Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
1999-11-02
2001-10-23
Le, Que T. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C340S602000, C318S483000
Reexamination Certificate
active
06307198
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a sensor for sensing water such as rain or dew on transparent plates such as windshields of vehicles, and window panes of houses or other facilities, to turn on wipers, defroster, warning device or some other device, and a system for producing holograms usable in such sensors.
Japanese Patent Provisional (Kokai) Publications Nos. H10(1998)-96791, H10(1998)-62336 and H9(1997)-257952 show rain or dew sensors having light emitting and light receiving elements.
SUMMARY OF THE INVENTION
A sensing system of the above-mentioned Japanese Publication H10(1998)-96791 has a light emitting device and a light receiving device so arranged that a light beam from the light emitting device and a visual field of the light receiving device intersect each other at an outside position at a predetermined distance from a windshield glass panel. However, consumption of energy for emitting infrared sensing light always to a wide sensing region is problematical specifically in the case of a heat blocking windshield of green type colored glass whose transmittance is equal to lower than 10% in a wavelength region of 3 &mgr;m or longer, and equal to or lower than 50% even in an infrared region. Besides, the control system of this example is large in size and complicated as a whole.
Prisms employed in a sensing system of the above-mentioned Japanese Publication H10(1998)-62336 tend to increase the size of the sensing system, constitute an obstacle to a driver, and require troublesome operations for accurately positioning the prisms and light emitting and receiving devices relative to one another.
A sensing system of the above-mentioned Japanese Publication H9(1997)-257952 is arranged to sense both rain and dew. However, this system requires a plate for guiding light, a half mirror and a mirror, so that the system is large in size, and obstructive to the visibility.
It is therefore an object of the present invention to provide a rain and/or dew sensor which is small in size and light in weight.
It is another object of the present invention to provide a compact rain and/or dew sensor which can be installed in a shade band region of a vehicle windshield without blocking the visual field of a driver.
It is still another object of the present invention to provide an exposing system for producing holograms.
A sensing system proposed by the inventors of the present application employs an entrance hologram for introducing sensing light and an exit hologram for taking out the sensing light. Fabrication of two distinct holograms normally requires two exposing operations, and two separate holograms requires a difficult alignment operation for attaching the holograms, as entrance hologram and exit hologram, to a windshield.
It is therefore still another object of the present invention to provide a hologram exposing system which is capable of facilitating the setting of an optical system and forming two holograms in a single hologram sheet in one exposing operation without the need for complicated light reducing operation of preventing irradiation of unwanted light (such as stray laser light falling upon a glass base plate at an angle greater than a critical angle of the glass base plate) to a hologram region, and without the need of complicated masking operation of preventing formation of unwanted hologram.
According to the present invention, a water sensor such as rain sensor or dew sensor, comprises: a transparent plate, such as a single layer glass panel or a laminated glass panel; a light emitting device for emitting sensing light so that the sensing light travels in the transparent plate by internal reflection in the transparent plate; a light receiving device for receiving the sensing light from the transparent plate to sense water on the transparent plate; and at least one hologram defining a light path of the sensing light through the transparent plate from the light emitting device to the light receiving device. There may be two or more holograms formed in different regions of a single hologram sheet.
An exposing system for producing a hologram according to the present invention, comprises: a transparent plate member for defining a reflection surface and a contact surface, and holding a light sensitive film between the reflection surface and the contact surface; and first and second prisms. The first prism has a contact face for contacting with the contact surface of the plate member, a first face for guiding a first reference beam so that the first reference beam travels through a first region of the light sensitive film, and a second face for guiding a laser beam so that the laser beam travels through the first region of the light sensitive film as a first object beam to form a first hologram in the first region of the light sensitive film with the first reference beam. The second prism has a contact face for contacting with the contact surface of the plate member, a first face for guiding a second object beam so that the second object beam travels through a second region of the light sensitive film, and a second face for guiding the laser beam reflected internally from the reflection surface of the plate member so that the reflected laser beam travels through the second region of the light sensitive film as a second reference beam to form a second hologram in the second region of the light sensitive film with the second object beam.
According to one aspect of the present invention, a water sensor such as rain sensor, comprises: a transparent plate, such as a windshield glass panel; a light emitting device for emitting sensing light so that the sensing light travels in the transparent plate by internal reflection in the transparent plate; a light receiving device for receiving the sensing light from the transparent plate to sense water on the transparent plate; and an optical element, such as a hologram or a concave mirror, disposed on a surface of the transparent plate or in the transparent plate, for converging the sensing light in the (non-convergent) form of a divergent beam or parallel beam and directing the sensing light in the convergent form to the light receiving device.
REFERENCES:
patent: 5341230 (1994-08-01), Smith
patent: 9-257952 (1997-10-01), None
patent: 10-62336 (1998-03-01), None
patent: 10-96791 (1998-04-01), None
Asakura Motoh
Hashimoto Chikara
Nishikawa Shinji
Central Glass Company Limited
Crowell & Moring LLP
Le Que T.
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