JPS58111716A - Scale reading device of theodolite - Google Patents

Abstract

PURPOSE:To read the scales highly accurately, by emitting luminous fluxes, which are reflected in the vicinity of the interrecting line of a second reflecting surface and a first reflecting surface, from the vicinity of the aligned line of a first prism, and removing the fluxes from an observing light path. CONSTITUTION:The luminous fluxes from the scales S1 and S2, which face each other on a minute and degree scale plate 1 separated by 180 deg., are reflected to the inside by reflecting prisms 2 and 2' in parallel with the scale plate 1, are made to be the parallel luminous fluxes by collimator lenses 3 and 3', and reach a light path synthesizing prism 4. Said luminous fluxes are reflected by reflecting surfaces 4a and 4b of the synthesizing prism 4, respectively, at a right angle with the scale plate 1, ad reach a matching prism 7 through an image forming lens 5 and a pair of parallel plane glasses 6 and 6' which can be inclined. The images of the scales S1 and S2 are formed on the emitting surface of the prism 7. A micrometer 8 is provided at the part adjacent to the emitting surface of the matching prism 7. The images of the scales S1 and S2 on the minute and degree scale plate 1 and the scale of the micrometer 8 can be observed through an eyepiece lens 9.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a scale reading device for a theodolite, and more particularly to an improvement in an optical system for reading scale lines that are separated by 180° and facing each other on a scale plate so that they all coincide.

Conventionally, in this type of device, it has been necessary to align the matching line with the scale line image plane to eliminate parallax during reading so as not to reduce measurement accuracy.

For this purpose, as shown in Fig. 1, a parallel plane glass 1
A mating prism formed by two sets of parallel entrance/exit surfaces and a ridge line (P) with an included angle α is known from JP-A-49-32661, etc., by removing the diagonally opposite corners of 0. There is.

However, with this configuration, the matching line, which is located at the center of the visual field and is observed and affects measurement accuracy, is formed as the ridge line (P) of two prism surfaces that intersect obliquely with each other, so it cannot be processed into a perfectly straight line. It is very difficult and rare. Further, since half of the scale line iron surface is not on the prism surface due to the notch, an additional reticle 20 is required, making it difficult to accurately align and adjust the reticle and the mating prism. Furthermore, in this configuration, since the light beams (I) (6) from scales 180° opposite to each other on the not-illustrated minute scale plate intersect when passing through the mating prism, the image near the mating edge is not visible before the mating prism. Since it is formed by light rays from an object point far from the optical axis of the imaging optical system shown in the figure, the part (3) with relatively many aberrations within the reading field is used, which reduces the scale reading accuracy. It was a disadvantage.

The object of the present invention is to have a clear matching line and easy processing,
Moreover, it is an object of the present invention to provide a scale reading device for a theodolite that can read the scale with high accuracy.

In order to achieve the above object, the present invention provides a scale of a theodolite having a matching prism for combining the luminous fluxes from scales facing each other at 180° on a minute scale plate within the same field of view and aligning the sensing bodies of both eyes. The reading device includes an entrance surface, an exit surface that is substantially orthogonal to the entrance surface, a first reflection surface that reflects a light beam from the entrance surface to the exit surface, and a first reflection surface that is inclined at a small angle with respect to the first reflection surface. a first prism having two reflective surfaces; and a first prism sandwiched between an entrance surface of the first prism and a second reflective surface so as to form an exit surface aligned on the same plane as the exit surface of the first prism. A second prism that is bonded to a corner portion and has a refractive index different from that of the first prism constitutes the matching prism, and the (4) bonding surface of the first prism and the second prism and the injection The line of intersection with the surface forms a matching line, and most of the light beam reflected by the first reflective surface exits the exit surface of the first prism,
Most of the light beam reflected by the second reflective surface exits the exit surface of the second prism, and the first reflected light beam is refracted by the bonded surface of both prisms and then exits the second prism. A light beam emitted near the matching line of the prism and removed from the observation optical path, and reflected near the intersection line of the second reflecting surface with the first reflecting surface passes near the matching forest of the first prism. The structure is such that the light is emitted and removed from the observation optical path.

Hereinafter, the present invention will be explained based on examples.

