JP6539886B2 - Image reversing prism - Google Patents

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image inverting prism, and more particularly, to an image inverting prism capable of making an erecting optical system such as binoculars and telescopes having a slim shape while suppressing loss of light transmittance.

  In order to be able to observe an inverted image formed by an objective lens system as an erect image, binoculars and ground telescopes are provided with an image inverting system. As an image inversion system, for example, a porro prism and a daha type prism are known.

  As shown in FIG. 5, the Porro prism 40 realizes an erected image, for example, by arranging the ridge lines of the two right angle prisms 41 and 42 to be orthogonal to each other. Since the light incident axis and the light emission axis of the Polo prism 40 are largely deviated, the arrangement space is increased, and as shown in FIG. 5, the binoculars 400 having the wide barrel 43 are obtained.

  The daha type prism 50 realizes an erected image by combining the daha prism 51 and the auxiliary prism 52 as shown in FIG. The roof type prism 50 can make the light incident axis and the light emission axis parallel or nearly parallel, so that the arrangement space can be made smaller than that of the porro prism 40, and the straight lens barrel 55 can be used. The slim binoculars 500 can be manufactured. Therefore, in recent years, the Daha type prism has become mainstream as an image inverting prism provided in binoculars. As the Daha prism, for example, Schmidt-Pechan prism and Abbe-Konig prism are known.

  The Daha prism shown in FIG. 6 is a Schmidt-Pechan prism 50. The Schmidt-Pechan prism 50 makes it easy to make the light incident axis and the light emission axis coaxial with each other, so that the objective lens 53, the Schmitt-Pechan prism 50, and the eyepiece 54 can be coaxially arranged. Accordingly, the binocular 500 provided with the Schmidt-Pechan prism 50 can make the lens barrel 55 straight and slim.

On the other hand, the Schmidt-Pechan prism 50 can not largely shift the light incidence axis and the light emission axis. Therefore, it can not be used with a large aperture objective lens 53. That is, when used together with the large-aperture objective lens 53, the left and right lens barrels 55 necessarily become thick, and the distance between the lens barrels 55 of the binoculars 500 becomes large. As a result, the distance D _L between the eyepieces 54 also increases. For example, if the diameter of the lens barrel 55 is 60mm, the distance between the lens barrel 55 becomes at least 60mm, also at least 60mm distance _{D L} between the eyepiece 54. In ISO and JIS, 56 mm to 72 mm are shown as minimum necessary values of the eye width adjustment range of binoculars. Therefore, in order to obtain binoculars having desired characteristics, the distance between the eyepieces 54 needs to be adjustable to at least 56 mm. However, the Schmidt Pechan prism 50 light incident axis and the exit axis are coaxial, it is not possible to adjust the distance D _L between the distance between the objective lens 53 D _S and the eyepiece 54 separately, the objective The distance D _L between the eyepieces 54 is determined in accordance with the distance D _S between the lenses 53. Therefore, when the diameter of the lens barrel 55 is 60mm it can not be smaller than 60mm the distance _{D L} between the eyepiece 54. Therefore, the Schmidt-Pechan prism 50 is generally used together with the objective lens 53 having a small to medium aperture, and the aperture of the objective lens 53 is limited to about 50 mm at maximum.

  Further, in the Schmidt-Pechan prism 50, since one of the light reflection surfaces of the auxiliary prism 52 is not a total reflection surface, the reflection film 56 is formed on this surface to suppress the loss of light transmittance. However, since the surface which is not the total reflection surface loses a certain amount of light even when the reflective film 56 is formed, the light transmittance is reduced compared to the prism in which all the reflection surfaces are the total reflection surface, The image to be observed becomes dark.

