Optical position detector

Details Optical position detector Optical position detector

2000-05-08

2001-03-06

Font, Frank G. (Department: 2877)

Optical waveguides

With optical coupler

Input/output coupler

C385S039000, C385S014000

Reexamination Certificate

active

06198862

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical position detector which detects a position by using a triangulation method.
2. Description of the Prior Art
Conventionally, optical position detectors have widely used a triangulation method Due to the low cost and simple structure, they have wide application as sensors for camera auto-focusing.
FIG. 5
shows a position detection method by triangulation in a conventional optical position detector as disclosed, for example, in the publication “Needs and Seeds of Optical Instrumentation” (P.167) by the Study and survey Committee for Optically Applied Measuring Technology, the Society of Weights and Measures. In
FIG. 5
, reference numeral
101
denotes a light source such as a laser which emits a parallel beam, and the light source is not provided with a lens for light projection.
102
is an image formation lens,
103
is a position detection element (for example PSD (position sensitive device) or the like). In this optical position detector, either the image pickup system is oblique to the displacement direction of the detected surface
104
or the incident direction of light is inclined against the displacement direction.
The operation of the conventional optical position detector will now be explained.
When the detected surface
104
is displaced from a reference position, the prospect angle with respect to the image formation lens
102
of the spot on the detected surface
104
varies. Since the image position on the position detecting element
103
varies in response to the variation of the prospect angle, the position of the detected surface
104
can be calculated.
Since conventional optical position detectors are constructed as above, when a compact semiconductor laser is used as a light source, a collimator lens must be provided, and when the light source
101
is a gas laser, the laser size must be inherently large though a lens system is not necessary. In other words, in the conventional optical position detector using a triangulation method, since a general image forming lens
102
is used for convergence of light and image formation, there is a limit to the degree to which the device can be miniaturized
Furthermore, an optical position detector which uses a bar shaped lens having uni-axial focussing operation and an optical fiber as an optical guide is disclosed, for example, in the publication JP-A 10-9813. However, the optical position detector also has a problem that there is a limit to the degree to which the device can be miniaturized, if it is required to obtain an excellent detection characteristic at long measurement distance.
SUMMARY OF THE INVENTION
The present invention is proposed to solve the above problems and has an object of providing a compact optical position detector with an excellent detection characteristic even at long measurement distance.
According to the present invention, an optical position detector comprises an input optical fiber, an output optical fiber, a slab light guide disposed on a substrate and having a branched light guide, a first cylindrical lens disposed adjacent to the slab light guide for converting an optical path of light emitted from the slab light guide and for condensing the light on the detected surface, and a second cylindrical lens disposed adjacent to the slab light guide for converting an optical path of light reflected from the detected surface and for guiding such the light to the slab light guide.
In this way, it is possible to obtain an optical position detector having an excellent detection characteristic even at long measurement distance.
The optical position detector of the present invention further comprises a lens positioning piece provided on the slab light guide for positioning the first and second cylindrical lenses.
In this way, it is possible to easily position the first and second cylindrical lenses.
In the present invention, the slab light guide is provided with a light guiding structure which is adapted to the core and cladding layers of the input and output optical fibers and which is manufactured by a thick film resist lithography process.
Thus, mass manufacture of the optical position detectors having fine structure is possible.


REFERENCES:
patent: 5418765 (1995-05-01), Misawa et al.
patent: 361072218A (1986-04-01), None
patent: 1-115156 (1989-05-01), None
patent: 1-124788 (1989-05-01), None
patent: 10-9813 (1998-01-01), None
“Needs And Seeds In Optical Measurement”, Corona Inc. pp. 202-203.

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