JPS58137859A - Exposure detecting device - Google Patents

Abstract

PURPOSE:To perform exposure detection without generating deficiency of image and without decreasing the amount of light that contribute to image formation, by providing a light transmitting part in a part of reflecting plane of an in- mirror lens and providing a light detecting section behind it. CONSTITUTION:Light emitted from an exposure lamp is reflected by the surface of an original and arrives at mirrors 11, 12 and an in-mirror lens 13. Light rays that contribute to image formation arrive at a photosensitive body 15 through a mirror 14. A small opening 17 that forms a transmitting part is provided in the reflecting plane 16 of the in-mirror lens 13. Light incident on this small opening arrives at a photosensor 18 and exposure detection is performed. Accordingly, the exposure detection is performed without causing deficiency of the image and without decreasing the amount of light that contribute to image formation.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device that detects the amount of exposure by detecting the illuminance on the surface of a document in a mold exposure device.

In general, the surfaces of the parts that make up the exposure device of a copying machine, such as lenses and mirrors, tend to get dirty, so the amount of light transmitted decreases after long-term use, and this is the main cause of deterioration in image quality on the photoreceptor. This is one of the causes. In other words, this causes a decrease in image density and causes image blanking.

Furthermore, the output of the lamp that illuminates the document surface decreases over time, so the amount of light reaching the photoreceptor decreases, causing a decrease in image quality.

Therefore, it has been considered to detect the illuminance of the document surface by some means and use the detected signal to control the output of the irradiation device or the photoreceptor device. Conventionally considered light detection means include one in which a detection portion t is provided in the vicinity of the round object surface mirror O closest to the space between the documents;
There are some types in which a detection section is provided near the gIIrM mirror closest to the photoreceptor, but all of them cause some kind of loss in the image.

Furthermore, there are nine other photodetection means shown in FIG. This light detecting means has a configuration in which the mirror lens 1 has a medium-transmissive surface 2, and a light detecting section 3 is disposed at the rear of the lens 1. Hot! Since only half contributes to image formation on the photoreceptor surface S, energy consumption increases. In addition, in such a device, the size of the photodetector 3 is approximately the same as the aperture diameter of the lens 1! Similarly, the secondary reflected light from the photoreceptor is also detected, making it impossible to accurately detect the amount of light.

Therefore, it is an object of the present invention to provide a traveling light amount detection device that can reduce the decrease in the amount of light contributing to image formation without causing any loss in the image.

In order to achieve this object, the present invention provides an optical device having an in-mirror lens, in which a light transmitting section is provided on a part of the reflective surface of the in-mirror lens, and a light amount detecting section is provided behind the nuclear light transmitting section. This device is characterized in that it is configured to perform illuminance photometry on the object surface.

That is, in the light amount detection device according to the present invention, a light transmitting portion is provided on a part of the reflective surface of the in-mirror lens, and a light amount detecting portion is provided behind the light transmitting portion. By providing a light amount detection section behind the mirror surface, the decrease in the amount of light that contributes to image formation can be made smaller than in a mirror. Furthermore, if the light amount detection section is placed on the extension line connecting the original surface exposure section and the light transmission section, the secondary reflected light from the photoreceptor will not reach the light amount detection section, and accurate light amount detection will be possible. It becomes possible.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of the present invention. In FIG. 11 and reaches the in-mirror lens 13. The light beam contributing to image formation reaches the photoreceptor 15 via the first mirror 11 . As shown in detail in FIG. 3, the reflective surface 1 of the in-mirror lens 13
6 is provided with a small opening 17 forming a non-reflective transmissive portion,
A light detection section (sensor) 19 is arranged on an extension line of the non-reflection transmission section 17 and the document surface exposure section 18. If the optical sensor 19 is arranged in this manner, the secondary reflected light from the exposure section 20 of the photoreceptor 15 will not reach the optical sensor 19, making it possible to accurately detect the amount of light. Furthermore, by making the range of light incident on the optical sensor 19 coincide with the document irradiation width ^, light detection can be performed efficiently.

In fact, the focal length f=2! fOwm, original irradiation width ^ = 70
■, Lens aperture diameter = 30 mm, non-reflective transmitting part diameter d =
In the case of 2 wI, the illuminance of the entire document irradiation width can be known by setting the center point 19 within about 5 degrees behind the lens. Further, as can be easily seen from the figure, the secondary reflected light from the exposure section 20 of the photoreceptor 15 is transmitted to the senna 19.
does not reach. In this fil, the in-mirror lens 13
Of the light incident on the lens, the light that reaches the center 19 has almost no adverse effect on imaging.

The non-reflective transmitting portion 11 may be located anywhere within the lens aperture. For example, it is also possible to install the sensor 1 at a slight inclination in the sty direction in FIG. 1 to detect light in the margin of the image. In this case, it is possible to detect the amount of light without being affected by the image of the original.

As described above, in the exposure amount detection device of the present invention, a light transmission section is provided on a part of the reflective surface of the ink 2-lens, and a light amount detection section is provided behind the light transmission section. Exposure amount detection can be performed without causing any defects in the image and without significantly reducing the amount of light contributing to image formation.

[Brief explanation of the drawing]

FIG. 1 is a side view of a conventional exposure amount detection device. FIG. 2 is a perspective view of the optical system that constitutes the exposure amount detection device of the present invention. Figure 3 is a side view of the exposure amount detection device shown in Figure 1. 1.13... In-mirror lens, 3.18...
...Photodetector, 11...Seventh mirror, 12...
・・First mirror, 14・・・・・First mirror, 1s・・・・
...Photoreceptor, 1T...Non-reflective transmissive part.

Claims (1)

[Claims] In an optical device having an in-mirror lens, a light transmitting part is provided on a part of the reflective surface of the in-mirror lens, and a light amount detecting part is provided behind the nuclear light transmitting part to perform illuminance photometry on an object surface. An exposure amount detection device characterized by the following.