The Abbe-Konig prism 60 realizes an erected image by combining the auxiliary prism 61 and the roof prism 62 as shown in FIG. Abbe Konig prism 60, unlike the Schmidt Pechan prism 50, since the incident axis I ₁ of light and the exit axis J ₁ can be shifted to some extent, between the eyepiece 64 to the width of the user's eyes The distance can be adjusted. Thus, the Abbe-Konig prism 60 can be used with an objective lens 63 having a large aperture. However, as shown in FIG. 7, the Abbe Konig prism 60, since the roof prism 62 is pushed out largely radially outward of the injection axis J _1, it is housed in a barrel 65 of a straight shape corresponding to the aperture of the objective lens 63 I can not That is, the binoculars provided with the Abbe-Konich prism 60 can not be made to be a straight-shaped barrel 65 matched to the aperture of the objective lens 63, and the size of the barrel 65 is the size of the Abbe-Konig prism 60. It is set by.

  On the other hand, in the Abbe-Konig prism 60, the reflection surface of all the light is a total reflection surface, so there is no loss of light transmittance, and the observed image becomes brighter than the Schmidt-Pechan prism 50.

  As described above, the Daha type prism has advantages and disadvantages depending on its type, so a specific Daha type prism has been selected according to the characteristics required for an image inverting optical device such as binoculars. On the other hand, a prism having all the advantages of the conventional Daha type prisms has been desired.

  An object of the present invention is to provide an image inverting prism that can make optical devices such as binoculars and telescopes having a slim shape while suppressing loss of light transmittance.

The means for solving the problems are as follows.
(1) An image inverting prism having an auxiliary prism and a roof prism, wherein
Wherein A and the auxiliary prism the roof prism, the refractive index n _e is from 1.56 greater than the optical glass,
The auxiliary prism includes a first reflection surface provided to totally reflect a light beam vertically incident on the incident surface, and a second reflection surface provided to totally reflect a light beam reflected by the first reflection surface And a light exit surface provided such that the light beam reflected by the second reflection surface is emitted perpendicularly to itself,
The roof prism is provided in parallel to the exit surface and is provided in parallel to the second incident surface on which the light beam emitted from the auxiliary prism is incident, and in parallel to the incident surface, and the light beam incident on the second incident surface is internally It is an image inverting prism characterized by having a second outgoing surface parallel to the incident light beam after reflection, and inverting an image on the incident surface vertically and horizontally.

The preferred means of the above (1) is as follows.
(2) The reflection angle of the incident light beam on the first reflection surface is 66 to 68 °, and the reflection angle of the light beam reflected on the first reflection surface on the second reflection surface is 43 to 46 ° The image inverting prism according to (1), characterized in that

  According to the present invention, it is possible to provide an image inverting prism that can make optical devices such as binoculars and telescopes having a slim shape while suppressing loss of light transmittance.

FIG. 1 is an end view of an image inverting prism, which is an example of the image inverting prism according to the present invention, as viewed from the direction orthogonal to the incident axis. FIG. 2 is a six-face view of an auxiliary prism which is an example of the auxiliary prism in the image inverting prism according to the present invention. FIG. 2A is a front view of the auxiliary prism. FIG. 2B is a left side view of the auxiliary prism. FIG. 2C is a right side view of the auxiliary prism. FIG. 2D is a top view of the auxiliary prism. FIG. 2 (e) is a bottom view of the auxiliary prism. FIG. 2F is a rear view of the auxiliary prism. FIG. 3 is a schematic explanatory view showing an image inverting prism which is an example of the image inverting prism according to the present invention disposed in a lens barrel. FIG. 4 is an end view of an auxiliary prism which is another example of the auxiliary prism in the image inverting prism according to the present invention, as viewed from the direction orthogonal to the incident axis. FIG. 5 is a schematic explanatory view showing binoculars provided with a porro prism. FIG. 6 is a schematic explanatory view showing a binocular provided with a Schmidt-Pechan prism. FIG. 7 is a schematic explanatory view showing the Abbe-Konig prism disposed in the lens barrel.

  An image inverting prism which is an embodiment of an image inverting prism according to the present invention will be described below with reference to FIGS. 1 to 3. The image inverting prism 100 has an auxiliary prism 10 and a roof prism 20.

