Abstract: A method and apparatus are disclosed for scanning a receiving medium. The apparatus comprises a motor-driven lead screw which is used to advance a print head relative to a receiving medium supported on a rotatable drum. In order to overcome the problem of banding in an image produced by the apparatus as a result of a sinusoidal pitch error of the lead screw, the pitch error of the lead screw is broken up into a random pitch error. In another embodiment, the pitch error frequency is shifted to a higher frequency which is less sensitive to the human eye.

Abstract: A beam scanning galvanometer is disclosed which oscillates a mirror in a non-resonant mode. The moving parts of the galvanometer are made with as small a moment of inertia as possible because the mirror is oscillated in a non-resonant mode. The galvanometer uses two sets of crossed leaf-springs to support the mirror instead of bearings which are usually used in non-resonant galvanometers. Each of the sets of leaf-springs is formed of a single strip of cold rolled stainless steel. The springs are embedded in uniquely shaped cavities in a permanent magnet that supports the mirror at a distance very close to an axis of rotation of the mirror. The mirror is specially shaped with beveled edges so that its moment of inertia is low and so that it can oscillate in very close proximity to a driving current coil which surrounds the mirror supporting magnet. A magnetic position sensor is used to detect an angular position of the mirror during operation of the galvanometer.

Abstract: An imaging system comprising a source of light movable with respect to a writing element and projectable thereon to generate an image, a focusing system is provided for focusing a light source which generates a first beam of light of a wavelength selected to be actinic with respect to the writing element. At least a portion of the first beam of light is absorbed by the writing element. The apparatus includes a supply of donor sheets and receiver sheets which are independently fed to a writing drum. The sheets are selectively wound in supply rolls so that the "active" surfaces are oriented properly at the imaging station and have a "set" which matches the curve of the drum.

Abstract: A laser scanning device has an optical axis, a laser source for producing a beam of light, and a rotating polygon mirror having a plurality of facets. The beam of light is directed to the rotating polygon mirror so that the beam completely fills at least one of the mirror facets and overflows onto an adjacent mirror facet. The beam is reflected from the rotating polygon mirror so that the reflected beam is symmetrically positioned about the optical axis. The laser scanning device is operated in both overfilled and symmetrical modes.

Abstract: An imaging system comprising a source of light movable with respect to a writing element and projectable thereon to generate an image, a focusing system is provided for focusing a light source which generates a first beam of light of a wavelength selected to be actinic with respect to the writing element. At least a portion of the first beam of light is absorbed by the writing element. The apparatus comprises a material supply which automatically supplies donor sheets and receiver sheets independently to a writing platen or drum, and selectively loads and unloads the donor sheets from superposition with the receiver sheet without disturbing the registration of the receiver sheet. An optical fiber mount and storage device is provided which has a cylindrical chamber within which excess fiber can be wound and a cover plate with a restricted access channel which permits the fiber to be inserted and withdrawn and yet retains the fiber normally within the device.

Abstract: A thermal printer is disclosed which is a adapted to form an image on a thermal print medium of a type in which a donor element transfers dye to a receiver element upon receipt of a sufficient amount of thermal energy. The printer includes a plurality of diode lasers which can be individually modulated to supply energy to selected dots on the medium in accordance with an information signal. The print head of the printer includes a fiber optic array having a plurality of optical fibers coupled to the diode lasers. The thermal print medium is supported on a rotatable drum, and the fiber optic array is movable relative to the drum. In order to prevent banding in an image produced on the print medium, the two outside fibers in the array are used for preheating and postheating of inner scan lines. The printer is particularly well adapted for use as a proof printer for half-tone reproductions of images.

Abstract: An imaging system comprising a source of light movable with respect to a writing element and projectable thereon to generate an image, a focusing system is provided for focusing a light source which generates a first beam of light of a wavelength selected to be actinic with respect to the writing element. At least a portion of the first beam of light is absorbed by the writing element. The system includes apparatus to automatically supply donor sheets and receiver sheets independently to a writing platen or drum, and to selectively load and unload the donor sheets from superposition with the receiver sheet without disturbing the registration of the receiver sheet.

Abstract: An imaging system comprising a source of light movable with respect to a writing element and projectable thereon to generate an image, a focusing system is provided for focusing a light source which generates a first beam of light of a wavelength selected to be actinic with respect to the writing element. At least a portion of the first beam of light is absorbed by the writing element. The apparatus comprises a material supply to automatically supply donor sheets and receiver sheets independently to a writing platen or drum, and to selectively load and unload the donor sheets from superposition with the receiver sheet without disturbing the registration of the receiver sheet. The material transport is arranged to selectively contact the donor and the receiver materials so that there is no cross-contamination.

Abstract: An imaging system comprising a source of light movable with respect to a writing element and projectable thereon to generate an image, a focusing system is provided for focusing a light source which generates a first beam of light of a wavelength selected to be actinic with respect to the writing element. At least a portion of the first beam of light is absorbed by the writing element. The apparatus comprises a material feeder to automatically supply donor sheets and receiver sheets independently to a writing platen or drum, and to selectively load and unload the donor sheets from superposition with the receiver sheet without disturbing the registration of the receiver sheet. Also included are components which contribute to the quality of the images generated, such as relatively inexpensive, low jitter transports and drives for the writing head and imaging drum. In particular, the positive air flow through the apparatus is carefully directed to prevent contamination of the image by air-borne dirt.

Abstract: An imaging system comprising a source of light movable with respect to a writing element and projectable thereon to generate an image, a focusing device is provided for focusing a light source which generates a first beam of light of a wavelength selected to be actinic with respect to the writing element. The focusing device includes a focusing light detector which is mounted adjacent the light source and is provided with a micromask to protect it from unwanted light to improve the sensitivity of the detector and the focusing device.

