Optics: measuring and testing – Range or remote distance finding – With photodetection
Reexamination Certificate
2000-05-19
2002-05-07
Tarcza, Thomas H. (Department: 3662)
Optics: measuring and testing
Range or remote distance finding
With photodetection
Reexamination Certificate
active
06384904
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a distance measuring apparatus having an attenuation filter for adjusting luminous energy of a luminous flux incident on light receiving converting means, and more particularly to a distance measuring apparatus in which at least a part of the attenuation filter is arranged as deflection means.
A distance measuring apparatus known to us is one such that visible light, non-visible light, modulated light or pulse light is projected as measuring light toward an object under measurement, and a reflected luminous flux reflected on the object under measurement is received, whereby a distance from a position at which measurement is carried out to a position at which the object under measurement is located, is measured.
In general, components of such a kind of distance measuring apparatus can be roughly classified into an optical section for irradiating and receiving measuring light and an electrical section for converting the received measuring light into an electrical signal to calculate the distance under measurement.
The optical section for irradiating and receiving measuring light is composed of a light emitting unit for emitting measuring light from a light source, a light irradiating system for irradiating the measuring light from the light emitting unit onto the object under measurement, a light receiving system for leading the reflected light from the object under measurement, and a light receiving unit for receiving reflected light led from the light receiving system.
FIG. 1
is a diagram schematically showing an optical system of the above-arranged distance measuring apparatus.
As shown in
FIG. 1
, in a general light wave distance measuring apparatus, a pulse luminous flux or modulated luminous flux generated from a light source
100
is projected through a rotative light shielding disk
102
, a rectangular prism
104
, an objective lens
106
toward an object
108
under measurement.
The rotative light shielding disk
102
alternately selects one of a reference luminous flux which is split by a half mirror
130
and a measuring luminous flux which has traveled the distance between the measuring position and the object under measurement, and then allows the selected one of the fluxes to become incident on a light receiving element
120
. The rotative light shielding disk
102
is rotatively driven by a motor, shields the reference luminous flux and the measuring luminous flux selectively, and allows them to enter the light receiving element
120
alternately.
An internal luminous flux is utilized for correcting an internal error within the light wave distance measuring apparatus. The measuring luminous flux reflected on the object
108
under measurement or a reflection mirror
110
is led through the objective lens
106
, the rectangular prism
104
, a luminous energy attenuation filter
112
to the light receiving element
120
. In order to make the apparatus free from influence of a light receiving characteristic caused by received luminous energy, the measuring luminous flux incident on the light receiving element
120
is subjected to a luminous energy adjustment effected by the luminous energy attenuation filter
112
so that the received luminous energy is kept constant.
The reference luminous flux split from the half mirror
130
is led through a mirror
132
, the rotative light shielding disk
102
, a pair of relay lenses
134
and
136
, mirrors
138
and a half mirror
140
disposed between the luminous energy attenuation filter
112
and the light receiving element
120
, into the light receiving element
120
.
Any ordinary reflection mirror may be utilized as the reflection mirror
110
. However, if a pulse luminous flux is utilized as the measuring luminous flux, the object
108
under measurement itself can serve as the reflection mirror. Alternatively, the reflection mirror
110
may be attached on the object
108
under measurement.
FIG. 9
is a diagram showing an arrangement of a conventional luminous energy attenuation filter. As shown in
FIG. 9
, the luminous energy attenuation filter
112
is composed of an outer toroidal portion and an inner toroidal portion. The outer toroidal portion is arranged as a measuring luminous flux attenuation filter
1121
while the inner toroidal portion is arranged as a reference luminous flux attenuation filter
1122
. If a distance under measurement is long, the measuring luminous flux will suffer from attenuation. Thus, the outer toroidal portion has at a part itself a through-hole aperture
1123
having no filtering function, and hence the measuring luminous flux passing through the through-hole aperture
1123
can be protected from attenuation. When only a small luminous energy is obtained from the measuring luminous flux, intensive attenuation is effected on the reference luminous flux.
The luminous energy attenuation filter
112
is controlled as follows.
FIG. 3
is a block diagram of the distance measuring apparatus. As shown in
FIG. 3
, a light receiving unit
154
composed of the light receiving element
120
and a light detecting unit
150
detects luminous energy of the measuring luminous flux which indicates the measuring luminous energy, and then supplies the detected result to a CPU
156
. The CPU
156
calculates a luminous energy control signal based on the measuring luminous energy and supplies the same to a driving circuit unit
158
.
The driving circuit unit
158
is arranged to drive and control a driving motor
164
of the luminous energy attenuation filter
112
on the basis of a supplied luminous energy control signal.
FIG. 7A
is a diagram schematically illustrative of an optical path system arranged between the light emitting side and the light receiving side of the distance measuring apparatus. As shown in
FIG. 7A
, a measuring light beam generated from the light emitting unit having a light source
1
is directed to a reflection mirror
2
on which it is reflected and then led to an objective lens
3
which is included in an irradiation optical system. The measuring light beam which is made into a parallel luminous flux by the objective lens
3
is led to an object
4
under measurement. A light beam reflected on the object
4
under measurement is again directed to the objective lens
3
. It should be noted that the object
4
under measurement is provided in the direction determined by the optical axis of the objective lens
3
.
The object
4
under measurement may be a corner cube, i.e., a recurrent reflection prism provided on the object under measurement. The object
4
under measurement may also be a reflection sheet provided on the object under measurement or the object under measurement itself.
A reflected light beam directed to the objective lens
3
is concentrated by the objective lens
3
, reflected on the reflection mirror
2
and focused on light receiving means
5
of the light receiving unit.
In a general measuring apparatus, if a single objective lens
3
is arranged (as a single lens type) to serve as an objective lens for the light irradiating system and an objective lens for the light receiving system, as for example shown in
FIG. 7A
, the objective lens may be divided into two portions, e.g., an upper portion and a lower portion, a right portion and a left portion, and a central portion and a peripheral portion, and either of them is arranged for the light irradiating system or the light receiving system. Further, known in a distance measuring apparatus in which the light irradiating system and the light receiving system have objective lenses independently (two lens type).
Incidentally, in the distance measuring apparatus arranged as described above, if the object
4
under measurement is a corner cube, as shown in
FIG. 7A
, the irradiation parallel light beam and the reflection parallel beam travel separate optical paths, respectively. Therefore, even if the light irradiating system including the light source
1
and the light receiving system including the light receiving sensor
5
are not positioned on
Ohishi Masahiro
Tokuda Yoshikatsu
Baker & Botts LLP
Kabushiki Kaisha Topcon
Mull Fred H
Tarcza Thomas H.
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