JPS6290639A - Fitting structure for automatic exposure sensor - Google Patents

Abstract

PURPOSE:To eliminate an error in the quantity of sensor photodetection by providing plural light sources which are higher in brightness toward both end parts in a direction perpendicular to the scanning direction of an optical system and fitting an optical sensor which photodetects reflected light from an original slantingly according to the brightness of a light source. CONSTITUTION:An optical system light source unit 1 is formed in a hollow box shape and a reflector 2 and plural light sources 3 are provided inside. Further, an opening part 1a is provided and light from the light sources 3 are distributed. A sensor box 4 is provided on the reverse surface of the unit 1, and optical (AE) sensors are provided therein to photodetect the reflected light from the original through the hole part 2a. Further, the plural light sources 3 are higher at both end parts than at the center part and the AE sensors are fitted at different tilt angles according to their arrangement positions. Consequently, the quantities of photodetection arranged at the end parts is equalized to that of an AE sensor arranged horizontally at the center part. Thus, the AE sensors are fitted slantingly according to the deviation from the center position, so the output value of each AE sensor corresponds to the reference brightness of the light sources and an accurate exposure adjustment is made.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a mounting structure for an automatic exposure sensor (hereinafter referred to as an AE sensor) that detects the density of a document to be copied in an electrophotographic copying machine.

<Background of the Invention> In an electrophotographic copying machine, an image of a document placed on a document table is scanned by light from a light source including an optical system, and the reflected light is distributed onto the surface of a photoreceptor for exposure. The reflected light from the original passes through an optical system lens and is distributed onto the surface of the photoreceptor. This is to accurately form the image of the original onto the surface of the photoreceptor.

Generally, in a copying machine, the illuminance at both ends in a direction perpendicular to the scanning direction of the optical system is lower than that at the center due to the characteristics of the optical system lens. That is, as shown in FIG. 4, the light from the light source reflected on the document surface 1 forms an image on the photoreceptor surface 23 via the optical system lens 22. As shown in FIG. At this time, one point x on the photoreceptor surface 23
1, the illuminance L1 at the central point X on the photoreceptor surface 23 is
When the illuminance of is L, it is expressed as L l = Lc,,' θ. Here, θ is the angle between the point X and the point X1 with respect to the optical system lens 22, and the angle between the optical system lens 22 and the point
The distance between! , where X is the distance between point X and point x1, there is a relationship of θ=van −' (X/N). Therefore, the farther the point X1 is from the point X and the larger the angle θ becomes, the lower the illuminance L1 becomes.

For this reason, conventionally, in order to eliminate the difference in image density in the direction perpendicular to the scanning direction of the optical system, multiple light sources are arranged in a straight line so that the brightness is higher at both ends in the direction perpendicular to the scanning direction of the optical system. Ta. However, with automatic exposure equipment that detects the density of the original by receiving the reflected light from the original, and changes the amount of exposure to the photoreceptor surface according to the detected value, the reflected light generally does not reach the optical system lens. At step 11, the reflected light is received by an optical sensor. Therefore, if this sensor is installed far away from the light source having the luminance that is the reference for concentration detection in the direction perpendicular to the scanning direction of the optical system, an error will occur in the amount of light received, and it will not be accurate. Automatic exposure adjustment could not be performed.

<Object of the Invention> In view of the above-mentioned conventional drawbacks, the object of the present invention is to eliminate errors in the amount of light received by an AE sensor caused by differences in the brightness of the light source in the direction perpendicular to the scanning direction of the optical system, and to provide accurate automatic exposure adjustment. It is an object of the present invention to provide a mounting structure for an AE sensor that can be used.

<Configuration and Effects of the Invention> The mounting structure of the AE sensor of the present invention is such that the brightness becomes higher at both ends in the direction perpendicular to the scanning direction of the optical system.
f5j, in which several light sources are installed in a straight line, an optical sensor that receives the light reflected from the light source from the document table and changes the output value according to the amount of received light is connected between the light source and the optical system lens. It is characterized in that it is mounted with an inclination angle that corresponds to the brightness of the light source facing the mounting position.

