Self-resonant scanner biasing system

A circuit apparatus for controlling drive to a self-resonant scanner of a light beam, said apparatus comprising:

• Start-of-Trace sensor means for detecting all times of first-type occurrences that a light beam tracing an oscillatory course responsive to a self-resonant scanner of such said light beam does traverse so far in a first direction of said oscillatory course so as to impinge upon a first point, called a start-of-trace point;
• first-polarity first-variable-voltage drive means responsive to said Start-of-Trace sensor means for driving a self-resonant scanner of a light beam
• during a first one-half of Beginning-of-Trace to End-of-Trace oscillatory cycle
• at a first polarity causative that said self-resonant scanner of a light beam should continue in oscillation
• at a variable first voltage derived proportionately to the numbers of times of said first-type occurrences detected by said Start-of-Trace sensor means relative to the total number of times of all oscillations of said light beam;
• End-of-Trace sensor means for detecting all times of second-type occurrences that a light beam tracing an oscillatory course responsive to a self-resonant scanner of such said light beam does traverse so far in a second direction of said oscillatory course so as to impinge upon a second point, called a end-of-trace point;
• second-polarity second-variable-voltage drive means responsive to said End-of-Trace sensor means for driving a self-resonant scanner of a light beam
• during a second one-half of Beginning-of-Trace to End-of-Trace oscillatory cycle
• at a second polarity causative that said self-resonant scanner of a light beam should continue in oscillation
• at a variable second voltage derived proportionately to the numbers of times of said second-type occurrences detected by said End-of-Trace sensor means relative to the total number of times of all oscillations of said light beam.

A method for controlling the amplitude and centering of an oscillatory light beam directed by a self-resonant scanner, said method comprising:

• first detecting, in first sensor circuitry, all times of a first-type occurrence that an oscillatory light beam positionally directed by a self-resonant scanner of such light beam does traverse so far as a first fixed point in a first direction of oscillatory excursion;
• first accumulating, in first-accumulating circuitry, the numbers of said first-type occurrences in order to produce a first voltage level proportional to the numbers and times of said first-type occurrences;
• first coupling, in coupling and amplifying circuitry, said first voltage level amplified to drive said self-resonant scanner during that one-half of each oscillatory cycle during which said light beam is caused to traverse in a second direction of excursion, said amplified drive being in a direction to reinforce said oscillation;
• second detecting, in second sensor circuitry, all times of a second-type occurrence that an oscillatory light beam positionally directed by a self-resonant scanner of such light beam does traverse so far as a second fixed point in said second direction of oscillatory excursion;
• second accumulating, in second-accumulating circuitry, the numbers of said second-type occurrences in order to produce a second voltage level proportional to the numbers and times of said second-type occurrences;
• second coupling, in coupling and amplifying circuitry, said second voltage level amplified to drive said self-resonant scanner during that one-half of each oscillatory cycle during which said light beam is caused to traverse in said first direction of excursion, said amplified drive being in a direction to reinforce said oscillation;
• wherein the greater the numbers of said first-type occurrences causes the lesser said drive of said self-resonant scanner in said first direction of oscillatory excursion, while the greater the numbers of said second-type occurrences causes the lesser said drive of said self-resonant scanner in said second direction of excursion;
• wherein the combined effect of first detecting, first accumulating, first coupling, second detecting, second accumulating, and second coupling will tend to create an amplitude of oscillatory excursion which is from said first fixed point to said second fixed point, with the center in space of said oscillatory excursion being at the midpoint between said first fixed point and said second fixed point, with the center in time of said oscillatory excursion being midtime between the time of closest proximity of said oscillatory light beam to said first point and the time of closest proximity of said oscillatory light beam to said second point, said midtime being equivalent to that time whereupon the oscillatory light beam is in closest proximity to said midpoint.