  The auxiliary prism 10 changes a light beam vertically incident on the center of the incident surface 1 (hereinafter referred to as incident light beam) in a direction rotated at a predetermined angle with respect to the incident axis I of the incident light beam, It has a function of emitting light from the auxiliary prism 10. The auxiliary prism 10 includes a first reflecting surface 2 provided so as to totally reflect an incident light beam, and a second reflecting surface 3 provided such that light rays totally reflected by the first reflecting surface 2 are totally reflected. It has at least an exit surface 4 provided so that a light beam totally reflected by the second reflection surface 3 is emitted perpendicularly to itself. That is, in the auxiliary prism 10, the incident light beam vertically incident on the center of the entrance surface 1 is totally reflected by the first reflection surface 2 and then totally reflected by the second reflection surface 3, and is emitted perpendicularly to the exit surface 4. It is formed to be. Since the first reflection surface 2 and the second reflection surface 3 that internally reflect until the incident light beam exits from the auxiliary prism 10 are both total reflection surfaces, a reflection film should be formed on a surface that is not a total reflection surface. The loss of the light quantity at the time of reflection can be suppressed compared with the reflective surface formed by this. Moreover, since the light emission surface 4 is provided so that the light ray reflected by the 2nd reflective surface 3 may radiate | emit perpendicularly | vertically to a surface, it can suppress the loss of the light quantity by the reflection of the light at the time of radiate | emitting. Therefore, according to the auxiliary prism 10, the loss of light transmittance can be suppressed. As described later, the outgoing light beam emitted from the auxiliary prism 10 is incident on the roof prism 20 at a predetermined angle with respect to the incident axis I, is image inverted vertically and horizontally, and is emitted from the roof prism 20 parallel to the incident axis I .

  The incident surface 1 is, for example, a surface on which the light beam transmitted through the objective lens 31 shown in FIG. 3 is incident. The auxiliary prism 10 is disposed, for example, such that the optical axis of the objective lens 31 and the incident axis I are coaxial. Although the end surface shape of the entrance surface 1 of this embodiment is a square in which two corner portions are chamfered as shown in FIG. 2 (b), the end surface shape is as long as the object of the present invention can be achieved. It is not particularly limited.

  As shown in FIG. 1, the first reflection surface 2 is provided so as to totally reflect an incident light beam perpendicularly incident on the incident surface 1. The first reflection surface 2 of this embodiment is formed on the entrance surface 1 and the exit surface 4 so that the angle θi between the normal to the first reflection surface 2 and the normal to the entrance surface 1 is 67.5 °. It is provided adjacent to each other. That is, the first reflection surface 2 is provided such that the incident light beam is reflected by the first reflection surface 2 at a reflection angle θa of 67.5 °. The reflection angle θa is not particularly limited to 67.5 °, and the reflection angle θa is preferably 66 ° to 68 °. The end face shape of the first reflection surface 2 in this embodiment is substantially rectangular as shown in FIG. 2D, and the side surfaces 5a and 5b orthogonal to the entrance surface 1 and the entrance surface 1 and the first reflection surface 2 respectively. Although the two adjacent corners are chamfered, the end face shape is not particularly limited as long as the object of the present invention can be achieved.

  As shown in FIG. 1, the second reflecting surface 3 is provided so that the light beam reflected by the first reflecting surface 2 is totally reflected. The second reflective surface 3 in this embodiment is provided such that an angle θii between the normal of the second reflective surface 3 and the normal of the incident surface 1 is 90 °. That is, the second reflection surface 3 is provided so that the light beam reflected by the first reflection surface 2 at a reflection angle θa of 67.5 ° is reflected at a reflection angle θb of 45 °. The reflection angle θb is not particularly limited to 45 °, and the reflection angle θb is preferably 43 ° to 46 °. The end face shape of the second reflecting surface 3 in this embodiment is substantially rectangular as shown in FIG. 2 (e), and the ridge lines adjacent to the side faces 5a and 5b are chamfered, but the problem of the present invention The end face shape is not particularly limited as long as it can be achieved.

