JPH052225A - Scanning optical system - Google Patents

Abstract

PURPOSE:To reduce the manufacture cost by omitting a polishing process for a reflecting mirror unit which constitutes the optical system of a copying machine and is arranged in a V shape and to secure the read precision required for the optical system. CONSTITUTION:This scanning optical system which consists of an original plate 11, a light source for irradiating the surface of an original mounted on the original platen 11, a main lens 16, plural reflecting mirrors 14, 15A, 15B, 17A, 17B, and 18, and a driving system features the couple of reflecting mirrors 15A and 15B which have curved surfaces with mutually reverse power. Namely, the opposite reflecting surfaces of the couple of reflecting mirrors 15A and 15B consisting of two glass plates arranged in the V shape are the positive power curved surface and negative power curved surface having nearly equal radius of curvature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a plurality of reflecting mirrors of a scanning exposure optical system in an optical system such as a copying machine, and more particularly to an improvement of a pair of reflecting mirror units arranged in a V shape. .

[0002]

2. Description of the Related Art FIG. 1 is a block diagram showing an example of an optical system 10 of an electrophotographic copying machine. The document D placed on the document table 11 is
The reflected beam emitted by the exposure lamp 12 and the lamp house 13 is bent at a right angle by the first mirror 14 to form a V-shaped mirror unit, that is, a second mirror 15A and a third mirror 15B.
Incident on. The beam whose optical path is bent by 180 degrees by the second and third mirrors 15A and 15B passes through the main lens 16 of the imaging system, and is again V
Type mirror unit 4th mirror 17A, 5th mirror 17
It is incident on B, changes its direction by 180 °, is reflected by the sixth mirror 18, and forms an original image on the photosensitive drum 21 of the image forming unit 20.

In this case, in an optical system using a plurality of reflection mirrors as described above, the flatness of the reflection mirrors is required due to influences of magnification change, deterioration of resolution due to change of optical path length at each image height, and the like. Generally, a precision-polished reflective mirror is used. The plate glass that serves as the reflection mirror is generally curved to some extent in one of the manufacturing processes.

FIG. 2 is a perspective view of the reflection mirror of the optical system.

Conventionally, as shown in the figure, L21-L22 and L21
It is general that the plate glass 3 is ground to be processed into a flat plate glass by parallel planes of 23-L24, but there is a drawback that it takes a lot of processing time and is very expensive. On the other hand, as an inexpensive method, there is a reflection mirror using float glass, but it is extremely difficult to make a perfect flat surface due to manufacturing problems, and it will be in a wavy state. Since it cannot be used as a high-precision optical system with the glass plate of, the curvature at a certain level was selected and used. Therefore, there are drawbacks that the range of use of the plate glass is limited, the manufacturing cost is high, and a highly accurate optical system cannot be held.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been conceived specifically in order to eliminate the above-mentioned drawbacks. That is,
The present invention reversely utilizes the wavy state generated in the manufacturing process of the plate glass used for the optical system, the same curved surface after dividing into the glass plate used as the inner optical system of the plate glass having the curved surface generated by the waviness The plate glass having is selected using an autocollimator, a flattester, an optical interferometer, or the like, and by processing the glass plate having the same curved surface into a reflective glass, it becomes possible to manufacture a large number of usable reflective mirrors. Further, it is intended to solve the above-mentioned drawback by making it possible to use it as a reflecting mirror of a highly accurate optical system.

[0007]

SUMMARY OF THE INVENTION To solve the above problems, the present invention provides a document table, a light source for illuminating a document surface placed on the document table, a main lens, and a plurality of reflecting mirrors. ,
In a scanning optical system configured by a driving mechanism for scanning and exposing a document surface to form an image on an image carrier surface, at least one pair of reflecting mirrors having curved surfaces having mutually opposite powers is provided. It is a scanning optical system characterized by the above.

Further, in the scanning optical system of the present invention, of the plurality of mirrors, at least one pair of reflecting mirrors made of two plate glasses arranged in a V shape are provided with facing reflecting surfaces.
It is characterized in that it is arranged so as to be a set of positive power curved surface and negative power curved surface having substantially the same radius of curvature.

[0009]

EXAMPLE An example of the present invention is shown in FIG. This is an excerpt of a set of a second mirror 15A and a third mirror 15B forming a first V-type mirror in the optical system of the copying machine of FIG. 1 of the present embodiment.

In this first V-type mirror unit,
A float mirror having a convex curvature is used as the second mirror 15A, and a float mirror having a concave curvature is used as the third mirror 15B. This can be expressed by the following equation.

Concave mirror f1 = −1 / 2 × r1 (Equation-1) Convex mirror f2 = + 1/2 × r2 (Equation-2) f1, f2; Focal length of mirror r = Radius of curvature where radius of curvature r is the same When a concave mirror and a convex mirror are combined, (r1 = r2) f1 + f2 = -1 / 2r1 + 1 / 2r2 = 0 (plane) (Equation-3), which can be treated as a pseudo plane. In the case of a mirror,
The fact that there is no influence of aberrations such as chromatic aberration is also a major factor that can be treated as a pseudo plane.

