JPH0876056A - Optical system - Google Patents

Abstract

PURPOSE: To eliminate need for aligning the optical axes of a prism and a lens in an optical system constituted so that the image of a light source surf ace is formed on an image forming surface by being enlarged or reduced by integrally forming the optical system constituted so that two prisms are arranged opposedly to each other by interposing the lens, as one of parts. CONSTITUTION: The lens and prism-incorporated type optical system 4 is integrally formed out of an identical material of such as glass or plastic. The optical system 11 is constituted so that two prisms 5 and 6 are arranged to face each other by interposing the lens 7 between them. The prisms 5 and 6 and both ends of the lens 7 are coupled by coupling parts 8 and 8 so as to constitute a rectangular frame body. Besides, a projection or a recessed part for positioning can be formed on the outside of the coupling parts 8 and 8. Then, the image of the light source surface is formed on the prescribed image forming surface decided by the arrangement of two prisms 5 and 6 while it is enlarged or reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical system in which a lens and a prism are integrated so that they can be handled as one component.

[0002]

2. Description of the Related Art LED printers, as shown in FIG.
The LEDs in the LED array 1 are selectively caused to emit light, which is magnified and projected on an image forming surface 3 such as a photosensitive drum to perform exposure to obtain a predetermined print pattern. Since the number of light emitting elements that one LED array 1 has is limited, a plurality of pairs of the LED array 1 and the magnifying lens 2 are arranged so that one line of the image plane 3 in the main scanning direction can be exposed at the same time.

An optical system for reading a fax is
The illuminated image of the original is reduced to form an image on an image sensor such as a one-dimensional photodiode array and is read by photoelectric conversion. This optical system for fax is also configured by arranging a set of an image sensor and a reduction lens in a straight line, as in FIG.

[0004]

There is a strong demand for downsizing of the above-mentioned LED printers and fax machines, especially for their thinness. Attempts to reduce the thickness will hinder the optical path length of the optical system.

This will be described by taking the optical system of the LED printer shown in FIG. 8 as an example. FIG. 9 shows the LED array 1
And one pair of magnifying lenses 2 are shown. For example, 1
The effective light emission length of one LED array 1 is 6.5 mm, and this must be magnified to 17 mm on the imaging plane by the magnifying lens 3 to form an image. In this case, it is assumed that the distance h between the LED array 1 and the image plane 3 is narrowed to h = 15 mm in order to reduce the thickness of the device. In this case, since the optical path length h is shorter than the image height, the angle of view θ becomes as large as 38.1 °, and the peripheral light amount ratio to the central light amount is cos ⁴
(38.1 °) = 0.38, which is a small value of 38%. Further, the aberration becomes large and the resolving power also decreases, so that it is not practical. This occurs as a similar problem in the reduction optical system for fax.

In order to solve this problem, this type of optical system also requires a small number of parts in order to facilitate the work of incorporating it into an optical device and reduce the manufacturing cost.

Therefore, the present invention provides an optical system in which the optical path length is sufficiently long with respect to the image height and the angle of view θ is not large, while satisfying the condition that the distance between the light source surface and the image forming surface is narrowed. It is intended to be provided as a part.

[0008]

[Means for Solving the Problems]

(1) The optical system of the present invention is an optical system in which two prisms are arranged so as to face each other with a lens in between, and the light incident on one prism is emitted from the other prism through the lens. The basic structure is that the entire structure is integrally formed of the same material.

(2) This optical system can be integrally molded by resin molding.

(3) The above-mentioned problem is that the lens is a magnifying lens (when used as a magnifying optical system used in an LED printer or the like) or a reducing lens (when used as a reducing optical system used in a fax reader or the like). In the configuration, by making each prism and lens have a horizontally long shape in accordance with the horizontally long image formation or the shape of the light source, the cross-sectional shape of the optical path formed by the prism and the lens is thinned, and the light source surface and the image formation surface are formed. The orientation of the two prisms is determined so that is located on the front and back sides of the optical system, and the width between the light source surface and the image forming surface of the optical system is set to a small value corresponding to the image forming or the short side of the light source. The distance between the two prisms is set so that the optical path length is sufficiently long so as not to reduce the peripheral light amount ratio with respect to the long side of the image formation or the light source. In this case, if the length of the image formation (enlarged projection image in an LED printer or the like) or the length of the light source (illuminated original document device or the like read by fax) is larger than the optical path width of one optical system, a plurality of optical systems are used. The required length W is obtained by arranging the systems as shown in FIG.

(4) As described above, when it is necessary to arrange in a straight line in order to correspond to a long image formation or a light source, FIG.
It is also possible to form all of the prisms and lenses as a unit as shown in (1) to form a single component having a plurality of image forming systems in parallel.

