WO2005033624A1 - Dispositif servant a ajuster le retard optique dans un trajet optique - Google Patents

Dispositif servant a ajuster le retard optique dans un trajet optique Download PDF

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Publication number
WO2005033624A1
WO2005033624A1 PCT/EP2004/010312 EP2004010312W WO2005033624A1 WO 2005033624 A1 WO2005033624 A1 WO 2005033624A1 EP 2004010312 W EP2004010312 W EP 2004010312W WO 2005033624 A1 WO2005033624 A1 WO 2005033624A1
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WIPO (PCT)
Prior art keywords
delay
delay element
optical
mirror
beam path
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PCT/EP2004/010312
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German (de)
English (en)
Inventor
Jesús-Miguel CABEZA-GUILLEN
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Carl Zeiss Meditec Ag
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Publication of WO2005033624A1 publication Critical patent/WO2005033624A1/fr

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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/0059—Measuring for diagnostic purposes; Identification of persons using light, e.g. diagnosis by transillumination, diascopy, fluorescence
    • A61B5/0062—Arrangements for scanning
    • A61B5/0066—Optical coherence imaging
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B3/00—Apparatus for testing the eyes; Instruments for examining the eyes
    • A61B3/10—Objective types, i.e. instruments for examining the eyes independent of the patients' perceptions or reactions
    • A61B3/102—Objective types, i.e. instruments for examining the eyes independent of the patients' perceptions or reactions for optical coherence tomography [OCT]
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B3/00—Apparatus for testing the eyes; Instruments for examining the eyes
    • A61B3/10—Objective types, i.e. instruments for examining the eyes independent of the patients' perceptions or reactions
    • A61B3/12—Objective types, i.e. instruments for examining the eyes independent of the patients' perceptions or reactions for looking at the eye fundus, e.g. ophthalmoscopes
    • A61B3/1225—Objective types, i.e. instruments for examining the eyes independent of the patients' perceptions or reactions for looking at the eye fundus, e.g. ophthalmoscopes using coherent radiation
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/0059—Measuring for diagnostic purposes; Identification of persons using light, e.g. diagnosis by transillumination, diascopy, fluorescence
    • A61B5/0073—Measuring for diagnostic purposes; Identification of persons using light, e.g. diagnosis by transillumination, diascopy, fluorescence by tomography, i.e. reconstruction of 3D images from 2D projections

Definitions

  • the present invention relates to a device for adjusting the optical delay in a beam path, in particular in a reference beam path of an OCT interferometer, with a first mirror device which can be pivoted at least in a first pivot plane about a first pivot axis for selectively deflecting beams of the beam path onto a first Delay route from a number of first delay routes with different optical delays. It further relates to a corresponding delay element and a method for producing such a delay element for a device according to the invention.
  • a large number of optical applications use the interference phenomena that occur when separate wave trains of a light source are brought together again. This makes it possible, for example, to make statements about the geometry or nature of certain bodies by directing a measuring beam separated from a reference beam onto the body. The measuring beam reflected at least partially on the surface of the body or, more generally, on refractive index transitions is then combined again with the reference beam. In this case, interference phenomena occur between the measuring beam and the reference beam if and only if the difference in length of the optical path that the reference beam and the measuring beam have traveled lies below the coherence length of the light used.
  • the length of the optical path can be determined from the known optical path length in the reference beam path, which causes such interference phenomena of the measuring beam and thus the location of the reflection location.
  • This method is used, for example, in medical technology, in particular in the field of ophthalmology, frequently in so-called OCT devices (Optical Coherence Tomography) for diagnostic purposes or for operation support.
  • OCT devices Optical Coherence Tomography
  • a device is known from US Pat. No. 5,321,501 with which, using the described method, tests are carried out on a human eye, among other things.
  • BESTATIGUNGSKOPIE the boundary beam path varies in order to obtain depth information for a tomographic image.