With the above configuration, according to the present invention, in order to compensate for the decrease in illuminance of exposure in the direction perpendicular to the scanning direction of the optical system caused by the characteristics of the lens, the brightness is made higher at both ends than at the center. When the AE sensor receives the light reflected from the original by the configured light source, it is possible to give an inclination angle corresponding to the deviation of the mounting position of the AE sensor from the center. This angle of inclination reduces the area of the light-receiving surface of the AE sensor in the horizontal position, and reduces the amount of reflected light received. Since the tilt angle given to the AE sensor is determined according to the brightness of the light source facing the mounting position, the amount of decrease in the amount of received light also corresponds to the brightness of the light source facing the mounting position. As a result, it is possible to eliminate errors in the amount of received light due to differences in the intensity of the light source, and it is possible to set the output value from the AE sensor to a value that corresponds to the reference brightness of the light source, allowing accurate automatic exposure adjustment. I can do it.

<Embodiment> FIG. 2 is a perspective view of a main part of an optical system in which an AE sensor mounting structure according to an embodiment of the present invention is used.

The optical system light source unit 1 is formed into a hollow box shape. A reflector 2 is provided inside the optical system light source unit 1, and a plurality of light sources 3 are provided in the center of the reflector 2. An opening 1a having a longitudinal direction perpendicular to the scanning direction of the optical system is formed in a part of the outer surface of the optical system light source unit 1. The reflector 2 distributes light #3 in the direction of the opening 1a. A sensor box 4 is attached to the bottom surface of the optical system light source unit 1. This sensor box 4 has a built-in AE sensor, which will be described later. A hole 2a is provided in the reflector 2 at a position corresponding to the mounting position of the sensor box 4. As a result, the reflected light of the light source distributed from the opening 1a toward the document table passes through the hole 2a and is received by the AE sensor in the sensor bomb lath 4.

FIG. 1 is a perspective view of a sensor box that constitutes a part of the above-mentioned mounting structure.

An AE sensor is mounted at an inclined angle approximately in the center of the sensor box 4 .

The angle of inclination given to the AE sensor 5 is determined according to the brightness of the light source facing the mounting position of the sensor box 4. That is, as shown in FIG. 3, a plurality of optical system lights rA3 are provided in a straight line in a direction perpendicular to the optical system scanning direction, and are configured so that the brightness at both ends is brighter than that at the center. There is. By appropriately tilting the AE sensor 5 that receives the reflected light of the optical system light rX3 from the document table according to its placement position, the AE sensor 5 is placed horizontally in the center indicated by the two-dot chain line in the figure. ' is the optical system light source 3 in the central part
The amount of light received can be made equal to the amount of light received at the brightness S0. As a result, the brightness S at the center becomes the reference for the optical system light source at any position in the direction perpendicular to the optical system scanning direction.

It is possible to output the same detection value as when receiving light in a horizontal state.

Therefore, the AE caused by the difference in brightness of the optical system light source 3
Errors in sensor output values can be eliminated.

Note that the angle of inclination of the light-receiving surface of the AE sensor 5 facing the optical system light source 3 is reduced to C8,α, where α is the inclination angle.

The inclination angle of the AE sensor 5 can be calculated by selecting the value of cos α so that it is the reciprocal of the increase rate of the brightness S of the optical system light source 3 facing the position where the AE sensor is installed relative to the reference value S0. can. But actually A
Since the amount of light received may vary depending on the material of the light-receiving surface of the E-sensor 5, etc., the actual tilt angle should be determined through experiments with reference to the calculated angle α.

Further, in this embodiment, only one AE sensor is installed, but even if multiple AE sensors are installed in the direction perpendicular to the scanning direction of the optical system, this invention can easily be applied to a real gun and the same effect can be obtained. I can do it.

[Brief explanation of drawings]

Fig. 1 is a perspective view of a sensor box constituting a part of the mounting structure of an AE sensor according to an embodiment of the present invention;
f1l is a perspective view of the main parts of the optical system using the same mounting structure, and FIG. 3 is a diagram showing the relationship between the brightness of the light source and the tilt angle of the AE sensor, which constitutes a part of the optical system using the same mounting structure. It is. FIG. 4 is a diagram showing the light distribution state of the optical system. 3-Optical system light source, 5-Ami sensor.

Claims (1)

[Claims] (1) Optical system Multiple light sources are arranged in a straight line so that the brightness becomes higher at both ends in the direction perpendicular to the scanning direction, and the light reflected from the light sources from the document table is received and the A mounting structure for an automatic exposure sensor, characterized in that an optical sensor that changes an output value is mounted between the light source and an optical system lens with an inclination angle corresponding to the brightness of the light source facing the mounting position.