Multiharmonic galvanometric scanning device
View Patent ↗A scanning apparatus for a printer or similar instrument. A multiharmonic oscillator is used to provide a composite motion of a laser beam or other light beam to scan an imaging surface. The multiharmonic oscillator may have multiple sections each having a different resonant frequency. One section includes a reflector that intercepts the light beam, and drive electronics move the reflector so the light beam scans the imaging surface. Linear and complex non-linear motions of the light beam may be achieved. Microelectromechanical systems (MEMS) technology may be used to fabricate the oscillator.
1. A scanning apparatus comprising:
a light beam;
a multiharmonic oscillator having a plurality of connected oscillating sections, each oscillating section having a resonant frequency, wherein at least one oscillating section comprises a reflector positioned to intercept the light beam; and
drive electronics configured to move each oscillating section at substantially the oscillating section's resonant frequency, wherein the connected oscillating sections and the drive electronics are configured to move the reflector in a motion that approximates a deflection waveform having a substantially non-uniform angular rate of motion,
and wherein the drive electronics comprise a plurality of drive units each configured to separately drive at least one of the plurality of oscillating sections.
2. The scanning apparatus of claim 1 wherein the multiharmonic oscillator comprises a microelectromechanical system.
3. The scanning apparatus of claim 1 wherein the multiharmonic oscillator comprises two connected oscillating sections connected to a stationary frame.
4. The scanning apparatus of claim 1 wherein the connected oscillating sections comprise a center oscillating section and comprise at least one oscillating section that is concentric with and outside the center oscillating section, and wherein the center oscillating section comprises the reflector.
5. The scanning apparatus of claim 1 further comprising an imaging surface and wherein the connected oscillating sections and the drive electronics are configured to intrinsically scan the light beam across the imaging surface at a substantially constant velocity.
6. The scanning apparatus of claim 1 further comprising an imaging surface and a transform lens, wherein the light beam passes through the transform lens and the transform lens directs the light beam across the imaging surface at substantially a constant velocity.
7. The apparatus of claim 1 further comprising an imaging surface and a transform lens, wherein the transform lens, the multiharmonic oscillator, and the drive electronics are configured such that a constant velocity of the light beam across the imaging surface is achieved and is partially achieved by the substantially non-uniform angular rate of motion of the reflector and partially achieved by the transform lens.
8. The apparatus of claim 1 wherein the connected oscillating sections and the drive electronics are configured to move the reflector in a motion that approximates a deflection waveform having V-shaped inflection points.
9. The apparatus of claim 1 wherein the connected oscillating sections and the drive electronics are configured to move the reflector in a motion that approximates a deflection waveform having a maximum rate of change of the deflection angle when the deflection angle is approximately zero.
10. The apparatus of claim 1 further comprising an imaging surface wherein the light beam is intercepted on an axis of rotation of the reflector that deflects the light beam onto the imaging surface along a straight line normal to the beam at its center position, and a normalized angular motion of the reflector approximates the functional form of:
Φ
(
t
)
=
1
Φ
max
tan
-
1
(
v
(
t
-
t
c
)
d
)
where Φ(t) is a normalized instantaneous angle of the reflector as a function of time t, with a total scan range of ±Φ max , t c is a time at which the light beam passes through a central point of the scan, v is a linear velocity of the light beam on the imaging surface, and d is a minimum distance between the axis of rotation of the reflector and the imaging surface.
11. The apparatus of claim 1 wherein the scan motion approximates the ideal scan motion needed to produce a linear constant velocity scan on the imaging surface without use of an f-θ lens.
12. The apparatus of claim 1 wherein the scan motion approximates the scan motion needed to produce a linear constant velocity scan with the use of a transform lens that is not an f-θ lens.
