JP2009008404A - Distance measuring apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a non-prism type distance measuring apparatus which can perform distance measurement promptly and with high precision without depending on the distance to a target. <P>SOLUTION: The distance measuring apparatus includes a light transmitting system (1 to 4) for transmitting a measuring light flux to a target through a reflecting member (3) arranged on an optical axis and an objective (4) arranged in front of the reflecting member and a light receiving system (3, 5, 7, 8) for receiving the measuring light flux reflected by the target through the objective and the reflecting member. The light receiving system has a relay optical system (7) for connecting a rear focal position (6A) and a light receiving surface (8) of the objective in a conjugate manner and a deflecting means which is provided in the optical path between the rear focal position and the light receiving surface to deflect a measuring light flux from a target which is in a short distance. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a distance measuring device, and more particularly to a device for measuring a distance to a target based on a measurement light beam received and reciprocated between the target and the target.

  In a conventional distance measuring device using a light wave, a measurement light beam supplied from a light source is reflected by a reflecting member arranged on the optical axis, and converted into a parallel light beam through an objective lens arranged on the front side of the reflecting member. And it injects towards the corner cube which is the target. Then, the measurement light beam reflected by the corner cube is received through the objective lens and the reflection member, and the distance to the target is measured based on the received measurement light beam.

  On the other hand, apart from the prism type distance measuring device that uses a corner cube as a target, there are also non-prism type distance measuring devices that use, for example, an artificial object such as a reflex sheet or a wall, or a natural object such as a tree or a cliff. Are known. In the non-prism type distance measuring device, the reflecting surface of the target is often a scattering surface, and the amount of received light is often significantly smaller than that of the prism type distance measuring device. In view of this, the non-prism distance measuring device is devised to reduce the spot size of the measurement light beam irradiated to the target so as to increase the amount of light reflected by the target.

  As described above, in the conventional distance measuring apparatus, only the measurement light beam that has passed through the periphery of the reflecting member is received among the measurement light beams that are reflected by the target and transmitted through the objective lens. In other words, of the measurement light beam reflected by the target and transmitted through the objective lens, the light beam blocked by the reflecting member does not contribute to the measurement. When there is no focusing mechanism in the light receiving system, the condensing position of the measurement light beam varies depending on the distance to the target, and the light beam is in a hollow state where the central portion is missing at a position deviating from the condensing position in the optical axis direction. .

  In conventional non-prism distance measuring devices, the amount of measurement light beam from a target at a long distance is small, so the light receiving surface is arranged according to the condensing position of the measurement light beam from a target at a long distance. ing. Therefore, only a part of the measurement light beam in the hollow state from the target at a short distance reaches the periphery of the light receiving surface, or all of the measurement light beam passes around the light receiving surface. As a result, due to the decrease in the amount of received light, measurement may take time, measurement accuracy may decrease, or measurement itself may be impossible.

  The present invention has been made in view of the above-described problems, and provides a non-prism type distance measuring device capable of performing distance measurement quickly and with high accuracy without depending on the distance to a target. For the purpose.

In order to solve the above problems, in the present invention, a light transmission system that transmits a measurement light beam to a target via a reflection member disposed on the optical axis and an objective lens disposed on the front side of the reflection member; In a distance measuring device comprising a light receiving system that receives the measurement light beam reflected by the target through the objective lens and the reflecting member,
The light receiving system is provided in the optical path between the rear focal position of the objective lens and the light receiving surface in a conjugate manner with a relay optical system that conjugates the rear focal position of the objective lens and the light receiving surface, and is at a short distance. There is provided a distance measuring device having a deflecting means for deflecting a measurement light beam from a target.

  In the present invention, the measurement light beam in the hollow state reflected by the target at a short distance and passing through the reflecting member is appropriately deflected by the action of the deflecting means provided in the relay optical system, for example, and is measured in the hollow state. Part of reaches the light receiving surface with certainty. As a result, in the present invention, even when applied to a non-prism type distance measuring device, distance measurement can be performed quickly and with high accuracy without depending on the distance to the target.

  Embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a diagram schematically showing a basic configuration of a distance measuring apparatus according to an embodiment of the present invention. In the present embodiment, for example, the present invention is applied to a non-prism type distance measuring apparatus that targets an artificial object such as a reflex sheet or a wall, or a natural object such as a tree or a cliff. In the following description of the basic configuration of the apparatus, it is assumed that the target is at infinity in FIG. 1 in order to facilitate understanding of the description.

  The distance measuring apparatus according to the present embodiment includes an LD (laser diode) that emits infrared light of 660 nm, for example, as the light source 1 for supplying a measurement light beam. As the light source 1, another suitable light source such as an LED (light emitting diode) can be used. The measurement light beam emitted from the light source 1 is reflected by the light transmission reflecting member 3 via the light transmission optical system 2. The measurement light beam reflected by the reflecting member 3 is converted into a parallel light beam via the collimating objective lens 4 and then irradiated onto a target (not shown).

  For example, a measurement light beam reflected and scattered (hereinafter also simply referred to as “reflection”) by a target at infinity and background light from the outside enter the dichroic prism 5 via the objective lens 4 and the reflection member 3. . The dichroic prism 5 has a characteristic of reflecting light having a wavelength larger than 650 nm, for example, and transmitting visible light having a wavelength of 400 nm to 650 nm, for example. The light reflected by the dichroic prism 5, that is, the measurement light beam from the target is once condensed at a position indicated by reference numeral 6 </ b> A, and then passed through a relay optical system 7 composed of one or a plurality of lenses, for example, APD ( The light is condensed on the light receiving surface of the light receiving element 8 such as an avalanche photo diode.

  The focusing position 6A of the measurement light beam from the target at infinity is nothing but the rear focal position of the objective lens 4. The hatched region 31 in FIG. 1 is arranged on the optical axis on the rear side (opposite side of the target side) of the objective lens 4 out of the measurement light beam reflected by the target and transmitted through the objective lens 4. The measurement light beam reaching the light receiving surface of the light receiving element 8 without being blocked by the reflecting member 3 is shown.

  On the other hand, the light that has passed through the dichroic prism 5, that is, the light flux (visible light) from the outside, places the target at the position of the focusing screen 13 via the focusing lens 11 and the erecting prism 12 that can move in the optical axis direction. An intermediate image of the outside world is formed. At this time, an erect image of the outside world is formed at the position of the focusing screen 13 by the action of the erecting prism 12. The intermediate erect image formed at the position of the focusing screen 13 is observed with the naked eye through the eyepiece lens 14 together with collimation information formed on the focusing screen 13. In FIG. 1, the eye point of the naked eye is indicated by the reference symbol EP.

  Thus, the light source 1, the light transmission optical system 2, the reflecting member 3, and the objective lens 4 constitute a light transmission system that transmits the measurement light beam to the target. The objective lens 4, the dichroic prism 5, the focusing lens 11, the erecting prism 12, the focusing screen 13, and the eyepiece lens 14 constitute a collimation system for collimating the target. The objective lens 4, the dichroic prism 5, the relay optical system 7, and the light receiving element 8 constitute a light receiving system that receives the measurement light beam reflected by the target. For the principle of measuring the distance to the target based on the measurement light beam received by the light receiving element 8, reference can be made to, for example, JP-A-8-292259.

  Prior to the description of the characteristic configuration of the distance measuring apparatus according to the present embodiment, the disadvantages of the conventional non-prism type distance measuring apparatus will be described with reference to FIG. In FIG. 2, the measurement light beam reflected by the target at infinity and transmitted through the objective lens 4 is received by the light receiving element 28 disposed at the focal position 6 </ b> A of the objective lens 4 without being blocked by the reflecting member 3. A measurement light beam condensed on the surface is indicated by a region 21 defined by a one-dot chain line.

  Further, the measurement light beam reflected by the target at a short distance and transmitted through the objective lens 4 is not obstructed by the reflecting member 3 and is behind the light receiving surface of the light receiving element 28 (the side opposite to the objective lens side). The measurement light beam condensed at the position 6B is indicated by a hatched area 22. Thus, when the target is at infinity or a long distance, a part of the measurement light beam from the target is blocked by the reflection member 3, but all the measurement light beams 21 that have passed around the reflection member 3 are received by the light receiving element. 28 light-receiving surfaces are reached.

