JPS63163473A - Image reproducing device - 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 [Field] The present invention relates to an automatic density optimization image reproducing device for a copying machine or the like.

[Prior art]

Conventionally, automatic density adjustment mechanisms in copying machines and the like use a photodetector to detect light reflected from the surface of the original during exposure of the original, determine the density of the original according to the output level, and control the appropriate amount of developing bias to achieve the appropriate density. It is used to obtain images. However, since it takes time for the photosensitive drum etc. to rotate or move from the image exposure position to the development position, it is necessary to memorize the appropriate development bias value at the image exposure position until the development position is reached. In addition, since multiple pieces of data are sampled in the section from the image exposure position to the development position, there are multiple storage devices that sequentially store these data, and the data is read out sequentially from this storage device to determine the appropriate bias value at the correct timing. The disadvantage was that a control device was required to output the .

At the same time, the detection position of the photodetecting element must be placed at the image exposure position, which eliminates the drawback that there is little freedom in setting the position.

〔the purpose〕

The present invention eliminates the above-mentioned drawbacks of the conventional example. During exposure of an original, the installation position of a photodetecting element that detects light reflected from the original surface, and calculation to obtain an appropriate density from the detected value of the photodetecting element. By determining the time required for processing, an appropriate density image can be obtained with a minimum storage device and a simple control mechanism. Thereby, it is possible to provide a copying apparatus with low cost and improved operability.

(Example) FIG. 1 shows an example of the present invention. Reference numeral 6 denotes a photodetector element for detecting light reflected from the original, and in the embodiment of the present invention, a photosensor IC whose duty ratio of output pulses is variable according to the amount of light is used. The amount of light reflected from the original is reflected by the mirror 5 through the slit of the light shielding plate 9, and then detected by the light detection element 6.
reach. 3 is a light source lamp for exposure, and an image is formed on the photosensitive drum 1 by a SELFOC lens 4 to form a latent image. The latent image on the photosensitive tram 1 is developed by the developing sleeve 2 and becomes a toner image, which is then subjected to the transfer and fixing process (
(not shown), an image is formed on the transfer paper.

Reference numeral 11 denotes an arithmetic processing section that determines a developing bias value according to the amount of reflected light. Reference numeral 12 denotes a dimming circuit that controls the amount of light from the exposure lamp 3 to a constant level, and the light detection element 10 detects the amount of exposure.

The distance between the image exposure position A and the reflected light amount detection position B is expressed as , and the distance from point A' of the latent image exposed on the photoreceptor 1 at point A until it is developed at point 0 is Ll.
It is indicated by.

FIG. 2 is an outline of the arithmetic processing part, and Ql is the P from the microcomputer tear light detection element 6 that performs the arithmetic processing.
A WM (pulse width modulation) signal is input to the PIN terminal. The calculated developing bias value is output as a PWM signal from POUT, inputted to the integrating circuit 13, converted into a voltage value necessary for high voltage transformer control, and a predetermined developing bias output is applied to the developing sleeve 2 from the high voltage transformer HVT. Ru.

FIG. 3 shows a schematic flowchart of arithmetic processing inside the microcomputer Q1. First, in step 1, the pulse width of the PWM signal from the light amount detection element 6 is read. This pulse width detection is performed by the microcomputer Q1.
This is done by comparing the timer counter value in the PWM signal with the value at the rising edge and the falling edge of the PWM signal. In step 2, the sampled data read in step 1 is added to the addition memory. In step 3, it is determined whether or not the set number of samplings has been performed, and in this embodiment, sampling is performed eight times. If the set sampling number is not reached, jump to step 4, increment the read counter, and jump to the exit of this routine. When the number of samplings set in step 3 has been performed, go to step 5 for 8 lines, divide the contents of the addition memory by the number of samplings, and calculate the average value.
In step 6, a developing bias value corresponding to the amount of reflected light is output. In step 7 the read counter and addition memory are cleared.

