JPS62281676A - Picture density adjusting device - Google Patents

Abstract

PURPOSE:To secure the proper picture density even with a thin original by using a 1st optical senser having the spectral sensitivity approximately equal to that of an area of a photosensitive body having the maximum spectral sensitivity and a 2nd optical sensor having the spectral sensitivity of a complementary color to the 1st optical sensor. CONSTITUTION:An optical sensor 9 serving as the 2nd optical sensor which detects the texture density of an original 1 has the spectral characteristics of blue complementary to yellow. While an optical sensor 11 serving as the 1st optical sensor has the complementary color relation with the sensor 9 and also has the spectral transmittance characteristics. A yellow original is decided by a DC controller 13 when the output value of the sensor 11 is high and that of the sensor 9 is respectively. While an ordinary original is decided when the output values of both sensors 9 and 11 are set at the same level. Therefore the lamp lighting voltage is fixed at 60V with a yellow or thin original. While the lamp lighting voltage is controlled in response to the CCD output value with other types of originals.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an image density adjustment device that fully automatically adjusts image density in an electrophotographic copying device.

(Prior Art) Conventionally, methods for detecting the degree of background # of a document include a method that detects only a small area regardless of the size of the document;
There is a method that always detects the entire screen of the document. However, with the former method of detecting only a certain area, it may not be possible to obtain accurate information on the background density of the document depending on the document. The latter method is becoming mainstream. In this latter method, the user inputs the original size into the main unit before copying, or if the main unit is equipped with a means to automatically detect the original size, the original size corresponds to the original size. No problem occurs when the background density of the document is detected only in the area. However, when the document size is irregular or small, devices that do not have automatic document size detection means on the main body side may detect the entire screen area (maximum A3 size) regardless of the document size. Because of this, it was impossible to obtain accurate manuscript information.

(Problem to be Solved by the Invention) Conventionally, in order to completely prevent this, a document pressure plate having a spectral sensitivity that almost matches the maximum spectral sensitivity region of the photoreceptor is used to detect the background density of the document. By using a filter to adjust the spectral sensitivity of the sensor to a characteristic that has a complementary color relationship with the color of the document pressure plate, it is possible to detect the background density of the document only in the document area, even when the size of the document is irregular or small. However, this is not a problem for normal manuscripts, but for example, for second manuscripts or thin letters such as those used in government offices, the problem is that the image density decreases and it is not possible to obtain a proper image. there were. Incidentally, this is because the original background density detection handle employs a method in which the original is scanned with the original illumination lamp turned on before the copying operation, and the reflected light from the original is inputted to an optical sensor such as tccD. In other words, if the original is a thin letter, the light from the original illumination lamp will pass through the entire original, and the color of the original pressure plate will be added to the background of the original, making it appear as if the color of the background of the original is the same as the color of the background of the original pressure plate. This is because the light is input to a light sensor such as a COD as close light.

Therefore, the present invention has been made to solve the above-mentioned problems of the conventional example, and its purpose is to automatically print even in the case of second original drawings or thin letter manuscripts used in government offices. An object of the present invention is to provide an image density adjustment device that adjusts an appropriate image.

(Means for Solving the Problems) In order to achieve the above object, the present invention includes a first optical sensor having a spectral sensitivity tW that substantially matches the maximum spectral sensitivity region of the photoreceptor; The first optical sensor and a second optical sensor with complementary color spectral sensitivity detect document information, and based on the detection result, control the background a degree detection output of the document. .

(Function) In the present invention, a first optical sensor that develops a spectral sensitivity that almost matches the maximum spectral sensitivity region of the photoreceptor;
By detecting document information using two photosensors: a second photosensor and a second photosensor that has spectral sensitivities of complementary colors, appropriate image density can be obtained even for thin originals such as letters.

(Example) The present invention will be explained below based on the illustrated example. 1st
The figure is a schematic diagram showing an embodiment of the image wk degree adjusting device according to the present invention. In the figure, 1 is a document;
is placed on the document glass 2 and tightly fixed to j' by the document pressure plate 15. Although not shown, the photoreceptor 7 used in this apparatus is an OPC photoreceptor having a spectral sensitivity as shown by C in FIG. 2. For this reason, the original pressure plate 15
What is the color?

