Optical interferometer

Details Optical interferometer Optical interferometer

1999-11-24

2003-04-22

Font, Frank G. (Department: 2877)

Optics: measuring and testing

By light interference

For dimensional measurement

C356S450000

Reexamination Certificate

active

06552801

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical interferometer to be used in the field of, for example, metrology.
2. Description of the Related Art
FIG. 6
is a plan view schematically showing an example configuration of a conventional optical interferometer. In the drawing, reference numeral
1
designates incident light;
2
designates a beam splitter;
3
and
4
designate mirrors; and
5
designates a photodetector.
As shown in the drawing, by means of a beam splitter
2
, the incident light
1
is divided into two optical paths which are orthogonal to each other; that is, transmitted light and reflected light. Light reflected by the mirror
3
provided in and oriented at right angles to the optical path for the reflected light and light reflected by a mirror
4
provided in and oriented at right angles to the optical path for the transmitted light are again merged into a single ray by means the beam splitter
2
.
At this time, the mirror
3
is moved along the optical path at constant velocity by means of an unillustrated stage on which the mirror
3
is mounted. Consequently, a difference in length arises between the optical path over which the light reflected by the mirror
3
travels and the optical path over which the light reflected by the mirror
4
travels, thus resulting in a variation in the intensity of interference fringes.
The photodetector
5
extracts, as an electric signal, such a variation in the intensity of interference fringes.
As mentioned above, in the above-described conventional optical interferometer, the mirror
3
is moved along its optical path over a long distance, thus resulting in time-consuming operation. Moreover, the accuracy of the optical interferometer must increases with the distance over which the mirror is to travel.
For these reasons, a limitation is imposed on a reduction in the size of and the measurement time required by the conventional optical interferometer. Further, there is also desired an improvement in the optical interferometer in terms of accuracy management.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide an optical interferometer of reduced measurement time, and improve measurement accuracy, and facilitated accuracy management.
Another object of the present invention is to provide a compact optical interferometer.
To these ends, according to a first aspect of the present invention, there is provided an optical interferometer, wherein incident light is divided by means of a beam splitter into reflected light and transmitted light which travel along respective optical paths, which are orthogonal to each other; the reflected light is subjected to total reflection by a first reflector and the transmitted light is subjected to total reflection by a second reflector; and the reflected light rays are again merged by the beam splitter into a single ray so as to fall on a photodetector, the interferometer comprising:
a third reflector which reflects the incident light at right angles so as to fall on the beam splitter;
a fourth reflector which reflects the light, having been transmitted through the beam splitter, at right angles so as to fall on the second reflector; and
a moving member on which the beam splitter and the third and fourth reflector are mounted and which can be moved along an optical path extending between the first reflector and the photodetector.
The reflector is typified by a mirror. However, a corner cube or a reflector may be used in place of the mirror.
The photodetector extracts, as an electric signal, a variation in the intensity of interference fringes.
The moving member is usually called a stage.
To these ends, according to a first aspect of the present invention, there is provided an optical interferometer, wherein incident light is divided by means of a beam splitter into reflected light and transmitted light which travel along respective optical paths, which are orthogonal to each other; the reflected light is subjected to total reflection by a first reflector and the transmitted light is subjected to total reflection by a second reflector; and the reflected light rays are again merged by the beam splitter into a single ray so as to fall on a photodetector, wherein a moving member on which the beam splitter and the third and fourth reflector are mounted is moved along an optical path extending between the first reflector and the photodetector. Consequently, the optical path over which the light reflected by the first reflector travels and the optical path over which the light reflected by the second reflector travels can be changed simultaneously. Thus, the optical interferometer of the present invention can achieve the same optical path difference as that achieved by the conventional optical interferometer, by employment of a travel distance which is one-half that required by the conventional optical interferometer.
Since the optical interferometer of the present invention requires one-half the travel distance required by the conventional optical interferometer, measurement time can be shortened.
Further, since a required travel distance is short, blurring stemming from movement of the moving member can be diminished. Therefore, there can be realized facilitation of accuracy management of parts, an improvement in measurement accuracy, and miniaturization of the optical interferometer.
Preferably, the optical interferometer further comprises:
a fifth reflector which reflects the light reflected by the beam splitter in a direction parallel to the path of the light reflected by the beam splitter (hereinafter called “in a parallel direction”) so as to fall on the first reflector; and
a sixth reflector which reflects the light reflected by the fourth reflector in a parallel direction so as to fall on the second reflector, wherein the first and second reflectors are mounted on the moving member.
As mentioned above, the light reflected by the beam splitter is reflected in a parallel direction by means of the fifth reflector so as to fall on the first reflector. Further, the light reflected by the fourth reflector is reflected in a parallel direction by means of the sixth reflector so as to fall on the second reflector. The first and second reflectors are mounted on the moving member on which the beam splitter and the third and fourth reflectors are mounted. Hence, the travel distance can be shortened to one-half that required by the previously-described optical interferometer of the present invention. Accordingly, the travel distance required by the optical interferometer of the present invention can be shortened to one-fourth that required by the conventional optical interferometer.
According to a second aspect of the present invention, there is provided an optical interferometer, wherein incident light is divided by means of a beam splitter into reflected light and transmitted light which travel along respective optical paths, which are orthogonal to each other; the reflected light is subjected to total reflection by a first reflector and the transmitted light is subjected to total reflection by a second reflector; and the reflected light rays are again merged by the beam splitter into a single ray so as to fall on a photodetector, the interferometer comprising:
a third reflector which reflects the light, having transmitted through the beam splitter, at right angles so as to fall on the second reflector; and
moving means which synchronously moves the first and second reflectors inn opposite directions so as to approach or depart from each other, along an optical path extending between the first reflector and the photodetector.
As mentioned above, incident light is divided by means of a beam splitter into reflected light and transmitted light which travel along respective optical paths, which are orthogonal to each other; the reflected light is subjected to total reflection by a first reflector and the transmitted light is subjected to total reflection by a second reflector; and the reflected light rays are again me

Affiliated with

Also associated with

Rating

Optical interferometer does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Optical interferometer, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical interferometer will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3088901