  • the examination i.e. also the variation of the optical path length in the reference beam path
  • the examination either has to be carried out in a very short time or the movement or the changes in the state of the examination object are complex must be recorded in order to be able to take into account and eliminate undesirable influences on the examination result caused by such movements or changes in state.
  • the measurement must be completed within a few milliseconds in order to eliminate the influence of unintentional eye movements.
  • the speed at which such an ⁇ CT system can generate a tomographic image of the examination object is limited by a number of factors such as the positioning speed between the individual depth scans, the signal-to-noise ratio and the computing speed of the processing electronics.
  • the main limiting factor is the speed of adjustment of the optical path length in the reference beam path for the respective depth scan.
  • the typical stroke frequency of a longitudinally movable mirror, as is known from US Pat. No. 5,321,501, is a few hundred Hz.
  • a device for adjusting the optical delay in a reference beam path is known from US Pat. No. 6,421,164 B2, in which the optical delay can be adjusted via an optical grating and a pivotable mirror.
  • depth scanning frequencies of two to four kHz can be achieved with this device, the adjustment or depth range is only a few millimeters, so that, for example, the complete measurement of a human eye, which requires a depth range of approximately 25 mm, is not possible.
  • this device requires a relatively high light output, which appears unsuitable for use in biological samples with regard to tissue damage to be avoided.
  • a device of the generic type is known from DE 199 30408 A1 in connection with an OCT-based surgery system, in which an axially movable mirror in the reference beam path effects the adjustment of the optical delay required for the depth scan.
  • the light in the reference beam path is directed by a pivotable mirror synchronized with the movement of the axially movable mirror on several separate fiber optic delay lines with different optical delays.
  • An adjustment range of approximately 50 mm can be achieved with a stroke movement of the axially movable mirror which is only a fraction of the adjustment range.
  • the device is comparatively complex due to the two moving mirrors.
  • the present invention is therefore based on the object of providing a device, a delay element and a method of the type mentioned at the outset which do not have the disadvantages mentioned above, or at least to a lesser extent, and in particular with simple design, high adjustment frequencies and allows a large adjustment range of the optical delay.
  • the present invention solves this problem on the basis of a device according to the preamble of claim 1 by the features specified in the characterizing part of claim 1. It further solves this problem starting from a delay element according to the preamble of claim 18 by the features specified in the characterizing part of claim 18. It finally solves this problem on the basis of a method according to the preamble of claim 20 by the features specified in the characterizing part of claim 20.
  • the present invention is based on the technical teaching that, with a simple construction of the adjusting device, both high adjustment frequencies and a large displacement Adjustment range of the optical delay can be achieved if the first delay lines are formed in at least one delay element which has at least one first surface stepped in a first direction in order to vary the optical delay.
  • the stepped first surface can be comparatively easily produced using manufacturing or replication techniques known from the field of micro-optics.
  • the gradation of the first surface of the delay element allows a defined, very fine gradation of the optical delay in a manner that would not be possible or would only be possible with very great effort if delay lines were used in separate delay elements, for example separate glass fibers or the like.
  • a correspondingly small transverse dimension of the steps in a very small space enables a comparatively high number of steps and thus a high density of different delay lines to be achieved, which overall ensures a large adjustment range of the optical delay. Due to the pivotable first mirror device, which already allows significantly higher adjustment frequencies than a conventional axially movable mirror, and the compact arrangement of the first delay lines in the delay element, high adjustment frequencies are also possible, which are also suitable for real-time measurements, for example in vivo human eye, sufficient.
  • the stepped first surface of the delay element can be arranged on the side of the delay element facing or facing away from the first mirror device. Likewise, it goes without saying that both the surface of the delay element facing the first mirror device and the surface of the delay element facing away from the first mirror device can be correspondingly stepped in the first direction. Furthermore, a plurality of delay elements with a correspondingly stepped first surface can be arranged next to one another in the first direction in order to achieve a predetermined number of steps.