  As shown in FIG. 1, the emission surface 4 is provided so that the light beam reflected by the second reflection surface 3 can be emitted perpendicularly to itself. The first reflection surface 2 and the second reflection surface 3 have an emission surface 4 of this embodiment such that an angle θiii = θb formed between the normal to the emission surface 4 and the normal to the second reflection surface 3 is 45 °. It is provided adjacent to and. That is, the exit surface 4 is provided such that an angle θiv between the normal of the exit surface 4 and the normal of the entrance surface 1 is 45 °. The angle θiii formed is not limited to 45 °, but is set according to the reflection angle θb of the second reflection surface 3 and is set to the same value as the reflection angle θb. The end face shape of the exit surface 4 in this embodiment is substantially rectangular as shown in FIG. 2D, and two corner portions adjacent to the second reflection surface 3 and the side surfaces 5a and 5b are chamfered. However, the end face shape is not particularly limited as long as the object of the present invention can be achieved.

When the reflection angle θa, the reflection angle θb, and the forming angle θiii are within the above range, all the reflection surfaces, ie, the first reflection surface 2 and the first reflection surface that internally reflect the incident light before exiting the image inverting prism 100 The size in the direction orthogonal to the incident axis I can be reduced while making the total reflection surface of the 2 reflection surface 3 be a total reflection surface and that a light beam be emitted perpendicularly to the emission surface 4. In other words, when the reflection angle θa, the reflection angle θb, and the formed angle θiii are within the ranges, for example, the objective of binoculars is minimized while the loss of the transmittance of light incident on the image inverting prism 100 is minimized. It can be made large enough to be stored in the lens barrel matched to the aperture of the lens.

  The auxiliary prism 10 of this embodiment has at least an incident surface 1, a first reflecting surface 2, a second reflecting surface 3 and an emitting surface 4, and these surfaces extend in the direction orthogonal to the paper surface of FIG. ing. As shown in FIG. 3, the auxiliary prism 10 preferably has a recess 7 in the portion adjacent to the incident surface 1 and the second reflecting surface 3. That is, assuming that the incident surface 1, the second reflecting surface 3 and the side surfaces 5a and 5b extend in the direction adjacent to each other, the virtual incident surface 1 ', the virtual second reflecting surface 3' and the virtual side surface 5a Assuming that ', 5b', the first surface 6a and the emission provided parallel to the virtual incident surface 1 ', the virtual second reflecting surface 3', the virtual side surfaces 5a ', 5b' and the second reflecting surface 3 It is preferable that a portion surrounded by the second surface 6b provided parallel to the surface 4 is cut away to form a recess 7 formed by the first surface 6a and the second surface 6b. As shown in FIG. 3, when the light beam enters the incident surface 1 and is internally reflected and then the light beam is emitted from the second exit surface 22 of the roof prism 20 as shown in FIG. It is a part which does not pass. On the other hand, a light beam which is incident on the incident surface 1 but not emitted from the second emission surface 22 may pass through the cut-off portion. Therefore, if there is a portion that has been cut off, there is a risk that the light beam incident on the incident surface 1 will be directly incident on the eyepiece without exiting from the second exit surface 22. There is a risk of causing it to occur. Therefore, it is preferable to cut off not only the portion adjacent to the incident surface 1 and the second reflecting surface 3 but also the portion where the ray does not pass in calculation, leaving only the portion where the ray passes in calculation.

