MEMS oscillator
View Patent ↗A device comprising, a mirror which is configured to oscillate in response to an oscillation signal, wherein the device is configured such that oscillation of the mirror will induce a signal; and a circuit in operable cooperation with the mirror such that an induced signal can be measured by the circuit and wherein the circuit is configured to provide an oscillation signal proportional to the measured induced signal; wherein the device is configured such that the mirror can receive the oscillation signal so that the oscillation signal is filtered due to oscillation limitations of mirror, to provide a filtered signal.
1. A device comprising, a mirror which is configured to oscillate in response to an oscillation signal, wherein the device is configured such that oscillation of the mirror will induce a signal; and
a circuit in operable cooperation with the mirror such that an induced signal can be measured by the circuit and wherein the circuit is configured to provide an oscillation signal in relation to the measured induced signal;
wherein the device is configured such that the mirror can receive the oscillation signal so that the oscillation signal is filtered due to oscillation limitations of mirror, to provide a filtered signal;
wherein the device further comprises a comparator circuit for comparing the phase or amplitude of the induced signal (Y(t)) which has resulted from the oscillation of the mirror, with the phase or amplitude of the oscillating signal (X(t)) provided by the circuit, and to provide a control signal (Z(t)) which controls the circuit such that the circuit provides an oscillation signal (X(t)) which will tend to adjust the oscillation of the mirror so that the mirror tends to oscillate at the resonant frequency of the mirror,
wherein the comparator circuit is configured to compare the phase of the induced signal (Y(t)) with the phase of the oscillating signal (X(t)) by coupling directly the induced signal (Y(t)) with another oscillating signal (X(t)), wherein the coupling the induced signal (Y(t)) with said oscillating signal provides an oscillating signal composed of sine-waves when the phase of induced signal (Y(t)) and oscillating signal (X(t)) are equal.
2. A device according to claim 1 , comprising, at least one first electrode which cooperates with the mirror and at least a second electrode which cooperates with a fixed part of the device, wherein the first and second electrodes define a capacitor.
3. A device according to claim 1 , comprising one or more magnets and at least one coil which is configured such that it will conduct the induced signal as the mirror oscillates.
4. A device according to claim 1 , wherein the device comprises a single coil which is attached to the mirror, wherein the single coil is configured to conduct both the oscillation signal and the induced signal as the mirror oscillates.
5. A device according to claim 1 , wherein the device comprises a first and second coil, wherein the first coil is configured to conduct the oscillation signal and the second coil is configured to conduct the induced signal.
6. A device according to claim 5 , wherein the first and second coils are attached to a part of the device which oscillates as the mirror oscillates.
7. A device according to claim 5 , wherein the first and second coils are arranged in the device such to reduce cross coupling between the first and second coils.
8. A device according to claim 5 , further comprising a shield means which prevents cross coupling between the first and second coils.
9. A device according to claim 5 , wherein the first coil is attached to a part of the device which oscillates as the mirror oscillates; and the second coil is attached to a fixed part of the device, such that as the mirror oscillates, the magnetic field provided by the one or more magnets and the movement and the first coil which conducts the oscillation signal, can induce the induced signal in the second coil.
10. A device according to claim 1 , further comprising a circuit which is configured to remove a parasitic component in the filtered signal.
11. A device according to claim 1 , further comprising,
a circuit, which is configured to receive the induced signal and the oscillation signal provided by the circuit, and to compare the induced signal with the oscillation signal, and to provide a control signal based on the comparison;
an oscillator circuit, wherein the oscillator circuit is controlled by the control signal provided by the circuit such that the oscillator circuit provides an oscillation signal which will adjust the oscillation of the mirror so that the mirror oscillates closer to the resonant frequency of the mirror.
12. The device according to claim 11 , wherein the oscillator circuit is arranged such that the oscillating signal defines a clock signal for a circuit.
13. The device according to claim 11 , further comprising a means for dividing frequency of an oscillating signal which is provided by the oscillator circuit.
14. The device according to claim 11 , further comprising a rectifier means which is configured to modify the control signal which controls the oscillator circuit so as to compensate for sinus movement of the mirror as the mirror oscillates.
15. The device according to claim 11 , further comprising a switch device which is selectively operable to provide a constant signal, wherein the constant signal is equal to an output of the circuit which is configured to compare the induced signal with the oscillation signal, at the instant the switching device is switched.