Eye-imaging apparatus and method employing sequential flashing of illumination light in synchronization with the operation of an image sensor
An eye-imaging apparatus and system is described including circular fiber array ends arranged at skewed angles relative to the optical axis of the imaging path, a light intensity distribution converter along the illumination path to convert a bell-shaped distribution into a top-hat distribution, an image sensor, and high frequency response light source(s) operating in flash illumination mode in synchronization with the image sensor. As a result, unnecessary exposure of illumination light to a patient eye is minimized while the illumination light can span a wide enough coverage range with desired intensity and spectral distribution to cover the desired angular field of view and spectral range on a retina.
1. An eye-imaging apparatus comprising:
a light source selected from the group consisting of red, green, and blue light sources, white light sources, and red, green, blue, and white light sources;
an image sensor with a shutter having a frame rate, the image sensor being operable to produce a live video signal;
one or more optical lenses defining an imaging path comprising an optical axis;
a contact lens; and
illuminator fibers positioned next to the contact lens;
wherein the light source is flashed repetitively in synchronization with the operation of the image sensor in producing a live video display for image or video capturing by flashing the light source on when the shutter of the image sensor is opened and the flashing the light source off when the shutter of the image sensor is closed; and
wherein an averaged amount of light output from each flashing is controlled through pulse width modulation (PWM) having a duty cycle, a pulse peak value, and a pulsing frequency, with the pulsing frequency being at least 10 times the frame rate of the image sensor.
2. The apparatus of claim 1 wherein the illuminator fibers further comprise a prism array-based light profile redistribution element along an illumination light path from the light source to emitting ends of the illumination fibers.
3. The apparatus of claim 1 wherein the light source comprises a white light source.
4. The apparatus of claim 1 wherein the light source comprises red, green and blue light sources.
5. The apparatus of claim 1 wherein the light source comprises red, green, blue, and white light sources.
6. The apparatus of claim 1 wherein the illuminator fibers are positioned such that emitting ends thereof form a circular array disposed and are at a skewed angle relative to the optical axis rather than on a meridional plane containing the optical axis.
7. The apparatus of claim 1 wherein the image sensor is a one-chip color sensor.
8. The apparatus of claim 1 wherein the image sensor is a three-chip color sensor comprising red, green, and blue color sensors.
9. The apparatus of claim 1 wherein the light source comprises red, green and blue light sources with each color channel individually addressable and the flashing is done through a sequentially cycling the flashing of red, green and blue colors.
10. The apparatus of claim 9 wherein the duty cycle of the red, green and blue colors are controlled to white balance the red, green and blue channels of the image sensor.
11. The apparatus of claim 9 wherein the pulse peak value of the red, green and blue bands of the light source are controlled to white balance the red, green and blue channels of the image sensor.
12. The apparatus of claim 9 wherein the duty cycle and the pulse peak value are controlled in combination to white balance red, green and blue channels of the image sensor.