Wavefront sensor having multi-power beam modes, independent adjustment camera, and accommodation range measurement
View Patent ↗An improved wavefront sensor is provided that enhances the initial focus and precision of imaged spots used to determine the monochromatic wave aberrations of the eye. The wavefront sensor includes an adjustment camera that is independent of a lenslet camera. A laser in a lower power mode is projected onto the retina of the eye and is brought into more precise or sharp focus by a control system employing data from the adjustment camera, which aids in focusing the imaged spots. “Trombone”-type optics are used to adjust the focus of the light projected onto the retina and the imaged spots onto a sensor. The laser has a higher power mode used when acquiring data of the imaged spots from the sensor.
1. A technique for focusing a wavefront sensor that creates aerial images that form centroids, comprising the steps of:
projecting a spot of light onto a retina;
dividing a reflected portion of the spot of light to form a plurality of aerial spots, each having a centroid;
monitoring spacing of the centroids;
adjusting the focus of the centroids on the sensor; and
determining when the sensor is in focus by determining when the average centroid spacing equals a focused sensor centroid spacing.
2. The method of claim 1 wherein the focus is adjusted from myopic to hyperopic.
3. The method of claim 2 , further for determining accommodation range further comprising the steps of:
after determining when the sensor is in focus, continuing to adjust the focus until the centroid spacing again begins to change; and
determining the accommodation range as the difference between the focal power of the sensor when the centroid spacing equals the focused sensor centroid spacing and the focal power when the centroid spacing again began to change.
4. The method of claim 3 , further for determining the change of shape of the lens of an eye over its accommodation range, further comprising the steps of:
capturing a wavefront when the sensor goes into focus;
capturing a wavefront when the wavefront sensor again goes out of focus; and
determining the difference between the two captured wavefronts.
5. The method of claim 4 , further comprising the step of:
determining the change of shape of optical components of the eye to be the difference in the two wave fronts multiplied by a constant.
6. A wavefront sensor, comprising:
a lenslet array adapted to receive an image of a light spot on a retina of the eye and for creating aerial images of the light spot;
a sensor adapted to receive the aerial images from the lenslet array;
focusing optics adapted to adjust the focus of the wavefront sensor;
a processor adapted to receive signals from the sensor corresponding to the aerial images and to determine the wave aberrations from the signals; and
a focus control system adapted to adjust the focus of the wavefront sensor by performing the computer implemented steps of:
monitoring spacing of the aerial images;
adjusting the focus of the centroids on the sensor; and
determining when the sensor is in focus by determining when the average spacing of the aerial images equals a focused sensor aerial image spacing.
7. The wavefront sensor of claim 6 , wherein the focus is adjusted from myopic to hyperopic.
8. The wavefront sensor of claim 7 , the sensor further determining accommodation range, the focus control system further performing the computer implemented steps of:
after determining when the sensor is in focus;
continuing to adjust the focus until the centroid spacing again begins to change; and
determining the accommodation range as the difference between the focal power of the sensor when the centroid spacing equals the focused sensor centroid spacing and the focal power when the centroid spacing again began to change.
9. The wavefront sensor of claim 8 , the processor further determining the change of shape of the lens of an eye over its accommodation range, the processor and focus control system further performing the computer implemented steps of:
capturing a wavefront when the sensor goes into focus;
capturing a wavefront when the wavefront sensor again goes out of focus; and
determining the different between the two captures wavefronts.
10. The wavefront sensor of claim 6 , wherein the focus control system employs the processor.
11. A wavefront sensor, comprising:
a lenslet array adapted to receive an image of a light spot on a retina of the eye and for creating aerial images of the light spot;
a sensor adapted to receive the aerial images from the lenslet array; focusing optics that adjust the focus of the wavefront sensor;
a processor adapted to receive signals from the sensor corresponding to the aerial images and to determine the wave aberrations from the signals; and
a focus control system that adjusts the focus of the wavefront sensor by performing the computer implemented steps of:
determining when the wavefront sensor goes into focus;
adjusting the wavefront sensor until the wavefront sensor begins to go out of focus; and
determining the accommodation range as the difference between the focal power of the sensor when the sensor goes into focus and the focal power of the sensor when the sensor begins to go out of focus.
12. The wavefront sensor of claim 11 , the processor further adapted to determine the change of shape of the lens of an eye over its accommodation range, the processor and focus control system further performing the computer implemented steps of:
capturing a wavefront when the sensor goes into focus;
capturing a wavefront when the wavefront sensor again goes out of focus; and
determining the different between the two captures wavefronts.