Optical coherence tomography with refractive indexing of object
An optical tomographic image forming method including: splitting low coherence light emitted from a light source is split into a measuring light and a reference light; forming an optical tomographic image of a measured object by detecting an interference light that is obtained by superposing reflected light, reflected from the measured object when the measuring light is irradiated onto the measured object via a condenser lens, and reflected light, reflected from a reference mirror, which is positioned a predetermined length of optical path away from the splitting position, when the reference light is irradiated onto the reference mirror, wherein the method further includes: inputting a refractive index of the measured object; correcting the tomographic image in accordance with the inputted refractive index of the measured object; and outputting the corrected tomographic image.
1. An optical tomographic image forming method comprising:
splitting low coherence light emitted from a light source into a measuring light and a reference light;
positioning a reference mirror at a predetermined length of optical path away from the splitting position;
irradiating said measuring light onto a measured object via a condenser lens;
irradiating said reference light onto said reference mirror;
superposing a reflected light reflected from said measured object and a reflected light reflected from said reference mirror to detect an interference light; and
forming an optical tomographic image of said measured object by the detecting the interference light,
wherein the method further comprises:
inputting a refractive index of said measured object;
correcting said tomographic image in accordance with the inputted refractive index of said measured object; and
outputting the corrected tomographic image,
wherein the method further comprises:
moving at least one of said measured object, said condenser lens, and said reference mirror along an optical path to obtain a first position of said measured object, said condenser lens, and said reference mirror in which the intensity of an interference light of a reflected light reflected from said first reflecting surface and a reflected light from said reference mirror is maximized;
moving said measured object or said condenser lens along said optical path, while holding said reference mirror at the first position, to obtain a second position in which the intensity of an interference light of a reflected light reflected from said second reflecting surface and said reflected light from said reference mirror is maximized,
moving said reference mirror along said optical path, while holding said measured object or said condenser lens at the first position, to obtain a third position in which the intensity of an interference light of a reflected light reflected from the second reflecting surface and said reflected light from said reference mirror is maximized; and
obtaining said refractive index of said measured object based on the first position, second position and the third position.
2. The optical tomographic image forming method of claim 1 , wherein a known datum is being inputted as said refractive index of said measured object.
3. The optical tomographic image forming method of claim 1 , wherein, in a case in which said measuring light is incident upon a first reflecting surface of said measured object obliquely to the first reflecting surface, the method further comprises:
irradiating said measuring light upon a first reflecting surface of said measured object obliquely to the first reflecting surface to refract the measurement light;
replacing an optical path length of said refracted light from the first surface to the second surface by an optical path length between said first reflecting surface and said second reflecting surface in said straight line of said incident angle;
correcting said optical tomographic image in accordance with said replaced optical path length and in accordance with a refractive index between said first reflecting surface and said second reflecting surface; and
outputting the corrected tomographic image.
4. The optical tomographic image forming method of claim 1 , wherein, in a case in which said measuring light is incident upon a first reflecting surface of said measured object obliquely to the first reflecting surface, the method further comprises:
irradiating said measuring light upon a first reflecting surface of said measured object obliquely to the first reflecting surface to refract the measurement light;
determining an optical path length of said refracted light from the first surface to the second surface in accordance with: an incident angle of said measuring light upon said first reflecting surface, a refractive index of an incident side of said first reflecting surface, and a refractive index between said first reflecting surface and said second reflecting surface;
correcting said optical tomographic image in accordance with the determined said optical path length between said first reflecting surface and said second reflecting surface; and
outputting the corrected tomographic image.
5. The optical tomographic image forming method of claim 1 , wherein coherency distance Δl of said low coherence light, which is expressed by the following equation, is less than or equal to 30 μm:
Δ l= 2(ln 2)λ o 2 /(πΔλ)
where
λ o : Center wavelength of said low coherence light, and
Δλ: Bandwidth of said low coherence light (range of intensity more than or equal to half of the maximum intensity).
6. The optical tomographic image forming method of claim 1 , wherein said refractive index of said measured object is obtained based on a distance of the first position and second position and a distance of the first position and the third position.