The auxiliary prism 10 measures the distance R from the incident axis I of the incident light beam perpendicularly incident on the center of the incident surface 1 to the second reflecting surface, and the ridgeline of the incident surface 1 to the first reflecting surface 2 from the incident axis I The distance r can be about 1.8 times the distance r. Further, as shown in FIG. 3, the roof prism 20 is set so as not to exceed the size in the direction orthogonal to the incident axis I of the auxiliary prism 10. Therefore, the size of the lens barrel that can be accommodated in the image inverting prism 100 is determined by the size in the direction orthogonal to the incident axis I of the auxiliary prism 10. On the other hand, in the Abbe-Konig prism shown in FIG. 7, the maximum distance R _{1 in the} direction orthogonal to the incident axis I ₁ , which corresponds to the distance R of the image inverting prism 100 of the present invention, corresponds to that of the image inverting prism 100 of the present invention. This is 2.2 times the radial distance r _{1 on} the incident surface, which corresponds to the distance r, and is larger than the image inverting prism 100 of the present invention. Therefore, the image inverting prism 100 having the auxiliary prism 10 can reduce the size in the direction orthogonal to the incident axis I as compared with the Abbe-Konig prism shown in FIG. 7.

  In this auxiliary prism 10, all the reflection surfaces that are internally reflected before the incident light rays vertically incident on the incident surface 1 exit from the auxiliary prism 10 are total reflection surfaces, so a reflection film is formed on a surface that is not a total reflection surface. The loss of light quantity at the time of reflection can be suppressed as compared with the case of having a reflective surface formed by filming. Therefore, according to the auxiliary prism 10, the loss of light transmittance can be suppressed. Further, as described above, in the image inverting prism 100 having the auxiliary prism 10, the size in the direction orthogonal to the incident axis I can be reduced. Therefore, according to this auxiliary prism 10, it is possible to reduce the size in the direction orthogonal to the incident axis I while suppressing the loss of light transmittance, and as a result, for example, a mirror matched to the aperture of the objective lens of binoculars It can be made large enough to be stored in a cylinder.

  The roof prism 20 has a function of inverting the image on the incident surface 1 of the auxiliary prism 10 vertically and horizontally. The roof prism 20 is provided parallel to the emission surface 4 and provided with a second incident surface 21 on which the light beam emitted from the auxiliary prism 10 is incident, and provided parallel to the incident surface 1 and incident on the second incident surface It has at least a second emission surface 22 and a roof surface 23 which are emitted parallel to the incident light beam after the reflected light beam is internally reflected.

  The roof prism 20 is not particularly limited as long as the image on the incident surface 1 of the auxiliary prism 10 can be vertically and horizontally inverted and emitted, and the size in the direction orthogonal to the incident axis I can be in a predetermined range. As the daha prism 20, a Schmidt prism etc. can be mentioned, for example.

  The roof prism 20 in this embodiment is a prism called a so-called Schmidt prism. The structure of the roof prism 20 of this embodiment will be briefly described below. The second incident surface 21 is disposed in parallel with the exit surface 4 at a predetermined interval, and an air gap is provided. That is, the emission surface 4 and the second incident surface 21 are disposed so as not to be in close contact with each other. In the image inverting prism 100, for example, an air gap is provided by having a plate-like member (not shown) between the output surface 4 and the second incident surface 21. The plate-like member is, for example, a frame-like body, and is disposed so as not to shield an area through which light is transmitted.

  The second incident surface 21 is provided such that an angle θv between the normal of the second incident surface 21 and the normal of the incident surface 1 is 45 °. The angle θv formed is not particularly limited to 45 °. The angle θv formed is set according to the reflection angle θb on the second reflection surface 3 and a value satisfying θv = 90−θb when the angle θii formed between the incident surface 1 and the second reflection surface 3 is 90 °. It becomes.

  The second emission surface 22 is provided in parallel to the incident surface 1. The second exit surface 22 in this embodiment is adjacent to the second entrance surface 21 so that the angle θvi between the normal to the second exit surface 22 and the normal to the second entrance surface 21 is 45 °. It is provided. The second incident surface 21 and the second emission surface 22 are adjacent to each other via a ridge line 24 orthogonal to the paper surface of FIG. 1, and the edge opposite to the ridge line 24 is adjacent to the roof surface 23. There is.

  The roof surface 23 has a first roof surface 23a and a second roof surface 23b, which are orthogonal to each other. The ridgeline 25 formed by the first roof surface 23a and the second roof surface 23b is parallel to the paper surface of FIG. 1 and is orthogonal to the ridgeline 24 formed by the second incident surface 21 and the second emission surface 22. .

