Eastman-Kodak Company

William R Markis

James E Roddy

Barry David Silverstein

Kurt Michael Sanger

David John Nelson

J Kelly Lee

Thomas A Mackin

Robert W Spurr

Seung H Baek

Robert J Zolla

James M Papa

William A Orfitelli

Robert H Cuffney

Richard A Littlefield

Michael T Murray

A system and method of stabilizing laser output levels includes a laser (), an injection circuit for injecting a radio frequency waveform, and a control circuit for energizing and stabilizing the laser. The radio frequency waveform injected by the injection circuit has a high duty cycle to maintain high output power while providing a stable multimode spectrum. A back facet photodiode sensor () detects radiation emitted from a back facet semiconductor laser () and provides a feedback signal to the control circuit () for maintaining the laser output power. The response of the photodiode is not fast enough to track intensity variations due to the RF waveform, and thus provides feedback to the control circuit () only when there is a substantial need to adjust laser power.

System and method for improving laser power and stabilization using high duty cycle radio frequency injection

The need is met according to the present invention by providing a method of correcting pixel by pixel variations in a display, the method including the steps of creating a defect map of pixel intensity offsets for the display; correcting an input signal according to the defect map; and displaying the corrected input signal on the display, wherein the offset defect map is created by modulating a pixel in the display at a predetermined rate at a predetermined intensity; sensing the display with a photosensor to generate a sensed signal; demodulating the signal with a synchronous demodulator at the predetermined rate to produce a demodulated signal representing a sensed intensity; and employing the sensed intensity and the predetermined intensity to generate a correction offset.

Method and apparatus for determining and correcting for illumination variations in a digital projector

A closed loop three color alignment system for a digital projector comprises a light source and an optical engine ( ) which splits a beam of light from the light source into first, second, and third wavelength bands. A first, second, and third spatial light modulator ( ) imparts image data and a first, second, and third fiducial data to the first, second, and third wavelength bands. A combiner combines the modulated first, second, and third wavelength bands. A diverter diverts a portion of the combined modulated wavelength bands to a sensor. The sensor ( ) senses a relative position of each of the fiducials and sends the position information to a microprocessor. The microprocessor then determines an error based on the relative position of the fiducials. The microprocessor then sends a signal to at least one component of the system to resolve the error.

Closed loop three color alignment system for a digital projector

An apparatus and method for calibration of each individual driver channel in a multichannel driver circuit for a spatial light modulator used in an image display apparatus. A separate calibration sequence is initiated in which, for each positive and negative half-cycle of the driver circuit, a ramped voltage, applied as the drive circuit voltage ( ), is compared against a standard black-video drive voltage. When the ramped voltage equals the standard drive voltage, calibration for this half-cycle is complete and a digital value corresponding to a correction component of the ramped voltage is stored in memory ( ). The process is duplicated for each positive and negative half-cycle of the drive voltage signal ( ). For gain calibration, a ramped voltage is applied as the drive circuit voltage and compared against a standard white-video signal level. When the ramped voltage equals the standard white-video signal level, gain calibration is computed and the digital value for gain correction is stored in memory ( ). Display driver voltages are thereby calibrated so that, for each driver channel, the spatial light modulator is presented with a substantially equal black-video level and a controllable white-video level.

Multichannel driver circuit for a spatial light modulator and method of calibration

A method and projection system ( ) for increasing the color gamut of images projected onto a display surface ( ) by using four or more light sources ( ), where the light sources ( ) are selected for high brightness and narrow wavelength characteristics and are selected from optimal wavelengths for color gamut expansion. Light sources ( ) for large-scale projection environments are preferably lasers. Smaller systems may employ LEDs or other relatively saturated, relatively bright light sources ( ).

Method and apparatus for increasing color gamut of a display

A system and method for reducing or eliminating the speckle intensity distribution of a laser imaging system. In one embodiment of the invention, a radio frequency signal is injected into a semiconductor laser light source ( ) for a projection system ( ) to create different speckle patterns that blend together on a projection surface ( ). In another embodiment of the invention, optical feedback is used to induce a laser light source for a projection system ( ) to create different speckle patterns that blend together on a projection surface ( ). In another embodiment of the invention, the laser light source wavelength is Doppler shifted to produce different speckle patterns. In another embodiment of the invention, a means of deflection is used to directionally move the beam to reduce noticeable speckle.

