JPH02230232A - Copying machine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Technical Field] This invention relates to a copying apparatus that detects the image density of a document and automatically sets copying conditions according to the detected image density. [Prior Art] Conventionally, in a device that optically detects the image density of a document and controls copying conditions, the document is illuminated with an exposure lamp such as a halogen lamp during pre-scanning, and the intensity of the reflected light is used to adjust the density of the image. A system is used in which the judgment is made and the result is fed back to the lamp lighting voltage or developing bias. [Problems to be Solved by the Invention] However, even when the halogen lamp is turned on at a constant voltage, there is overshoot, so when the image density of the original is detected (for example, 0 to 0.5 seconds after the halogen lamp is turned on)
For example, as shown in FIG. 10, there is a difference of about 5% in the amount of light when copying conditions are set based on the detected image density (6 to 8 seconds after the halogen lamp is turned on).

In other words, since the amount of light is greater when detecting the image density of the original than when setting the copying conditions, the image density detection output (11th
As shown in the figure), the original is judged to be brighter overall, and the copied image becomes darker (Figure 12P) than the appropriate density (Figure 12O).

The present invention has been made in view of the above points, and its purpose is to prevent erroneous setting of copying conditions due to the difference in light amount between the time of detecting the image density and the time of setting the copying conditions, and to always ensure that the copied image has an appropriate density. The objective is to provide a copying device that can be obtained. [Means for Solving the Problems] To this end, the present invention provides an exposure means for exposing a document, a detection means for detecting the image density of the document exposed by the exposure means, and an image density detected by the detection means. a first control means for controlling the copying conditions accordingly, and a second control means for controlling the exposure means to reduce the difference between the exposure amount of the exposure means when detecting the image density of the document and the exposure amount when setting the copying conditions. The configuration includes a control means.

[Function] This reduces the difference in light amount between when image density is detected and when copying conditions are set, making it possible to always obtain a copied image with appropriate density.

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

FIG. 1 is a diagram showing a schematic configuration of a copying apparatus to which the present invention is applied. 1 is the original to be copied, 2 is the original table glass on which the original l is placed, 3 is a halogen lamp that exposes the original,
Slit exposure is performed by moving back and forth against the document platen glass 2 together with a mirror, etc. Further, 4 is a light receiving element that receives reflected light from the document, and 5 is a control unit that controls the lighting voltage of the halogen lamp 3 in accordance with the output from the light receiving element 4.

Further, IO is a photosensitive drum, which rotates in the direction of the arrow. After the photosensitive drum 10 is uniformly charged positively or negatively by the primary charger 1l, it is irradiated with reflected light from the original via a mirror, lens, etc., and an electrostatic latent image corresponding to the original image is formed. .

The electrostatic latent image formed on the photosensitive drum 10 is developed by a developing device 12, transferred onto a sheet by a transfer charger 13, and fixed by a fixing device 15, after which the sheet is discharged outside the machine. Ru.

Here, the operation of detecting the image density of the original and the operation of setting the copying conditions will be explained. When a copy command is issued, the halogen lamp 3 is turned on and the document 1 is pre-scanned.
During this preliminary scanning, the exposure element 4 detects the reflected light from the document 1, and the control section 5 controls the halogen lamp 3 according to the detection output.
Adjust the lighting voltage. For example, when the image density of the document is high, the lighting voltage of the halogen lamp 3 is set high to increase the exposure amount, and when the image density is low, the lighting voltage of the halogen lamp 3 is set low to reduce the exposure amount. Note that this preliminary scanning may be performed over the entire document, or may be performed on a portion of the document.

In the main scan that is performed continuously after the preliminary scan, the halogen lamp 3 is turned on with a lighting voltage set according to the image density as described above, and the original 1 is exposed to light so that the original image is formed on the sheet as described above. A corresponding copy image is formed.

The lighting voltage of the halogen lamp 3 is adjusted before shipment from the factory so that the output of the light-receiving element 4 becomes the reference value when a reference chart of a predetermined density is exposed.