  The roof prism 20 shows ridgelines 24 of the second incident surface 21 and the second outgoing surface 22 when viewed from the direction in which the second incident surface 21 and the second outgoing surface 22 extend, that is, the direction orthogonal to the sheet of FIG. It is a substantially isosceles triangle whose point is a vertex.

  The second incident surface 21, the second exit surface 22 and the roof surface 23 in the roof prism 20 are such that light rays vertically incident on the second entrance surface 21 can be totally reflected and emitted inside the roof prism 20, It is designed. Similarly to the auxiliary prism 10, the roof prism 20 preferably has a shape that leaves only a portion through which a ray passes. Therefore, in the roof prism 20 of this embodiment, the ridge line 24 where the second incident surface 21 and the second emission surface 22 are adjacent, the corner where the second incident surface 21 and the roof surfaces 23a and 23b are adjacent, the second emission surface The corner where the 22 and the roof surface 23a and 23b adjoin is chamfered.

  The roof prism 20 is set such that the maximum distance in the direction orthogonal to the incident axis I is not larger than the maximum distance in the direction orthogonal to the incident axis I of the auxiliary prism 10. In this embodiment, the portion of the second incident surface 21 farthest from the incident axis I, ie, the ridgeline 24 and the second reflecting surface 3 have the same distance from the incident axis I, and the incident axis of the roof prism 20. The size in the direction orthogonal to I is smaller than the size in the direction orthogonal to the incident axis I of the auxiliary prism 10.

  The roof prism 20 forms a reflection film on a surface that is not a total reflection surface, since all reflection surfaces that internally reflect light rays vertically incident on the second incident surface 21 before the light is output from the roof prism 20 are total reflection surfaces. It is possible to suppress the loss of light quantity at the time of reflection as compared with the case of having a reflective surface formed by performing. Therefore, according to this roof prism 20, the loss of light transmittance can be suppressed. Further, this roof prism 20 is set such that the maximum distance in the direction orthogonal to the incident axis I is not larger than the maximum distance in the direction orthogonal to the incident axis I of the auxiliary prism 10. Therefore, according to this roof prism 10, it is possible to reduce the size in the direction orthogonal to the incident axis I while suppressing the loss of light transmittance, and as a result, for example, a lens barrel matched to the aperture of the objective lens of binoculars Size can be stored in the

  As shown in FIG. 1, an incident axis I of an incident light beam vertically incident on the center of the incident surface 1 of the auxiliary prism 10 and an emission axis J of the outgoing light beam emitted from the roof prism 20 through internal reflection. A certain distance away. In the image inverting prism 100 of this embodiment, the distance d between the entrance axis I and the exit axis J is 0.83 times the distance r. The distance d can be appropriately set according to the reflection angle θa and the reflection angle θb. When the incident axis I and the exit axis J are separated by a predetermined distance d, for example, when the image inverting prism 100 is used by being provided in binoculars, between the two eyepieces according to the width of the user's binoculars Can provide binoculars with adjustable distance.

The auxiliary prism 10 and roof prism 20, e-line (wavelength: 546.1 nm) larger than the refractive index n _e is 1.56 referenced to, usually formed by less than 2.0 optical glass. As the refractive index _ne is larger, the critical angle at the first reflecting surface 2 and the second reflecting surface 3 described later becomes larger, the degree of freedom in the structural design of the auxiliary prism 10 becomes higher, and the loss of light transmittance is suppressed. Thus, a bright observation image can be obtained. Further, in case of providing the image inverting prism 100 to the image inversion optical apparatus such as binoculars, as the refractive index n _e of the image-inverting prism 100 is large, a small bright lens F-number on the objective lens can be used.

