Optical: systems and elements – Mirror – With selective absorption or transparent overcoating
Reexamination Certificate
1998-12-04
2001-11-27
Chang, Audrey (Department: 2872)
Optical: systems and elements
Mirror
With selective absorption or transparent overcoating
C359S529000, C356S004010
Reexamination Certificate
active
06324024
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a distance measuring system using an electric distance meter, and particularly relates to a reflector used therein.
An electric distance meter is broadly used to measure a distance between two distal positions.
FIG. 1
is a schematic view showing a principle of a distance measuring system using the electric distance meter. In order to detect the distance of two positions P
1
and P
2
, the electric distance meter
110
is located at one position P
1
. Further, a reflector unit
120
, which has a reflector
121
(such as a prism), is located at the other position P
2
. The electric distance meter
110
emits modulated light (such as infrared rays) to the reflector unit
120
. The emitted light is reflected by the reflector
121
and returns to the electric distance meter
110
. The electric distance meter
110
detects a phase difference of the emitted light and returned light, to calculate the distance between the positions P
1
and P
2
. Such an electric distance meter can be coupled with an goniometer (such as an electronic theodolite), to constitute a measuring system known as a ‘total station’.
FIG. 2A and 2B
are a front view and a sectional view of the conventional reflector unit
120
. The reflector unit
120
includes the reflector
121
, and a U-shaped support
134
which supports the reflector
121
. The reflector
121
is a so-called corner cube which reflects the incident light in parallel to the direction of the incidence. The reflector unit
120
further includes e leveling board
140
mounted on a tripod and a stage
137
adjustably provided on the leveling board
140
. The U-shaped support
134
is mounted to the adjustable stage
137
via a shaft
135
.
As shown in
FIG. 1
, the direction of the light emitted from the electric distance meter
110
must be directed to the reflector unit
120
. For this purpose, the electric distance meter
110
has a sighting telescope
111
through which an operator can observe the reflector unit
120
. With this, the operator is able to correctly direct the electric distance meter
110
toward the reflector unit
120
, while observing the reflector unit
120
through the sighting telescope
111
.
In order to focus the sighting telescope
111
on the reflector unit
120
, the sighting telescope
111
generally includes an autofocus unit of a phase detection focusing type (which is generally used in a single lens reflex camera).
However, when the autofocus unit operates, the sighting telescope
111
may be focused on a virtual image of the electric distance meter
110
reflected by the reflector
121
. In such case, the reflector unit
120
is out of focus and can not be seen from the operator. Thus, the operator can not correctly direct the electric distance meter
110
toward the reflector unit
120
.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a reflector which is used with an electric distance meter having an autofocus unit for sighting and which can be correctly focused by the autofocus unit.
For the above purpose, according to an aspect of the present invention, there is provided a reflector including a reflecting member which reflects incident light in parallel to the direction of incidence, and a selective transmission member provided to an incidence side of the reflecting member. The selective transmission member allows light of first wavelength range to pass, while the selective transmission member prevents light of second wavelength range from passing. The reflector is used with a electric distance meter provided with a sighting telescope (having an autofocus unit).
With such an arrangement, if the autofocus unit is arranged to use the light of the second wavelength range, the sighting telescope is not focused on a virtual image of the electric distance meter (reflected by the reflecting member), since the light of the second wavelength range does not reach the reflecting member of the reflector. That is, the sighting telescope is focused on the reflector. Accordingly, the operator is able to direct of the sighting telescope toward the reflector, observing the sighting telescope. Further, the electric distance meter is possible to perform the distance measurement by using the light of the first wavelength range, since the light of the first wavelength range is reflected by the reflecting member and returns to the electric distance meter. Preferably, the light of the first wavelength range is infrared rays, while the light of the second wavelength range is visible light.
Optionally, the selective transmission member is provided with a indication mark (such as a cross line) on an incident surface. With such an arrangement, an operator is able to adjust the direction of the electric distance meter, observing the indication mark on the selective transmission member through the sighting telescope.
Advantageously, the selective transmission member is detachably attached to the reflecting member. With this, the selective transmission member can be mounted to a conventional reflector. Alternatively, the selective transmission member is directly attached to the surface of the reflecting member. With this, a fixing member (for fixing the selective transmission member to the reflecting member) is not needed.
In a preferred embodiment, the reflecting member includes a corner cube having three perpendicular surfaces. The corner cube has an advantage such that the corner cube reflects the incident light in parallel to the direction of the incidence.
According to another aspect of the present invention, there is provided a reflector having a selective reflection surface (which reflects the light of the first wavelength range, while allowing the light of the second wavelength to pass), and an absorbing surface which absorbs light which passes the selective reflection surface.
With such an arrangement, if the autofocus unit is arranged to use the light of the second wavelength range, the sighting telescope is not focused on a virtual image of the electric distance meter, since the light of the second wavelength range passes through the selective reflection surface and absorbed by the absorbing surface. That is, the sighting telescope is focused on the reflector. Further, the electric distance meter is able to perform the distance measurement by using the light of the first wavelength range, since the light of the first wavelength range is reflected by the selective reflection surface and returns to the electric distance meter.
According to still another aspect of the present invention, there is provided a reflector including a reflecting member which reflects an incident light in parallel to the direction of incidence, and an indication mark which is provided on a surface of the reflecting member, the incident light being incident of the surface.
If the distance to be measured is sufficiently short, the sighting telescope is not focused on a virtual image of the electric distance meter (even though the visible light is reflected by the reflection member). Thus, the autofocus unit is able to focus the sighting telescope on the indication mark (such as a cross line) on the glass disk. Since the cross line can be clearly observed through a sighting telescope, the operator is able to adjust the direction of the electric distance meter toward the reflector.
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Kaneko Atsumi
Shirai Masami
Asahi Kogaku Kogyo Kabushiki Kaisha
Chang Audrey
Greenblum & Bernstein P.L.C
Winstedt Jennifer
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