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1. WO2020206414 - COMPENSATING FOR POLARIZATION CHANGES

Note: Text based on automatic Optical Character Recognition processes. Please use the PDF version for legal matters

[ EN ]

What is claimed is:

1. An optical system using polarized light to interrogate birefringence properties of a retina of an eye in order to detect the fixation condition of the eye by sensing characteristic

birefringence patterns of retinal structures, comprising:

a source of polarized light;

a double-pass imaging system to image the polarized light onto the retina and to capture the light reflected back;

a scanning system to vary a location on the retina where the birefringence properties are interrogated;

a detection system to analyze changes in a polarization state of the reflected light from the retina as a measure of the retinal birefringence amount and orientation,

an optical system, wherein the optical system contains unwanted retardance, wherein the unwanted retardance can cause interference with polarization measurements which alters the polarization state of the light entering the eye and of the light reaching the detection system; and,

a compensating retarder provided in each of the forward and return light paths to nullify an effect of the unwanted retardance in each of the forward and return light paths so that

polarization states of the light entering the eye and the light reaching the detection system are not contaminated by the effects of the unwanted retardance.

2. The system of claim 1, further comprising a cold mirror, configured to introduce visible light from a fixation target into the eye, wherein a compensating retarder in the forward path restores the polarization state reaching the eye to the polarization state at the beginning of the path, wherein a compensating retarder in the return path restores the polarization state reaching the sensors to the polarization state of the light exiting the eye.

3. The system of claim 1, further comprising a dichroic beamsplitter as the last component between the optics and the eye, configured to introduce light from another imaging system into the eye, wherein a compensating retarder in the forward path restores the polarization state reaching the eye to the polarization state at the beginning of the path, wherein a compensating retarder in the return path restores the polarization state reaching the sensors to the polarization state of the light exiting the eye.

4. The system of claim 1, where the compensating retarder in the input path also comprises a variable compensator module, which compensates for the corneal birefringence of the individual patient’s eye in the forward path in addition to compensating for the retardances of the optical components in the forward path.

5. The system of claim 1, where the compensating retarder in the return path also comprises a variable compensator module, which compensates for the corneal birefringence of the individual patient’s eye in the return path in addition to compensating for the retardances of the optical components in the return path.

6. The system of claim 1, where the compensating retarder in each of the input and return paths compensates for unwanted retardance introduced only by those optical components that are unique to the respective path, and a variable compensator module is arranged in a double-pass configuration with those optical components that are common to both input and return paths, to compensate not only for the unwanted retardance introduced by those optical components that are common to both forward and return paths, but also to compensate via feedback control for the corneal birefringence of the individual patient’s eye.

7. The system of claim 1 further comprising one selected from a group consisting of a light emitting diode (LED) or a liquid crystal display (LCD) screen.

8. A method for calculating a compensator for the system of claim 1 further comprising calculating a compensator for the forward path based on the measured Mueller matrix of the path as a whole, or all of its components taken separately.

9 A method for calculating a compensator for the system of claim 1 further comprising calculating a compensator for the return path based on the measured Mueller matrix of the path as a whole, or all of its components taken separately.

10. The system of claim 1 further comprising a non-transitory computer readable medium.

11. A method using polarized light to interrogate birefringence properties of a retina of an eye in order to detect the fixation condition of the eye by sensing characteristic birefringence patterns of retinal structures, comprising:

imaging the polarized light onto the retina and to capture the light reflected back using a double-pass imaging system;

varying a location on the retina where the birefringence properties are interrogated using a scanning system;

analyzing changes in a polarization state of the reflected light from the retina as a measure of the retinal birefringence amount and orientation using a detection system,

accounting for interference with polarization measurements caused by unwanted retardance, which alters the polarization state of the light entering the eye and of the light reaching the detection system using an optical system; and,

nullifying an effect of unwanted retardance in each of the forward and return light paths using a compensating retarder provided in each of the forward and return light paths such that polarization states of the light entering the eye and the light reaching the detection system are not contaminated by the effects of unwanted retardance.

12. The method of claim 11 further comprising introducing visible light from a fixation target into the eye using a cold mirror, wherein a compensating retarder in the forward path restores the polarization state reaching the eye to the polarization state at the beginning of the path, wherein a compensating retarder in the return path restores the polarization state reaching the sensors to the polarization state of the light exiting the eye.

13. The method of claim 11, further comprising using a dichroic beamsplitter as a last component between the optics and the eye, wherein the dichroic beamsplitter is configured to introduce light from another imaging system into the eye, wherein a compensating retarder in the forward path restores the polarization state reaching the eye to the polarization state at the beginning of the path, wherein a compensating retarder in the return path restores the

polarization state reaching the sensors to the polarization state of the light exiting the eye.

14. The method of claim 11, compensating for the corneal birefringence of the individual patient’s eye in the forward path in addition to compensating for the retardances of the optical components in the forward path using a variable compensator module.

15. The method of claim 11, compensating for the corneal birefringence of the individual patient’s eye in the return path in addition to compensating for the retardances of the optical components in the return path using a variable compensator module.

16. The method of claim 11, compensating for unwanted retardance introduced only by those optical components that are unique to the respective path using the compensating retarder in each of the input and return paths, and compensating not only for the unwanted retardance introduced by those optical components that are common to both forward and return paths, but also compensating via feedback control for the corneal birefringence of the individual patient’s eye using a variable compensator module arranged in a double-pass configuration with those optical components that are common to both input and return paths.

17. The method of claim 11 further comprising calculating a compensator for the forward path based on the measured Mueller matrix of the path as a whole, or all of its components taken separately.

18. The method of claim 11 further comprising calculating a compensator for the return path based on the measured Mueller matrix of the path as a whole, or all of its components taken separately.