FIG. 2 is a block diagram showing a control section of the copying apparatus shown in FIG. 1. 100 is ROM. C, which is composed mainly of a well-known one-chip microcomputer with built-in RAM, etc.
It is PU. Further, 101 is a lighting voltage adjustment circuit for lighting the halogen lamp 3 at a voltage according to an output signal from the CPUIOO. Further, 103 is a main motor for driving the photosensitive drum 1 and the sheet conveyance section, and is driven via the driver 102 in response to a control signal from the CPU IOO. A scanner motor 105 serves as a driving source for reciprocating an optical system for scanning an original, which includes a halogen lamp 3, a mirror, etc., and is driven via a driver 104 by a control signal from the CPU 100. Further, 106 is a non-volatile RAM, which stores data corresponding to the lighting voltage of the halogen lamp 3 adjusted at the stage of industrial shipment as described above. Next, a first embodiment of adjusting the light amount of the halogen lamp 3 will be described with reference to FIGS. 3 to 5.

First, the lighting voltage adjustment operation at the factory shipping stage will be explained using FIG. 3. First, after setting the copying machine to a specific mode, a reference chart of a predetermined density is placed on the platen glass.
The halogen lamp 3 is lit at a predetermined lighting voltage, and the lighting voltage adjustment circuit 101 adjusts the lighting voltage of the halogen lamp 3 so that the output V of the light receiving element 4 becomes A (
Step 1.2) When V=A, data corresponding to the lighting voltage vA at this time is stored in the non-volatile RAM 1 0 6
(Step 3). 6-8 to make this adjustment
Since it takes several seconds, this adjustment is performed in a state where the amount of light is stable, as can be seen from FIG. However, the reading of the original density is 0.5 after the halogen lamp is turned on.
Since this is carried out in approximately 1.0 seconds, a difference in the light amount (FIG. 5a) occurs between the time of setting the copying conditions and the time of reading the density due to overshoot of the light amount of the light source. In other words, when reading a document, the amount of light is greater than when setting the copying conditions, so the detection output from the light receiving element 4 increases, and the document is judged to be brighter overall, so the resulting image is darker than the appropriate density. . To prevent this, the lighting voltage (VA-0 in this example) is lower by a certain value than the lighting voltage obtained when setting the lighting voltage of the halogen lamp 3 according to the reference chart.
．． 7V), the difference between the two becomes small (Fig. 5b), and images with proper density without blurring can always be obtained. FIG. 4 is a flowchart for executing this control. When the coby key is turned on (Staρ10), the lighting voltage of the halogen lamp 3 is set to (VA-0.7)ν and the scanner motor 105. Turn on the main motor 103 (S
tepll, 12), and reads the image density of the original using the light receiving element 4 until the preliminary scanning is completed (Step 12).
l3.14), when the preliminary scan is completed, the halogen lamp 3
The lighting voltage is set according to the detected image density of the original (Step 15), and the copying operation begins. Then, the copying operation for the set number of sheets is executed (Steps 16 and 17), and when the copying operation is completed, the halogen lamp 3, scanner motor 105, and main motor 103 are turned off to end the operation.

Next, a second embodiment of the present invention will be described with reference to FIGS. 6 and 7. In the above embodiment, the lighting voltage of the halogen lamp 3 is lowered to a predetermined voltage when the copy key is turned on, but in this embodiment, the halogen lamp 3 is turned on at a voltage vA at the same time as the copy key is turned on, and after a certain period of time (e.g. After 2-3 seconds) Read the original density. perform the process. By doing so, as shown in FIG. 7, the difference in the amount of light during setting and reading can be reduced, and an image with an appropriate density can be obtained.

FIG. 6 is a flowchart for performing this control.

When the copy key is turned on (Step 10), the lighting voltage of the halogen lamp 3 is set to the voltage vA stored in the non-volatile RAM 106 and the main motor 1 is turned on.
03 is turned on (Step 21). Then, after waiting for a certain period of time to pass (Step 22), the scanner motor 10
Turn on 5 and start preliminary scanning. In addition, S t e p
Steps 2 4 to 2 9 are the same as Steps 3 to 18 in FIG. 4, so the explanation will be omitted.

