltage Es, etc.
Stored in AM203. In addition, FIG. 3 VSt.

The positions of VSL, vso and VSC on the EV curve are shown.

Next, the initial value E11 of the voltage applied to the primary charger stored in the RAM 203 is output to the primary charging high voltage transformer 30 (STE'P22), and then the initial value E21 of the voltage applied to the AC static eliminator is output to the AC static eliminator high voltage transformer. I want to output to 31 5T
EP23), and the dark area density signal ED read in 5TEPII is output to the blank exposure lamp 34, and the photosensitive drum l is irradiated with the amount of light corresponding to the dark area density (STE P
24).

Next, the rotation of the drum 1 is detected by reading the drum clock number CLK (STEP 25). Reading is done by catching the rise of the drum clock and adding 1 to the drum clock number CLK.
Add them one by one. Drum clock number CLK is 4
When it reaches 0, the portion of the photosensitive drum 1 irradiated with the amount of light corresponding to the dark area density in 5TEP 24 comes to a position facing the surface electrometer 35. In 5TEP26, the clock number CLK is 40.
If CLK is not 40, the process returns to 5TEP25, and when CLK becomes 40, the multiplexer 24 selects the input signal 9 from the surface electrometer 35 (5TEP27) and the A/D converter 25. 5TEP28), and read the dark surface potential vD1 (STEP29). Next, it is determined whether vDl is within a predetermined allowable range of dark area surface potential, and if it is within the allowable range, the process proceeds to 5TEP31, and if it is outside the allowable range, an error signal is output (STEP30).

In 5TEP31, the dark area surface potential VDI is stored in RAM20.
Store within 3. Further 5: Irradiate the photosensitive drum 1 with an amount of light corresponding to the bright area density of the original read in TEP5 (ST
EP32). Next, the drum clock number CLK is read again. When CLK reaches 60, the part of the photosensitive drum 1 irradiated with the light amount corresponding to the bright area density at 5TEP32 is detected by the surface electrometer 3.
It comes to the position opposite to 5. In 5TEP34, CLK is 6
If CLK is not 60, the process returns to 5TEP33, and when CLK becomes 60, the multiplexer 24 selects the input signal from the surface electrometer 35 (5TEP35) and converts the A/0 D converter 25. 5TEP to output the signal to operate
36), read the bright area surface potential VL 1 (S, TEP
37) , determine whether VL 1 is within the permissible range of bright area surface potential set in advance, and if it is within the permissible range, 5TE
Proceed to P39, and if it is outside the allowable range, output an error signal (STEP38). In 5TEP39, set VL 1 to R.
Stored in AM203. Next, VDI- with 5TEP40
Calculate VLI, use the result as Vc, and further calculate 5TEP4
1, the calculation E11+aCVsc-Vc)=Et2 is performed. Here, E11 is the initial value of the voltage applied to the primary charger, and VSC is the difference voltage between the standard dark surface potential van and the standard bright surface potential VSL, that is, the standard difference voltage.
Vc is the differential voltage determined by 5TEP40, and α is a coefficient determined from the relationship between the voltage applied to the primary charger and the surface potential.

In other words, in this calculation, if the voltage difference between the dark area and the bright area is small, it is not possible to expect a sufficiently reproduced image with large contrast and gradation. ) is added to make the primary charger applied voltage a correction value E12. Next, in 5TEP42, it is determined whether the correction value E12 is within a preset tolerance range, and if it is within the tolerance range, the process proceeds to 5TEP43, and if it is outside the tolerance range, an error signal is output.

5TEP44 outputs El2 to the primary charging high voltage transformer 30. Next, since the blank exposure lamp 34 emits a light amount corresponding to the bright image density of the original, the drum clock number CLK is read in order to measure the bright area surface potential VL2 after correcting the voltage applied to the primary charger. (STEP 45)
.

When CLK becomes 100, the corrected single charger applied voltage E
The part of the photosensitive drum l to which 12 was applied is the surface electrometer 3.
It will be in a position opposite to 5.

