Interleaving vertical pixels in raster-based laser printers

In a raster based laser beam imaging system having a predetermined normal DPI (dots per inch) resolution, and having a single laser beam making horizontal sweeps corresponding to said resolution, and using imaging materials having a predetermined threshold level, the improvement comprising:

• means for energizing the laser beam at a rate to provide a higher number of dots per inch in the horizontal scan direction than said predetermined DPI;
• means for selectively creating predetermined, interleaved dots located at points between the horizontal scan lines of the laser beam by energizing said laser beam at two points on said scan lines directly above and below each predetermined desired interleaved dot, with the energization at one or both of said additional points on said scan lines being selectively below said threshold level, but with the cumulative energization at the interleaved predetermined point being greater than said threshold level so that dots appear at the predetermined interleaved points;
• said apparatus including means for producing a complete image at a higher resolution than said predetermined normal DPI with a single pass of said laser beam;
• and
• said apparatus including means for producing a laser beam which extends more than half way between adjacent scan lines.

An apparatus for use with an image creation device such as a laser printer, the device including a body presenting an actuatable surface having image regions such as pixels defined thereon, and including a single selectively operable actuating means for actuating respective image regions for image creation and in order to present, for each actuated region, an actuated central zone surrounded by an actuated outer zone, said apparatus comprising:

• control means for controlling the device actuating means in order to actuate a pair of vertically aligned image regions such that at least one of the respective central zones thereof is insufficiently actuated for substantial image creation while the respective outer zones cooperatively interact to form, between said respective central zones, an intermediate zone which is sufficiently actuated for image creation;
• with the energization of said actuating means being determined solely by the desired bit configuration of precisely three vertically aligned pixels;
• means for operably coupling said control means with the device actuating means;
• said apparatus including means for producing a complete image at a higher resolution than the normal resolution of said image creation device with a single pass of said actuating means;
• and
• said apparatus including means for providing an actuating means which extends more than half way between adjacent vertically spaced image regions.

Apparatus for enhancing the image produced by a scanning laser beam printer, said laser printer having a resolution comprised of a predetermined DPI (dots per inch) including parallel laser beam scan lines with the number of scan lines per inch corresponding to said DPI, and a predetermined DPI bit rate of energizing said laser beam along said scan lines, said laser beam being normally selectively energized, at said predetermined rate along said scan lines, at a predetermined dot-writing level sufficient to exceed a predetermined threshold of the imaging components and also determinative of the size of the image dots, said threshold being determinative of the presence or absence of dots on the laser printer image, and said laser printer also having means for accepting an external video signal that controls the energizing of said laser beam, said apparatus comprising:

• means for providing digital signals corresponding to a double bit map having double DPI at least in the vertical direction of the desired image to be produced by said laser printer, said bit map having twice the predetermined DPI resolution of said laser printer;
• at least in the vertical direction;
• temporary storage means, coupled to receive said digital signals, for temporarily storing at least portions of three lines from said bit map, with one of said lines corresponding to a normal scan line of said laser printer and the other lines being the double DPI lines immediately above and below said scan line;
• means for extracting successive sets of three bits, one bit from each of said three lines at corresponding positions along said lines;
• logic means for decoding said three bits into up to five different values, each of said different values associated with one of a plurality of video pulse widths, some of said pulse widths being below said threshold level of said laser printer;
• means for generating scan lines of video signal with the same number of scan lines as said laser printer, said video signal comprised of consecutive pulses of said pulse widths corresponding to the decoded values associated with the combinations of said three bits, and at least some of said pulse widths being below the predetermined threshold level of said laser printer;
• means for coupling said video signal to energize the laser beam of said laser printer;
• said apparatus including means for producing a complete image at a higher resolution than said predetermined DPI with a single pass of said laser beam;
• said apparatus including means for providing a laser beam which extends more than half way between adjacent scan lines.

Apparatus for enhancing an image produced by a scanning beam marking engine, said marking engine having a nominal resolution comprised of a predetermined number of scan lines of a scanning beam of said marking engine, with each said scan line having a predetermined number of picture elements or pixels, said scanning beam normally being energized selectively at a predetermined rate along said scan lines to yield said predetermined number of pixels, said scanning beam energization being at a predetermined dot-writing level sufficient to exceed a predetermined threshold of imaging components included in said marking engine and also being determinative of a size of image dots, said threshold being determinative of a presence or absence of dots on an output image from the marking engine, said apparatus comprising:

• means for producing digital signals corresponding to pixels, at a desired output resolution different from said nominal resolution, of a bit map of a desired image to be produced by said marking engine;
• temporary storage means, coupled to receive said digital signals, for temporarily storing a plurality of consecutive lines of said bit map;
• means for selecting a plurality of actuating signals for said marking engine, such that some of said actuating signals are below an imaging threshold of said marking engine, but are of sufficient intensity to produce an image dot between scan lines when adjacent points on successive scan lines are energized just below the imaging threshold;
• means for selecting a position at which said marking engine is capable of producing an imaging signals;
• means for extracting from said temporary storage means a sample subset having a predetermined number of pixels in a predetermined configuration, having said selected position in said marking engine which coincides with an approximate center of said predetermined number of pixels in a predetermined configuration, and with at least one of said pixels being spaced between scan lines of said marking engine;
• logic means for decoding the predetermined configuration of pixels and selecting a corresponding one of said actuating signals for said marking engine;
• means for generating actuating signals for said marking engine from the configuration of pixels;
• means for generating said scan lines from said actuating signals for said marking engine;
• said apparatus including means for producing a complete image at said different output revolution with a single pass of said beam;
• and
• said apparatus including means for producing a scanning beam which extends more than half way between adjacent scan lines.