Presstek, Inc.

John Gary Sousa

Josh P Foster

Richard A Williams

John F Kline

Wayne Mueller

Frank G Pensavecchia

James R Moss

Glenn E Cabana

Mitchell C Ruda

Thomas C Dearman

Steven Stoltz

Cavity lasers exhibit a relatively high beam quality (e.g., M&#x3c;1.25) despite a relatively small cavity length (e.g., 50-53 mm) for a high (e.g., &#x2267;10 watt) output power device. This enables the construction of physically smaller laser and optical assemblies without sacrificing performance. Reduction of optical photonic interference, which can impair imaging performance, is also facilitated. Laser and optical assemblies may utilize an aperture defined within an optical barrier element to reduce the divergence of the light beam emanating from a diode-pumping laser.

Graphic-arts laser imaging with reduced-length laser cavities and improved performance

A laser-diode structure whose output is largely single-mode utilizes a ridged top layer that defines an amplification region within an underlying emission layer, and which is provided with grooves that suppress the higher modes.

Mode-limiting diode laser structure

A single laser crystal is driven with multiple pumping sources to obtain discrete, collimated outputs without substantial thermal crosstalk, so that the action of one pumping source does not adversely interfere with the action of another source driving the same crystal; that is, an imaging output emanating from one crystal region will neither defeat nor spuriously cause an imaging output in another region.

Multiple-beam, diode-pumped imaging system

A linear array of diode laser emitters is manufactured with sufficient thermal and electronic isolation among the emitters to permit separate addressability. The emitter bar has first and second opposed surfaces and a third surface through which the emitters direct output. A first surface of the emitter bar is affixed to a &ldquo;standoff&rdquo; element that has conductive surfaces connecting each emitter to a power source; these connections are maintained after a series of spaces is formed between the emitters of the emitter bar. The second surface of the emitter bar is affixed to a heat sink to form a finished assembly.

Emitter array with individually addressable laser diodes

A fixture containing a plurality of parallel optical fibers is aligned using a solder circuit that is itself mounted on the surface. The fixture is positioned on the circuit so as to be in contact with a quantity of solder. With the solder in the molten state, the fixture is aligned with respect to an element receiving light output from the optical fibers, and the alignment is secured by allowing the solder to solidify with the fixture immobilized.

Alignment of laser imaging assembly

Individually addressable laser crystals are optically coupled to a single slab of an optical carrier that transmits substantially without distortion. The crystals are separate for thermomechanical isolation but may be closely spaced (generally on the order of 0.003 inch apart), and may originate as a single crystal cut into separate segments.

Pumped laser diode assembly with optically coupled heat sink

Multi-mode laser radiation is focused to a preselected spot size on a recording construction using a controlled-angle diffuser. The diffuser concentrates the radiation, counteracting the dispersive effects of multi-mode output.

Method and apparatus for laser imaging with multi-mode devices and optical diffusers

Optimization of distances between each of an array of imaging devices and the surface of an oppositely disposed rotating drum is accomplished without disturbing the mechanical mounting of the imaging devices. For each device, an optimal distance from the recording construction is established; at this optimal distance, corresponding to substantially proper focus, maximum energy density is delivered to a recording medium on the drum. Rather than alter the actual device-to-drum distance to conform to this optimum, the optical paths between the devices and the drum are changed by varying the spacing between the radiation source (e.g., the end of a fiber-optic cable) and the assembly. This alters the point of focus, and therefore has the same practical effect as moving the device itself. The invention also provides a technique for determining the optimal device-to-drum distance by means of a sequence of imaged regions applied at different device-to-drum distances.

Method of calibrating distances between imaging devices and a rotating

Compensation for the effects of duty cycle on the output level of an imaging device, and for the effects of periodically varying distance between the output of the imaging device and its target, is accomplished electronically. An exemplary apparatus includes a source of radiation (generally a laser) having an output level that varies both with an input power level and, undesirably, with the duty cycle. The radiation source is operated to produce, on the recording surface, an imagewise pattern of spots, and an adjustment facility compensates for output-level variations resulting from duty cycle--that is, from the recent pattern of laser activity.

Method and apparatus for diode-laser imaging with compensation for

Pumped laser crystals for use in an imaging apparatus are designed and housed so as to minimize variation in dot size across the spectrum of duty cycles ranging generally from 1% to 100%--that is, from print densities ranging from every hundredth pixel to every consecutive pixel.

Diode-pumped system and method for producing image spots of constant size

A laser system for imaging graphic-arts constructions avoids the need to demagnify a divergent beam by using the output of a semiconductor or diode laser to optically pump a laser crystal, which itself emits laser radiation with substantially less beam divergence. A preferred implementation utilizes, as a pumping source, at least one laser device that emits in the IR, and preferably near-IR region, to image ablative or transfer-type printing members. The output of the pumping source is provided to the laser crystal via a focusing lens arrangement. The output of the laser crystal, in turn, is focused onto the surface of a recording medium to perform the imaging function. Crystal excitation and decay times are minimized by continuously maintaining the pumping source at a bias power level, which keeps the crystal at a continuous, baseline power level just short of lasing or imaging; and then selectively and intermittently increasing power to the pumping source to cause the crystal to lase (or lase at higher power) in an imagewise pattern. By selectively varying the pulse width within certain limits, it is possible to obtain image dots of different sizes while retaining a round dot shape.

Diode-pumped laser system and method

Laser guiding and focusing apparatus for imaging lithographic printing members responsive to the output of laser devices. Radiation passes through at least one discrete layer of a printing member and ablates one or more underlying layers, resulting in an imagewise pattern of features on the printing member. The radiation is obtained from a laser diode and its dispersion reduced to produce an image spot with maximum depth-of-focus tolerance.

Apparatus for laser-discharge imaging including beam-guiding assemblies

A focusing assembly includes features that allow numerical aperture to be reduced and optimized by reducing aberrations and ghost reflections and easily controlling stop size, thereby increasing depth-of-focus. The assembly includes a single, bi-aspheric focusing lens that optimizes image quality at a specific off-axis field point. Passage of excessively divergent radiation is prevented by a baffle having a sharp, flared edge that minimizes reflection. A second aperture or baffle can be included to restrict high-divergence radiation emerging from the bi-aspheric focusing lens. All interior surfaces of the focusing assembly are preferably blackened, once again to minimize internal reflections.

Growing community of inventors

Hudson, NH, United States of America

John Gary Sousa