Coherent, Inc.

Emi, LLC

Robert J Rorden

Gregory Dumond

David A Dewey

Michael W Sasnett

David Trost

Jerzy Orkiszewski

Michael Arnett

Larry A Gibson

Ralph Saunders

William E Smith

Typically, a laser emits significant energy after a control signal is generated to disable the power supply. The inherent delay between generation of a control signal for shutting off a laser power supply and actual termination of an output beam pulse in response to the control signal, is compensated in the context that the control signal is generated automatically upon coincidence of measured output beam power with a preset threshold value. Power supplied to a laser is modulated to cause generation of a pulsed laser output beam. The cumulative energy of each output beam pulse is monitored and a feedback signal indicative of measured output beam pulse energy is supplied to the power supply. The feedback signal is compared with a user-selected threshold value, and a control signal is generated for terminating the output beam pulse (by terminating input power to the laser) when the measured output pulse energy reaches the threshold value. By generating the threshold signal to have a value representing a threshold output beam pulse energy that is lower than a desired output beam pulse energy, the threshold signal is generated in a manner which compensates for the inherent delay between generation of the control signal and the actual termination of the output beam pulse in response to the control signal. This prevents delivery of significant output beam energy in excess of a user-selected amount.

Electronically pulsed laser system

A laser power supply including circuitry for converting standard, 115-120 volt, AC power from a wall outlet to current pulses for powering a laser, to generate a pulsed laser output beam having laser pulse amplitude and duration matching pre-selected parameters. In a preferred embodiment, the invention powers an argon laser tube and generates output laser beam pulses having power in the range from about 50 milliwatts to 2 watts, and duration in the range from about 0.01 second to 2 seconds. The invention converts standard AC power to current pulses having controlled duration, average amplitude, and ripple amplitude for powering a laser, and can produce laser output beam pulses with a turn-on time of less than 1 millisecond, with a switching frequency in the range from about 10 to 20 KHz without significant overshoot. A preferred embodiment of the invention powers a gas laser tube, and includes a magnet control circuit which enables the laser tube magnet in the absence of a special magnet control signal received at the magnet control circuit from a fiber optic link. The invention is particularly suitable for powering gas laser systems for use in ophthalmic and surgical applications, but is also useful for powering other types of laser systems. An important advantage of the invention is that its ability to accept standard, AC power from a wall outlet enables the inventive apparatus to be moved conveniently between treatment rooms (for use in any of the rooms), without the expense and inconvenience of installing special wiring.

Method and apparatus for supplying pulsed power to an ophthalmic laser

A voltage controller for converting AC line voltage (which may fluctuate, or vary from site to site) to AC power (having substantially constant average power) for a laser tube cathode heater. The voltage controller of the invention receives standard AC line voltage and a feedback signal proportional to the voltage applied to the cathode of a laser gas tube by the cathode heater. In a preferred embodiment, the feedback signal is processed to generate a DC signal representing time-averaged power applied to the cathode. Preferably, the DC signal is then compared with a preset reference voltage in a comparator, and the comparator output is fed to the data input of a flip flop circuit. A clock signal derived from the AC line voltage is supplied to the clock input of the flip flop. The flip-flop will thus respond to the comparator output once per line cycle (approximately at a zero crossing). The flip-flop output is employed to control a solid state switch, which turns power to the cathode heater on or off for full line cycle intervals. In response to variations in the line voltage, the ratio of 'on' to 'off' cycles will change to maintain substantially constant average power to the cathode heater. The control technique employed in the inventive apparatus avoids switching transients and DC current in the cathode heater's transformer primary.

Laser cathode voltage controller

A high voltage power supply for energizing a gas discharge laser in either an enhanced pulse mode or a continuous mode, which power supply is simple to manufacture and minimizes the voltage that other parts of the energizing circuit are required to withstand. The voltage provided by a high voltage DC power supply is boosted by the interaction of first and second reactive components. A first reactance is provided which stores charges at the boosted potential. This charge is provided to the laser to initiate electrical breakdown. The second reactance generates a potential which is additive with respect to the potential provided by the high voltage DC power supply so that the first reactance is charged to a potential equal to the generated potential plus the potential of the high voltage power supply.

Power supply for gas discharge lasers

A therapeutic radiographic apparatus includes a source of a pencil-like beam of penetrating radiation which requires to be positioned relative to a patient's body so that the radiation passes, at all times during therapy, through an anomaly, such as a tumor, in the patient's body. It is difficult to maintain coincidence of the beam with the anomaly, and this invention provides means for indicating optically a point of contact of the beam with the patient's body. The point of contact may, for example, be the point of emergence of the beam from the body.

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Los Altos, CA, United States of America

Robert J Rorden