13. A method of producing a scanning light beam, the method comprising:
providing a light beam;
providing a multiharmonic oscillator having a plurality of connected oscillating sections, each oscillating section having a resonant frequency;
providing a reflector on the multiharmonic oscillator;
intercepting the light beam with the reflector;
simultaneously driving each of a plurality of the oscillating sections at substantially the resonant frequency of each driven oscillating section, wherein the light beam reflects from the reflector in a motion that approximates a deflection waveform having a substantially non-uniform angular rate of motion, and wherein the light beam intercept on an axis of rotation of the reflector that deflects the light beam onto the imaging surface along a straight line normal to the beam at its center position, and a normalized angular motion of the reflector approximates the functional form of:
Φ
(
t
)
=
1
Φ
max
tan
-
1
(
v
(
t
-
t
c
)
d
)
where Φ(t) is a normalized instantaneous angle of the reflector as a function of time t, with a total scan range of ±Φ max , t c is a time at which the light beam passes through a central point of the scan, v is a linear velocity of the light beam on the imaging surface, and d is a minimum distance between the axis of rotation of the reflector and the imaging surface.
14. The method of claim 13 wherein the step of providing a multiharmonic oscillator comprises providing the multiharmonic oscillator having a plurality of connected oscillating sections, each oscillating section having a resonant frequency that corresponds to a different frequency peak of the frequency domain transform of a periodic function defining a motion comprising a substantially uniform angular rate.
15. The method of claim 14 wherein:
the step of providing a multiharmonic oscillator comprises providing the multiharmonic oscillator having at least three connected oscillating sections, each oscillating section having a resonant frequency that corresponds to a different frequency peak of the frequency domain transform of a periodic function comprising a segment having a substantially uniform angular rate of motion; and
the step of simultaneously driving a plurality of the oscillating sections at substantially their resonant frequencies comprises driving at least three oscillating sections at substantially their resonant frequencies.
16. The method of claim 13 wherein the step of providing a multiharmonic oscillator comprises providing a multiharmonic oscillator having a plurality of connected oscillating sections, each oscillating section having a resonant frequency that corresponds to a different frequency peak of the frequency domain transform of a periodic function comprising a segment having a substantially a non-uniform angular rate of motion.
17. The method of claim 13 wherein the step of providing a multiharmonic oscillator comprises providing a multiharmonic oscillator having a plurality of connected oscillating sections, each oscillating section having a resonant frequency that corresponds to a different frequency peak of the frequency domain transform of a periodic function defining a motion that intrinsically moves the light beam across the imaging surface at a substantially linear function of time.
18. The method of claim 13 wherein:
the step of providing a multiharmonic oscillator comprises providing the multiharmonic oscillator having at least three connected oscillating sections, each oscillating section having a resonant frequency that corresponds to a different frequency peak of the frequency domain transform of a desired scanning motion.
19. The method of claim 13 wherein the connected oscillating sections and the drive electronics are configured to move the reflector in a motion that approximates a deflection waveform having V-shaped inflection points.
20. The method of claim 13 wherein the connected oscillating sections and the drive electronic are configured to move the reflector in a motion that approximates having a maximum rate of change of the deflection angle when the deflection angle is approximately zero.
21. A scanning apparatus comprising:
a light beam;
a multiharmonic oscillator having a plurality of connected oscillating sections, each oscillating section having a resonant frequency, wherein at least one oscillating section comprises a reflector positioned to intercept the light beam;
drive electronics configured to move each oscillating section at substantially the oscillating section's resonant frequency, wherein the connected oscillating sections and the drive electronics are configured to move the reflector in a motion that approximates a deflection waveform having a substantially non-uniform angular rate of motion; and
an imaging surface wherein the light beam is intercepted on an axis of rotation of the reflector that deflects the light beam onto the imaging surface along a straight line normal to the beam at its center position, and a normalized angular motion of the reflector approximates the functional form of:
Φ
(
t
)
=
1
Φ
max
tan
-
1
(
v
(
t
-
t
c
)
d
)
where Φ(t) is a normalized instantaneous angle of the reflector as a function of time t, with a total scan range of ±Φ max , t c is a time at which the light beam passes through a central point of the scan, v is a linear velocity of the light beam on the imaging surface, and d is a minimum distance between the axis of rotation of the reflector and the imaging surface.
22. A method of producing a scanning light beam, the method comprising:
providing a light beam;
providing a multiharmonic oscillator having a plurality of connected oscillating sections, each oscillating section having a resonant frequency;
providing a reflector on the multiharmonic oscillator;
intercepting the light beam with the reflector; and
simultaneously and separately driving each of the plurality of the osculating sections at substantially the resonant frequency of each driven oscillating section, wherein the light beam reflects from the reflector in a motion that approximates a deflection waveform having a substantially non-uniform angular rate of motion.