JPS61281229A - Quantity of light detecting device in copying machine - Google Patents

Abstract

PURPOSE:To obtain a correct detecting value even when the density is shifted in the width direction of an original by providing a photodetecting window whose central part is narrow but becomes gradually winder as it goes to the end part and providing a hood to regulate the photodetecting scope of a photodetecting element. CONSTITUTION:The output value of a photodetecting element 43 is gradually reduced as the directional angle is increased. To correct the output of the photodetecting element 43 having such a directional characteristic, the opening degree in the vertical direction of a photodetecting window 41 is made to become larger as it goes to the end part. Thus, after the irregular reflection is executed directly from an original surface 27 or in a copying machine 1, the disturbance light to arrive at a luminous energy detecting device 40 is interrupted by a hood 42, only the reflecting light to arrive through respective mirrors 22, 23 and 24 passes through the photodetecting window 41, and is photodetected by the photodetecting element 43 in the condition being corrected by matching with the directivity of the photodetecting element 43.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a light amount detection device that is used with an automatic exposure adjustment device in a copying machine and detects light reflected from a document.

BACKGROUND OF THE INVENTION In recent years, automatic exposure devices have been provided in electrophotographic copying machines and the like that control the amount of exposure depending on the image and color condition of a document to automatically obtain an appropriate density of a copied image.

Generally, these devices measure density changes by detecting reflected light from a document illuminated by a lamp, and control the power supplied to the lamp according to the detected value. Various proposals have been made as detection means. is being done.

As one means of this, there is a device disclosed in Japanese Patent Application Laid-Open No. 57-29060. As shown in Fig. 5, the light receiving element (3) is provided near the projection lens (5), and the original
The reflected light is detected after passing through a mirror system (6) and a lens (5). Therefore, the light receiving element (3) can receive all the reflected light from the document illumination area.

Problems to be Solved by the Invention However, in this device, as shown in FIG. This has the disadvantage that accurate detection values cannot be obtained because it is a range in which not only reflected light (but also other disturbance light (B+) is received).

Furthermore, the light-receiving element (3) has a directional characteristic that outputs different values depending on the incident angle even if the amount of light is the same, and when receiving reflected light from a document with a biased density distribution, There is an inconvenience that the detected value differs depending on whether the deviation is at the center or at the end in the slit direction.

The present invention aims to solve the above-mentioned frame problems.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides a light-receiving element disposed on the side of the projection lens, a light-receiving element that is narrow at the center, and wide (formed) toward the ends. and a hood for regulating the light receiving range of the light receiving element so as to receive only reflected light arriving from the document illumination area via the mirror system.

Function In the present invention, disturbance light is blocked by the hood, and only the reflected light that reaches the mirror system passes through the light receiving window.
Further, the light is detected in a state in which the directivity characteristics of the light receiving element are corrected depending on the shape of the window.

Example Embodiments of the present invention will be described below with reference to the drawings.

FIG. 4 schematically shows the configuration of an electrophotographic copying machine (11) that performs one-sided sheet feeding as an example of a copying machine equipped with the light amount detection device of the present invention. A photoreceptor drum (10) is supported rotatably in a counterclockwise direction, and an erase lamp (11) is arranged around it.
, a charging charger (12).

Developing device (13), transfer charger (14), separation charger (technique 5), and cleaning device (16)
etc. are arranged in order.

In the scanning optical system (20), the lamp (21) and the first scanning mirror (22) integrally move to the left in the figure, and the second scanning mirror (20) moves at a speed b. The third scanning mirrors (23) and (24) also scan the original (0) on the original glass (27) by moving to the left, and the projection lens (25).

A rotating photoreceptor drum (
10) Slit-expose the original image on top.

A toner image corresponding to the original image is formed on the surface of the photoreceptor drum (10) by passing through the steps of charging two images, exposure and development, and this toner image is transferred to the transfer charger (14).
) part, the Mi roller (31) of the copy paper conveyance system (30)
, a timing roller (32), etc., onto a copy sheet that is conveyed in synchronization with the image forming operation.

The copy paper that has passed the transfer process is transferred to a separation charger (15)
The image is separated from the surface of the photoreceptor drum (10) by the fixing roller (33), and then transferred to the tray (34).
) and the copying is completed.