Further, this arithmetic processing routine is executed during timer interrupt processing of the microcomputer Q1, and the arithmetic processing time t is the time from performing a predetermined number of samplings to outputting a developing bias value. The calculation processing time t can be set by varying the timer interrupt time and sampling frequency of the microcomputer Q1.

Next, in the above configuration, the time taken for the latent image on the photosensitive drum 1 exposed at the image exposure position A to reach the position C of the developing sleeve 2 after the start of image exposure is defined as tl, and the amount of reflected light is detected from the image exposure position A. If the time it takes for the document table to move to position B is t2, then 1. ．． If the relationship between 12 and the arithmetic processing time t satisfies the following equation, then 1,=12+1 (Equation-1) The document density and the corresponding developing bias value can be output at accurate timing.

Expression-1 is expressed as the distance L1 between the exposure position A' on the photosensitive drum and the development position C, and the distance 11! between the image exposure position A and the reflected light amount detection position B on the document table. Formula-2 is expressed by I L 2
It is. P is the process speed.

t,, L2 − = −+ 1 (Equation-2)P As described above, when the reflected light amount detection position B is determined, Equation-2 can be satisfied by varying the calculation processing time t. In addition, if the calculation processing time t has been determined, it is possible to satisfy Equation-2 by varying the reflected light amount detection position B.

Figure 4 shows that when there is a narrow dark image in the width direction of the original, the density of only that part is reduced and one page of the original is prepared in advance in order to prevent the density from becoming uneven over the entire page of the original.
It scans and reads the average density of the original, and then determines the bias.

In other words, when you command to start copying by turning on the copy key,
First, the concentration measurement mode or the real-time t in Fig. 3. but,
A select key for selecting one of the above averages is determined (step 1). In the former case, execute the steps shown in Figure 3, and in the latter case, execute steps 2 and below to move the document back and forth, measure and average the entire document area, output the bias value, and then start scanning the document again to calculate the bias value first. Developing is performed using a bias value that is set.

(Effect) As explained above, the sum of the distance from the image exposure position to the detection position of the amount of reflected light on the document and the distance the photosensitive drum rotates during the time it takes to calculate the development bias according to the amount of reflected light is the distance of the photosensitive drum. By making the distance equal to the distance from the image exposure position to the development, images with appropriate density can be reproduced with a simple control mechanism.

Furthermore, since measurement can be controlled by selecting exposure scanning, simultaneous measurement, or measurement using preliminary scanning, it is possible to reproduce a more appropriate density depending on the original density.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the optical system, FIG. 2 is an explanatory diagram of the arithmetic processing section, and FIGS. 3 and 4 are flow charts of the arithmetic processing. 1 is a photosensitive drum, 2 is a developing sleeve, 3 is an exposure lamp,
4 is a SELFOC lens, 5 is a reflecting mirror, 6 is a reflected light amount detection element, 7 is an original table glass, 8 is an original, 9 is a light shielding plate, 10 is an exposure lamp light amount detection element, and 12 is a dimming circuit.

Claims (3)

[Claims] (1) means for detecting image density; means for reproducing an image based on the image density; first means for controlling reproduction by the detecting means during image reproduction by the reproducing means to obtain an image of a predetermined density; and an image by the reproducing means. and second means for controlling reproduction by the detection means before starting. (2) In a device that detects the amount of light reflected from the surface of the document using a photodetector, determines the density of the document based on the detected value, and controls the developing bias according to the detected value, the photodetector detects the amount of light reflected from the document surface from the document exposure position. Whether or not the sum of the distance to the position and the distance the recording material is rotated or moved during the time until the development bias corresponding to the detected value is calculated is equal to the distance from the image exposure position of the recording material to the development. Image reproduction device as below. (3) A reciprocating means for exposing the original, a proximity optical system for inputting the exposed image, a detection means provided at a position different from the exposure position to detect the density of the original, and a means for reproducing at the density determined by the detection means. An image reproducing apparatus, characterized in that the amount of movement by the reciprocating means to reach the detection means is at least within the amount of movement of the recording member to reach the reproducing means.