Abstract: An imaging method creates a two-dimensional image of a voltage distribution or a capacitance distribution of a substrate under test using an electro-optic modulator. A coarse modulator calibration determines the effect of non-uniformities in the modulator and determines a look-up table relating the gap distance between the modulator and the substrate to the intensity of the light emerging from the modulator. A positioning means calibration determines a look-up table relating control voltage to response by the positioning means. The modulator is moved over a portion of the substrate and then undergoes a positioning step, a fine onsite calibrating step, and a measuring step. The positioning step can be accomplished using the intensity of emerging light to determine modulator gap distance, and the response verses control voltage look-up table to determine a control signal to vertically position the modulator.

Abstract: Method and apparatus for generating a distortion-free, frequency-modulated optical signal, whereby this signal from an optical semiconductor laser driven with a modulating voltage is distorted by the modulating voltage due to a thermally conditioned frequency transfer function of the transmitter for the modulation frequency of the modulating voltage. For generating the distortion-free, frequency-modulated optical signal, the modulating voltage and/or the distorted, frequency-modulated optical signal itself and/or a superimposition signal containing this optical signal is subjected to a distortion that entirely or partially compensates the distortion of this optical signal. This method is simple and, in combination with receivers for the frequency-modulated optical signal, avoids sensitivity losses.

Abstract: An optical shutter device for use, e.g., in an optical printer includes a plurality of electrooptic chips each having a plurality of very small segments for optical modulation. The optical shutter device has a voltage adjusting circuit which individually supplies the driving voltage to the chips depending on the light transmitting characteristics intrinsic to the chips. Thus, even when the chips have different light transmitting characteristics, the image produced by the chips will have a uniform intensity.

Abstract: A device for compensating for changes in temperature and strain in electro-optic modulators without altering the voltage field effects. Devices for modulating light intensity in response to a varying electrical signal are particularly useful with optical fiber information sensing systems. Such modulators basically receive a light signal, collimate and polarize the light, then pass it through a wave plate to cause circular polarization. The light signal then is passed through a modulator material which rotates the beam polarization in response to varying voltage signals imposed on the modulator. Unfortunately, changes in temperature and strain also change the state of polarization. I have now found that by transmitting the light signal through two equal crystals in series that are rotated 180.degree. from each other, a uniform strain or temperature change will result in canceled polarization effects. Thus, effects of changes in temperature and/or strain are canceled without affecting the voltage field effects.

Abstract: An apparatus for creating an optical noise of a predetermined bandwidth that uses an optical amplifier which amplifies optical noise components and produces unpolarized optical noise by spontaneous emission, a mirror to reflect the optical noise components back to the optical amplifier and a filter that filters out optical noise components outside the predetermined optical bandwidth. The filter is located so that optical noise components passed by the filter are amplified in the optical amplifier during an additional amplification. Optionally, a polarizer and Faraday rotator are used in the apparatus. The optical noise created in the optical amplifier is polarized in the polarizer after two amplifications, rotated in the Faraday rotator, then amplified two more times before leaving the apparatus.

Abstract: In a raster output scanner, a system for using one original beam and one facet of a rotating polygon to generate two consecutive scan lines. The original beam is first separated into two beams in a beam splitter. The resultant beams are polarized ninety degrees apart, and directed to the modulator. The beams are a sufficient distance apart so that the A/O modulator can modulate each beam with a minimum of crosstalk. The output beams are then brought together to within one scan line separation by a beam recombiner, which is a reversed beam splitter. The beams can be brought together to this close proximity without optical interference because the beams are plarized ninety degrees apart.

Abstract: In a raster output scanner, a system for using one original beam and one facet of a rotating polygon to generate a scan line which can be turned on to have three levels of intensity. The original beam is first separated into two beams in a beam splitter. The resultant beams are polarized ninety degrees apart, and directed to the modulator. The beams are a sufficient distance apart so that the A/O modulator can modulate each beam with a minimum of crosstalk. The output beams are then brought together and combined into one beam without optical interference because the beams are polarized ninety degrees apart. The beam can have several levels of intensity and be used to create several levels of gray scale at the output.

