JPH02253275A - Copying machine - Google Patents

Abstract

PURPOSE:To facilitate the compensation of focus deviation by detecting a deviation of brightness distribution of a scanning beam which responds to a deviation in length of an optical path with a line photo sensor. CONSTITUTION:When there is ruggedness on the surface of an original (b) which is set on an original platen (a), or when there is a space in between the original platen (a) and the original (b) due to a defective setting, a brightness peak in the brightness distribution of the scanning beam (c) which is passed through a half mirror 20 and a lens 40 is deviated from a beam axis of the lens 40 by a length of DELTAl. In a microcomputer, by deriving the size, etc., of the DELTAl, the deviation of the optical path length is always recognized, and the relative position of an optical structure for original scanning 12 against an optical structure for drum projecting 11 is compensated responding to this. As a result, in the state where there is a space between the original platen (a) and the original (b), a bright image without deviation of focus is obtained.

Description

[Detailed description of the invention] <Industrial application field> The present invention relates to an electrophotographic copying machine.

<Prior art> Among copying machines, those with a fixed document table require a constant optical path length from the document surface to the photoreceptor drum regardless of its scanning position. An optical system drive mechanism is provided that drives the scanning optical mechanism in the document scanning direction at a speed ratio of 2:1. Here, the drum projection optical mechanism is an optical unit that includes a light source that emits light toward the document surface, while the document scanning optical mechanism is an optical unit that directs light reflected from the document surface toward the photoreceptor drum. This is an optical unit that includes a guiding mirror and the like.

Conventional copying machines employ a structure using wires and pulleys as shown in FIG. 6 as an optical system drive mechanism for driving them. That is, the drum projection optical mechanism 11 and the document scanning optical mechanism 12 (both of which are only partially shown) are composed of a steel wire 75 and pulleys 71, 72, 74.
By controlling the drive of a motor 73 connected to a steel wire 75, the optical mechanism 11 for drum projection and the optical mechanism 11 for scanning an original are controlled. The optical device 112 is moved to keep the optical path length from the document surface to the photosensitive drum constant regardless of its scanning position.

<Problems to be Solved by the Invention> Since the drum projection optical mechanism 11 and the document scanning optical mechanism 12 are mutually restrained by steel wires 75, the optical path length may be affected for some reason. A disadvantage is that it is structurally impossible to correct any deviations that occur. Discrepancies in the optical path length occur when there are irregularities on the document surface, or when copying from a relatively thick book with the center open, resulting in a shift in focus. This has become a major problem when trying to improve machine performance.

The present invention was devised in view of the above circumstances, and an object of the present invention is to provide a copying machine having a function of detecting a shift in optical path length, which is a cause of focus shift.

<Means for Solving the Problems> A copying machine according to the present invention includes a mirror optical system that guides scanning light from a light source reflected on a document surface on a document table toward a photoreceptor drum, a mirror optical system, and the light source. an optical system drive mechanism that drives each in the document scanning direction; a half mirror provided in the middle of the mirror optical system to take out a portion of the scanning light; and an optical system drive mechanism arranged on the optical axis of the scanning light taken out by the half mirror. and a line photosensor that detects the brightness distribution of the scanning light.

<Function> If the document set on the document table has unevenness or is lifted, the optical path length from the document surface to the photoconductor drum may shift based on the normal case. Similarly, the brightness distribution of the scanning light extracted by the half mirror is shifted.

<Embodiment> An embodiment of a copying machine according to the present invention will be described below. Fig. 1 is a longitudinal sectional view of the copying machine mainly to explain the mirror optical system, Fig. 2 is a perspective perspective view of the copying machine to explain the optical system drive mechanism, and Fig. 3 is an electrical configuration diagram of the copying machine. , 4th
Figures 5 and 5 are diagrams for explaining the principle of detecting deviations in optical path length based on the brightness distribution of scanning light. The cases in which the is abnormal are shown respectively.

First, the mirror optical Uo provided below the document platen a, which is a transparent plate inside the copying machine, will be explained with reference to FIG. The mirror optical system 1o is broadly divided into a drum projection optical mechanism and an original scanning optical mechanism 12, and is movable by being connected to an optical system drive 419iJI50 (see FIG. 2).

