Eastman-Kodak Company

Other

James G Davis

James A Hardy

Mark D Bedzyk

Sreeram Dhurjaty

Gregory N Heiler

A laser imaging apparatus includes a laser diode which is controlled to produce a laser beam the power of which varies linearly as a function of a digital image input signal. The laser beam is deflected by scanning optics to expose photosensitive media such as film. When the digital image input signal is in a first range of values to operate the laser diode in its linear region, the laser diode is controlled to operate in an amplitude modulation mode. When the digital image input signal is in a second, lower, range of values which would operate the laser diode in its non-linear operating region, the laser diode is controlled to operate in the linear region but in a pulse amplitude modulation mode.

Laser diode operated in amplitude modulation and pulse amplitude modes

Laser diode operated in hybrid modulation modes

A laser imaging system includes a laser diode and an automatic power control circuit with a laser diode protection circuit. The protection circuit includes a shunt circuit for shunting power around the laser diode in response to one or more of the following conditions: laser light power over a predetermined maximum value, temperature of the laser diode is below or above a predetermined temperature range, the electrical power supply is below or above predetermined voltage values during power up and power down.

Laser diode automatic power control circuit with means of protection of

A technique for automatically setting a threshold current for a laser diode which has a linear laser operating region and a lower non-linear operating region. The laser diode is controlled (1) during a warm-up period during which no operating current is supplied to the laser diode, to allow the electronics and laser diode to stabilize; (2) during an initialization period, during which the current through the laser diode is brought up to a threshold operating point above said non-linear operating region and during which no image data is applied to the laser diode; and (3) during an operating period in which digital image data is applied to the laser diode to operate it in the linear laser operating region.

Automatically setting a threshold current for a laser diode

Laser apparatus containing an electrically operated laser (laser diode) is temperature stabilized so that it is able to generate a beam of laser light of sufficient intensity to be suitable for use in a laser printer without entering a failure mode due to overheating. The laser diode is integrated into a hybrid thick film integrated circuit wherein the laser diode is bonded to one side of the hybrid's substrate of thermally conductive and electrically insulating material of the hybrid. The hybrid has conductors thereon which are connected to the leads from the laser diode. A circuit containing temperature sensitive material (elements formed of positive or negative temperature co-efficient resistive material) is distributed in spaced areas on the opposite side of the hybrid's substrate from the laser diode. The distributed thermistor circuit and its close thermal coupling to the cooler and the diode laser reduce thermal mass (capacitance), which must be heated or cooled, to maintain athermal conditions. A control circuit responsive to the thermistor resistance which includes a proportional gain stage which follows rapid changes in thermistor resistance and an integral stage which prevents slow changes in thermistor resistance from rendering the temperature unstable, provides current in the proper direction through the cooler so as to maintain and stabilize the temperature of the laser.

Temperature stabilizable laser apparatus

A solar-powered rapid transit system is provided, which travels suspended above ground along a horizontal rail, supported by vertical/horizontal supports. The guide rail is basically a parallelogram, with five inner surfaces. It can be configured as either an overhead monorail system, or a birail system. The rail car is attached to and suspended from such rail by power transmission and support shafts, each of which attaches to a wheel box that fits into the horizontal guide rail. Power is transmitted to the wheels in each wheel box from several electric motors by a series of pulleys and belts in a unique configuration. Such wheels then propel the rail car or cars, which can be connected in series, down the rail. Power for electric motors is supplied by rectangular solar panels supported by vertical supports attached to the roof of each rail car, which extend several feet above the rail car and guide rails. Hinges allow the solar panels to pivot in the direction of the sun, to receive optimum sunlight for power generation. Storage batteries mounted atop each rail car would store generated solar power for night operation and periods when optimal sunlight is unavailable. An electronic sensor rod extending from each wheel box to a groove in the inner surface of the rail picks up system control signals and auxiliary power supplied by a municipal power utility from such groove.

Solar-rapid rail mass transit system

A controller for a laser diode causes the diode to generate an illuminative output which varies linearly in response to changes in image signals which range between minimum and maximum brightness levels. A switchover point between first and second modes of operation is selected to be above the knee region of the laser diode operating curve. If the input signal values are above the switchover point, diode illuminative output is a function of these signal values. However, if the input signal values are below the switchover point, then the input signals are modulated to switch the diode several times between an 'on' state which is above the knee region and an 'off' state, to form one picture element (pixel). In order to vary the illuminative output as a linear function of the change in image signal level, the diode 'on' time during formation of one pixel is a function of the image signal value.

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Rochester, NY, United States of America

James G Davis