The copying machine (1) that performs the copying operation as described above operates with a lamp (
21) Equipped with an automatic exposure device that controls the amount of light emitted,
Copies with appropriate density can always be obtained.

The light amount detection device (40) has a light receiving window (
A cylindrical hood (41) with a cylindrical hood (42) on the tip surface.
2), and a light-receiving element (43) fixed to the bottom of the document surface (27), as shown in FIG.
) is arranged on the side of the projection lens (25) in such a direction that it can receive reflected light from the projection lens (25) through the light receiving window (41). In this embodiment, a photodiode is used as the light receiving element. The horizontal length (X) of the light receiving window (41) corresponds to the width of the document (0) to be scanned, and in this example, the horizontal length of A4 size, which is often used as the document width, is used as the standard. It is said that Maximum vertical width of light receiving window (41) (Yl)
is the first of the mirrors (22), (23), and (24) that guide the reflected light from the original (0) to the projection lens (25).
The length of the mirror (22) in the horizontal direction is 72 mm, and
The maximum length in the vertical direction (Yl) is set to 2H.

Here, the shape of the light receiving window will be explained in detail using FIG. 3.

Since the light receiving element (43) has directional characteristics, the third r
g: Jfb+, the output value of the light receiving element (43) gradually decreases as the directivity angle increases, as shown in (A) in the figure. For example, if the directivity angle is 00, it is 100%, then the directivity angle corresponding to the end of the light receiving window (41) is 14%.
It decreases by 4% when the temperature is . In order to correct the output of the light receiving element (43) having such directional characteristics, the light receiving window (41
) should be increased toward the end, and if the aperture is changed as shown in (b) according to the directivity angle, the output value of the light receiving element (43) will be as rX+. It becomes constant. Therefore, the light receiving window (41
) is set as shown in Table 1.

In this embodiment, the light amount detection device (40) is used directly from the document surface (27) or after being diffusely reflected within the copying machine (1).
) is blocked by the hood (42), and only the reflected light that reaches the mirrors (22), (23), and (24) passes through the light receiving window (41). ), the light is received by the light receiving element (43) after being corrected according to the directivity of the light receiving element (43).

Note that the present invention is not limited to the above embodiments,
The dimensions of the light-receiving window change depending on the type of light-receiving element and its settings. Needless to say, it can also be applied to a copying machine.Furthermore, since the length and width of the reflected light from the document reaching the mirror system do not change even in a copying machine equipped with a variable magnification function, the above-mentioned embodiment can be applied. It can be applied in the same way.

Effects Since the light amount detection device of the present invention has the above-described configuration, the disturbance light that arrives directly from the document illumination area or after being diffusely reflected within the copying machine is blocked by the hood and is not received. Only the reflected light that reaches the mirror system is received by the light receiving window after being corrected to match the directivity of the light receiving element, so even if the density is uneven in the width direction of the document, it will be accurate. It is possible to obtain accurate detection values.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing a light amount detection device according to an embodiment of the present invention, Fig. 2 is a plan view showing the arrangement of the light amount detection device, and Fig. 3 (al is a front view showing the shape of the light receiving window; 3) is a graph showing the relationship between the aperture of the light-receiving window and the output value of the light-receiving element, FIG. 4 is a schematic configuration diagram of a copying machine according to the present invention, and FIG. 5 is an explanation showing a conventional light amount detection device. FIG. 6 is a diagram showing the light receiving range of the light amount detection device shown in FIG. 5. (1)... Copying machine, (10)... Photoreceptor, (20)
... Mirror type, (21) ... Lamp, (25)
...projection lens, (40) ...light amount detection device, (4
1)...Light receiving window, (42)...Hood, (43)...
··Light receiving element. Applicant Minolta Camera Co., Ltd. Figure 1 ? Figure 3 (α) Figure 3 (b) Direction inside Figure 4 Figure 5P

Claims (1)

[Claims] 1. An automatic exposure device that detects reflected light from a document illuminated by a lamp and controls the power supplied to the lamp according to the detected value, and includes a mirror system and a projection lens. A copying machine that slit-exposes an image of an original onto a photoreceptor, comprising a light receiving element disposed on the side of the projection lens, and a light receiving window that is narrow in the center and widens toward the ends; A light amount detection device comprising: a hood that regulates a light receiving range of the light receiving element so as to receive only reflected light arriving from a document illumination area via a mirror system.