JPH0521054Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] This invention relates to an optical device used, for example, as an optical system of a light splitter or distributor that divides and transmits a light image in two directions in a tandem space. It is something.

[Conventional technology]

This type of conventional optical system has a configuration as shown in FIG. That is, the optical image K to be transmitted
The light emitted from the position I1 of 90% of the light is reflected in the direction of arrow a by the 90% reflective surface P1,
Further, the light is focused by one exit lens L2, and is imaged at a position I2 of one transmission portion D1, so that the light image K is transmitted with 90% of the light intensity.

On the other hand, 10% of the light transmitted through the 90% reflective surface P1 is totally reflected by the total reflective surface P2 on the upper surface of the prism P, and then the 10% 90 %, that is, 9% of the light intensity, is further focused by the other exit side lens L3, and is imaged at the position I3 of the other transmission section D2, so that the light image K is transmitted with 9% of the light intensity. . In this way, the optical image K at the position I1 is transmitted to both transmission parts D1 and D2.
The light is divided into light images of 90% and 9% light intensity and transmitted to the respective positions I2 and I3.

[Problem that the invention attempts to solve]

By the way, in the optical system using the above-mentioned method, as shown in FIG. % reflected by the reflective surface P1 and emitted from one exit surface f2 of the prism P.
On the other hand, the light rays l2 and l3 incident from one side of the entrance surface f1 of the prism P are transmitted to one exit surface f2.
After being totally reflected by the 90% reflecting surface P1, the light is emitted from one exit surface f2. These two types of light rays l1, l2, and l3 head in directions symmetrical to each other with respect to the axis in the direction of the arrow a, so when they pass through one exit lens L2, one light ray l
1 is imaged at the F1 position of one transmission part D1, whereas the other light rays l2 and l3 are imaged at the F2 position, which is symmetrical to the F1 position with respect to the optical axis of the lens L2, The optical image formed at the F2 position becomes a ghost image (double image) and cannot transmit clear light rays. A similar ghost image is also formed in the light rays emitted from the other exit surface f3.

This idea was created in view of these problems, and it eliminates the occurrence of ghost images that are symmetrical with respect to the optical axis of the lens in optical systems that use prisms to transmit light images. This was done in an attempt to provide an optical device.

[Means for solving problems]

In order to achieve the above-mentioned problems, the optical device of this invention has a prism shape with a right isosceles triangle cross section, and a pair of mutually perpendicular surfaces are an incident surface and an exit surface, respectively, and an inclined surface is a reflective surface. ,
An optical device in which light emitted from an optical image to be transmitted is made incident from the incident surface through a lens, reflected by the reflecting surface, and reflected light emitted from the exit surface is imaged by the lens. When the light emitted from the outermost edge of the prism enters the prism through the lens on the entrance side, the angle of incidence within the prism is θ.
If the length of one side of the prism required in terms of light quantity is A, then the incident surface and the exit surface are each protruded by at least a thickness of Atanθ/2, and the side surfaces of each protruding portion are respectively The gist is a configuration with a light absorption surface.

[Effect]

In the optical device of this invention with the above structure, the entrance and exit surfaces of the prism are protruded by the required thickness, so that the light exits from the outermost edge of the prism and hits the prism at an incident angle of θ. The incident light is totally reflected at the output surface, but it is absorbed by the light absorption surface formed on the side surface of the protruding part that extends by a predetermined thickness and disappears, and does not exit from the output surface, so a ghost image is created. will not occur.

〔Example〕

Hereinafter, a preferred embodiment of this invention will be described in detail based on the drawings.

Figure 1 shows a prism 1 used in this invention,
The optical system other than this prism 1 is the same as that shown in FIGS. 3 and 4. This prism 1 is designed so that the incident angle within the prism 1 of a light ray l3 that exits from the outermost edge of the optical image to be transmitted and enters the prism 1 via the incident side lens L1 is θ, and the amount of light of the prism 1 is required. When the length of one side of It protrudes by the thickness, and each of these protruding parts 2'~
Each side surface of 5' serves as a light absorption surface 7.
Further, the formation of the 90% reflective surface 6 is the same as in the conventional device described above, and the optical image transmission function is exactly the same as in the case of FIG. 3 described above, so a description thereof will be omitted. The light ray l3 from the outermost edge of the optical image incident on the prism 1 at an incident angle of θ is
After being totally reflected on one exit surface 3 that protrudes by the thickness of Atanθ/2, it is absorbed by the light absorption surface 7 and disappears.
No radiation is emitted from the emission surface 3. Therefore, all of the light rays 12 which are on the inner circumferential side of the light ray 13 and are totally reflected by one exit surface 3 are necessarily absorbed by the light absorption surface 7. Similarly, since all of the light rays that are totally reflected by the other exit surface 5 are absorbed by the light absorption surface 7, no ghost images are generated in both transmission directions.

