JPH027035B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a light wave distance meter that optically measures distance using transmitted light and reflected light.

BACKGROUND TECHNOLOGY AND PROBLEMS Generally, this type of optical distance meter has a light transmitting optical system and a light receiving optical system arranged coaxially in order to reduce the size. Since the amount of reflected light is much smaller than the amount of transmitted light, a large-diameter light receiving lens (objective lens) is required, and therefore the light transmitting optical system is usually arranged coaxially within the objective lens barrel.

However, when a light wave distance meter requires longer distance measurement performance or direct distance measurement capability without placing a reflector at the measurement point, the light source output of the light transmitting system and the sensitivity of the light receiving element must be increased. A need arises.

In such a case, if the output of the light-receiving light source is strengthened, a small amount of internally reflected light in the machine will be received by the light-receiving element as stray light after passing through the inner surface of the objective lens, the inner surface of the lens barrel, etc., and a large error will occur in the measured value. Furthermore, when the sensitivity of the light receiving element is increased, the light receiving element becomes more susceptible to electrical induction from the light emitting source, causing measurement errors.

Furthermore, in order to enhance the ranging performance of the light wave distance meter,
In addition to dealing with the above-mentioned error factors, the calibration by the calibration optical system must be made more accurate. The calibration optical system is an optical system that directly introduces the light from the light emitting source into the light receiving element within the lens barrel without intervening reflection from the measurement point, and uses this calibration light to determine the optical path length and electrical circuit inside the device. Correction calculations can be performed to remove distance measurement errors based on phase changes.

It is desirable for the calibration optical system to have similar physical conditions to those of the measurement optical system, but in reality, a portion of the light emitted from the light source is reflected within the lens barrel using a reflector such as a prism or mirror, or an optical fiber. etc., to introduce the light into the light receiving element, so accurate calibration cannot be expected.

Purpose of the Invention In view of the above-mentioned problems, the present invention ensures optical and electrical separation between the light transmitting optical system and the light receiving optical system, and also brings the physical conditions of the calibration optical system closer to those of the measuring optical system. The objective is to obtain a light wave distance meter with high performance and low distance measurement errors.

Example The structure of the present invention will be explained below based on examples.

FIG. 1 is a longitudinal sectional view of a light wave distance meter to which the present invention is applied.

In FIG. 1, a large-diameter light-receiving lens 2 is mounted inside an outer tube 1 (main barrel), and a light-receiving element 3 and a detection circuit 4 are provided at a focal point on the rear optical axis. A parallel glass plate 5 is fitted into the open end of the outer tube 1 in front of the light receiving lens 2.
At the center of the optical axis on the inner surface of the parallel glass plate 5, a right angle prism 6 having a slope 8 forming an angle of 45 degrees with respect to the optical axis is attached. The light 9 emitted from the light transmitting section 7 provided on the outside of the outer cylinder 1 is incident on the slope 8 of the right angle prism 6 in parallel with the parallel glass plate 5, and is bent at a right angle by total reflection or specular reflection. , are guided toward the measuring point through the parallel glass plate 5.

The light transmitting section 7 is housed in a housing 10 attached to the side of the outer cylinder 1, and includes a light emitting element 11 that is a light source of the transmitted light 9, a driving circuit 12 thereof, and a collimator lens 13. The light from the light emitting element 11 is converted into a parallel beam by a collimator lens 13, and is incident on the slope 8 of the right angle prism 6 through a hole 14 formed in the outer cylinder 1.

The transmitted light 8 guided toward the measuring point through the parallel glass plate 5 hits a reflective object on the measuring point and is reflected. The reflected light 15 enters the light receiving lens 2 through the parallel glass plate 5 and is focused on the light receiving element 3. The photoelectric conversion output of the light receiving element 3 is sent to the detection circuit 4.
The distance to the measurement point is calculated by phase detection.

Note that a diaphragm 17 is interposed in the light transmission optical path, and the diaphragm 17 is rotated by an diaphragm adjustment motor 18 via a drive gear 19 to adjust the amount of light to be transmitted.

According to the above configuration, since the light transmitting optical system and the light receiving optical system are orthogonal to each other, and the light transmitting optical system is located in front of the light receiving lens, mutual optical interference can be significantly reduced. In other words, the conventional light receiving lens 2
As with the configuration in which the light transmitting optical system is placed behind the light emitting element, reflected light from the inner surface of the light receiving lens 2 and the inner surface of the outer tube 1 does not enter the light receiving element 3 as stray light (leak light). By increasing the output of the light receiving element 11 or increasing the sensitivity of the light receiving element 3, the distance measurement limit can be extended and the resolution can be improved.

Further, the light receiving section and the light transmitting section 7 can be electrically separated by the outer tube 1 and the housing 10, respectively. Therefore, it is possible to shield the radiated electric field from the carrier oscillator in the drive circuit 12, and therefore eliminate electrical induction to the light receiving element 3 and the detection circuit 4.
It becomes possible to receive light with higher output or with higher sensitivity.