  • the beams of the beam path for example the reference beam path of an OCT interferometer
  • the beams of the beam path can be combined in any way with the measurement beams in the measurement beam path.
  • the beams are focused on an optical fiber after passing through the respective delay line by means of a suitable lens device or the like, via which the beams are then combined with the measurement beams in the measurement beam path.
  • a suitable lens device or the like
  • any other light guide devices such as mirrors, prisms, etc. may be provided.
  • a second mirror device is provided on the side of the delay element facing away from the first mirror device, which reflects the beams of the beam path in the direction of the first mirror device in such a way that the reflected beams pass through the same delay line again. Due to the fact that the speed of the light beams is several orders of magnitude greater than the swiveling speed of the first mirror device, the first mirror device is practically still in the same swivel position in which it preceded the light beams when the light beams reflected by the second mirror device reappear has distracted to the delay line in question. This makes it possible in a simple manner to use the components of the device for the return of the light rays, which results in a particularly inexpensive and compact arrangement.
  • the second mirror device can be a separate mirror or the like.
  • the second mirror device can in principle be arranged at any distance from the delay element. However, it is preferably arranged as close as possible to the delay element for reasons of space saving.
  • the second mirror device can be formed by a correspondingly reflective coating on the side of the delay element facing away from the first mirror device, which results in a particularly compact arrangement.
  • the delay element preferably has a first surface section of the first surface and an assigned second surface section of a second surface, on which the main beam of the beam path strikes essentially perpendicularly.
  • the delay element can be curved.
  • the respective first and second surface sections can in particular also be curved.
  • the radius of curvature of the respective surface section corresponds to the distance between the point of incidence of the main beam of the beam path on the first mirror device and the point of impact of the main beam of the beam path on the respective surface section.
  • At least the respective first surface section is preferably essentially flat. More preferably, both the first surface section and the second surface section are substantially flat.
  • the grading of the surface of the delay element which is carried out for varying the optical delay can be provided both on the side facing the first mirror device and on the side facing away from the first mirror device as well as on both sides.
  • the second surface sections are preferably formed from a stepless second surface of the delay element because of the simpler manufacture.
  • a lens device is arranged between the first mirror device and the delay element, the optical axis of which lies in the first pivot plane, the first pivot axis running through the point of incidence of the main beam of the beam path on the first mirror device and the optical axis of the lens device cuts at the focal point of the lens device.
  • the main beam of the beam path emerges from the lens device parallel to the optical axis, regardless of the pivot position of the first mirror device.
  • the distance between the lens device and the delay element can in principle be chosen arbitrarily. It is preferably provided that the optical axis of the lens device intersects the stepped first surface of the delay element in the focal point of the lens device and in the area of a delay line with a medium optical delay.
  • the focal point of the lens device on the delay element side is preferably in the region of a delay line with a medium optical delay on the first surface of the delay element since this ensures, for example, in the case of delay elements with optical deceleration continuously increasing or decreasing along the first direction that the widening of the beam upon striking the first surface also occurs with the delay sections furthest away along the first direction - with minimal or maximum optical delay - still keeps within narrow limits.
  • the delay line can thus have very small overall dimensions, which, as described above, has a favorable effect on the density of the delay lines in the delay element and thus on the achievable adjustment speed and the achievable adjustment range of the optical delay.
  • the delay element can only be stepped along the first direction.
  • this enables, on the one hand, the choice between a lens device with one or more spherical lenses and a lens device with one or more cylindrical lenses.
  • a particularly high adjustment speed and a particularly large adjustment range of the optical delay can, however, be achieved if the delay element is stepped in two directions running transversely to one another.
  • a plurality of stepped delay elements can be arranged next to one another transversely to the first direction, the gradation of which along the first direction is then selected such that a corresponding gradation also results in a second direction running transversely to the first direction.
