Abstract: A display device for a transportation includes: a display unit displaying a display image on front and rear face sides, the display images displayed on the rear face side being in mirror image relationship with each other; and an optical member for inverting the display image displayed on the rear face side; wherein the display image displayed on the front face side is directly seen by a driver and the display image displayed on the rear face side is inverted by the optical member, so as to see in the same direction of the display image displayed on the front face side. The above display unit may be constituted by a light source having plural color spectra; an attenuation filter in which a transmittance for light emitted from the light source can be partly changed by an external signal; and a transparent light guide plate which guides light emitted from the light source to at least one of front and rear faces of the attenuation filter.

Abstract: In the vehicle antenna, a GPS antenna, a radio wave beacon antenna for VICS/automatic rate, and an optical beacon antenna are incorporated into between the mirror of a room mirror and a cover and they are united together into an integrated body. The vehicle antenna is structured such that it is allowed to transmit and receive signals with respect to a GPS, a VICS/automatic rate beacon, and an optical beacon through the windshield of a vehicle. This structure eliminates the need to install the respective antennas of the vehicle antenna onto a vehicle body and an instrumental panel, thereby being able to improve the appearance of the interior of the vehicle. Also, since the vehicle antenna is incorporated in the room mirror, the vehicle antenna is not visible directly to the eyes of a driver and is kept from reflecting its shade into the windshield to thereby prevent interference with the driving operation of the driver.

Abstract: In an optical head for optical beacon, a prism 5 is arranged immediately after light emitting elements 1 of an optical head 10 in light radiating directions of the light emitting elements 1, so that the paths along which light rays travel immediately after the radiation can be curved by the prism 5. As a result of this configuration, if the index of refraction of a material of which the prism 5 is made and the angle of a slope of the prism 5 are set to proper values, the light rays can be injected from the prism 5 to an optical head 10 on the side of a light receiving element 2 in arbitrary directions. Further, a surface 21 of a body 13 in which a transmission window 14 is formed is so shaped as to be inclined backward with respect to the travelling direction of an automobile from an upper edge a to a lower edge b.

Abstract: A source-sensitive gyroscope guides light beams emitted from a light emitting device into both ends of the fiber coil, makes the beams propagate in the coil clockwise and counterclockwise, and retrieves the beams into the light emitting device itself. The phase difference is obtained from the change of the driving current or the change of the driving voltage of the light emitting device, or from the change of a photocurrent of the monitoring photodetector mounted behind the light emitting device in the light source. A birefringent medium having an optical path difference longer than the coherent length of the light is interposed between the light emitting device and the end of the fiber. When the light beams are non-polarized, the birefringent medium is aligned in the orientation in which the anisotropic axis is perpendicular to the beam line.

Abstract: An AC component of the photodetector includes two quasi-sine waves in a cycle of phase-modulation. T.sub.1 and T.sub.2 are time lengths of the quasi-sine waves. When a fiber coil is rotating, T.sub.1 differs from T.sub.2. The difference between T.sub.1 and T.sub.2 is in proportion to an angular velocity of the fiber coil. This invention obtains the angular velocity by measuring time durations T.sub.1, T.sub.2 or both T.sub.1 and T.sub.2. Zero-crossing detection defines the moments of the beginning and the end of T.sub.1 and T.sub.2. Since this gyroscope depends on the measurement of time lengths, it is fully immune from the fluctuation of light power due to the light source, or the fluctuation of the gain in the electric circuit.

Abstract: Conventional fiber-optic gyroscopes were provided with an independent photodetector for detecting interfering beams. The existence of the independent photodetector required two beam dividing-and-combining devices for equalizing the experiences of the clockwise-spreading beams and the counterclockwise-spreading beams. Curtailment of an expensive beam dividing-and-combining device is desirable for reducing the cost of gyroscopes. This invention dispenses with the independent photodetector. Instead of the independent photodetector, the light source itself or the monitoring photodiode detects the interfering beams by the change of driving current, applied voltage or photocurrent. Elimination of the independent photodetector saves one beam dividing-and-combining device by equalizing the path of the progressing beams to the path of the regressing beams. Optimum light sources, interposition of polarizer, position of depolarizer and use of birefringent material as polarizer are explained.

Abstract: An optical fiber type polarizer comprises a first optical fiber constituted by a birefringent optical fiber wound at a predetermined winding radius and having winding start and end fixed to each other by an adhesive, the first optical fiber having short extra portions respectively extending from the winding start and end, and the length of each of the short extra porions being at least as small as the predetermined winding radius. The optical fiber type polarizer further comprises a second optical fiber spliced to one of the short extra portions of the first optical fiber, and a third optical fiber spliced to the other of the short extra portions of the first optical fiber.