FIG. 2 is a schematic optical path diagram of a scale reading device according to the present invention. The luminous flux from the scales (81), <st) facing each other at a distance of 1800 degrees on the minute scale plate 1 is reflected inward by the reflecting prisms 2, 2' parallel to the scale plate 1, and then
The collimator lenses 3 and 3' turn the light into a parallel beam, which reaches the optical path combining prism 4. The optical path combining prism 4 has reflective surfaces 4a and 4b that are orthogonal to each other, and is arranged so that the ridge line where these flesh-emitting surfaces intersect coincides with the optical axis of the collimator lens 3.3'. Minor scale (st),
The light beam from (St) is reflected by the reflecting surface 4a of the combining prism 4.

4b, a pair of parallel plane glasses 6, 6' and a matching prism, each of which is tiltably provided in order to be reflected perpendicularly to the scale plate 1, subjected to a converging action by the imaging lens 5, and to displace the luminous flux by a minute amount. images of scales (Sl) and (St) are formed on the exit surface of the matching prism 7 through T.

A micrometer 8 is installed adjacent to the exit surface of the mating prism 7.
is provided, and the minute scale plate 1 is displayed through the eyepiece 9.
The image of the upper scale (81) (St) and the scale of the micrometer 8 can be observed.

Next, the configuration of the matching prism T will be explained in detail with reference to the sectional view in FIG. 3(,) and the field view in FIG. 3(b). The matching prism 7 is composed of a large first prism 7a and a small second prism 7b having a higher refractive index bonded thereto. The first prism 7a has an entrance surface (A-B), an exit surface (p-A) perpendicular to the entrance surface, a first reflection surface (CD) inclined at an angle of about 45 degrees with respect to the entrance surface and the exit surface, and a 1 reflective surface (C-D) and a second reflective surface tilted by a small angle θ (
D-F), and the second prism 7b is bonded to the corner portion sandwiched between the exit surface (P-A) and the second reflective surface (D-F) of the first prism 7a, Its injection 'm (E −P
) is aligned with the same plane as the exit surface (PA) of the first prism 7a.

The bonding surface of the first prism 7a and the second prism 7b (P
-F) and the exit surface (E-A) form a line of intersection (P).

Here, most of the first luminous flux (I) from the scale (Sl) is reflected by the first reflecting surface (C-D) of the first prism '7'a, and the exit angle (P) of the first prism 7a is -A), most of the second luminous flux (n) from the other scale (S2) (7) is reflected by the second reflective surface (D-F) of the first prism 7b, and After being refracted at the mating surface (P-F), the exit surface of the second prism 7b (
E-P) is injected.

Since the second reflecting surface (D-F) is inclined by an angle θ (approximately 2° to 10° in practice) with respect to the first reflecting surface (C-D), the The second beam (II) is tilted by 2θ more than when reflected by the first reflecting surface, but
This inclination is corrected by the refractive action of the bonding surface (P-F) of the first prism 7a and the second prism 7b based on the difference in refractive index between the two prisms.

Therefore, the second luminous flux (I[) that exits the exit surface (E-P) of the second prism 7b is reflected by the first reflective surface (C-D) of the first prism 7a, and is reflected by the exit surface (P-A) of the first prism 7a. ) can be made parallel to the emitted first beam (I). However,
As shown by the dotted line in Figure 3 (,), the first luminous flux (I)
The inner partial light beam reflected near the intersection line (D) with the second reflecting surface (8) (D-F) on the first reflecting surface (D=F) is reflected by the bonding surface of both prisms. (p-F), the second prism 7b receives the refraction action on this bonded surface.
The light beam obliquely reaches near the matching edge of the exit surface (E-P), where it is largely refracted and removed out of the observation optical path.

In addition, the inner partial luminous flux of the second luminous flux (II) that is reflected in the vicinity of the 1OiJ intersection line (D) on the second reflecting surface (C-D) is reflected from the bonding surface (P-F) of both prisms. The light does not pass through the beam, but reaches obliquely near the matching edge of the exit surface (PA) of the first prism 7a, where it is largely refracted and removed out of the observation optical path. In this way, as shown in FIG. 3(b), the scales (st
), the 1st degree second luminous flux (I) from (Sl ),
A part of the innermost luminous flux of (n) is removed, and both scales (st
), (s2) images (81') and (82) are clearly imaged.