The reflection angle at the first reflecting surface 2 when the auxiliary prism 10 having a refractive index n _e is formed by 1.56 greater than optical glass, specifically described below. First, assuming that the refractive index of air is 1.0, the incident angle is θ _X0 , and the emission angle is θ _X , the following relational expression (1) is established.
n _e × sin θ _{X 0} = 1.0 × sin θ _X (1)
The critical angle is θ _X0 when θ _X is 90 °. Therefore, the critical angle when the refractive index _{n e} is 1.56 auxiliary prism 10 is 39.8 °, the critical angle when the refractive index _{n e} of 2.0 is 30 °. Accordingly, when the refractive index _{n e} is 1.56, light rays incident on the first reflecting surface 2 at an incident angle of 39.8 ° to 90 ° is totally reflected. When the refractive index _ne is 2.0, a ray incident on the first reflection surface 2 at an incident angle of 30 ° to 90 ° is totally reflected. That is, the numerical range of the incident angle when light rays incident on the first reflecting surface 2 the larger refractive index n _e is the total reflection is wider. Similarly, the numerical range of the incident angle when light rays incident on the second reflecting surface 3 as the refractive index n _e is large total reflection becomes wider. Accordingly, the refractive index and n _e is greater than 1.56, so as to reduce the direction of a magnitude perpendicular to the incident axis I while suppressing the loss of light transmittance, degree of freedom when structural design auxiliary prism 10 Becomes high, and it becomes possible to use an objective lens with a small f-number.

The refractive index _{n e} is 1.56 greater than optical glass, for example, BASF, BAF, SSK, SK , PSK, BAK, LF, F, SF, LAF, LAK, and the like optical glass such as LASF and LASK it can.

  Next, the operation of the image inverting prism 100 of this embodiment will be described.

  The incident light beam vertically incident on the center of the incident surface 1 of the auxiliary prism 10 is first totally reflected by the first reflection surface 2 at a reflection angle of 67.5 °. The light beam reflected by the first reflection surface 2 is totally reflected by the second reflection surface 3 at a reflection angle of 45 °. The light beam reflected by the second reflection surface 3 is emitted perpendicularly to the emission surface 4 from the emission surface 4. At this time, the outgoing light beam emitted from the outgoing surface 4 is emitted in the direction rotated 45 degrees with respect to the incident axis I of the incident light beam.

  A light beam emitted from the emission surface 4 is perpendicularly incident on the second incident surface 21 of the roof prism 20. A light beam incident on the second incident surface 21 is totally reflected on the second emission surface 22 at a reflection angle of 45 °. The light beam reflected by the second emission surface 22 is totally reflected by the roof surface 23, and the image is inverted vertically and horizontally. The light beam reflected by the roof surface 23 is totally reflected by the second incident surface 21 at a reflection angle of 45 °. The light beam reflected by the second incident surface is emitted perpendicularly to the second outgoing surface 22 from the second outgoing surface 22. At this time, the outgoing light beam emitted from the second outgoing surface 22 is a direction rotated by an angle of 135 ° with respect to the incident light beam that is perpendicularly incident on the second incident surface 21 and is perpendicularly incident on the incident surface 1 Emit parallel to the incident ray. Further, the image of the light emitted from the second emission surface 22 is observed as an image in which the image of the light incident on the incident surface 1 is vertically and horizontally reversed.

  The incident light beam vertically incident on the incident surface 1 of the auxiliary prism 10 and the emission light beam emitted from the second emission surface 22 of the roof prism 20 are parallel and separated from each other by a predetermined distance d.

  According to this image inverting prism 100, the size in the direction orthogonal to the incident axis I can be made, for example, a size that can be accommodated in a lens barrel matched to the aperture of the objective lens of binoculars while suppressing the loss of light transmittance. be able to. Therefore, optical instruments such as binoculars and telescopes provided with the image inverting prism 100 can obtain a bright observation image and can be made slim. Further, according to the image inverting prism 100, the incident axis I of the incident light beam incident on the auxiliary prism 10 and the emission axis J of the outgoing light beam emitted from the roof prism 20 can be separated by a predetermined distance. If the distance d between the incident axis I and the exit axis J is separated by a predetermined distance, for example, when using this image inverting prism in binoculars, two of them may be fitted to the width of the user's eyes. It is possible to provide binoculars in which the distance between the eyepieces can be adjusted. When the entrance axis I and the exit axis J are separated by a predetermined distance, for example, the lens barrel housing the image inverting prism is rotated around the entrance axis I of the auxiliary prism by a desired angle. The distance between the eyepieces can be adjusted.