[0012]

The basic structure in which the two prisms are arranged opposite to each other with the lens interposed therebetween, the image of the light source (including a lighted body such as an LED array and an illuminated original) facing one prism is magnified by the lens. Alternatively, the image is reduced and emitted from the other prism to form an image. The positional relationship between the light source surface and the image formation surface is a combination of the reflection directions of the two prisms,
When the optical system is sandwiched, it is on the same side with respect to the optical system, when it has a predetermined angle, it can be set arbitrarily. The present invention
Since this structure is integrally formed of the same material, it can be incorporated in an optical device as one component, the number of components is small, and it is not necessary to assemble the prism and the lens by individually aligning the optical axes. Therefore, the manufacturing cost can be reduced.

The above-mentioned basic structure enlarges or reduces the image of the light source to form an image on an image forming surface which does not face the light source. Due to a use in which the light source and the image forming surface cannot be arranged opposite to each other, for example, due to space constraints. It is effective for special imaging equipment and surveillance scopes used.

The above structure enables mass production and cost reduction by performing resin molding.

In the above basic structure, when the prism and the lens are horizontally long as described above, the width of the optical system sandwiched between the light source surface and the image forming surface is set to be the short side of the image forming or light source having different vertical and horizontal lengths. The optical path length can be made sufficiently large with respect to the image formation or the long side of the light source while making it thin corresponding to. For example, as shown in FIG. 2, the distance L between the two prisms is set to 20.
mm, the distance between the light source surface 1 and the imaging surface 3 with respect to the prism, and the thickness of the optical system are 5 mm, the optical path length is 35 mm as shown in FIG. The distance between the image planes is 15 mm, and the long side of the light source is 6.5.
When imaging mm to 17 mm, the angle of view is 18.56.
The peripheral light amount ratio (cos ⁴ θ) is 0.81 (81%), and an optical system having no practical problems can be realized.

This is true for one optical system of the present invention, and a plurality of LED printers or fax readers are arranged in a straight line. In this case, if a plurality of optical systems shown in FIG. 4 are integrally molded as one component as shown in FIG. 5, the number of assembling steps can be reduced and the cost can be reduced.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the lens / prism integrated optical system 4 of the present invention shown in FIG. 1 is integrally formed of the same material such as glass or plastic. In this optical system, as shown in FIG. 2, two prisms 5 and 6 are arranged so as to face each other with a lens 7 in between, and both ends of the prisms 5 and 6 and the lens 7 are connected by connecting portions 8 and 8. , Form a rectangular frame. On the outside of the connecting portions 8 and 8, positioning protrusions or recesses (not shown) can be formed.

The prisms 5 and 6 and the entrance and exit surfaces of the lens 7 are mirror-finished so that their optical performance can be exhibited, and the slopes of the prisms 5 and 6 are mirror-finished or a reflective film such as a metal deposition film. To form a reflective surface. In this embodiment, the lens 7 has a double-lens configuration in which a biconvex lens and a meniscus lens are combined in order to reduce aberrations, but a single lens may be used or an aspherical lens may be used.

When the optical system shown in FIG. 2 is designed to have the dimensions shown in the drawing, the optical path length is 35 mm as shown in FIG. 3, and the peripheral light quantity ratio is 0.81 (8).
1%) is obtained.

The embodiment of FIG. 1 is designed with a magnifying optical system for the purpose of reducing the thickness of the LED printer. As shown in FIG. 4, a plurality of LED printers are provided so that a required printing width W can be obtained. Are used side by side. Prism 5, to make it thinner
6 has a lateral length in which a side in a direction orthogonal to the incident and reflecting directions is longer than the other sides, and corresponds to the shape of an elongated image plane (enlarged image of the LED array). Further, the lens 7 has a rectangular shape that is cut in one diameter direction in order to align the lengths with the short sides of the prisms 5 and 6.

Instead of arranging a plurality of optical systems as shown in FIG. 4, a lens and a prism are provided as shown in FIG.
It is also possible to form them integrally and make the whole into one part.

This lens 7 has a light source surface (L
A magnifying lens is used because it is a magnifying optical system that magnifies an image of the ED array and forms an image on an image forming surface (such as a photosensitive drum of a printer). However, when this optical system is used in a fax reader, a reduction lens is used. Any lens can be used as long as it can be integrally formed in the optical system, and a single lens as shown in FIG. 6 or 7 can be used in addition to the combined lens as shown.

The lens in each of the above-mentioned embodiments has a shape of only one side part in order to facilitate the die cutting of the lens part in the case of resin molding and to reduce the number of molding steps. Needless to say, the shape may be a rectangle cut into.