The drum projection optical mechanism 11 has a structure in which a light source 111 such as a halogen lamp, a reflecting mirror 112, etc. are attached to a base 113, and in addition to these, a half mirror 20 and a lens 40° line, which will be described later, are attached to the base 113. A photosensor 30 and the like are attached.

On the other hand, the original scanning optical mechanism 12 is a reflection mirror! 21.
122 is attached to a base 123. Both are movable in the document scanning direction indicated by arrows in the figure, and a zoom lens 41, a reflecting mirror 42, and a photosensitive drum 43 are respectively arranged at positions where these cannot come into contact. That is, the scanning light C emitted from the light source 111 in the drum projection optical mechanism 11 is already reflected by the original set on the original platen a, and is reflected by the original 1. A portion of the light is reflected by the notebook mirror 20 and guided toward the original scanning optical mechanism. The scanning light C reflected by the half mirror 20 is reflected by the reflection mirror 1 in the original scanning optical mechanism 12.
21 and 122, and is guided to the photosensitive drum 43 through the zoom lens 4L and reflection mirror 42 in sequence. Furthermore, the scanning light C that has passed through the half mirror 20 is condensed by a lens 40 and guided onto a line photosensor 30 such as a CCD, so that the brightness distribution of the scanning light C can be detected. It has become.

Next, the structure of the optical system driver 1A50 will be explained with reference to FIG. 2. The optical system drive mechanism 50 includes a linear motor 51 for driving the drum projection optical mechanism 11 and a linear motor 5 for driving the document scanning optical mechanism 12.
It consists of 2nd class. First, the configuration of the linear motor 51 will be explained. This consists of movers 512 and 512 respectively attached to both sides of the drum projection optical mechanism 11.
and stators 511, 511, which are attached to the main body of the copying machine, facing the movable element 512, 512,
The movement of one movable element 512 is restricted by the guide member 53. The linear motor 52 also has a completely similar structure, with the only difference being that the stator 511.5i1 and the guide member 53 are common. The linear motors 51 and 52 are all controlled by a linear motor control circuit 6o, which will be described later, and are controlled by the drum projection optical mechanism 11. The document scanning optical mechanism 12 is driven at a speed ratio of 2:1, and the photosensitive drum 5 is scanned from above the surface of the document.
The optical path length up to 3 is made to be the same regardless of the scanning position. Note that the linear motors 51 and 52 are provided with a drum projection optical mechanism 11. Original scanning optical mechanism 12
Encoder 5.1 for detecting each stroke position of
3.523, and although not shown, in the center of each movable element 512.522, a Hall element for detecting the magnetic pole of the stator 511 facing the movable element 512.522 is provided. 514 and 524 are provided respectively.

Next, the linear motor control circuit 60 will be explained with reference to FIG. The linear motor control circuit 60 is a circuit mainly composed of a microcomputer 61 called a software servo, and generates three-phase excitation currents to be supplied to the movers 512 and 522 of the linear motors 51 and 52, respectively. The basic configuration is such that the drum projection optical mechanism 11 and the document scanning optical mechanism 12 are independently driven according to a predetermined speed pattern. To explain in more detail, the microcomputer 61 includes encoders 512 and 52.
3, the data of each stroke position of the drum projection optical device is i i and the document scanning optical mechanism 12 are sequentially introduced, and this data is combined with the pre-stored data giving the speed pattern. Compare the
PWM signals 613 and 614 are respectively generated according to the comparison results. This PWM signal 613.6
14 are respectively introduced into three-phase driver circuits 62 and 63, where three-phase excitation currents to be supplied to the mover 512 and 522 are generated based on the magnetic pole data from the Hall elements 514 and 524. . The microcomputer 61 also has a near motor 51.5 as described above.
2 (drive control unit 611), it also calculates the deviation in optical path length based on data on the brightness distribution of the scanning light C from the line photosensor 30, and also calculates the degree of deviation in the calculated optical path length. Depending on the drum projection optical mechanism 1
1 and the document scanning optical mechanism 12, and corrects a deviation in optical path length (a defocus correction unit 612).

