Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
2002-03-13
2004-12-14
Luu, Thanh X. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C250S553000, C250S221000
Reexamination Certificate
active
06831266
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
The present invention relates to optical transducers (sometimes referred to as optical sensors,) which utilize optical means for sensing mechanical displacements, such as movements of a body or deformation of a membrane, and converting them to electrical signals. The invention also relates to methods of making such optical transducers. The invention is particularly useful in making optical microphones for converting sound into electrical signals and is therefore described below especially with respect to this application.
Optical transducers of this type are described, for example, in U.S. Pat. Nos. 5,771,091; 5,969,838; 6,091,497; and 6,239,865, the contents of which patents are incorporated herein by reference.
Such optical transducers generally include an optical unit containing a light source, a laterally spaced light detector, an optical shield between the light source and light detector, and a displaceable member aligned with the optical window defined by the light source, light detector, and optical shield between them. The displaceable members in the optical transducers described in the above patents are generally in the form of deformable membranes, but may be physically movable members, such as in an accelerometer. Optical transducers of this type can be constructed to be very accurate for measuring very small displacements.
In general, such optical transducers provide only one light detector spaced laterally of the light source, or two light detectors on the opposite sides of the light source, and therefore utilize only a part of the light produced by the light source for sensing movement of the membrane. This limits the sensitivity of the optical transducer for detecting or measuring displacements of the membrane.
BRIEF SUMMARY OF THE PRESENT INVENTION
An object of the present invention is to provide an optical transducer which utilizes substantially more of the light generated by the light source within it, and thereby is capable of providing increased sensitivity.
According to one aspect of the present invention, there is provided an optical transducer, comprising: a base member; a light source carried on a face of the base member; a light detector carried on the face of the base member; a displaceable member overlying and spaced from the light source and light detector and effective to reflect light from the light source to the light detector; and light shielding means effective to shield the light detector from exposure to the light source except for the light reflected by the displaceable member from the light source to the light detector; the light detector being configured to substantially surround all sides of the light source such as to receive light emitted in substantially all directions from the light source for reflection to the light detector by the displaceable member.
As will be described more particularly below, such an optical transducer utilizes a substantially higher percentage of the light generated by the light source within it, and therefore is capable of providing higher sensitivity.
Several preferred embodiments of the invention are described below for purposes of example. In all the described embodiments, the light source and light-blocking layer, and in most cases also the light detector elements, are embedded in a transparent plastic potting material. The outer surface of the transparent plastic potting material includes a light-blocking layer to block the exit of light from the light source externally of the optical transducer, and to block the entry of external light into the optical transducer.
In one described preferred embodiment, the light detector includes an array of at least four discrete light detector elements located on four sides of the light source so as to substantially surround the light source. The light shielding means in this embodiment includes a light-blocking layer around the light source such as to shield all the light detector elements from the light source except for the light reflected by the displaceable member.
A second embodiment of the invention is described below wherein the light detector is of annular configuration surrounding the light source with the light source centrally thereof. More particularly, the light detector of annular configuration is carried on a semiconductor wafer which wafer is carried on the common base. The semiconductor wafer is formed with a central opening for accommodating the light source. The light shielding means includes a light-blocking layer on the surface of the semiconductor wafer defining the central opening.
Further embodiments of the invention are described below wherein the light source includes a plurality of discrete light-generating elements carried on a face of the light detector. The light detector include surfaces in the spaces between the discrete light-generating elements and the light shielding means includes a light blocking layer around each of the discrete light-generating elements such as to shield the light detector surfaces from all the discrete light-generating elements except for the light reflected by the displaceable member.
In the described preferred embodiments, the plurality of discrete light-generating elements are carried in the form of a matrix on a face of the light detector. In one described embodiment, the discrete light-generating elements are in abutting relation to each other in the matrix; and in another described embodiment, they are in spaced relation to each other, being deposited in a honeycomb of boxes formed in the light detector.
As will be described below, optical transducers can be constructed in accordance with the foregoing features to provide relatively high sensitivity to displacements of the displaceable member (e.g., deformations of the deformable membrane) as well as high degree of sturdiness enabling such optical transducers to withstand rough handling.
Further features and advantages of the invention will be apparent from the description below.
REFERENCES:
patent: 5771091 (1998-06-01), Paritsky et al.
patent: 5969838 (1999-10-01), Paritsky et al.
patent: 6091497 (2000-07-01), Paritsky et al.
patent: 6239865 (2001-05-01), Paritsky et al.
Kots Alexander
Paritsky Alexander
G.E. Ehrlich (1995) Ltd.
Luu Thanh X.
Phone-Or Ltd.
Sohn Seung C.
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