5TEP46 determines whether CLK has reached 100, and if CLK has not reached lOO, 5TEP45
Return to , and when CLK reaches 100, proceed to 5TEP47. In the 5TEP47, the multiplexer 24 is connected to the surface electrometer 3.
The input signal 5 or 3 is selected to operate the A/D converter 25 (STEP 48), and the bright area surface potential VL2 after correction of the voltage applied to the primary charger is read (STEP 49). 5TEP50
In, E21+β(V SL −VL 2)=E2
Perform calculation 2. E21 is the initial value of the applied voltage for AC static elimination, and VSL is the standard bright area surface potential. β is a coefficient determined from the relationship between the voltage applied to the AC static eliminator and the surface potential. In other words, in this calculation, if the bright area surface potential VL2 after correcting the voltage applied to the primary charger is a potential that causes fogging, the voltage applied to the AC static eliminator will be increased to lower the bright area surface potential. This is a calculation formula for calculating the supplementary voltage value E22. It is determined whether E22 is an appropriate value, and if it is not an appropriate value, an error signal is output, and if it is an appropriate value, the process proceeds to the next 5 TEP (STEP 51). 5TEP52
Then, the correction value E 22 is stored in the RAM 203.

Next, E22 is output to the AC static elimination high voltage transformer 31 (
STEP 53). By 5TEP53, the voltage applied to the electric device and the voltage applied to the AC static eliminator were determined.
In the following 5 TEP, the appropriate value of the aperture value of the aperture 38 is determined. The aperture value is now the standard aperture value NEX, as determined by 5TEP19. In Figure 3, the aperture value is NEX.
For example, if the amount of light irradiated from the bright part of the original onto the photosensitive drum l is E5 and the amount of light irradiated from the dark part of the original is El, the dynamic range of the E-V curve is not sufficiently taken, so the gradation changes. A sufficient copy image cannot be expected. Since the amount of light E1 emitted from the dark area is in the dark area saturation region,
If the aperture is opened and the amount of light passing through the aperture 38 is doubled, the amount of light irradiated from the bright part of the original onto the photosensitive drum l will be from E5 to E.
lo, and the amount of light irradiated from the dark part of the document to the photoreceptor becomes from El to E2, and since a sufficient dynamic range of the EV curve can be obtained, a copied image with good gradation can be expected.

On the other hand, if the amount of light is too large, that is, the amount of light from the dark area is E
4, when the amount of light from the bright area is E12, a copied image with sufficient gradation cannot be expected because the dynamic range of the EV curve is not sufficiently taken. The amount of light emitted from the bright area E12 is in the bright area saturation region, so if the aperture 38 is stopped and the amount of light passing through the aperture 38 is set to 3/4, the amount of light from the dark area will change from E4 to E3, and the amount of light from the dark area will be El2
to E9, and since a sufficient dynamic range of the EV curve can be obtained, a copied image with good gradation can be expected.

By controlling the aperture value as described above, effects that cannot be obtained by simply controlling the voltage applied to the negative charger and the voltage applied to the AC static eliminator can be obtained.

This aperture value control will be explained below according to 5TEP.

K, a signal for the blank exposure lamp 34 to output an amount of light slightly smaller than the amount of light in the dark area of the document, is a constant determined by the characteristics of the photoreceptor. E in 5TEP54
Calculate 1XK=EL and output the calculated value EL' to the blank exposure lamp 34 (STEP 55). Next, the portion of the photosensitive drum 1 irradiated with the same amount of light comes to a position corresponding to the surface electrometer 35 . 5TEP57 determines whether the drum clock number CLK has reached 120, and
When it reaches 120, proceed to the next step. At 5TEP58 a multiplexer selects the signal from the surface electrometer and at 5TEP59
The A/D converter is operated at 5TEP60, and the surface potential vL' is read at 5TEP60. In 5TEP61, γ(■sL”
−vL, )+AP is calculated. γ is a constant determined from the relationship between the surface potential and the aperture value, and SL' is the surface potential of a slightly darker area than the standard bright area determined by 5TEP21, and has a value as shown in FIG. 3, for example. AP is an aperture correction value. The AP serially outputs the aperture correction value to the pulse motor 39 to change the aperture value (STEP 62).