The color is yellow as shown by g in FIG. 3 so as to almost match the maximum spectral sensitivity region of the photoreceptor 7, and the light sensor 9 as a second original sensor for detecting the background density of the original 1 is as shown in FIG. As shown in Figure a, the component properties of blue, which is a complementary color to yellow, are as follows. Further, the background information of the original is inputted to the light sensor 9 through the reflected light from the original 1 via the mirror 4.degree. 5.6 and the lens 8. The original sensor 9 is composed of a filter with characteristic tV as shown in Fig. 2a and a C0D (charge coupled device). By scanning the original 1, the original illumination lamp 3 (a halogen lamp with a rating of 80 V and 200 W) lights up at 60 V, and the original 1 is moved to the mirror 4.
By running the mirror 5.6 at the same process speed Ml m/SeC and at Ml/2 m/sec, the background information of the document is input to the optical sensor 91C. The information input to the original sensor 9 is input to the DC controller 13 via the A/D conversion circuit 10t. Then, the CCD output value inputted to the DC controller 13 determines the original lamp lighting voltage according to the original information according to the original background reflection density and the original lamp lighting voltage shown in FIG. By illuminating the document 1t with the lighting voltage during the copying operation, a proper image can be obtained.

Here, for example, the background reflection density of the original is 07 and 0.30.
The spectral reflectance of d is as shown in FIG.

When f and F, the CCD output value from the light sensor 9, which is sensitive only to the blue region, is as shown in Fig. 4 [Yes], ■, and when the background reflection degree of the original is 0.07 (blank paper), The lamp lighting voltage during copying operation is 60V, and the degree of reflection # on the background of the original is 0.
．． 30 (a newspaper-sized original), the lamp lighting voltage during the copying operation is controlled to 70V.

By the way, if the manuscript 1 is a second manuscript or a thin letter used in government offices, illuminating it with the manuscript illumination lamp 3 will cause
The illumination light passes through the original 1f and illuminates the original pressing plate 15. Therefore, the reflected light from the original 1 is d in Figure 3.
Although the original sensor 9 has the spectral reflectance characteristics shown in
cannot distinguish between yellow and black due to its photosensitive properties. Therefore, it is determined that the background of the image is dark, and the COD output is shown in FIG. 4 O]. Normally, the lamp lighting voltage is 60V and a proper image can be obtained, but since the lamp is turned on at 70V during the copying operation, the image density decreases. For this reason, in this embodiment, as shown in FIG. 2b, an original sensor 11 is newly arranged as a first optical sensor that has a complementary color relationship with the original sensor 9 and has a spectral transmittance characteristic. be. The output of the original sensor 11 is input to a DC controller 13 via a conversion circuit 12.

In other words, the spectral reflectance of the light reflected from the second original drawing or the thin letter or yellow manuscript used in government offices is low in the range of 400 to 500 nm, as shown in d in Figure 3, and is 50 nm.
It is high in the range of 0 to 700 nm. On the other hand, for normal blank paper or originals with background density, 400
As shown in e and f of FIG. 4, the values are almost uniform in the range of ~7QQnm.

Thus, the output value of the original sensor 11 is high, and the optical sensor
When the output value of 9 is low, the yellow original is used, and the light sensor -1
If the output values of 1 and the original sensor 9 are both at the same level,
The DC controller 13 may determine that it is a normal document. As a result, the lamp lighting voltage is fixed at 60V for yellow or thin originals, and for other originals, the lamp lighting voltage is controlled according to the CCD output value, so that an appropriate image can always be obtained. You will get it.

(Effects of the Invention) The image density adjusting device according to the present invention has the above-described configuration and operation, and includes a primary sensor @1 having a spectral value approximately equal to the maximum spectral sensitivity region of the photoreceptor, and this first sensor. The optical sensor and the second source sensor with complementary color spectral sensitivity detect all of the original information, and the background density detection output of the original is controlled based on the detection result, so it is possible to detect thin originals and original pressure plates. This has the effect that an appropriate image can always be automatically obtained even for originals with the same color as the background.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of an image density adjusting device according to the present invention, FIG. The figure is a graph showing the spectral reflectance of the document pressure plate and various documents in the same embodiment, and FIG. 4 is a graph showing the relationship between the CCD output value and the lamp lighting pressure in the same embodiment. Explanation of symbols 1... Original, 7... Photoconductor, 9... Original sensor (second original sensor), 10... Le conversion circuit, 11... Optical sensor (second original sensor). 1 original sensor), 12...
・, guy conversion circuit, 13...DC controller. 3. Go to Figure 1 fI+fl Figure 2

Claims (1)

[Claims] Document information is detected by a first photosensor having a spectral sensitivity that almost matches the maximum spectral sensitivity region of the photoconductor, and a second photosensor having a spectral sensitivity of a complementary color to this first photosensor, and this detection An image density adjustment device characterized by controlling the background density detection output of a document based on the result.