  • the first mirror device can then be designed in such a way that it can be pivoted in several directions in such a way that the beams of the beam path can be directed onto all the delay lines generated by the steps.
  • one or more further mirror devices can be provided in addition to the first mirror device, by means of which, in cooperation with the first mirror device, the beams of the beam path can be directed to all the delay lines generated by the steps ,
  • the first mirror device for selectively deflecting beams of the beam path onto a second delay path from a number of second delay paths with different optical delays can preferably be pivoted about a second pivot axis in a second pivot plane.
  • the second swivel plane transverse, in particular perpendicular, to the first pivot plane.
  • the second delay lines are then at least partially formed in the delay element which, for varying the optical delay, has at least one surface stepped in a second direction running transversely to the first direction.
  • the delay element can be graded in the second direction at any suitable location.
  • the first surface of the delay element is preferably stepped in the second direction.
  • a lens device can be provided between the first mirror device and the delay element, via which the beams of the beam path are directed onto the delay element.
  • the optical axis of this lens device preferably lies in the second swivel plane, the second swivel axis running through the point of incidence of the main beam of the beam path on the first mirror device and intersecting the optical axis of the lens device at the focal point of the lens device.
  • the lens device is preferably a simple spherical lens.
  • first and second surface sections can then, for example, each be aligned parallel to the optical axis of the lens device.
  • the delay element has a first surface section of the first surface and an assigned second surface section of a second surface for each delay section , wherein the optical axis of the lens device is substantially perpendicular to the plane of the respective first and second surface section.
  • the focusing of the beam of rays of the beam path which is carried out by the lens device, also has the advantage that the transverse dimensions of the respective delay line, in particular the transverse dimensions of the first surface section, can be chosen to be particularly small.
  • the dimensions are therefore preferably
  • the first surface section is smaller, more preferably at least half smaller, than the transverse dimension of the beam that strikes the first mirror device from the side facing away from the delay element.
  • the total optical path difference OPD to tai achieved in the case of k passes of the light through the respective delay path between two delay paths adjacent along the first direction can in principle be selected in accordance with the desired or required resolution for the respective application.
  • the maximum achievable resolution for example the maximum achievable depth resolution in an interference-based depth measurement using the device according to the invention, is limited by the coherence length of the light used. Therefore, the total optical path difference OPD tota ⁇ between two delay lines adjacent along the first direction preferably corresponds at most to the coherence length of the light used in the beam path.
  • the total optical path difference OPDt o tai between two delay lines adjacent along the first direction preferably corresponds to at most half the coherence length of the light used, since this ensures in each case that the maximum resolution can be achieved. In other words, with such a gradation of the delay element, in spite of the discrete change in the optical delay from delay line to delay line, the result is no difference to a continuous change in the optical delay.
  • the optical path difference OPD between two delay lines adjacent along the first direction preferably corresponds at most to the coherence length of the light used in the beam path.
  • the optical path difference OPD between the adjacent delay lines preferably corresponds to at most half the coherence length of the light used.
  • the optical path difference OPD between two delay lines adjacent along the first direction accordingly preferably corresponds to at most half the coherence length of the one used in the beam path Light.
  • the optical path difference OPD between the adjacent delay lines preferably corresponds at most to a quarter of the coherence length of the light used, since this variant ensures that the maximum resolution is achieved in spite of the discrete changes in the optical delay can.
  • the optical path length OPL of a delay line is determined from the geometric path length GPL of the delay line and the refractive index n of the material of the delay line:
  • the change in the optical delay that is to say the optical path difference OPD between two delay sections adjacent along the first direction, is accordingly:
  • the material of the delay element has the lowest possible refractive index n.
  • a material with a refractive index below n 1.6 is preferably provided.
  • the delay element can be produced in any suitable manner.
  • any manufacturing processes and replication techniques known from the field of micro-optics can be used. Spatial ion doping, hot stamping or other nanoreplication techniques, as are usually used for the production of microlens arrays, may be mentioned here as examples.