In addition, since the light transmitting section 7 is arranged outside the light receiving system outer cylinder 1, the effective area of the light receiving lens 2 is not reduced due to obstruction by the drive circuit 12 of the light transmitting section 7, etc. It is possible to further increase the light-receiving sensitivity by using the same amount of transmitted light.

Moreover, as shown in FIG. 1, it is possible to narrow down the diameter of the beam of the transmitted light 8 to be sufficiently smaller than the diameter of the light-receiving lens. This is effective in the case of so-called direct distance measurement in which no reflecting prism is placed at the measurement point. In other words, when a reflecting prism is placed at the measurement point, the reflected light is a parallel beam with approximately the same diameter as the transmitted light, but in the case of direct distance measurement, as shown in FIG. Parallel transmitted light 9
After being reflected, the light diverges (diffusely reflects) and enters the light receiving lens 2 as reflected light 15. Therefore, by reducing the beam diameter of the transmitted light 8, the dispersion of the light energy applied to the object to be measured 20 is further reduced, and the reflected light 1 diverged by the light receiving lens 2 having a large effective area is reduced.
5 can be efficiently collected, high-resolution direct distance measurement becomes possible.

When performing direct distance measurement where the reflected light 15 is not a parallel beam, the amount of light incident on the light receiving element 3 can be maximized by adjusting the correction lens 21 interposed between the light receiving lens 2 and the light receiving element 3. It is possible to obtain distance measurement information with a higher S/N ratio. This is particularly effective when measuring close distances of several meters to more than ten meters, and by converging the reflected light 15 with the light receiving lens 2 and further adjusting the position of the correction lens 21 in the optical axis direction, the light receiving element It is possible to focus on the photoelectric conversion surface of No. 3. The position of the correction lens 21 can be adjusted from the outside of the outer cylinder 1, and the adjustment can be made by, for example, adjusting while looking at the light receiving level display, or by aligning the position with a mechanical distance scale carved in advance. You can get a focused state.

Preferably, the correction lens 21 is mechanically interlocked with the focus adjustment section of the collimating telescope. The collimating telescope is housed in a lens barrel 23 attached to the outside along the outer tube 1. In order to introduce outside light into this telescope, a slope 8 of a right-angle prism 6 is attached to the center of the inner surface of the parallel glass plate 5 of the light transmitting and receiving system.
Another rectangular prism 24 is attached to the. If this right-angle prism 24 is attached, the total reflection performance on the slope 8 of the right-angle prism 6 will be lost, so in this case, the prism 6
The inclined surface 8 on one side, which is the joint surface of the parts 24 and 24, is coated and used as a semi-transparent mirror. As a coating material, visible light from the outside passes through, but specular reflection of 95% or more occurs on the slope 8 for light of a specific wavelength emitted from the light emitting element 11 (light emitting diode, semiconductor laser, etc.). Materials such as:

Therefore, the external light 25 from the measurement point passes through the parallel glass plate 5 and the prism 6, passes through the coating film on the slope 8, is totally reflected at the slope 26 on the opposite side of the right angle prism 24, and is reflected by the outer cylinder 1. The light enters a right-angle prism 28 disposed at the front end of the telescope barrel 23 through a hole 27 formed in the telescope tube 23 . The outside light that is further bent by 90 degrees by this right-angle prism 28 passes through an objective lens 29 and erecting lenses 30 and 31 of the telescope, and is guided to an eyepiece system 32.

Some lenses 33 of the eyepiece lens system 32 can be adjusted in position in the optical axis direction like a normal telescope,
Through this adjustment, a focused state can be obtained and the optical axis of the light wave distance meter can be correctly aligned with the measurement center point of the object to be measured.

As mentioned above, the lens 3 of this eyepiece system 32
By mechanically interlocking the adjustment mechanism 3 and the adjustment mechanism of the correction lens 21 of the light receiving system as shown by the dotted line 34 in FIG. 1, it is possible to obtain a rangefinder that is extremely easy to use. That is, if the object to be measured is correctly sighted by adjusting the eyepiece lens of the collimating telescope, the light receiving optical system correction lens 21 is also automatically moved to a substantially in-focus position, and the light receiving element 3 receives light with maximum sensitivity. Can be done.

According to the collimating optical system shown in the embodiment of FIG. 1, the optical axis of the collimating optical system and the optical axis of the measuring optical system can be made to coincide, so that accurate collimation is possible.
Furthermore, since the prism 24 for the collimating optical system is placed in front of the light receiving lens 2, there is little interference with the light receiving optical system. In other words, if a prism for the collimation optical system is placed behind the light receiving lens 2, the amount of incident external light converged by the light receiving lens 2 will be reflected in the light receiving element 3.
The degree of interference will increase. Furthermore, since the light receiving lens 2 (objective lens) is not interposed in the collimation optical system, the collimation image is less likely to be distorted.

Furthermore, in the embodiment shown in FIG. 1, the calibration optical path is constructed using the rectangular prism 24 of the above-mentioned collimating optical system. The calibration optical system is an optical system that directly introduces the light from the light emitting source into the light receiving element within the lens barrel without intervening reflection from the measurement point, and uses this calibration light to determine the optical path length and electrical circuit inside the device. Correct calculations can be performed to remove measurement errors based on phase changes.

