Laser speckle reduction in ophthalmic images, using current pulse-shaping
The eye imaging system for producing images with reduced speckle artifacts may comprise a laser diode for providing a beam of radiation to the eye; a detector for collecting light returning from the eye and generating output signals in response thereto, the detector having a sensor integration time; a driver circuit for applying a modulated drive signal to the laser diode, the modulated drive signal inducing a spectral broadening of the beam of radiation during the sensor integration time. The laser diode may be a single-mode laser designed to operate at a fixed current and wavelength. The drive signal may be modulated by shaping a drive current pulse. The drive signal may be modulated by imposing an RF modulation on a drive current pulse. The drive signal may be further modulated by shaping a drive current pulse.
1 . An eye imaging system for producing images with reduced speckle artifacts, the system comprising:
a single-mode laser diode configured for providing a beam of radiation to the eye;
a photo detector configured for collecting light returning from the eye and generating output signals in response thereto, the photo detector having a sensor integration time; and
a driver circuit configured for applying a modulated drive signal to the laser diode, the modulated drive signal configured for inducing a spectral broadening of the beam of radiation during the sensor integration time.
2 . The system of claim 1 , wherein the single-mode laser diode is designed to operate at a fixed current and wavelength.
3 . The system of claim 2 , wherein the spectral broadening induced by the modulated drive signal is broader than the spectrum of the laser diode's designed operating wavelength.
4 . The system of claim 1 , wherein the drive signal is modulated by mode hopping achieved by at least one of shaping a drive current pulse and radio frequency modulation of the laser drive current pulse.
5 . The system of claim 1 , wherein the drive signal is modulated by imposing a radio frequency (RF) modulation on a drive current pulse.
6 . The system of claim 1 , wherein the drive signal is modulated by a combination of drive current pulse shaping with high-frequency modulation to generate wavelength diversification to induce speckle reduction.
7 . The system of claim 1 , wherein the drive signal is modulated by mode hopping achieved by thermal tuning.
8 . The system of claim 1 , wherein the eye imaging system is a fundus imager.
9 . The system of claim 1 , wherein the applied modulated drive signal avoids excess drive current.