  • At least the stepped first surface of the delay element is preferably through made an impression process. This enables inexpensive and rapid series production of the delay element.
  • any suitable mirror devices such as simple swivel mirrors etc.
  • the frequency of the pivoting movement of the first mirror device is preferably 500 Hz to 10 kHz.
  • larger measurement volumes can be recorded even with living objects. It is thus possible, for example, to measure a human eye in real time in vivo.
  • the pivoting angle of the pivoting movement of the first mirror device in the first or second pivoting plane is preferably up to ⁇ 40 ° in order to be able to control as many delay lines as possible.
  • higher adjustment frequencies can generally be achieved with smaller swivel angles, so that the swivel angle of the swivel movement of the first mirror device is preferably up to ⁇ 20 °, depending on the requirements of the respective application.
  • the present invention further relates to a delay element for a device according to the invention.
  • the delay element has at least one first surface stepped in a first direction in order to form a number of first delay lines with different optical delays.
  • the delay element according to the invention can furthermore have all of the features detailed above and the associated advantages. To avoid repetition, reference is therefore made to the above statements.
  • the delay element preferably has at least one surface which is stepped in a second direction running transversely to the first direction in order to form a number of second delay lines with different optical delays. More preferably, the first surface of the delay element is stepped in the second direction.
  • the delay element according to the invention can also have all of the features detailed above and the advantages associated therewith. To avoid repetition, reference is therefore made to the above statements.
  • the present invention further relates to a method for producing a delay element according to the invention for a device according to the invention for adjusting the optical delay in a beam path. It is provided according to the invention that a number of first delay lines with different optical delays are formed in the delay element by providing a first surface of the delay element with a step in a first direction.
  • the first surface of the delay element is preferably provided with a step in order to form a number of second delay lines with different optical delays in a second direction running transverse to the first direction, in order to achieve the large adjustment range described above.
  • the delay element is composed of a carrier and a step body which has been provided with the step.
  • Figure 1 is a schematic representation of an OCT system with a preferred embodiment of the device according to the invention for adjusting the optical delay in the reference beam path of the OCT system;
  • FIG. 2 shows the device according to the invention for adjusting the optical delay from FIG. 1;
  • FIG. 3 shows a schematic illustration of a detail of the device according to the invention for adjusting the optical delay from FIG. 1;
  • 4A to 4D are schematic views of the delay element of the device for adjusting the optical delay from FIG. 1;
  • FIG. 5 shows a schematic illustration of a further embodiment of the device according to the invention for adjusting the optical delay
  • 6A to 6D are schematic views for explaining the design of the delay element of the device for adjusting the optical delay from FIG. 5;
  • FIGS. 7A and 7B are schematic representations of a further embodiment of the delay element according to the invention.
  • FIG. 1 shows a schematic representation of an OCT system 1 with an inventive device 2 for adjusting the optical delay in the reference beam path of the OCT system 1, which is used to create three-dimensional images of a schematically represented biological sample 3.
  • a light source in the form of a so-called super-luminescent diode (SLD) 1.1 emits a narrow bundle 5 of strongly collimated light with a short coherence length in the direction of a beam splitter 6.
  • the beam splitter 6 deflects a measuring beam 5.1 into the measuring beam path 7 as part of the light bundle 5 OCT system 1, specifically on the biological sample 3.
  • the other part of the light beam 5 is transmitted as a reference beam 5.2 from the beam splitter 6 into the reference beam path 8 in the direction of the device 2.
  • a fraction of the measuring beam 5.1 is reflected back in the direction of the beam splitter 6. This in turn allows a certain portion of this to pass through to an evaluation unit 9 connected to the device 2.
  • the device 2 in turn reflects the reference beam 5.2 at least partially back in the direction of the beam splitter 6, which in turn reflects at least a part thereof in the direction of the evaluation unit 9.
