Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
2000-03-10
2003-12-02
Allen, Stephone B. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C250S23700G, C359S237000
Reexamination Certificate
active
06657181
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an interference measuring apparatus and a grating interference-type encoder for generating a phase difference signal and highly accurately measuring a length and an angle in an industrial apparatus such as FA (factory automation).
2. Related Background Art
A laser interferometer or an incremental encoder has heretofore been utilized as a highly accurate positioning apparatus such as FA. These apparatuses convert positional deviation into a pulse train, and count the pulse number at this time to thereby detect relative positional deviation. At this time, it is also necessary to detect a direction of movement and therefore, usually two or more phase difference signals A phase and B phase are outputted and phase shift of 90° is given with a sine wave signal of a cycle being 360°.
In such a high resolving power incremental encoder and laser interferometer, there is known a method of disposing two detecting optical systems with their spatial positions deviated from each other to thereby generate phase difference signals of A phase and B phase. There is also known a method of causing polarized light beams orthogonal to each other to interfere with each other through a quarter wavelength plate, converting them into a linearly polarized light beam of which the polarization direction rotates correspondingly to the phase difference between the wave fronts of the two light beams, and then further dividing it into a plurality of light beams. Those light beams are caused to be transmitted through polarizing plates disposed with their polarization axes deviated in different directions to thereby generate a phase difference signal light beam.
FIG. 1
of the accompanying drawings shows a perspective view of a non-contact distance sensor of the conventional laser interference-type, and a laser beam L from a coherent light source
1
passes through a collimator lens
2
and a non-polarizing beam splitter
3
and is polarized on the polarizing surface
4
a
of a probe-like polarizing prism
4
. S-polarized light reflected by the polarizing surface
4
a
emerges from the probe-like polarizing prism
4
toward a slider
5
, is reflected by the surface
5
a
to be measured by the slider
5
, and again returns along the original optical path to the polarizing surface
4
a
of the probe-like polarizing prism
4
.
On the other hand, P-polarized light transmitted through the polarizing surface
4
a
is reflected by the upper reference mirror surface
4
b
of the probe-like polarizing prism
4
and likewise returns to the polarizing surface
4
a
. These two polarized lights are re-combined on the polarizing surface
4
a
, travel through the probe-like polarizing prism
4
, are reflected by a non-polarizing beam splitter
3
, pass through a quarter wavelength-plate
6
and an aperture in an aperture plate
7
, and are amplitude-divided by a four-division diffraction grating
8
. These amplitude-divided light beams pass through polarizing plates
9
a
-
9
d
, and are received by the four areas
10
a
-
10
d
of a light-receiving element
10
. The minute displacement of the slider
5
is measured by an interference signal at this time.
However, in the above-described example of the prior art, the phase shift is given by arrangement or the like of the polarizing plates
9
a
-
9
d
and therefore, there is a possibility that if there are an alignment error and manufacturing errors of the polarizing plates
9
a
-
9
d
, the phase difference signal is not stable. On the other hand, in the case of the interference between linearly polarized lights orthogonal to each other, a space is required for arrangement of optical parts such as the quarter wavelength plate
6
and the four polarizing plates
9
a
-
9
d
and therefore, the apparatus becomes bulky and the assembly adjustment of all these is necessary.
SUMMARY OF THE INVENTION
In view of the above-described example of the prior art, it is an object of the present invention to provide a compact interference measuring apparatus easy to assemble for collectively detecting a plurality of stable phase difference signals.
It is another object of the present invention to provide an interference measuring apparatus such as a compact and highly accurate grating interference-type encoder.
Other objects of the present invention will become apparent from the following description of some embodiments of the present invention.
REFERENCES:
patent: 3316799 (1967-05-01), Daley et al.
patent: 3822942 (1974-07-01), Hock
patent: 5000572 (1991-03-01), Nose et al.
patent: 5283434 (1994-02-01), Ishizuka et al.
patent: 5390022 (1995-02-01), Ishizuka et al.
patent: 5424535 (1995-06-01), Albion et al.
patent: 5448358 (1995-09-01), Ishizuka et al.
patent: 5481106 (1996-01-01), Nyui et al.
patent: 5483332 (1996-01-01), Takamiya et al.
patent: 5483377 (1996-01-01), Kaneda et al.
patent: 5498870 (1996-03-01), Ishizuka
patent: 5502466 (1996-03-01), Kato et al.
patent: 5557396 (1996-09-01), Ishizuka et al.
patent: 5569913 (1996-10-01), Ishizuka et al.
patent: 5621527 (1997-04-01), Kaneda et al.
patent: 5629793 (1997-05-01), Takamiya et al.
patent: 5640239 (1997-06-01), Takamiya et al.
patent: 5663794 (1997-09-01), Ishizuka
patent: 5666196 (1997-09-01), Ishii et al.
patent: 5680211 (1997-10-01), Kaneda et al.
patent: 5717488 (1998-02-01), Watanabe
patent: 5737070 (1998-04-01), Kato
patent: 5737116 (1998-04-01), Kadowaki et al.
patent: 5742577 (1998-04-01), Horimai et al.
patent: 5754282 (1998-05-01), Kato et al.
patent: 5774218 (1998-06-01), Takamiya et al.
patent: 5796470 (1998-08-01), Ueda et al.
patent: 5815267 (1998-09-01), Kato et al.
patent: 5880839 (1999-03-01), Ishizuka et al.
patent: 5926276 (1999-07-01), Takamiya et al.
patent: 5956140 (1999-09-01), Ishizuka et al.
patent: 6075235 (2000-06-01), Chun
patent: 0 525 446 (1993-02-01), None
patent: 0 903 559 (1999-03-01), None
Horyu Sakae
Ishizuka Ko
Kadoshima Takayuki
Kadowaki Hidejiro
Kaneda Yasushi
Allen Stephone B.
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
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