Abstract: As the dielectric constant and the halfwave voltage of electro-optic crystals having a fourfold axis of rotary inversion are oppositely dependent on the absolute temperature, but their product is nearly independent of temperature, temperature compensation in an ac voltage measuring system utilizing such an electro-optic crystal is provided by measuring the time averaged current through the crystal. Good electric isolation is achieved by a current sensing circuit which produces a pulsed light signal having a pulse rate proportional to the time averaged current through the crystal. The pulsed light signal is converted to an electrical signal for input to a digital computer which calculates therefrom, and from a reference current and voltage measured at a reference temperature, and a time averaged voltage measurement, a temperature correction factor which is applied to the crystal halfwave voltage used by the computer in calculating the instantaneous value of the voltage to be measured.

Abstract: In a polarization-state converting apparatus for use as an optical isolator, an optical modulator and the like, there are provided a waveguide including a magnetic semiconductor, a device for applying a magnetic field to the waveguide in a first predetermined direction, a device for applying an electric field to the waveguide in a second predetermined direction, and a mode conversion is caused via electrooptic and magnetooptic effects due to the electric and magnetic fields to change the polarization state of light propagating through the waveguide. When used as an optical isolator, the optical isolation is performed to compensate for degradation of the mode conversion rate due to a phase mismatch between light incident upon the waveguide and light emerging from the waveguide.

Abstract: An optical film having high optical uniformity is disclosed, including a thermoplastic resin film having no periodic thickness variation of sine waveform having a pitch of 50 mm or less and a thickness change of 0.5 .mu.m or more on continuous thickness measurement in the machine direction, and an optical film having a retardation value of 1200 nm or less with a fluctuation of not more than 10% and a rate of change of not more than 1.3%/cm, which is obtained by stretching said thermoplastic resin film. The optical film is laminated on a polarizing sheet to serve as a phase retarder.

Abstract: An apparatus and method that permit the transmission of secure communications. The invention uses quantum mechanical effects to establish nonlocal correlations between a pair of photons. This is analogous to an automatic encryption code that exists at only one location and is immediately destroyed after either of the photons is detected. This latter feature also provides a means for detecting any unauthorized tap on the transmission line.

Abstract: A device for damping the vibrations of an elongated, substantially rectangular crystal in response to an applied high voltage electrical field comprises a pair of dielectric panes which are impedance matched with the crystal and are attached to opposite sides thereof. As attached to the crystal, each of the panes is disposed at the periphery of the electrical field, and an aluminum block is attached to each of the panes on a surface which is opposite from the crystal. The mass of aluminum blocks, and the texture of their exposed outer surfaces cooperate to mechanically dampen the acoustic vibrations transmitted from the crystal through the panes. Additionally, the rectangular dimensions of the crystal are chosen to delay the propagation of acoustic waves from the surfaces of the crystal to its center.

Abstract: An imaging method creates a two-dimensional image of a voltage distribution or a capacitance distribution across a surface of a substrate under test using an electro-optic modulator which is positioned and biased with respect to the surface of the substrate. The method involves a first coarse offsite calibrating step to compensate for nonuniformities in the light emerging from the modulator. Then, for each successive portion of the substrate over which the modulator is to detect characteristics of the substrate, the system undergoes a modulator relocating step, a modulator levelling step, a modulator gapping step, a fine onsite calibrating step, and a measuring step.

Abstract: A light printer with a light shutter having an array of electro-optical elements is disclosed. The light printer provides with a detection circuit for monitoring temperature and/or time dependent variations regarding the electro-optical elements of the light shutter and a driving voltage control circuit for controlling an optimum driving voltage of the light shutter according to results detected by the detection circuit.

Abstract: A method of and a device for driving a light shutter having an electrooptical effect to polarize an incident light by applying an electric field to the light shutter. When the light shutter is made activate, an excessive electric field in addition to a half-wave electric field which is a specific one to polarize an incident light at 90.degree. in the static characteristics of the light shutter is applied to the light shutter initially, and subsequently, the half-wave electric field only is applied to the light shutter. To discharge the electric charge accumulated in the light shutter, no voltage is applied to electrodes each of which is provided on the wall of the light shutter so as to oppose each other subsequent to the application of the electric field until the next application thereof.

Abstract: An optical intensity modulator includes a compound semiconductor substrate of a first conductivity type having first and second surfaces, and a compound semiconductor active layer of the first conductivity type formed on the first surface of the compound semiconductor substrate. An incident laser beam to be intensity-modulated is applied to the compound semiconductor active layer. The modulator further includes a compound semiconductor layer of the first conductivity type formed on the compound semiconductor active layer, an opposite conductivity type compound semiconductor layer of a second conductivity type opposite to the first conductivity type, a first electrode formed on the opposite conductivity type compound semiconductor layer, and a second electrode formed on the second surface of the compound semiconductor substrate.