7 Here, the bright area surface potential was compared with the surface potential at a light intensity slightly lower than the bright area of the original, but the dark area surface potential may be compared with the surface potential at a light intensity slightly higher than the dark area of the original. Now that I have finished correcting the aperture value, it is 5TEP63.
returns the blank exposure lamp applied voltage to the standard applied voltage Es, and then outputs a copy OK signal (STE P
64). When the copy OK signal is output, the standard copying operation described in the explanation of FIG. 1 is performed, and when the predetermined number of copies are completed or the copy stop button 29 is pressed, the process returns to 5TEPl and the next original is copied. (STEP 65).

As is clear from the above, when the contrast is low, 1
While increasing the voltage applied to the next charger, the voltage applied to the AC static eliminator is increased to lower the surface potential of bright areas to eliminate fog, and the exposure light amount is adjusted to provide the optimum light amount for a wide dynamic range. As a result, a reproduced image with gradation can be expected.

In addition, it is preferable to automatically read the image density of the bright and dark areas of the document according to the present invention during one pre-rotation when the copy start button is pressed. Setting is difficult, and reading the original image density is practically difficult due to complete automation. A light pen is not only easy to operate, has a small number of components, and can be constructed at low cost, but also allows accurate reading of the density of bright and dark areas.

As described above, according to the present invention, it is possible to accurately read the image density of any part on a document with a simple configuration, and it is possible to obtain a proper copy image.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of an electronic copying apparatus to which the present invention can be applied;
Figure 2 is a characteristic diagram showing the surface potential at each timing of the photosensitive drum, Figure 3 is a characteristic diagram showing the relationship between the photosensitive drum surface potential and exposure amount, and Figures 4 and 5 are characteristics diagrams showing changes in surface potential. 6 is a control circuit diagram of a copying machine to which the present invention is applied, FIG. 7 is a schematic sectional view of a light pen, and FIG. 8 is a schematic sectional view of a light pen. 9, FIG. 10, FIG. 11, and FIG. 12 show flowcharts for explaining the operation of the control circuit shown in FIG. 6, respectively. In the figure, l is a photosensitive drum, 4 is a primary charger, and 5 is an AC
A static eliminator, 6 a blank exposure light source, 20 a processing device, 21
3 is a light pen, 36 is a primary charger high-voltage transformer, 37 is an AC static eliminator high-voltage transformer, 35 is a surface electrometer, and 38 is a diaphragm device. Patent applicant: Canon Co., Ltd. Mulberry 2 Figure 3 Figure 4 Figure 5 Figure special opening oGO-247211i3 C11) Scho EP
8 STEF74- 137E/" 75 9TEf 76 STE-PI3 TEF78 S ajfyq S7EI"2ρ 57EF'21 TEr22 '3TEF29 S'rEF'24 '5TEr25 5゛η=rz, t 5TEFB0 crr 'EF'36 Procedural correction blind motion) June 27, 1985 Manabu Shiga, Commissioner of the Patent Office1, Indication of the case 1984 Patent Application No. 2849412, Name of the invention Manuscript density reading device3, Person making the amendment Relationship to the case Address of the patent applicant 3-30-2 Shimomaruko, Ota-ku, Tokyo Name (100
)Representative of Canon Co., Ltd. Ryu Kaku 3, Department 4, Agent address: Canon Co., Ltd., 3-30-2 Shimomaruko, Ota-ku, Tokyo 148 (telephone: 758-2111) 5, Date of amendment order (shipment date): 1985 May 28, 2016 6, Specification subject to amendment, drawings and power of attorney 7, Contents of amendment (+) As per the engraving and attachment of the specification and drawings originally attached to the application (no change in content) (2) Please fill out the power of attorney as shown in the attached document. 8. Attached documents (1) Seal impression certificate (1 copy)

Claims (1)

[Claims] The light emitting means includes a light emitting means for irradiating the original, a light receiving means for receiving light from the original irradiated by the light emitting means, and a control means for controlling output of the original density signal read by the light receiving means, and the light emitting means 1. A document density reading device characterized in that a means, a light receiving means, and a control means are integrally constructed and are movable manually.