JPH0436381B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Technical Field> The present invention relates to a document density detection and exposure adjustment device in an electrophotographic copying machine.

<Prior Art> Currently, there are two main types of document reading methods in electrophotographic copying machines: through-lens systems and focusing light transmission body (optical fiber lens) systems. Exposure adjustment in these methods was carried out manually, in which an operator looked at the obtained copy and adjusted the exposure dial or volume. For this reason, not only does the appropriate exposure of the document change depending on the operator's visual perception, but also there is a disadvantage that there is a lot of work waste as multiple copies are required to adjust the exposure in order to obtain a single copy with the appropriate exposure. It was hot.

<Objective of the present invention> The present invention has been made in view of the above circumstances, and it improves the above drawbacks and provides an improvement to the conventional optical means for forming an image on a photoreceptor using a converging light transmitting lens. It is an object of the present invention to provide a copying machine equipped with an exposure light amount control system that can detect the density of a document based on average light reception and adjust the exposure amount with a simple configuration.

<Embodiment> FIG. 1 is a sectional view showing an embodiment in which the present invention is applied to a copying machine with a convergent optical transmission system. This embodiment shows a case in which the copying machine has a movable document table which sequentially exposes the documents 9 while moving in the right direction 14 and returns to the left direction 14' after exposure. In the figure, reference numeral 1 denotes a converging light transmitting body for irradiating a document 9 on a document table 4 with light from a light source 2 and for focusing the reflected light from the document 9 onto a drum-shaped photoreceptor 8. It is. The light source 2 is provided with a reflector 3 to irradiate the document 9 with light in a concentrated manner.
This configuration is such that the exposure image forming portion 9a of the original 9 is irradiated in a concentrated manner. An electrostatic latent image is formed on the photoreceptor 8 by projecting the image of the document 9 onto the photoreceptor 8 using the convergent light transmitter 1 .

On the other hand, in order to control the amount of light from the light source 2 according to the density of the original 9, a document density detection device is arranged adjacent to the convergent light transmitter 1. In other words,
9 of the original 9, especially a little away from the imaging exposure area 9a.
Opening 6 through which reflected light from b (exposure detection section) passes
A light shielding member 6 having an opening 7 a and a light shielding member 7 having an opening 7 a are provided, and an optical path 11 is formed by the openings 6 a and 7 a of these light shielding members 6 and 7 . On this optical path 11, light receiving elements 5 are provided in a dotted manner. Here, the term "point-like" refers to the openings 6a, 7a.
This means that the reflected light is smaller and converges behind the opening. Therefore, the light amount control of the light source 2 is executed according to the amount of light received by the light receiving element 5.
For example, if the amount of light received is large, the document 9 itself will appear white, and control such as reducing the amount of light from the light source 2 will be performed.

Therefore, the light shielding member 6 is for holding the convergent light transmitting body 1, for example, and transmits the reflected light from the exposure amount detection section 9b of the original 9 to the light receiving element 5 on its upper surface.
An opening 6a is formed to form an optical path 11 for guiding the light. Further, the light shielding member 7 is located between the light shielding member 6 and the light receiving element 5, and is, for example, a frame 15.
installed on. The light-receiving element 5 is mounted via a support member 17 on a light-shielding plate 16 that forms a slit when the photoreceptor 8 is exposed to light using the focusing light transmitter 1 .

As described above, the irradiation light 12 obtained by focusing the light from the light source 2 with the reflector 3 irradiates the imaging exposure area 9a of the document, and the reflected light 13 is transmitted through the converging light transmission body (optical fiber lens) 1. The light is guided to the surface of the photoreceptor 8 and forms an image corresponding to the image of the imaging exposure section 9a. On the other hand, the openings 6a and 7a provided on the light shielding members 6 and 7 and the light receiving section 5 are connected to the imaging exposure section 9.
The light amount of the light amount detecting section 9b in front of the light receiving section 5
The exposure light amount detection light section 11 is arranged so as to be able to be detected by the exposure light amount. The light shielding members 6 and 7 in the present invention block unnecessary light that enters the light receiving section 5 from sources other than the exposure amount detection section 9b, such as specular reflection light from the document mounting table and the document, and direct light from the light source, thereby accurately determining the exposure amount. This is provided to enable the exposure amount to be controlled by the reflected light from the detection section 9b, and this embodiment shows a case where two light shielding members 6 and 7 are used. However, it goes without saying that any one of the light shielding members may be used as long as unnecessary light can be completely blocked. It is also clear that an optical path for detecting the amount of exposure light can be formed by using an opening provided in one light-shielding member and a light receiving section, with an arbitrary portion of the document serving as the exposure amount detection section.

In this embodiment, the specularly reflected light is reflected from the document surface and the document table through the specularly reflected optical path 10 at the same angle as the angle α of illumination between the document surface and the exposure optical path. Therefore, the exposure light amount detection optical path 11 is the specular reflection optical path 10.
A signal with a better S/N ratio can be obtained by setting it as far away as possible. However, if the exposure light amount detection optical path 11 and the specular reflection optical path 10 are too far apart, the exposure amount detection section 9b may be far away from the imaging exposure section 9a, or the exposure amount detection section 9b may be located behind the imaging exposure section 9a. Therefore, there may be a delay between the image exposed on the photoreceptor and the image information to be controlled. For these reasons, the position of the light-receiving element in this embodiment is such that the specular reflection component is not received as much as possible, and the exposure amount detection section 9b is set so that the image portion is exposed to the photoreceptor at the same time or the next time. It is convenient to set this.