  The image inverting prism of the present invention is not limited to the above-described configuration as long as the object of the present invention can be achieved, and appropriate modifications can be made.

  The auxiliary prism 10 in the image inverting prism 100 shown in FIGS. 1 to 3 has a first surface 6 a and an exit surface provided in parallel to the second reflection surface 3 in the portion adjacent to the entrance surface 1 and the second reflection surface 3. Although the generation of the ghost is prevented by forming the recess 7 formed by the second surface 6 b provided parallel to 4, the shape of the recess 7 is not particularly limited. For example, as in the auxiliary prism 11 shown in FIG. 4, the occurrence of ghost can be prevented by providing the slit 9 on the inclined surface 8 adjacent to the incident surface 1 and the second reflection surface 3. In this embodiment, one slit 9 extending from the inclined surface 8 in a direction perpendicular to the inclined surface 8 is provided, but two or more slits may be provided. Moreover, the slit extended in the direction which inclines with respect to the inclined surface 8 may be provided. The slit 9 is provided at an appropriate position of a portion through which the light beam does not pass when the light path when the light beam entering the incident surface 1 is internally reflected and then emitted from the second exit surface of the roof prism 20 is calculated. As shown in FIG. 4, the slit 9 is preferably provided at least at a position where the distance from the inclined surface 8 in the direction orthogonal to the inclined surface 8 is maximum at the portion where the light beam does not pass.

  The image inverting prism of the present invention can be suitably used to obtain an erected image by inverting an inverted image formed by an objective lens, provided in an optical apparatus such as binoculars and a ground telescope.

100 image inverting prisms 10 and 11 auxiliary prism 20 double prism 1 incident surface 2 first reflecting surface 3 second reflecting surface 4 exit surface 5 a and 5 b side surface 6 a first surface 6 b second surface 7 concave portion 8 inclined surface 9 slit 21 second incident Surface 22 second emission surface
23 roof surface 23a first roof surface 23b second roof surface 24, 25 ridge line 31 objective lens 32 eyepiece lens 33 barrel

Claims (2)

An image inverting prism having an auxiliary prism and a roof prism, wherein
Wherein A and the auxiliary prism the roof prism, the refractive index ne is rather greater than 1.56, made from optical glass has smaller than 2.0,
The auxiliary prism is provided to totally reflect a first reflection surface which is a flat surface provided to totally reflect an incident light beam perpendicularly incident on the incident surface, and a light beam reflected by the first reflection surface. A second reflecting surface which is a plane provided orthogonal to the incident surface, and a light beam reflected by the second reflecting surface is provided so as to emit perpendicularly to itself, and the first reflecting surface Have different exit planes,
The roof prism is provided in parallel to the exit surface and is provided in parallel to the second incident surface on which the light beam emitted from the auxiliary prism is incident, and in parallel to the incident surface, and the light beam incident on the second incident surface is internally After being reflected, having a second exit surface that emits parallel to the incident light beam ,
The light beam incident on the second incident surface is totally reflected on the second emission surface, then totally reflected on the roof surface, and then totally reflected on the second incident surface ,
An image inverting prism characterized by inverting the image on the incident surface vertically and horizontally. The reflection angle at the first reflecting surface of the incident light is 66 to 68 °, the reflection angle at the second reflecting surface of the light reflected by the first reflecting surface Ri 43 to 46 ° der,
The auxiliary prism claim 1, characterized in Rukoto to have a concave portion formed by a second surface provided in parallel to the first surface and the exit surface provided parallel to the second reflecting surface Image reversal prism described in.

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