The radius of curvature (r1 = r2) is determined by the required accuracy of the copying machine, but generally r = 100 to 200 m is sufficient.

Further, the radius of curvature can be measured quickly by using an optical interference flatness measuring device, for example, a laser beam oblique incidence interference fringe type flatness tester. It can be easily classified and sorted.

FIG. 4 is a schematic cross-sectional view showing a process for producing a plate glass for a reflection mirror. FIG. 5 is a plan view thereof.

In FIG. 4, reference numeral 1 is a tank holding a melted glass solution 3, and a nozzle 2 for dropping the glass solution 3 into a plate shape with an appropriate thickness is formed under the tank. The glass solution that has dropped further moves on the receiving plate 4 to form a half-solution plate glass 3A. When the plate glass 3A is rolled by rollers 5A, 5B, 6A, 6B so as to be a specified plate glass, and when rolled to a predetermined length, a cutter 7
Disconnect with. The cut plate glass is cooled on the two-dimensional receiving plate 8. At that time, the rolled sheet glass is rollers 5A, 5B.
Also, due to a rotation error of the rollers 6A and 6B, a processing error of the roller body, or the like, when being rolled by the roller group, either one of them is bent as shown in the figure, and is set in a wavy state. In this embodiment, of the plate glass thus solidified in the corrugated state, only the glass pieces 3B and 3C are cut out at the lengths L1 and L2 (large plate cutting).

FIG. 6 is a diagram showing a step of cutting the reflection mirror plate glass.

Reference numeral A in the figure denotes the cut glass pieces 3B and 3C, which are curved in either direction in the rolling direction. As shown in FIG. 6B, the glass piece 3B has a constant width L3, L4,
Cut at the lines L5, L6, L7, L8, L9, L10, L11.
Similarly, the glass piece 3C is also L12, L13, L14, L15, L1.
Cut with 6, L17, L18, L19 and L20 lines (cutting the middle plate).
In this way, many cut strip-shaped glass pieces are slightly curved in the longitudinal direction.

The curvature of this glass piece is measured using, for example, an autocollimator, a flattester, an optical interferometer, etc. (none of which is shown) which has been conventionally used for measuring the curvature of a lens. For example, the shape of interference fringes, the number of fringes, whether they are concave or convex, etc. are measured one by one.

Then, among these plate glass pieces, those having the same or similar curvature are classified and selected. As a selection method, only the glass pieces with the same degree of curvature are selected,
Next, depending on the precision of the model to be used, the error is classified into several types within an allowable range. 6C shows a pair of glass pieces 3D and 3E whose curvatures are perfectly matched by measurement with an autocollimator or the like. 3D has a concave curved surface upward, and 3E has a convex curved surface upward. The
Both are curved surfaces with the same radius of curvature. FIG. 7 shows a perspective view of a set of reflecting mirrors.

The glass pieces 3D and 3E can be applied to the mirror unit of the second mirror 15A and the third mirror 15B and the mirror unit of the fourth mirror 17A and the fifth mirror 17B. Further, it is applicable to a combination mirror unit other than the V-shaped arrangement.

[0021]

As described above in detail, the V-shaped reflective mirror unit that constitutes the optical system of the copying machine according to the present invention does not require precision polishing of the plate glass and measures the radius of curvature of general floating glass. Then, since it is only necessary to sort and select, the processing time required for the polishing process is unnecessary,
It is extremely effective in reducing the manufacturing cost of reflective mirrors.

[Brief description of drawings]

FIG. 1 is a block diagram of an electrophotographic copying machine.

FIG. 2 is a perspective view of a reflection mirror of an optical system.

FIG. 3 is a sectional view of a V-shaped mirror unit.

FIG. 4 is a schematic cross-sectional view illustrating a manufacturing process of a plate glass for a reflection mirror.

FIG. 5 is a plan view thereof.

FIG. 6 is a diagram showing a step of cutting a plate glass for a reflection mirror.

FIG. 7 is a perspective view of a pair of reflecting mirrors.

[Explanation of symbols]

3B, 3C glass pieces 10 Optical system 11 Platen 14 First mirror 15A Second mirror 15B Third mirror 16 Main lens 17A 4th mirror 17B 5th mirror 18 6th mirror 20 Image forming unit 21 photoconductor drum

Claims (2)

[Claims] 1. An original table, a light source for illuminating an original surface placed on the original table, a main lens, a plurality of reflecting mirrors, and a drive mechanism, and the image is formed by scanning and exposing the original surface. A scanning optical system for forming an image on a surface of a carrier, wherein, among the plurality of mirrors, at least one pair of reflecting mirrors having curved surfaces having mutually opposite powers is provided. 2. A document table, a light source for illuminating a document surface placed on the document table, a main lens, a plurality of mirrors, and a drive mechanism, and the image is formed by scanning and exposing the document surface. In a scanning optical system of a copying machine for forming an image on the surface of a carrier, at least one pair of reflecting mirrors made of two V-shaped plate glasses among the plurality of mirrors have substantially the same reflecting surfaces. The scanning optical system is characterized in that it is selectively arranged so as to have a pair of positive power curved surface and negative power curved surface having a radius of curvature of.