Next, a third embodiment of the present invention will be explained with reference to FIGS. 8 and 9. In this embodiment, when setting the lighting voltage of the halogen lamp 3 at the time of shipment from the factory, the first. As in the case of the second embodiment, after setting the lighting voltage of the halogen lamp 3 using the reference chart, the halogen lamp 3 is turned on again after a few seconds, and the output of the light receiving element 4 with respect to the reference chart is measured. From the output difference with the setting of (9th
Figure) The lighting voltage difference corresponding to the difference is calculated and the lighting voltage at the time of reading is determined. This makes it possible to always obtain images with appropriate density and no blur.

FIG. 8 is a flowchart for performing this control.

First, after setting the copying machine to a specific mode, a reference chart of a predetermined density is placed on the original platen glass 2, the halogen lamp 3 is turned on at a predetermined lighting voltage, and the output voltage of the light receiving element 4 is
The lighting voltage of the halogen lamp 3 is adjusted by the lighting voltage adjustment circuit 101 so that A becomes A (step 30.31).
When the voltage becomes VA-A, data corresponding to the lighting voltage vA at this time is stored in the RAM of the CPUIOO (step 32).
), and after turning off halogen lamp 3 (step 3
3) Fixed time (several seconds)! Wait until it is sent (step 34)
). After a certain period of time has elapsed, the halogen lamp 3 is turned on at a lighting voltage v
The light is lit again at A (step 35), and the voltage vc corresponding to the difference C between the output V of the light receiving element 4 at this time and A is calculated (
step 36), and set the data corresponding to (VA - Vc) to the non-volatile RA as the lighting voltage of the halogen lamp 3.
Store in M106 (step) As explained above, according to the present invention, by reducing the difference between the light amount when setting the copying conditions and the light amount when reading the image density of the original, which is caused by overshoot of the light source, the original image density is always maintained. This has the effect of making it possible to obtain images without blur and with automatic density adjustment.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a schematic configuration of a copying apparatus to which the present invention is applied, FIG. 2 is a block diagram showing a control section of the copying apparatus shown in FIG. 1, and FIG. A flowchart showing the lighting voltage setting operation of the halogen lamp in the embodiment, FIG. 4 is a flowchart showing the operation after the copy key is activated in the first embodiment of the present invention, and FIG. 5 shows the image density in the first embodiment. Figure 6 is a flowchart showing the operation after the copy key is turned on in the second embodiment; Figure 7 is a diagram showing the amount of light when reading and setting copying conditions; Figure 7 is a diagram showing the amount of light when reading image density and setting copying conditions in the second embodiment. FIG. 8 is a flowchart showing the lighting voltage setting operation of the halogen lamp in the third embodiment of the present invention, and FIG. 9 is a flowchart showing the lighting voltage setting process in the third embodiment. Diagrams for explanation: Figure 1゜0 is a diagram showing the relationship between the amount of light when reading conventional image density and setting copying conditions; Figure 11 shows the sensor output when reading conventional image density and setting copying conditions. Figure 12 is a diagram showing the difference in aperture value set due to the difference in light amount when reading conventional image density and when setting copying conditions. 1...Original 2...Original table glass 3...Halogen lamp 4...Light receiving element 5...Control unit Figure 4 Figure 5 Figure q /0〆鵠-1! 1111;

Claims (4)

[Claims] (1) an exposure means for exposing a document; a detection means for detecting the image density of the document exposed by the exposure means; a first control means for controlling copying conditions according to the image density detected by the detection means; A copying apparatus comprising: second control means for controlling the exposure means to reduce the difference between the exposure amount of the exposure means when detecting the image density of the original and the exposure amount when setting the copying conditions. (2) The copying apparatus according to claim 1, wherein the second control means controls a lighting voltage of the exposure means. (3) The copying apparatus according to claim 2, wherein the lighting voltage of the exposure means is lowered by a predetermined voltage when detecting the image density of the original. (4) The copying apparatus according to claim 1, wherein the image density detection of the document is performed a predetermined time after the exposure means is turned on.