Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
1999-03-24
2001-11-13
Pascal, Leslie (Department: 2633)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S199200, C359S199200
Reexamination Certificate
active
06317237
ABSTRACT:
TECHNICAL FIELD
This invention relates to a voice monitoring system using laser beam and, more particularly, to a system for irradiating a laser beam of non-visible wavelength band onto a window pane of a room, etc. to monitor voice within the room on the basis of positional change of a reflected beam.
BACKGROUND ART
Since it has been passed about forty years from finding or discovery of laser, the laser technology is utilized in wide variety of technical fields. Particularly, in the technical field for measuring physical action, very high accuracy measurement can be made by making use of high coherent characteristic of a laser beam. For example, in the field where very small mechanical vibration is measured, a laser beam is irradiated onto an object to be measured and a reflected light is monitored, whereby high accuracy analysis of very small vibration is carried out.
On the other hand, for the purpose to monitor voice, a system having a microphone is still utilized from the past several ten years up to the present. However, in such a conventional system having a microphone, there is a problem that it is difficult to monitor voice from remote place. For this reason, in order to monitor voice in a room from the outside of the room, it is necessary to install a microphone within the room or in the vicinity of the room. However, in special or particular circumstances such as criminal investigation, etc., there are many instances where it is difficult to install a microphone within the room to be monitored or in the vicinity thereof, and there is no margin in point of time. In such a case, hitherto, it was inevitably required to employ a remote monitoring method in which a microphone having uni-directivity is installed at a remote place from the room and voice wave propagated through the space is collected by the microphone.
In view of the above, an object of this invention is to provide a voice monitoring system using laser beam which can monitor voice within a room from a remote place.
DISCLOSURE OF INVENTION
(1) A first feature of this invention resides in a voice monitoring system using laser beam for monitoring voice within a room from an outside of the room, the system comprising:
a laser transmitter for irradiating a laser beam of invisible wavelength band toward a predetermined target to be monitored; and
a laser receiver for converting a positional change of a reflected beam from the target into an electric signal and extracting a voice band component from the electric signal to output it.
(2) A second feature of this invention resides in a voice monitoring system using laser beam according to the first feature,
wherein a beam scanning mechanism for scanning with a laser beam is provided in the laser transmitter so that a laser spot formed on the target by irradiation of the laser beam can be moved within a plane of the target.
(3) A third feature of this invention resides in a voice monitoring system using laser beam according to the second feature,
wherein the laser transmitter includes a coordinate display unit for displaying coordinates indicating a scanning position at a current time of the laser beam and a communication device for transmitting a signal indicative of the coordinates to the laser receiver; and
wherein the laser receiver includes a communication device for receiving the signal indicative of the coordinates transmitted from the laser transmitter and a coordinate display unit for displaying the coordinates.
(4) A fourth feature of this invention resides in a voice monitoring system using laser beam according to the second feature, wherein there is further provided a beam detector including:
a light receiving plate in which a plurality of light receiving elements are arranged, each of the light receiving elements producing an electric signal when it receives a reflected beam from the target; and
a signaling unit for informing of existence of the reflected beam on the basis of the electric signal.
(5) A fifth feature of this invention resides in a voice monitoring system using laser beam according to the fourth feature,
wherein the laser transmitter has a function to operate in two modes of a continuous mode for irradiating a laser beam as a continuous signal and a modulation mode for irradiating a laser beam as a modulated signal having a predetermined audible frequency; and
wherein the signaling unit in the beam detector is constituted by a unit having a function to present sound of the audible frequency by using the modulated signal when a reflected beam produced in the modulated mode is received.
(6) A sixth feature of this invention resides in a voice monitoring system using laser beam according to the second feature, wherein there is further provided a beam detector including:
a light receiving plate in which a plurality of light receiving elements are arranged, each of the light receiving elements producing an electric signal when it receives a reflected beam from the target; and
a communication device for transmitting, to the laser transmitter, a scanning control signal for controlling the beam scanning mechanism on the basis of the electric signal.
(7) A seventh feature of this invention resides in a voice monitoring system using laser beam according to the first feature, wherein the laser transmitter includes:
a CCD camera having a sensitivity for a wavelength of the laser beam, an optical axis of the CCD camera being adjusted so that images of the target and a laser spot formed on the target can be taken; and
a target display unit for displaying the images taken by the CCD camera.
(8) A eighth feature of this invention resides in a voice monitoring system using laser beam according to the first feature, wherein the laser receiver includes:
a CCD camera having a sensitivity for a wavelength of the laser beam;
a target display unit for displaying an image taken by the CCD camera;
a positional change detecting unit for converting a positional change of the reflected beam from the target into an electric signal;
a sound circuit for extracting a voice band component from the electric signal;
an optical device for selectively forming a first path for guiding the reflected beam from the target to the CCD camera and a second path for guiding the reflected beam to the positional change detecting unit; and
an installation state adjustment device for adjusting an installation state of the laser receiver.
(9) A ninth feature of this invention resides in a voice monitoring system using laser beam according to the first feature, wherein the laser receiver includes:
a knife edge provided along an optical path of the reflected beam from the target for shielding a portion of the reflected beam;
a shielding position adjustment device for adjusting a shielding position of the knife edge; and
a light receiving element to receive light flux of the reflected beam which has not been shielded by the knife edge and to output an electric signal corresponding to energy of received light flux;
thus to convert a positional change of the reflected beam into an electric signal.
(10) A tenth feature of this invention resides in a voice monitoring system using laser beam according to the ninth feature, wherein the laser receiver further includes:
a light receiving sensitivity display unit for displaying a value of an electric signal that the light receiving element outputs; and
an installation state adjustment device for adjusting an installation state of the laser receiver.
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Hara Masahiko
Nakao Masashi
Kyoyu Corporation
Ladas & Parry
Pascal Leslie
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