Abstract: An imaging system having a source of light movable with respect to a writing element and projectable thereon to generate an image. A focusing system is provided for focusing a light source which generates a first beam of light of a wavelength selected to be actinic with respect to the writing element. At least a portion of the first beam of light is absorbed by the writing element, The apparatus includes a material supply to automatically supply donor sheets and receiver sheets independently to a writing platen or drum, and to selectively load and unload the donor sheets from superposition with the receiver sheet without disturbing the registration of the receiver sheet.

Abstract: A method is disclosed for measuring the performance of individual lasers in a multiple channel laser printer. A laser is first preheated and then a test cycle is begun as follows. The laser is first set to a point just below but substantially equal to its threshold value and then set to a test value by supplying it with a preselected current pulse within its operating range. The power output of the laser is then read a substantial number of times and the average value of the readings of laser power output is recorded. The test cycle is repeated for a substantial number of different test values with respectively different preselected current pulses within the laser's operating range.

Abstract: An imaging system comprising a source of light movable with respect to a writing element and projectable thereon to generate an image, a focusing system is provided for focusing a light source which generates a first beam of light of a wavelength selected to be actinic with respect to the writing element. At least a portion of the first beam of light is absorbed by the writing element. The apparatus includes an automatic supply for donor sheets and receiver sheets which are supported independently to a writing platen or drum. Apparatus is provided which selectively loads and unloads the donor sheets from superposition with the receiver sheet without disturbing the registration of the receiver sheet.

Abstract: There is disclosed a method for providing precise color-to-color registration of color dots in a multicolor proof with a thermal printer comprising a CPU and Printer Controller, a Motion Controller, a writing drum, and a writing head coupled to a translation means. Using the disclosed method, a proof and a dye donor member with a predetermined dye color thereon are mounted on the writing drum. The writing head is then moved to a predetermined start position defined by a sensor at a predetermined position along the translation means which has its optical path blocked by the writing head. The writing head is then moved forward to a predetermined home position which is defined by a next subsequent pulse from a multi-pulse radial position-indicating encoder coupled to the translation means occurring after the writing head leaves the start position.

Abstract: An imaging system comprising a source of light movable with respect to a writing element and projectable thereon to generate an image, a focusing means is provided for focusing a light source which generates a first beam of light of a wavelength selected to be actinic with respect to the writing element. At least a portion of the first beam of light is absorbed by the writing element. The apparatus comprises means to automatically supply donor sheets and receiver sheets independently to a writing platen or drum, and to selectively load and unload the donor sheets from superposition with the receiver sheet without disturbing the registration of the receiver sheet. A method of squeegeeing the donor sheet into contact with the receiver sheet, including moving the squeegee member in opposite directions, is provided to assure air removal from between the sheets.

Abstract: An imaging system comprising a source of light movable with respect to a writing element and projectable thereon to generate an image, a focusing system is provided for focusing a light source which generates a first beam of light of a wavelength selected to be actinic with respect to the writing element. At least a portion of the first beam of light is absorbed by the writing element. The apparatus comprises a material feeder to automatically supply donor sheets and receiver sheets independently to a writing platen or drum, and to selectively load and unload the donor sheets from superposition with the receiver sheet without disturbing the registration of the receiver sheet. Also included are components which contribute to the quality of the images generated, such as relatively inexpensive, low jitter transports and drives for the writing head and imaging drum.

Abstract: Methods of and apparatus for advancing a carriage utilize a displacement pump for displacing a selected quantity of fluid. The displacement pump is driven continuously by a motor to provide a series of fluid displacements which are accumulated in a hydraulic cylinder. A ram projecting from the hydraulic cylinder is coupled to the carriage and is advanced stepwise as the individual fluid displacements are accumulated in the hydraulic cylinder. The method and apparatus is especially useful for minimizing banding effects when advancing a carriage which supports a scanning device used in laser printers.

Abstract: The present invention relates to thermal printers including a thermal print head mounting a plurality of N thermal heating devices such as lasers or resistive heating elements. In the thermal printer, a receiver member is mounted on a rotating drum with a dye carrier member engaging the outer surface of the receiver member in a dye frame image printing area. The thermal heating devices are aligned at a predetermined acute angle .THETA. to a line normal to the rotation of the drum. During the high speed rotation of the drum, the thermal heating devices are selectively energized by micropixel clock pulses which are synchronized to the rotational speed of the drum. During each rotation of the drum, N columns of micropixels are printed on the receiver member. Additionally, the energizing of each of the thermal heating elements is timed using the micropixel clock pulses so as to print corresponding micropixels of the N columns of micropixels in a line normal to the rotation of the drum.

Abstract: An improved method of, and electrical circuit for driving with precision and accuracy an electro-mechanical device such as a galvanometer is disclosed. The method precisely controls high speed linear scanning of the device in a forward scan segment of each cycle of operation, and further provides very fast re-set of the device without position overshoot during a re-trace segment of a cycle. The electrical circuit includes memory means for generating an electrical command waveform for controlling the device during each cycle of operation, and drive servo means for applying electrical power to the device. The servoing action of this circuit substantially eliminates any difference between an actual position of the device and the position directed by the command waveform during each forward scan segment of a cycle of operation, with the result that each forward scan segment is highly accurate and repeatable.

Abstract: An imaging system comprising a source of light movable with respect to a writing element and projectable thereon to generate an image, a focusing device is provided for focusing a light source which generates a first beam of light of a wavelength selected to be actinic with respect to the writing element. At least a portion of the first beam of light is absorbed by the writing element. The focusing device includes a focusing laser diode which is mounted on, and movable with, a movable write head to minimize noise in the focusing signal.