OCT-based ophthalmological measuring system
An ophthalmological measuring system for determining distances and/or for tomographic imaging of ocular structures, based on an OCT method. The measuring system includes a light source with a spectral centroid (λ), an interferometric measuring device, a scanner system, which in addition to the lateral deflection of the sample beam also has axial modulations with a frequency (f) in the sample arm, and a control and evaluation unit. The scanner performs a lateral, two-dimensional deflection of the sample beam with the aid of one or even two separate mirror elements and can in particular have axial modulation amplitudes z M >>λ/2. The system can also be used for scanner systems in other fields that use an OCT method, in particular a swept-source OCT method.
1. An OCT-based ophthalmological measuring system, comprising:
a tunable light source emitting light with a spectral centroid λ;
an interferometric measuring arrangement;
a scanner system which, in addition to lateral deflection of a sample beam, also causes axial modulations with a frequency fin a sample arm; and
a control and evaluation unit;
wherein the measuring system comprises a swept-source OCT system and a tuning speed dλ/dt of the tunable light source is adapted to the maximum measuring depth z and a frequency f of the axial modulation of the scanner system.
2. The OCT-based ophthalmological measuring system according to claim 1 , wherein the spectral centroid λ of the light source lies in a range of from 700 nm to 900 nm.
3. The OCT-based ophthalmological measuring system according to claim 2 , wherein the spectral centroid λ of the light source is 800 nm.
4. The OCT-based ophthalmological measuring system according to claim 1 , wherein the spectral centroid λ of the light source lies in a range of from 1000 nm to 1100 nm.
5. The OCT-based ophthalmological measuring system according to claim 4 , wherein the spectral centroid λ of the light source is 1060nm.
6. The OCT-based ophthalmological measuring system according to claim 1 , wherein the light source has, at the spectral centroid λ, a bandwidth Δλ, of 3 nm to 100 nm.
7. The OCT-based ophthalmological measuring system according to claim 1 , wherein an amplitude z M of the axial modulation of the scanner system during the tuning speed dλ/dt is more than λ/10 to λ/2.
8. The OCT-based ophthalmological measuring system according to claim 1 , wherein an amplitude z M of the axial modulation of the scanner system during the tuning speed dλ/dt is more than 1 μm.
9. The OCT-based ophthalmological measuring system according to claim 1 , wherein an amplitude z M of the axial modulation of the scanner system is smaller than the resolution δz of the swept-source OCT system, and
δ z= 2*ln(2)*λ 2 /(Δλ*π)
wherein Δλ corresponds to the bandwidth of the light source.
10. The OCT-based ophthalmological measuring system according to claim 1 , wherein, in the case of expected axial modulations with frequencies f between 100 Hz and 10,000 Hz, the tuning speed dλ/dt of the light source is at least λ 2 *f/(4z).
11. The OCT-based ophthalmological measuring system according to claim 1 , wherein, in the case of expected axial modulations with frequencies f between 100 Hz and 10,000 Hz, the tuning speed dλ/dt of the light source is more than λ 2 *f/z.
12. The OCT-based ophthalmological measuring system according to claim 1 , further comprising:
an additional known reference structure; and
wherein the interferometric measuring arrangement is designed such that reference structure signals of the additional known reference structure and measurement signals of the eye can be generated simultaneously, and the control and evaluation unit is programmed to evaluate interference of the reference structure signals, which interferences are caused by the axial modulations of the scanner system, and to utilize results of the evaluation of the interference of the additional known reference structure signals to correct the measurement signals of the eye.
13. The OCT-based ophthalmological measuring system according to claim 12 , wherein the additional known reference structure has at least one boundary surface.
14. The OCT-based ophthalmological measuring system according to claim 12 , wherein the additional known reference structure is a planar glass plate.
15. The OCT-based ophthalmological measuring system according to claim 12 , wherein the additional known reference structure is arranged before the eye.
16. The OCT-based ophthalmological measuring system according to claim 12 , further comprising an element that decouples a portion of the measuring beam such that reference structure signals of the additional known reference structure and measurement signals of the eye are simultaneously generated by the interferometric measuring arrangement; and
wherein the control and evaluation unit is programmed to evaluate the interferences of the reference structure signals, which interferences are caused by the axial modulations of the scanner system, and to utilize results of the evaluation to correct the measurement signals of the eye.
17. The OCT-based ophthalmological measuring system according to claim 16 , that the element that decouples a portion of the measuring beam is arranged downstream of the scanner system.