Next, we will discuss the principle by which a shift in optical path length can be detected based on the luminance distribution of the scanning light C from the line photosensor 30.
This will be explained with reference to the drawings and FIG.

Regarding Figures 4 and 5, (a) shows half mirror 2.
0, and (b) is a graph showing the relationship between the position of each element of the line photosensor 30 and the luminance output detected by the element.

The original surface of the original set on the original table a is shown in Figure 4(a).
In an ideal state as shown in FIG. 4(b), the brightness distribution of the scanning light C passing through the half mirror 20 and the lens 40 is as shown in FIG. 4(b).
It has a pattern as shown in FIG. 2, and its brightness peak corresponds to the optical axis of the lens 40. The optical path length in this state is appropriate.

On the other hand, due to unevenness on the surface of the original on the original plate set on the original table a, or due to improper setting, etc., the gap between the original plate and the original plate as shown in FIG. 5(a). When there is a gap between the half mirror 20 and the lens 40, the brightness distribution of the scanning light C that has passed through the half mirror 20 and the lens 40 becomes a pattern as shown in FIG. It will be slightly off. The reason why this brightness peak deviates is that there is a gap between the document table a and the document table, and therefore, the size of Δl depends on the size of this gap. In this state, the optical path length deviates from the appropriate value,
The magnitude of this shift also depends on Δl.

In other words, the magnitude of Δl and the like are data that give the optical path length deviation, and can be used to detect the optical path length deviation.

The microcomputer 61 constantly recognizes the deviation of the optical path length by determining the magnitude of Δl, and accordingly adjusts the original scanning optical mechanism 1 to the drum projection optical mechanism 11.
If the relative position of 2 is corrected, the optical path length deviation will be automatically corrected, and as a result, the original platen a
This means that even if there is a gap between the image and the document, a clear image with no out-of-focus can be obtained. However, if the surface of the original document has complex irregularities, the brightness distribution of the scanning light C will deviate considerably from the pattern shown in FIG. 5(b). The method may be applied in the same manner after data processing is performed using a method determined through experiments or the like.

It should be noted that the copying machine according to the present invention is not limited to the above embodiment, and Δ! If the size of the document exceeds a predetermined value, the copying operation may be stopped and the user may be informed that the document is set abnormally.

<Effects of the Invention> As described above, in the case of the copying machine according to the present invention, the deviation in the brightness distribution of the scanning light corresponding to the deviation in the optical path length is obtained by the line photo sensor, so that the focus can be adjusted. It is possible to detect the deviation in optical path length which is the cause of the deviation. Therefore, if a deviation occurs in the optical path length for some reason, it can be corrected, which is of great significance in improving the performance of the apparatus.

[Brief explanation of drawings]

1 to 5 are diagrams for explaining one embodiment of a copying machine according to the present invention, and FIG. 1 is a longitudinal sectional view of the copying machine mainly for explaining the mirror optical system, and FIG. 2
The figure is a transparent perspective view of a copying machine to explain the optical system drive mechanism, Figure 3 is an electrical configuration diagram of the copying machine, and Figures 4 and 5 show deviations in optical path length based on data on brightness distribution of scanning light. FIG. 4 shows a case where the document state is normal, and FIG. 5 shows a case where the document state is abnormal. FIG. 6 is a perspective view of an optical system drive device for explaining a conventional copying machine. 10...Mirror optical system 111...Light source 20...Half mirror 30...Line photo sensor 43, 50, b Photosensitive drum optical system drive mechanism Document plate Original scanning light Patent applicant Sharp Corporation

Claims (1)

[Claims] (1) a mirror optical system that guides the scanning light from the light source reflected on the document surface on the document table toward the photoreceptor drum; an optical system drive mechanism that drives the mirror optical system and the light source in the document scanning direction; A half mirror that is provided in the middle of the mirror optical system and takes out a part of the scanning light; and a line photo that is placed on the optical axis of the scanning light taken out by the half mirror and that detects the brightness distribution of the scanning light. A copying machine characterized by comprising a sensor.