  • the device 2 adjusts the optical delay in the reference beam path 8 over a specific adjustment range in a depth scan cycle.
  • interference phenomena can be recorded in the evaluation unit 9 in a known manner, which, based on the knowledge of the currently set optical delay in the device 2, allows a conclusion to be drawn about the Z coordinate, ie. H. enable the depth position of the reflective tissue layer in the sample 3.
  • the measuring beam bundle 5.1 is moved point by point in the X and Y directions with respect to the biological sample 3 in a known manner, with a depth scan in the direction for each point (X, Y) is performed as described above.
  • the mode of operation of the device 2 according to the invention for adjusting the optical delay in the reference beam path 8 is explained in more detail below in connection with FIGS. 2 and 3.
  • FIG. 2 shows the device 2 according to the invention with a first mirror device in the form of a flat first mirror 10 which can be pivoted in a defined manner about a first pivot axis in a first pivot plane coinciding with the drawing plane.
  • a corresponding pivoting device (not shown) of the first mirror 10 is provided, which is connected to the evaluation unit 9 in order to always provide the latter with information about the current pivoting angle of the first mirror 10.
  • the first pivot axis runs perpendicular to the plane of the drawing through the point of incidence 11 of the main beam 5.3 of the reference beam 5.2 on the first mirror 10.
  • the first mirror 10 In its neutral position shown, the first mirror 10 is inclined by 45 ° to the main beam 5.3, so that it deflects the reference beam 5.2 in this position by 90 °.
  • the first mirror 10 can, as indicated by the arrow 12, be deflected from this neutral position at a frequency of 5 kHz by a swivel angle of ⁇ 10 °.
  • the first mirror 10 directs the still collimated reference beam 5.2 onto a lens device in the form of a lens 13, the optical axis 13.1 of which lies in the first pivot plane and in the neutral position of the first mirror 10 with that of the first mirror 10 in the direction of the lens 13 reflected part of the main beam 5.3 coincides.
  • the lens is arranged such that its focal point on the side of the first mirror 10 coincides with the point of incidence 11 of the main beam 5.3 on the first mirror 10.
  • the lens 13 is distant from the point of impact 11 by its focal length f.
  • This arrangement of the lens 13 ensures that the main beam 5.3 emerges from the lens 13 independently of the pivoting angle of the first mirror 10 parallel to the optical axis 13.1, as indicated by the dashed lines 14 and 15.
  • the distance of the main beam 5.3 from the optical axis 13.1 depends on the current swivel angle of the first mirror 10.
  • the reference beam 5.2 is directed by the lens 13 on its side facing away from the first mirror 10 onto a delay element 16 which has a number of first delay lines with different optical delays. Depending on the pivot position of the first mirror 10, the reference beam 5.2 passes through delay lines with different optical delays. In other words, the optical delay that the reference beam 5.2 in the reference beam gear 8 experiences can be set by defined pivoting of the first mirror 10 in the first pivot plane.
  • the delay element 16 has on its side facing away from the lens 13 a first surface 16.1 stepped in a first direction (Y direction), while on its side facing the lens 13 it has a flat second surface 16.2 , which is aligned perpendicular to the optical axis 13.1.
  • each delay line is assigned a flat first surface section 16.3 of the first surface 16.1 and a flat second surface section 16.4 of the second surface 16.2.
  • Both the plane of the second surface sections 16.4 and the planes of the first surface sections 16.3 each run perpendicular to the optical axis 13.1, so that the main beam 5.3 hits them perpendicularly regardless of the pivoting angle of the first mirror 10 and therefore does not experience any deflection when the delay element passes through.
  • the main beam 5.3 consequently emerges from the delay element 16 parallel to the optical axis 13.1.
  • the optical path length OPL in the respective delay path and thus the optical delay which is achieved by the respective delay path is determined from the distance of the associated first surface section 16.3 from the associated surface section 16.4 according to equation (2).