Next, the production of the prism 1 will be explained. Prisms 1 having the above-mentioned deformation are generally difficult to produce. Therefore, as shown in Figure 2, 2
On each corresponding surface of the triangular prisms 1a and 1b,
It can be easily produced by using a means of optically bonding glass plates 8 having a thickness of Atan θ/2 and having light absorption surfaces 7 on their side surfaces using an adhesive having the same properties as prism glass.

In addition, anti-reflection coating is applied to the light entrance and exit surfaces of ordinary prisms, but by bonding the glass plate 8 to the triangular prisms 1a and 1b, 90% of each of the triangular prisms 1a and 1b is reflected. When applying anti-reflection coating after bonding the surfaces 6a and 6b together, it is very difficult to apply anti-reflection coating to two surfaces at the same time, so two coating operations are required. It is a waste of time, and it is common to apply coating by heating to increase the strength of the coating, but uniformly heating and cooling a prism, which is a lump of glass, is time-consuming. There's too much waste. Therefore, we put the glass plate 8 into the triangular prism 1.
Before bonding to the surfaces a and 1b, anti-reflection coating is applied in advance to the incident surface 2 or the exit surface 3, 5 of the glass plate 8, and a 100% anti-reflection coating is applied to the surface of the glass plate 8 which will become the total reflection surface 4. By coating the % reflective surfaces and then bonding these glass plates 8 to the corresponding surfaces of the triangular prisms 1a and 1b, the prism 1 having the structure shown in FIG. 1 can be obtained very easily. In addition, there is an advantage that the prism 1 has high performance without reducing the amount of light required. Incidentally, since the glass plate 8 is manufactured by bonding the triangular prisms 1a and 1b, it can be achieved by simply bonding the glass plate to an existing prism.

Note that this invention is not limited to the above-mentioned embodiment, and of course, various embodiments can be considered based on the scope of the claims. For example, in the embodiment, two triangular prisms 1a and 1b are used. Although the distributor prism 1 is shown as an example, it goes without saying that the present invention can also be applied to an optical system in which a single prism is used to transmit light in a perpendicular direction.

[Effect of idea]

As described in detail above, according to the optical device of this invention, the entrance and exit surfaces of the prism are made to protrude by the required thickness, and the side surfaces of these protruding portions are used as light absorption surfaces, so that the exit side Ghost images appearing symmetrically with respect to the optical axis of the lens can be completely prevented, and good optical image transmission can be achieved.

[Brief explanation of the drawing]

FIG. 1 is an optical diagram of the main parts of an embodiment of the optical device of this invention, FIG. 2 is an exploded view of the prism shown in FIG. 1,
FIG. 3 is an optical diagram of a conventional device, and FIG. 4 is an optical diagram showing the occurrence of ghosts in the device of FIG. 1... Prism, L1... Lens, 2... Incident surface, 3, 5... Output surface, 2' to 5'... Protruding portion,
6... Reflective surface, 7... Light absorbing surface, 8... Glass plate.

Claims (1)

[Scope of Claim for Utility Model Registration] A prism having a prism shape with a right isosceles triangular cross section, a pair of mutually orthogonal surfaces as an entrance surface and an exit surface, and an inclined surface as a reflection surface, from an optical image to be transmitted. In an optical device, the emitted light enters the incident surface through a lens, is reflected by the reflective surface, and is emitted from the exit surface and forms an image with the lens. When the light enters the prism through the lens on the incident side, the incident angle within the prism is θ,
When the length of one side of the prism required in terms of light quantity is A, the incident surface and the exit surface are each protruded by at least a thickness of Atanθ/2, and the side surfaces of each protruding portion are respectively exposed to light. An optical device characterized by having an absorption surface.