Abstract: A fiber-optic gyroscope having a depolarizer installed near the fiber coil and a polarizer disposed in the optical path before the light is divided in two partial lights to avoid the fluctuation of the light power passing reversely through the polarizer induced by the rotation of the polarization plane of the light. However, since the light emitting device emits a linearly polarized light, the light power first passing through the polarizer will fluctuate by the rotation of the polarization plane. This invention adds another depolarizer between the light emitting device and the polarizer in order to kill such a fluctuation.

Abstract: A fiber-optic gyroscope has a polarizer, a fiber coil and couplers. A light beam is polarized, divided into two beams and introduced into the fiber coil. Two depolarizers are provided; one between a light source and a polarizer, the other between the fiber coil and a coupler. To clarify the condition for avoiding interference between two depolarizers is a purpose of this invention. Four birefringent materials A, B C and D should satisfy inequalities;.vertline.P.sub.a B.sub.a L.sub.a +P.sub.b B.sub.b L.sub.b +P.sub.o B.sub.o L.sub.o +P.sub.d B.sub.d L.sub.d .vertline.-B.sub.5 L.sub.5 >Cwhere P.sub.a, P.sub.b, P.sub.o, and P.sub.d are triplet factors which take one of -1, 0 or +1 independently, B.sub.a, B.sub.b, B.sub.o and B.sub.d are birefringence and L.sub.a, L.sub.b, L.sub.o and L.sub.d are lengths of A, B, D and D. B.sub.5 L.sub.5 is extra birefringency of the fiber coil or couplers.

Abstract: A fiber-optic gyroscope having a single mode fiber coil for sensing the rotation suffers from drift or fluctuation of scale factor of the output signals owing to spontaneous rotation of polarization of beams propagated in the fiber coil. Thus, two depolarizers are required in front of and at the back of the polarizer to avoid the fluctuation. The depolarizer of prior art consists of two birefringent materials twistedly connected with each other at an about 45.degree. inclination angle between the principal axes of one and the principal axes of the other. A conventional fiber-type depolarizer has two polarization maintaining fibers connected together. A new, simplified depolarizer is proposed. The depolarizer is built by gluing a polarization maintaining fiber to an end of the polarizer with an about 45.degree. inclination angle between the principal axes of the fiber and the principal axes of the polarizer.

Abstract: A fiber-optic gyroscope having a depolarizer installed near the fiber coil and a polarizer disposed in the optical path before the light is divided in two partial lights to avoid the fluctuation of the light power passing reversely through the polarizer induced by the rotation of the polarization plane of the light. However, since the light emitting device emits a linearly polarized light, the light power first passing through the polarizer will fluctuate by the rotation of the polarization plane. This invention adds another depolarizer between the light emitting device and the polarizer in order to kill such a fluctuation.

Abstract: A phase modulation type fiber optic gyroscope having a greatly improved output stability without a large increase in the number of basic components of the gyroscope system. In accordance with the invention, the d.c. component of the output of a light detecting element which provides the two circulating beams is sensed and employed to control the output of the light-emitting element so as to be constant.

Abstract: The present invention provides optical integrated circuits in which both a light function zone and a light reception zone are monolithically formed on the same substrate to obtain high reliability and low noise and loss. The optical integrated circuits according to the present invention have improved electrode structure formed on a light wave guide layer to apply a major portion of the electric field generated by the current flowing in the electrode structure within the light wave guide layer to thus improve light receiving sensitivity. Further, the optical integrated circuits according to the present invention have the light reception zone of the large photoconductive effect on the substrate to develop a light receiving sensitivity to the light function zone without affecting propagation loss.

Abstract: A method and apparatus for detecting a frequency change of a light modulates the scattered light from the object of measurement using an acousto-optic modulator or the like, heterodyne-detects the scattered light after modulation to provide an electrical signal having a frequency (f.sub.d -f.sub.m) which is the difference between the Doppler frequency f.sub.d and the modulation frequency f.sub.m, passes this electrical signal to a filter while changing the modulation frequency f.sub.m, and obtains the modulation frequency f.sub.m at which the signal voltage is the largest or the smallest, that is, the Doppler frequency f.sub.d.

Abstract: A process for making a diffraction grating pattern on a substrate is disclosed. The process comprises the steps of coating the substrate with first and second materials, with one of the materials defining a selected area for the diffraction grating pattern, and the other material covering the substrate while forming a window at that portion of the substrate where the diffraction grating is desired. The window portion of the substrate is then etched, and the first and second materials are stripped off in order to leave behind the diffraction grating pattern at the desired location of the substrate.