  • the delay element 16 is arranged with respect to the lens 13 such that the focal point of the lens 13 on the delay element side is arranged on the first surface 16.1 in the region of the first surface section 16.5 of a delay line with medium optical delay.
  • the focal point of the lens 13 on the delay element side lies on the first surface section 16.5, the distance of which from the associated second surface section corresponds to the mean value of all distances between the associated first and second surface sections 16.3 and 16.4.
  • the focal point of the lens on the delay element side can also be arranged elsewhere in other variants of the device according to the invention.
  • the reference beam 5.2 After passing through the delay element 16, the reference beam 5.2 strikes a second mirror device in the form of a flat second mirror 17, the plane of which is also perpendicular to the optical axis 13.1.
  • the main beam 5.3 of the reference beam 5.2 is reflected by the second mirror 17 on itself in the direction of the first mirror 10. He goes through the path described above the delay element 16 and the lens 13 in the opposite direction. Finally, it hits the first mirror 10 again at the airing point 11.
  • the speed of the main beam 5.3 is several orders of magnitude greater than the pivoting speed of the first mirror 10, when the main beam 5.3 reappears, the first mirror 10 is practically still in the same pivoting position in which it previously pointed the main beam 5.3 has distracted the delay line concerned.
  • the main beam 5.3 is accordingly reflected by the first mirror 10 back onto the beam splitter 6 without lateral deflection.
  • no additional optical components are required for the return of the main beam 5.3 but also of the entire reference beam 5.2 to the evaluation unit 9.
  • the reference beam 5.2 is focused by the lens 13 regardless of the pivoting position of the first mirror 10 at a distance from the focal length f of the lens 13. Since a narrow, strongly collimated reference beam 5.2 is used, the system has a very small numerical aperture, which has the following advantages. On the one hand, there is a negligible spherical deviation while the reference beam 5.2 passes through the delay element 16. On the other hand, there is a large depth of focus.
  • the large depth of focus ultimately means that the converging reference beam 5.2 also passes through the relevant first surface section 16.3 with a very small diameter at a greater distance from the optical axis 13.1, which corresponds almost to the focal point.
  • This makes it possible to keep the transverse dimensions of the respective first surface section 16.3, in particular the length L of the respective step in the first direction (Y direction) small.
  • This makes it possible to implement the largest possible number of steps in a usable dimension of the delay element 16 in the first direction that is ultimately predetermined by the maximum pivoting angle of the first mirror 10 and the lens 13.
  • the number of steps corresponds to the number of different delay lines along the first direction and thus also determines the overall achievable adjustment range of the optical delay.
  • a numerical example for an embodiment of the above-described embodiment of the device 2 according to the invention is to be given below.
  • a narrow collimated reference beam 5.2 coming from the beam splitter 6 with a diameter of approximately 0.5 mm it can be expected that the diameter of the reference beam 5.2 in a depth range of approximately ⁇ 10 mm around the focus plane of the lens 13 on the delay element side is less than 100 ⁇ m.
  • a step length L 100 ⁇ m can therefore be selected, which is significantly smaller than the diameter of the reference beam 5.2 coming from the beam splitter 6.
  • a usable diameter of the lens 13 of approximately 55 mm, it is thus possible to provide 550 steps in the first surface 16.1 in the first direction, and thus 550 delay distances of different decelerations.
  • a depth scan carried out using the device 2 can have a depth resolution of 550 pixels. This value is in the range of conventional OCT systems with axially movable mirrors, which, however, can only work with significantly lower adjustment frequencies.
  • the optical path difference OPD between two stages adjacent in the first direction (Y direction) should, because of the twice passing through the respective delay path, be a quarter of the coherence length of the light used, in order to achieve a maximum depth resolution. With a coherence length of 20 ⁇ m, this results overall for the delay element 16 in an adjustment range of the optical delay of up to 5.5 mm in 550 steps of 10 ⁇ m each.
