Apparatus and method for velocity compensation of the scanning spot in non-linear scanning systems
AssigneeOlive Tree Technology, Inc.
InventorYee-Ming Chung
Life of this patent
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Abstract
Apparatus for generating a pixel clock to control the timing of data pulses in an optical scanning device. A VCO is utilized to generate the pixel clock. The control voltage for the VCO is provided by a digital-to-analog converter ("DAC") which converts the count generated by a pixel reference location counter driven by a reference clock. The output of the DAC is fed back as the reference voltage for the DAC. The effect is to either increase or decrease the DAC reference voltage depending on whether positive or negative feedback is implemented, thereby varying the pixel clock frequency for the image data stream as a function of pixel position. By selecting the appropriate feedback and feedback gain, the pixel placement can be made uniform across the scan line.
Claims20
A device, for use in an optical scanner to generate a pixel clock, comprising:
- pixel location reference means for determining the location of a pixel in a scan and for generating a digital signal representative thereof;
- digital to analog converter means for converting said digital signal to a corresponding analog voltage output signal;
- feedback means for feeding back said converter means analog voltage output signal as reference voltage signal to said converter means for continuously altering the conversion gain of said converter means;
- and
- voltage controlled oscillator means for generating, as an output signal, a plurality of pixel clock frequency signals corresponding to a pixel clock having a frequency signal varying in accord with said analog voltage output signal of the converter means.
A method of generating a pixel clock in an optical scanner comprising the steps of:
- determining the location of a pixel in a scan and generating a digital signal representative thereof;
- converting in a digital analog converter said digital signal to an analog voltage output signal;
- feeding back said analog voltage output signal as a reference voltage to said converter for continuously altering the conversion gain of said converter;
- and
- generating a pixel clock signal responsive to said analog voltage output signal, having a frequency varying directly in accord with said analog voltage output signal.
An optical scanning device comprising:
- a light source generating a light beam;
- means for directing said light beam along a scan line on a surface;
- pixel location reference means for determining the location of a pixel on said scan line, and for generating an electrical pixel location signal representative of the location of said pixel;
- amplifier means responsive to said pixel location signal for amplifying said pixel location signal and generating a timing control signal;
- feedback means responsive to said timing control signal for providing a reference voltage signal as an input signal to said amplifier means, said reference voltage signal adapted for continuously altering the gain of said amplifier means;
- voltage controlled oscillator means responsive to said timing control signal for generating a pixel clock timing signal having a frequency that varies in a predetermined relationship with said timing control signal;
- and,
- control means responsive to said pixel clock timing signal and a pixel data pulse signal for controlling said light beam to produce a pixel on said scan line.
Dependencies are inferred from the claim text.