The embodiments shown in FIGS. 1 to 7 are designed to narrow the distance between the light source surface and the image forming surface, as in the LED printer or the fax reader described as the problem to be solved by the invention. It is a thing.

The present invention can be applied to all devices having the same problem. For example, this corresponds to a case where information such as numbers and characters which are light-emitted and displayed on a horizontally long display such as an LED display is reduced by a lens and transferred to a film. In this case, when the optical path length becomes shorter, the peripheral light amount ratio becomes smaller,
Although there is a problem that it cannot be made thin, it can be solved by using the thin optical system of the above embodiment.

According to the present invention, the image of the light source surface is formed on the predetermined image forming surface 3 determined by the arrangement of the two prisms 5 and 6 while enlarging or reducing by the lens 7, and this optical system is used. The basic content is to provide it as one integrally formed part. Therefore, depending on the application
Its shape can be changed.

Other applications include a light projecting system for projecting one image on the other, an optical reading device such as a bar code reader, a special photographing device, and a light receiving system for a monitoring scope.

In these cases, the cross-sectional shape of the optical path (the shape of the prism and the lens) is matched with the shape of the light source or the image, and the aspect ratio of the optical path is arbitrary.

Further, the positional relationship between the light source surface and the image forming surface can be set according to the application by changing the positional relationship between the interval L between the prisms 5 and 6 and the total reflection surface (slope) of the prism.

For example, by making the reflecting surfaces of the two prisms 5 and 6 orthogonal to each other, the light source surface 1 and the image forming surface 3 can be arranged on the same side with respect to the optical system and apart from each other. These total reflection surfaces are 4 times larger than the connecting portion 8 that connects the two prisms.
It is not necessary to maintain the relationship of 5 °, it can be set arbitrarily, and the light source surface and the image forming surface can have 90 ° or an arbitrary angle.

[0031]

According to the present invention, an optical system in which two prisms are opposed to each other with a lens interposed therebetween is integrally formed as one component. Therefore, the optical system for enlarging or reducing the image on the light source surface to form an image on the image forming surface. It is not necessary to align the optical axes of the prism and the lens in (3), and it is possible to easily assemble the optical device and reduce the cost.

In particular, when the light source surface is horizontally long, the prism and the lens are horizontally long to secure a large optical path length with respect to the long side (image height) of the light source surface and prevent the angle of view from increasing. LED can be manufactured because the optical system can be made thin.
It is possible to cope with restrictions on the installation space in optical equipment such as printers.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of an optical system of the present invention.

2 is a cross-sectional view showing the positional relationship among a light source surface, a prism, a lens, and an image plane in the optical system of FIG.

3 is a diagram showing an equivalent optical system for calculating a peripheral light amount ratio in the optical system of FIG.

FIG. 4 is a diagram showing a state in which the optical systems of FIG. 3 are arranged for use in an LED printer or the like.

5 is a diagram showing a state in which a plurality of optical systems shown in FIG. 4 are integrally formed as one component.

6 is a diagram showing a configuration example in which a lens has a single lens configuration in the optical system of FIG.

7 is a diagram showing a configuration example in which the optical system of FIG. 1 has a single lens configuration.

FIG. 8 is a schematic view of an image forming optical system of a conventional LED printer.

9 is a diagram showing the thinned optical system shown in FIG. 8 for one unit.

[Explanation of symbols]

 4 Optical system in which prism and lens are integrally molded 5, 6 Prism 7 Lens 8 Connection part θ Angle of view

Claims (4)

[Claims] 1. An optical system in which two prisms are arranged so as to face each other with a lens interposed therebetween, and an optical system in which light incident on one prism is emitted from the other prism through the lens is a connecting portion in which the prism and the lens are provided at their end portions. An optical system in which the entire structure is integrally formed of the same material. 2. The optical system according to claim 1, wherein the optical system is integrally molded by resin molding. 3. The optical system according to claim 1, wherein the lens is a magnifying lens or a reducing lens, wherein each prism and lens have a laterally long shape corresponding to the shape of a horizontally long image forming or light source. , So that the cross-sectional shape of the optical path formed by the prism and the lens is thin, and the light source surface and the image forming surface are located on the front and back of the optical system.
Determine the orientation of the two prisms, and make the width between the light source surface and the image forming surface of the optical system small corresponding to the short side of the image forming or light source, and at the same time, set the optical path length to the image forming or light source long. An optical system characterized in that an interval between two prisms is set to be sufficiently long so as not to reduce a peripheral light amount ratio with respect to a side. 4. Instead of arranging the optical system according to claim 3 linearly to accommodate long imaging or light sources,
An optical system characterized in that all prisms and lenses are integrally formed into a single component having a plurality of image forming systems in parallel.