Resonant scanner control system

A control system for a laser printer which utilizes a resonant scanner, said system comprising:

• A. a laser source for producing a pulsed laser beam, the laser beam printing dots on a printing medium surface;
• B. a resonant scanner including an oscillating mirror that directs the laser beam across the surface of the printing medium in order to expose successive pixel locations to the laser beam, each complete mirror oscillation corresponding to a scan cycle;
• C. a controller for controlling the pulsing of the laser source in accordance with a selected image and in synchronism with a periodic laser pulse timing signal;
• D. synchronizing means for synchronizing the period of the laser pulse timing signal with the angular movement of the mirror, the synchronizing means adjusting the frequency of the laser pulse timing signal in response to changes in the angular velocity of the mirror and changes in the resonant frequency of the resonant scanner, the synchronizing means including:
• i. a memory for storing mirror velocity information relating to the pixels in locations addressable by a pixel count;
• ii. counting means for generating memory addresses corresponding to selected pixel locations and supplying the addresses to the memory;
• iii. converting means connected to receive the information contained in an addressed memory location, the converting means generating a control voltage which corresponds to the information;
• iv. voltage-controlled oscillating means connected to receive the control voltage, the oscillating means adjusting its frequency in accordance with the control voltage and supplying its output signal to (i) the controller as the laser pulse timing signal and (ii) the counting means to synchronize the operations of the counting means to the angular movement of the mirror;
• v. a phase error detector for detecting timing differences between a signal associated with a predetermined angular position of the mirror and a signal associated with a predetermined count of the counting means, the detector producing an error signal corresponding to the timing difference;
• and
• vi. multiplying means included in the converting means, the multiplying means multiplying the control voltage by a factor which corresponds to the error signal so as to reduce the timing difference.

A control system for a laser printer which utilizes a resonant scanner, said system comprising:

• A. a laser source for producing a pulse laser beam, the laser beam printing dots on a printing medium surface;
• B. a resonant scanner including an oscillating mirror that directs the laser beam across the surface of the printing medium in order to expose successive pixel locations to the laser beam, each complete mirror oscillation corresponding to a scan cycle;
• C. a controller for controlling the pulsing of the laser source in accordance with a selected image and in synchronism with a periodic laser pulse timing signal;
• D. synchronizing means for synchronizing the period of the laser pulse timing signal with the angular movement of the mirror, the synchronizing means continuously throughout the entire scan cycle adjusting the frequency of the laser pulse timing signal according to changes in the angular velocity of the mirror and changes in the resonant frequency of the resonant scanner the synchronizing means including a voltage-controlled oscillating means connected to receive a pixel-related frequency-control voltage, the oscillating means adjusting its frequency in accordance with the frequency-control voltage and supplying its output signal to the controller as the laser pulse timing signal to synchronize the operations of the controller to the angular movement of the mirror, the voltage-controlled-oscillating means including:
• i. a frequency-to-voltage converter for producing a voltage which is associated with the frequency of the voltage-controlled oscillating means output signal;
• and
• ii. comparing means for comparing the output of the frequency-to-voltage converter and the frequency-control voltage and producing a resulting error signal which relates to the difference;
• the oscillating means using the resulting error signal as the oscillator control voltage and adjusting its output signal so as to produce an output signal at a frequency which is linearly related to the control voltage.