FIG. 2 is a perspective view of the present invention applied to a copying machine with a convergent optical transmission system, and the numbers and names of the parts are the same as in FIG. 1. Here, openings 6a and 7a provided on the light shielding members 6 and 7
shows a shape that can uniformly receive light over the depth direction of the exposure detection section 9b, but its length may be arbitrarily set depending on the size of the document.

Regarding the width of the openings 6a and 7a, if the widths of the openings 6a and 7a are too narrow, the amount of incident light from the exposure amount detection section 9b of the original 9 will decrease, making it impossible to receive the light, and if the widths are too wide, the above-mentioned unnecessary light (regularly reflected light, direct light, etc.) will be reduced. enters the light receiving section, making it impossible to obtain accurate reflected light from the exposure amount detection section 9b. Therefore, taking into consideration the light-receiving characteristics of the light-receiving element used in the light-receiving section 5, the distance between the light-receiving section 5, the exposure amount detection section 9b, and the light shielding members 6, 7, etc., it is possible to detect the exposure amount detection section 9b of the document 9 from the light reception section. It is necessary to set the width so that a uniform and accurate signal can be obtained over the depth direction.

FIG. 3 shows a specific example of the shape of the apertures 6a and 7a that can uniformly receive light over the depth direction of the exposure detection section 9b with respect to the light receiving element 5 arranged at the center of the aperture. Shown in the figure.

Furthermore, it is also possible to arbitrarily set the light receiving distribution by providing a grid pattern in the openings 6a and 7a as shown in FIG. For the light-receiving element 5 placed at the center of the aperture, it is possible to obtain a uniform distribution by making the grid pitch of the aperture denser in the center and coarser in the periphery. Furthermore, instead of changing the grid pitch, it is also possible to make corrections by changing the grid width. Its characteristics are shown in FIG.

In addition, although it is ideal to install the light receiving element 5 at an angle such that the light receiving surface is perpendicular to the optical path, unnecessary light such as wraparound light may be reflected from the exposure amount detection part. It is okay to have some blur within a range that does not become large compared to the light. This embodiment shows a case where the exposure amount detection section 9b is located in front of the imaging exposure section 9a, but in this case, after the reflected light from the exposure amount detection section 9b is received by the light receiving section 5, its output signal is This is based on the control circuit (not shown) that controls the light intensity of the light source 2 and takes into account the delay until the light intensity actually changes. Of course, it is also possible to align the exposure amount detection section 9b with the imaging exposure section 9a.

In the above embodiments, the case where reflected light from the original is used has been described, but it is clear from the structure of the present invention that the same can be done when using transmitted light.

<Effects of the Invention> According to the present invention, in an optical path formed separately from the optical path for forming an image of the reflected light or transmitted light from the original on the photoreceptor, the reflected light or transmitted light from the original is transmitted to the original. Since a light shielding member is provided between the light receiving section and the light receiving section, the light shielding member is formed in a shape that allows almost uniform density detection over the depth direction of the exposure detecting section.
The light shielding member can remove unnecessary light from sources other than the exposure amount detection section, making it possible to accurately detect the density based on average light reception and control the exposure amount based on the density detection.

Further, since it is possible to average light over a wide range with a single dot-shaped light receiving element, stable exposure amount detection can be performed regardless of the detection location.

In addition, since the optical path for exposure detection is provided separately from the optical path of the imaging optical system, there are problems with installing an exposure detection unit in the optical path of the imaging optical system, such as background stains and the need for a light source. The above burden etc. can be removed.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing details of the exposure light amount detection portion according to the present invention, FIG. 2 is a perspective view of FIG. 1, and FIG.
Fig. 4 is a top view showing an example of the shape of the opening formed in the light shielding member of the present invention, and Figs.
FIG. 5 is a diagram showing light-receiving characteristics at the light-receiving section in FIGS. DESCRIPTION OF SYMBOLS 1... Focusing light transmission body, 2... Light source, 4... Light source mounting stand, 5... Light receiving element, 6, 7... Light shielding member, 6a, 7b... Opening, 8... Photoreceptor, 9 …
... Original, 11 ... Optical path for detection, 13 ... Optical path for imaging.

Claims (1)

[Scope of Claims] 1. Light from a light source arranged such that the longitudinal direction is perpendicular to the scanning direction of the document is irradiated onto an image-forming exposure area of the document, and the light reflected from the image-forming exposure area is In an electrophotographic copying machine that is provided with an optical path for forming an image of light on the surface of a photoreceptor through an optical system, an exposure amount detection section is located at a position slightly downstream in the document scanning direction from the exposure section for image formation on the document surface. and an opening configured to allow reflected light from any part of the exposure amount detection section to pass through so that the amount of light passing through the central portion is smaller than the amount of light passing through the end portions. , a light shielding member provided to block unnecessary light such as specularly reflected light from the original and direct light from the light source, and a part of the reflected light from the exposure amount detection section to be averaged through the aperture. A light-receiving portion is provided in a dotted manner behind the central portion of the aperture so as to be able to receive light, and an optical path for detecting the exposure amount formed by is provided outside the optical path for image-forming the document, and 1. An electrophotographic copying machine characterized in that the amount of light from a light source is controlled by correcting a time delay until the amount of light changes based on an output signal from a light receiving section that receives light.