Speckle suppressed laser projection system with partial beam reflection

A system and method for reducing or eliminating the speckle intensity distribution of a laser imaging system. In one embodiment of the invention, a radio frequency signal is injected into a semiconductor laser light source ( ) for a projection system ( ) to create different speckle patterns that blend together on a projection surface ( ). In another embodiment of the invention, optical feedback is used to induce a laser light source for a projection system ( ) to create different speckle patterns that blend together on a projection surface ( ). In another embodiment of the invention, the laser light source wavelength is Doppler shifted to produce different speckle patterns. In another embodiment of the invention, a means of deflection is used to directionally move the beam to reduce noticeable speckle. Since the eye is very sensitive to horizontal and vertical edges, but less sensitive to angles in between, beam movement of approximately 45 degrees may minimize the loss of MTF in the horizontal and vertical directions.

Speckle suppressed laser projection system using RF injection

Speckle suppressed laser projection system using a multi-wavelength doppler shifted beam

A stabilized laser is comprised of a laser for generating radiation responsive to a control signal. A control circuit connected to the laser provides the control signal and an injection circuit injects a radio frequency into the control circuit and the control signal. A back facet photodiode sensor detects radiation emitted from a back faceted laser diode and provides a feedback signal to the control circuit for adjusting laser output power.

Control circuit for a stabilized laser

A stabilized frequency oscillating circuit outputs a pixel clock signal to an image scanner for controlling pixel rate at various writing positions along a scan line. The circuit includes a synchronization circuit having a first control signal component output to adjust a nominal output frequency of the oscillator; and a frequency profiling circuit having a second control signal component output which varies as a function of writing position along the scan line to determine a corrected output frequency of the oscillator which varies as a function of writing position along the scan line.

Oscillator system with corrective frequency modulation

A laser diode controller (30) having a constant current source (60) which supplies current to a laser diode (90) is disclosed. A current shunt switch (40) directs current to either the laser diode (90) or to a bypass circuit (42). A thermal compensator (70) alters a current level of the constant current source (60) as a function of on-time of the laser diode (90) to compensate for changes in optical power conversion efficiency due to temperature changes in the laser diode. A thermo electric cooler controller (80) maintains a constant temperature of a substrate on which the laser diode is mounted. In one embodiment, an array of sample and hold amplifiers (50) eliminates a need for multiple DACs.

Laser diode controller

A diode laser writer having a high speed, high current, precision laser driver provides for switching a constant current source between a write laser and a dump load. An inductor is provided in a leg of the circuit such that the inductor and the constant current source form a series circuit with whichever of the dump load and the write laser that is switched ON. The inductor keeps the current constant because the inductor produces an e.m.f. counter to the e.m.f. of the load inductance. The added inductance will generate an e.m.f. counter to that of the load inductance, serving to augment the compliance voltage. The overall effect of the added inductor is to restore the constant current property of the circuit.

Laser writer having high speed high current laser driver

Beam scanning system includes a rotatable element for receiving a stationary light beam at successive element facets to thereby impart a scanning motion to the light beam so as to scan a beam receiving medium. Deviation in the mechanical or optical performance related to each successive facet are corrected by use of a high-speed beam deflector operated in either a closed loop or open loop servo system. The beam deflector includes a unique piezoelectric plate and reflecting body structure, wherein parallel plates of piezoelectric material are bonded at selected locations to a reflecting body with flexible adhesive. The plates are supported by a platform and operatively connected to a plate driving means to effect motion of the body in a push-pull arrangement with respect to the platform. The resulting structure has a high resonant frequency even though a reflecting body in the form of relatively large glass mirror may be employed.

Light beam scanning system including piezoelectric means for correction

A calibration method and apparatus is disclosed that includes a power stabilized laser diode to generate a laser beam that is passed through the hologon scanner to be calibrated and a mechanism for measuring the power intensity of the laser beam at a plurality of positions at an exposure plane for each facet of the hologon scanner. The measured light levels are converted to correction factors that are stored in a corresponding programmable read only memory (PROM) as a function of facet number and scan position. The hologon scanner and its corresponding programmable PROM are then installed in a laser scanning apparatus. The laser scanning apparatus adjusts the output of its light source in accordance with the correction factors stored in the PROM in order to compensate for variations in the light transmission efficiency of the facets of the hologon scanner.

Method and apparatus for providing correction of hologon transmission

The present servosystem positions a movable member such as an optical head over a rotating disk with a constant velocity and high positional accuracy by utilizing a fast analog feedback loop that is controlled by a slower digital loop. The analog feedback loop locks the speed of the movable member to the speed of the rotating disk in a spiral recording track. The progress of the movable member is constantly monitored with the digital loop. A velocity error of known magnitude and direction is introduced into the system. When the error exceeds a preset limit an error of the known magnitude but of the opposite direction is introduced. The servosystem thus zig-zags about the desired position with small velocity changes to provide a substantially constant velocity system with high positional accuracy.

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Spencerport, NY, United States of America

William R Markis