  On the other hand, when the target is at a short distance, a part of the measurement light beam from the target is blocked by the reflecting member 3, and the light beam is in a hollow state at the position 6A on the light receiving surface of the light receiving element 28. As a result, only a part of the measurement light beam 22 that has passed around the reflecting member 3 reaches the periphery of the light receiving surface of the light receiving element 28, or all the measurement light beams 22 that have passed around the reflecting member 3 have received the light receiving element 28. Passes around the light receiving surface. When the amount of light received by the light receiving element 28 decreases, not only measurement takes time, but also the measurement accuracy may decrease. Further, when the light receiving element 28 cannot receive light at all, the measurement itself becomes impossible.

  FIG. 3 is a diagram schematically showing a main configuration characteristic of the distance measuring apparatus according to the present embodiment. In FIG. 3, illustration of the light transmission system and the collimation system is omitted, and only the main part on the rear side of the dichroic prism 5 in the light receiving system shown in FIG. 1 is illustrated. In the distance measuring device according to the present embodiment, as shown in FIG. 3, the measurement light beam 31 reflected by the target at infinity and passed through the objective lens 4 and the reflecting member 3 is once at the focal position 6A of the objective lens 4. After condensing, the light is condensed on the light receiving surface of the light receiving element 8 via the relay optical system 7 constituted by one lens 7a. That is, all of the measurement light beam reflected by the target at infinity or a long distance (for example, about infinity to about 100 m) and passed through the objective lens 4 and the reflecting member 3 reaches the light receiving surface of the light receiving element 8.

  On the other hand, the measurement light beam 32A reflected by the target at a short distance (for example, several meters) and having passed through the objective lens 4 and the reflecting member 3 is arranged at the focal position 6A in a hollow state without being condensed at the focal position 6A. The incident light is incident on the background light cut stop (shielding member) 10. Of the measurement light beam 32 </ b> A that has entered the diaphragm 10, the measurement light beam 32 </ b> B that has passed through the opening (or the light transmission part) of the diaphragm 10 is incident on the lens 7 a that constitutes the relay optical system 7. A part of the measurement light beam 32 </ b> B diffused (deflected) by the diffusion surface 7 aa formed on the exit surface of the lens 7 a reaches the light receiving surface of the light receiving element 8.

  The diffusing surface 7aa is an area where the measurement light beam 31 in a hollow state from a target at infinity or a long distance (hereinafter also simply referred to as “far distance”) does not pass, and from the target at a short distance. It is formed in the region through which the measurement light beam 32B in the hollow state passes, that is, the central region of the exit surface of the lens 7a. Incidentally, if the diffusing surface 7aa is not formed on the exit surface of the lens 7a, whether only a part of the measurement light beam 32B reaches the peripheral portion of the light receiving surface of the light receiving element 8 as in the case of the prior art shown in FIG. Alternatively, all of the measurement light beam 32 </ b> B passes around the light receiving surface of the light receiving element 8.

  In the distance measuring apparatus according to the present embodiment, the light receiving surface of the light receiving element 8 is arranged in accordance with the condensing position 6A of the measurement light beam 31 from the target at infinity, so that the target at infinity or far distance. Of the measurement light beam from the object, all of the measurement light beam 31 that has passed through the reflecting member 3 reaches the light receiving surface of the light receiving element 8. On the other hand, of the measurement light beam from the target at a short distance, a part of the measurement light beam 32B having passed through the reflecting member 3 and the diaphragm 10 is diffused by the diffusion surface 7aa and reaches the light receiving surface of the light receiving element 8.

  As described above, in particular, in the non-prism type distance measuring device, the amount of the measurement light beam from the target at a long distance tends to be small, so that it is reflected by the target at a long distance and passes through the reflecting member 3. It is important that all of the measurement light beam 31 reaches the light receiving surface of the light receiving element 8. In other words, since the amount of the measurement light beam from the target at a short distance is relatively large, a part of the measurement light beam 32B reflected by the target at a short distance and passing through the reflecting member 3 and the diaphragm 10 is part of the light receiving element 8. It is sufficient to reach the light receiving surface.