Similarly, the matching prism T has the above-mentioned first. Second luminous flux (I)
, (II), a third . The fourth light beams (m) and (IV) are incident, and the third light beam (2) is reflected by the first reflection 'rM (C-D) and then onto the exit surface (P-A) of the first prism 7a. A scale numeral image is formed, and the fourth light beam (IV) is directed to the second reflective surface (D-F
), passes through the second prism, and passes through the matching prism 7.
The scale of a micrometer 8 placed adjacent to the exit surface (E-A) of the micrometer 8 is illuminated.

Therefore, as shown in the visual field diagram in Figure 3(b), the scale image (S+
An image (S') of the scale 8a of the micrometer and the scale numerals is observed within the same field of view, sandwiching ``)+(st').

In the above embodiment, the exit surface of the matching prism 7 is the focal plane,
A mask can be provided on this exit surface by vapor deposition or the like as shown in the field view of FIG. It is also possible to bond a thin focus plate 30 provided with a. In this case, since the micrometer is placed adjacent to the reticle, the scale of the micrometer is shifted from the focal plane by the thickness of the reticle 30 and the air gap, but the reticle 30 is located adjacent to the matching prism. 7 and supported over the entire surface, it can be made thinner, and the scale position of the micrometer can be placed within the depth of focus without any problems.

In addition, the light beam (III) forming the scale numeral image and the light beam (I) forming the scale line image do not produce astigmatism or chromatic aberration due to the bonded second prism, and form the other scale image. The light flux (n) has astigmatism and chromatic aberration in the direction perpendicular to the matching line (b), but this can be removed by the focus plate mask and the matching line (P), and the light flux (IV), which also has aberrations, is Since it is used for illuminating the micrometer, there is no effect and a clear image can be obtained. Moreover, since this matching prism is of a reflective type, the first. No aberration occurs due to the second reflecting surface, and (11) it also serves as a right-angle prism that is normally placed in front of the focusing plate.

As described above, according to the present invention, since the matching line is formed as the bonding surface of the two prisms, it can be polished after bonding the two prisms, making it easy to process and forming a clear straight line. Not only can it be done, but it can also be read as 18 on the scale plate.
Since the images of two scales facing each other with a 0° separation are formed by the central light beam close to the optical axis of each imaging light beam, aberrations are sufficiently corrected and the image is extremely clear, resulting in extremely high precision. Scale reading is possible.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of a conventional scale reading device, Fig. 2 is a schematic optical path diagram of a scale reading device according to the present invention, Fig. 3 (,) is a sectional view of a matching prism, and Fig. 3 (b) is a field of view It is. Fourth
The figure is a sectional view of another embodiment of the matching prism. [Explanation of symbols of main parts] S, , S2... 180 degrees apart and facing each other (12) Graduation 4... Optical path combining prism 7... Matching prism 7a... ...First prism 7b...Second prism Applicant 2 Nippon Kogaku Kogyo Co., Ltd.

Claims (1)

[Claims] In a scale reading device for a theodolite, which has a matching prism for combining the light beams from scales facing each other at 180° on a minute scale plate within the same field of view and matching the two scales in one image, an incident surface and a matching prism are used. a first prism having an exit surface substantially orthogonal to the exit surface, a first reflection surface that reflects the light beam from the entrance surface to the exit surface, and a second reflection surface inclined at a small angle with respect to the first reflection surface; and a corner portion sandwiched between the incident surface and the second reflective surface of the first prism so as to form an exit surface aligned on the same plane as the exit surface of the first prism; 1
The matching prism is composed of the prism and a second prism having a different refractive index, and the intersection line between the bonding surface of the first prism and the second prism and the exit surface forms a matching line, and the second prism has a different refractive index. Most of the luminous flux reflected by the first reflecting surface
Most of the luminous flux emitted from the exit surface of the prism and reflected by the second reflective surface exits the exit surface of the second prism, and near the intersection line of the first reflective surface with the second reflective surface. After being refracted by the bonded surface of both prisms, the light beam reflected by the second prism is emitted near the matching line and removed from the observation optical path, and A scale reading device characterized in that the luminous flux reflected near the line of intersection with the surface exits the first prism near the matching line and is removed from the observation optical path.