Multiharmonic galvonometric 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 comprising a plurality of connected oscillating sections that resonate at distinct fundamental and harmonic frequencies of each other, including a reflector positioned to intercept the light beam and reflect the light beam from the reflector to an imaging surface; and
drive electronics configured to move the multiharmonic oscillator according to a predetermined mathematical series function, thereby causing the light beam to scan the imaging surface as the light beam reflects from the reflector, the mathematical series function including a series of elements, each oscillating section of the multiharmonic oscillator being driven based upon a distinct element of the mathematical series function, the oscillating sections and the drive electronics being configured to move the reflector in a motion that approximates a waveform having a substantially non-uniform angular rate of motion corresponding to a summation of the distinct elements of the mathematical series function.
2. The scanning apparatus of claim 1 wherein the mathematical series function causes the light beam to intrinsically scan the imaging surface at a substantially constant velocity.
3. The scanning apparatus of claim 1 wherein the mathematical series function causes the light beam to scan the imaging surface in a bidirectional pattern.
4. The scanning apparatus of claim 1 wherein the mathematical series function causes the light beam to scan the imaging surface in a unidirectional pattern.
5. The scanning apparatus of claim 1 wherein the mathematical series function comprises a summation of at least three series elements.
6. The scanning apparatus of claim 1 further comprising a scanning lens disposed to intercept the light beam after it reflects from the reflector.
7. The scanning apparatus of claim 1 , wherein 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 an axis of rotation of the reflector and the imaging surface.
8. The scanning apparatus of claim 1 , wherein the drive electronics comprise a plurality of drive units each configured to separately drive at least one of the plurality of oscillating sections.
9. The scanning apparatus of claim 1 , wherein the drive electronics comprise a plurality of drive units each configured to separately drive at least one of the plurality of oscillating sections at the resonant frequency thereof.
10. The scanning apparatus of claim 1 , wherein the mathematical series function comprises a Fourier series.
11. The apparatus of claim 1 , wherein the predetermined mathematical series function comprises a Fourier series.
12. A method of producing a scanning light beam, the method comprising:
generating a light beam;
providing a multiharmonic oscillator having a reflector and a plurality of connected oscillating sections, each oscillating section having a resonant frequency, the resonant frequencies of the oscillating sections being at fundamental and harmonic frequencies of each other;
intercepting the light beam with the reflector; and
simultaneously and separately driving each of the oscillating sections at substantially the resonant frequency thereof, each oscillating section being driven according to a distinct series element of a predetermined mathematical series function, 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 corresponding to a summation of the distinct series elements of the mathematical series function.
13. The method of claim 12 , wherein the reflector deflects the light beam onto an imaging surface 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 12 , wherein the driving of the oscillating sections causes the light beam to scan the imaging surface at a substantially constant velocity.
15. The method of claim 12 , wherein the predetermined mathematical series function comprises a Fourier series.