  As described above, in the distance measuring device according to the present embodiment, the measurement light beam 32 </ b> B that is reflected by the target at a short distance and passes through the reflecting member 3 and the diaphragm 10 is the lens that forms the relay optical system 7. Since the light is diffused by the action of the diffusing surface 7aa formed in the central area of the exit surface 7a, a part of the measurement light beam 32B in the hollow state reliably reaches the light receiving surface of the light receiving element 8. As a result, the non-prism type distance measuring apparatus according to the present embodiment can perform distance measurement quickly and accurately without depending on the distance to the target.

  Further, in the present embodiment, the background light cut stop 10 disposed at the focal position 6A of the objective lens 4 efficiently blocks many background light components collected at the peripheral portion away from the optical axis at the focal position 6A. Can do. In particular, since the amount of the measurement light beam from the target at a long distance tends to be small, the noise component is measured when measuring the distance to the target at a long distance by blocking the background light from the long distance by the diaphragm 10. Can be significantly reduced, and it is effective for increasing the measurement distance and improving accuracy.

  As described above, the measurement light beam from the target at a short distance is also blocked by the background light cut stop 10, but the amount of received light is inversely proportional to the square of the distance, and thus the distance to the target at a short distance. There is no problem if the required amount of light required for the measurement is secured. Further, the position of the background light cut stop 10 as the shielding member is not limited to the focal position 6A of the objective lens 4, and is due to the balance between the shielding of the measurement light beam from the target at a short distance and the shielding of the background light. What is necessary is just to determine suitably.

  There is a concern that the use of the relay optical system 7 in the light receiving system may increase the deviation of the condensing position of the measurement light beam due to the distance to the target. This will be described below. For example, if the focal length of the collimating objective lens 4 is 100 mm, the focal length of the light receiving relay optical system 7 is 10 mm, and the relay magnification of the relay optical system 7 is 1, the distance to the target is infinite. The deviation of the condensing position of the measurement light beam is 0.2045 mm between the distance and the distance of 50 m.

  On the other hand, when the relay optical system is not provided in the light receiving system, the deviation of the focusing position of the measurement light beam is 0.2 mm when the distance to the target is infinity and 50 m. In other words, the amount of change in the deviation of the focusing position of the measurement light beam due to the addition of the relay optical system 7 is only 0.0045 mm. Therefore, when the target is at a long distance (about 100 m from infinity), when measuring the distance to the target, there is almost no effect on the decrease in the amount of received light due to the deviation of the condensing position of the measurement light beam due to the distance to the target. No.

  In the above-described embodiment, an example in which the relay optical system 7 is configured by one lens 7a is shown. However, the present invention is not limited to this, and the relay optical system 7 can also be configured by a plurality of lenses. . Specifically, as shown in FIG. 4, for example, the relay optical system 7 can also be configured by two lenses 7b and 7c. In the modification of FIG. 4, for example, by forming the diffusion surface 7 ca in the central region of the exit surface of the rear lens 7 c, the same effect as that of the embodiment of FIG. 3 can be obtained. Although it is more cost effective to configure the relay optical system with a single lens, the degree of freedom of arrangement of the diffusing surface (generally deflection means) increases when the relay optical system is configured with a plurality of lenses.

  In the above-described embodiment, the diffusing surface 7aa is formed on the exit surface of the single lens 7a in the relay optical system 7. In the above-described modification, the diffusing surface 7ca is formed on the exit surface of the rear lens 7c in the relay optical system 7. Is forming. However, the present invention is not limited to this, and a diffusing surface can be formed in a partial region of at least one optical surface in the relay optical system 7.

  Further, in the above-described embodiment and modification, the measurement light beam from the target at a short distance is deflected by being provided in the optical path between the rear focal position 6A of the objective lens 4 and the light receiving surface of the light receiving element 8. As a deflecting means, diffusion surfaces 7aa and 7ca as local optical surfaces having a diffusion action are formed in a partial region (central region) of one optical surface in the relay optical system 7. However, the present invention is not limited to this, and an optical element having a diffusing action (a diffusing optical element such as a diffusing plate) can also be used as the deflecting means. The optical element having a diffusing action is attached so as to be in contact with the optical surface in the relay optical system 7, or is provided at a position near the optical surface or at an appropriate position separated from the optical surface.

