Projection controlling method and MEMS projection apparatus

1. A projection controlling method, for controlling a microelectromechanical systems (MEMS) scanning mirror, wherein the MEMS scanning mirror scans an image light to perform repeated scanning operations on a surface to form a projection image, the projection controlling method comprising:

detecting a resonance frequency of the MEMS scanning mirror when the MEMS scanning mirror swings around a first swing axis with a plurality of frequencies;

providing the resonance frequency to a filter unit as a parameter of a filtering process;

generating a first periodic control signal with a first frequency, wherein the first periodic control signal has a plurality of harmonic components;

filtering the first periodic control signal by using the filter unit, wherein the filter unit filters the harmonic component with the resonance frequency out of the first periodic control signal according to the parameter; and

providing the filtered first periodic control signal to the MEMS scanning mirror to control the MEMS scanning mirror to swing around the first swing axis according to the first frequency, so as to scan the image light on the surface back and forth along a first direction.

2. The projection controlling method according to claim 1 , wherein the step of detecting the resonance frequency of the MEMS scanning mirror further comprises:

sequentially providing a plurality of periodic waves with different frequencies to the MEMS scanning mirror; and

when the MEMS scanning mirror swings around the first swing axis according to the frequencies of the periodic waves, detecting swing amplitude variations of the MEMS scanning mirror, and obtaining the resonance frequency.

3. The projection controlling method according to claim 2 , wherein the periodic waves are a plurality of sine waves with different frequencies.

4. The projection controlling method according to claim 1 , wherein the first periodic control signal is a triangular wave or a sawtooth wave.

5. The projection controlling method according to claim 1 further comprising:

providing a second periodic control signal with a second frequency to the MEMS scanning mirror to control the MEMS scanning mirror to swing around a second swing axis according to the second frequency, so as to scan the image light on the surface back and forth along a second direction.

6. The projection controlling method according to claim 1 , wherein the filter unit is a notch filter, and the resonance frequency is a center frequency of the notch filter.

7. A microelectromechanical systems (MEMS) projection apparatus, for projecting an image light on a surface to form a projection image, the MEMS projection apparatus comprising:

a MEMS scanning mirror, scanning the image light to perform repeated scanning operations on the surface to form the projection image;

a detection unit, detecting a resonance frequency of the MEMS scanning mirror when the MEMS scanning mirror swings around a first swing axis with a plurality of frequencies;

a filter unit, coupled to the MEMS scanning mirror and the detection unit, and receiving the resonance frequency from the detection unit as a parameter of a filtering process; and

a first control signal generator, coupled to the filter unit, generating a first periodic control signal with a first frequency, and providing the first periodic control signal to the MEMS scanning mirror,

wherein the first periodic control signal has a plurality of harmonic components, the filter unit receives the first periodic control signal and filters the harmonic component with the resonance frequency out of the first periodic control signal to control the MEMS scanning mirror to swing around the first swing axis according to the first frequency, so as to scan the image light on the surface back and forth along a first direction.

8. The MEMS projection apparatus according to claim 7 , wherein the filter unit comprises:

a notch filter, filtering out the harmonic component with the resonance frequency, wherein the resonance frequency is a center frequency of the notch filter; and

a low-pass filter, filtering out a part of the harmonic components.

9. The MEMS projection apparatus according to claim 7 , wherein the first periodic control signal is a triangular wave or a sawtooth wave.

10. The MEMS projection apparatus according to claim 7 further comprising:

a periodic wave generator, sequentially providing a plurality of periodic waves with different frequencies to the MEMS scanning mirror, wherein the MEMS scanning mirror swings around the first swing axis according to the frequencies of the periodic waves, and the detection unit detects swing amplitude variations of the MEMS scanning mirror and obtains the resonance frequency.

11. The MEMS projection apparatus according to claim 10 , wherein the periodic waves are a plurality of sine waves having different frequencies.

12. The MEMS projection apparatus according to claim 10 further comprising:

a multiplexer, coupled to the filter unit, the periodic wave generator, and the MEMS scanning mirror, wherein the multiplexer sequentially provides the periodic waves or provides the first periodic control signal to the MEMS scanning mirror.

13. The MEMS projection apparatus according to claim 10 , wherein the periodic wave generator further provides a second periodic control signal with a second frequency to the MEMS scanning mirror to control the MEMS scanning mirror to swing around a second swing axis according to the second frequency, so as to scan the image light on the surface back and forth along a second direction.