Method and apparatus for measuring temporal response characteristics of digital mirror devices

A method of measuring an impulse response characteristic of a micromirror array, the method comprising:

• illuminating a micromirror array with a coherent light source so as to generate a reflected diffraction pattern;
• aligning a photodetector with a spot of light of the diffraction pattern, wherein the spot of light corresponds to an order of the diffraction pattern;
• applying a dc bias to the micromirror array so that the micromirrors are disposed at an operating point so that the amplitude of an impulse response curve measured by the photodetector is at a maximum;
• applying a impulse signal to the micromirror array;
• and
• measuring the intensity of the spot of light with the photodetector for a period of time after the impulse signal has been applied to the micromirror array.

A method of measuring a forced resonant frequency characteristic of a micromirror array, the method comprising:

• illuminating a micromirror array with a coherent light source so as to generate a reflected diffraction pattern;
• aligning a photodetector with a spot of light of the diffraction pattern, wherein the spot of light corresponds to an order of the diffraction pattern;
• applying a periodic driving signal to the micromirror array so that a periodic response signal corresponding to the fluctuating intensity of the spot of light is measured by the photodetector;
• applying a DC bias to the micromirror array so that an amplitude of the response signal measured by the photodetector is at a maximum;
• and
• measuring the intensity of the spot of light with the photodetector as the frequency of the periodic driving signal is swept over a desired range.

A method of measuring an electromechanical compliance characteristic of a micromirror array, the method comprising:

• illuminating a micromirror array with a coherent light source so as to generate a reflected diffraction pattern;
• aligning a photodetector with a spot of light of the diffraction pattern, wherein the spot of light corresponds to an order of the diffraction pattern;
• applying a periodic driving signal to the micromirror array so that a response signal corresponding to the intensity of the spot of light is measured by the photodetector;
• applying a DC bias to the micromirror array so that an amplitude of the response signal measured by the photodetector is at a maximum;
• measuring the amplitude of the response signal;
• and
• determining a relative electromechanical compliance value corresponding to the ratio of an amplitude of the driving signal to the amplitude of the response signal.

A method of measuring a non-biased response characteristic of a micromirror array, the method comprising:

• illuminating a micromirror array with a coherent light source so as to generate a reflected diffraction pattern;
• aligning a first photodetector with a first spot of light of the diffraction pattern corresponding to an order of the diffraction pattern;
• applying a first dc bias to the micromirror array so that an amplitude of a response signal measured by the first photodetector is at a maximum;
• applying a second dc bias to the micromirror array so that the micromirrors in the micromirror array are landed;
• releasing the micromirrors in the micromirror array from the landed position by removing the second dc bias;
• and
• measuring the intensity of the first spot of light with the first photodetector for a first period of time after the micromirrors have been released from the landed position.

A system adapted to measure the temporal response characteristics of a micromirror array, the system comprising:

• a function generator adapted to provide a driving signal and a sync signal;
• a dc power supply adapted to provide a bias voltage;
• a signal summer adapted combine the driving signal with the bias voltage and provide a combined signal to the micromirror array;
• a coherent light source adapted to illuminate the micromirror array with a coherent light beam so as to generate a reflected diffraction pattern;
• at least one photodetector aligned with a spot of light of the diffraction pattern that corresponds to an order of the diffraction pattern;
• and
• a scope adapted to receive the response signal from the at least one photodetector and adapted to receive the sync signal from the function generator.