  Moreover, in the above-mentioned embodiment and modification, the structure provided with the deflection | deviation means which has a spreading | diffusion effect is illustrated. However, the present invention is not limited to this, and deflecting means having a refractive action, deflecting means having a diffractive action, and the like can also be used. Specifically, in the case of a deflecting means having a refractive action, a local optical surface having a refractive action formed in a partial region of at least one optical surface in the relay optical system, or a refraction arranged at a required position. An optical element having a function (a refractive optical element such as a lens or a prism) can be used.

  On the other hand, in the case of a deflecting means having a diffractive action, it has a local optical surface having a diffractive action formed in a partial region of at least one optical surface in the relay optical system, or a diffractive action arranged at a required position. An optical element (diffractive optical element) can be used. Furthermore, an optical member having a refractive index distribution can be disposed at a required position as the deflecting means.

  In the embodiment and the modification described above, the light receiving surface of the light receiving element 8 is arranged at the second focal position optically conjugate with the rear focal position 6A of the objective lens 4. However, the present invention is not limited to this, and the incident surface of the light guide such as an optical fiber is disposed at the second focal position, the incident surface is used as the light receiving surface, and the measurement light beam emitted from the emission surface of the light guide is Light can also be received by the light receiving element.

  In the above-described embodiments and modifications, the present invention is applied to the non-prism type distance measuring device. However, the present invention is not limited to this, and for example, a prism type distance with a corner cube as a target is used. The present invention can be similarly applied to a measuring apparatus.

It is a figure showing roughly the basic composition of the distance measuring device concerning the embodiment of the present invention. It is a figure explaining the disadvantage of the conventional non-prism type distance measuring device. It is a figure which shows roughly the characteristic principal part structure of the distance measuring device concerning this embodiment. It is a figure which shows roughly the characteristic principal part structure of the distance measuring device concerning the modification of this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source 2 Light transmission optical system 3 Reflective member 4 Objective lens 5 Dichroic prism 7 Relay optical system 7aa Diffusing surface 8 Light receiving element 11 Focusing lens 12 Erecting prism 13 Focus plate 14 Eyepiece

Claims (11)

A light transmission system for transmitting a measurement light beam to a target via a reflection member disposed on the optical axis and an objective lens disposed on the front side of the reflection member; and the measurement light beam reflected by the target for the objective In a distance measuring device including a lens and a light receiving system that receives light through the reflecting member,
The light receiving system is provided in the optical path between the rear focal position of the objective lens and the light receiving surface in a conjugate manner with a relay optical system that conjugates the rear focal position of the objective lens and the light receiving surface, and is at a short distance. A distance measuring apparatus comprising a deflecting unit for deflecting a measurement light beam from a target. 2. The distance measuring apparatus according to claim 1, wherein the deflecting unit is provided in a region where a measurement light beam from the target at a long distance does not pass. The distance measuring device according to claim 1, wherein the deflecting unit has a local optical surface having a diffusion action formed in a partial region of at least one optical surface in the relay optical system. . The distance measuring apparatus according to claim 1, wherein the deflecting unit includes an optical element having a diffusing action. The distance measuring device according to claim 1, wherein the deflecting unit includes a local optical surface having a refractive action formed in a partial region of at least one optical surface in the relay optical system. . The distance measuring apparatus according to claim 1, wherein the deflecting unit includes an optical element having a refractive action. The distance measuring device according to claim 1, wherein the deflecting unit includes a local optical surface having a diffractive action formed in a partial region of at least one optical surface in the relay optical system. . The distance measuring apparatus according to claim 1, wherein the deflecting unit includes an optical element having a diffractive action. The distance measuring device according to claim 1, wherein the deflecting unit includes an optical member having a refractive index distribution. The distance measuring apparatus according to claim 1, wherein the relay optical system includes a plurality of lenses. The distance measuring device according to claim 1, further comprising a shielding member that blocks passage of background light from a long distance other than the measurement light beam reflected by the target. .

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