The calibration optical path is constructed by interposing a twice-reflecting rhombic prism 36 in the light transmission optical path within the housing 10 . This rhombic prism 36 is mounted on a rotating shutter plate 37, and the emitted light 9 passes through a hole in the rotating shutter plate 37 during distance measurement, and the rotating shutter plate 37 is rotated by a shutter motor 38 during calibration. Thus, a rhombic prism 36 is interposed in the light transmission optical path.

During calibration, the light from the light transmitting element 11 is incident on the rhombic prism 36 via the collimator lens 8,
By the two reflections, the optical path is moved parallel to the light transmission optical axis. The light emitted from the rhombic prism 36 is
The light enters the slope 26 of the rectangular prism 24 of the collimation system through a hole 39 formed adjacent to the hole 14 of the light transmitting system, is bent 90 degrees here, and then passes through the center of the optical axis of the light receiving lens 2 to the light receiving element. I am guided by 3. As a result, a direct calibration optical path 40 (dotted line) from the light emitting element 11 to the light receiving element 3 is formed within the apparatus, and necessary calibration calculations can be performed.

Incidentally, in order to utilize the slope 26 of the rectangular prism 24 of the collimation system as a reflecting surface, the slope 26 is coated. Since the collimating optical path uses the slope 26 of the right-angle prism 24 as a total reflection surface, the coating on the slope 26 does not affect the collimation system. The coating material on both slopes 8, 26 of the right-angled prism 24 may be of the same type.

In this calibration optical path, the rectangular prism 24 is also used as a collimating optical path, so the configuration is simple and the optical path adjustment work during manufacturing and assembly is also easy. In addition, since the collimator lens 13 of the light transmitting system and the light receiving lens 2 of the light receiving system are both included in the calibration optical path, the calibration optical path is closer to the physical conditions of the measurement optical system, which allows accurate calibration and measurement. Distance accuracy can be improved. As a result, even if the length measurement limit is extended using the high output light emitting element 11 and the high sensitivity light receiving element 3 in the configuration shown in FIG. 1, high distance measurement accuracy can be obtained.

Effects of the Invention As described above, the present invention includes a parallel glass plate disposed in front of the light receiving lens, and an inner surface of the parallel glass plate arranged at an angle of 45° with respect to the optical axis.
An outward reflecting surface and an inward reflecting surface are provided, and the measuring light is directed to the outward reflecting surface and sent out, and the light from the light source is incident on the inward reflecting surface. A calibration optical system is provided in which the optical path is changed so that the measurement light is directly introduced into the light-receiving element via the light-receiving lens.

With this configuration, the light transmitting optical system and the light receiving optical system can be almost completely separated optically and electrically.
By using a high-output light emitting element and a high-sensitivity light-receiving element, a light wave distance meter with a longer measuring distance and higher measuring accuracy can be obtained without increasing length measurement errors due to stray light or electrical induction. It will be done. Furthermore, since the image space of the light-receiving optical system is less obstructed by the light-transmitting optical system, the diameter of the light-receiving lens can be effectively used to perform distance measurement with higher sensitivity.

Furthermore, since the light receiving lens is interposed in the calibration optical path, the physical conditions of the calibration optical system are closer to those of the measurement optical system, and accuracy can be further improved.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a light wave distance meter showing an embodiment of the present invention, and FIG. 2 is a diagram of the optical path at a measurement point. In addition, in the symbols used in the drawings, 1... outer cylinder, 2... light receiving lens, 3... light receiving element, 4...
Detection circuit, 5...Parallel glass plate, 6...Right angle prism, 7...Light transmitting section, 8...Slope, 9...Sending light, 10...Housing, 11...Light emitting element, 1
3... Collimator lens, 14... Hole, 15...
Reflected light, 20...Object to be measured, 21...Correction lens, 24...Right angle prism, 25...External light, 26
... slope, 29 ... objective lens, 36 ... rhombic prism, 37 ... rotating shutter plate, 40 ... calibration optical path.

Claims (1)

[Claims] 1. A light-receiving optical system comprising a light-receiving lens and a light-receiving section placed at its optical axis focal position housed in a lens barrel, and a parallel glass fitted into the open end of the lens barrel in front of the optical axis of the light-receiving lens. approximately relative to the optical axis at the center of the optical axis inside this parallel glass plate.
An outward reflecting surface is attached toward the front of the optical axis so as to form an angle of 45 degrees, and an outward reflecting surface is attached toward the rear of the optical axis so as to form an approximately 45 degree angle to the optical axis behind the outward reflecting surface. an inward reflecting surface; a light sending optical system configured to direct outgoing light from outside the lens barrel toward the outward reflecting surface and send the outgoing light to a target object via the parallel glass plate; Calibration in which a removable optical path changing means is interposed in the light transmitting optical system so that the transmitted light is guided toward the inward reflecting surface and converged on the light receiving element via the light receiving lens. A light wave distance meter having a calibration optical path, comprising: an optical system.