  • FIGS. 4A to 4D show different schematic views of a detail from the delay element 16 from FIG. 2.
  • FIG. 4A is a plan view of the detail in the direction of the arrow IV A from FIG. 4B.
  • FIG. 4B is a plan view of the detail in the direction of arrow IV B from FIG. 4A.
  • FIG. 4C is a top view of the detail in the direction of arrow IV C from FIG. 4B.
  • FIG. 4C is a perspective view of the detail.
  • the device 2 according to the invention from FIG. 1 comprises a delay element 16 which is stepped only in the first direction.
  • the lens 13 can be designed as a cylindrical or as a spherical lens.
  • FIGS. 5 and 6A to 6D A variant of the device according to the invention is described below in connection with FIGS. 5 and 6A to 6D, with which a significantly larger adjustment range of the optical delay can be achieved.
  • FIG. 5 shows a schematic section through a further preferred embodiment of the device 2 ′ according to the invention, the basic design and function of which is the same as that of the device 2 from FIG. 2. For this reason, similar components are provided with the same reference numerals. Only the differences will be discussed here.
  • the first mirror 10 ' is not only pivotable in the first pivot plane coinciding with the plane of the drawing.
  • the first mirror 10' can also be pivoted in a second pivot plane, which runs perpendicular to the first pivot plane through the optical axis 13.1 'of the lens 13'.
  • the second pivot axis 10.1 'of the first mirror 10' in turn runs through the point of incidence 11 of the main beam 5.3 on the first mirror 10 ', the focus of the lens 13' also coinciding with the point of impact 11 here.
  • the swivel angle and swivel frequency in the second swivel plane correspond to those in the first swivel plane which have already been described above.
  • FIGS. 6A to 6D show different schematic views of a delay element 18, on the basis of which the design of the delay element 16 'from FIG. 5 is to be explained with a significantly smaller number of stages.
  • FIG. 6A is a plan view of the delay element 18 in the direction of the arrow IV A from FIG. 6B.
  • Figure 6B is a plan view of the delay element 18 in the direction of arrow IV B of Figure 6A.
  • FIG. 6C is a plan view of the delay element 18 in the direction of the arrow IV C from FIG. 6B.
  • FIG. 6C is a perspective view of the delay element 18.
  • the delay element 16 ' there is a further difference in the design of the delay element 16 ', the first surface 16.1' of which is stepped not only in a first direction (Y direction) but also in a second direction (X direction) running perpendicular thereto is, while its second surface 16.2 'is again flat. This gradation in the second direction forms a series of second delay lines with different optical delays.
  • the reference beam in this variant can be deflected via the lens 13', which is now a rotationally symmetrical spherical lens, any delay path of the delay element 16 '.
  • the lens 13' which is now a rotationally symmetrical spherical lens, any delay path of the delay element 16 '.
  • a deflection on the delay lines of the delay element can also take place by an arrangement with a plurality of pivotable mirrors and corresponding lenses.
  • the delay element 18 and thus also the delay element 16 ' have a serpentine step, in which the length of the delay lines decreases in a line.
  • the geometric length of the delay lines initially decreases in the first direction (Y direction) in steps of height d until the end of the delay element 18 in the delay line 18.2 is reached in this direction.
  • a step of height d in the second direction to the adjacent delay line 18.3.
  • the geometric length of the delay lines then decreases again in steps of height d opposite to the first direction (Y direction) until the end of the delay element 18 in the delay line 18.4 is reached again in this direction.
  • This serpentine decrease in the length of the delay lines continues until the shortest delay line 18.6 is reached.
  • serpentine gradation just described in other variants of the device according to the invention also by several in the second direction lined up delay elements can be achieved, which have a corresponding gradation in the first direction.
  • FIGS. 7A and 7B show schematic representations of a further embodiment of the delay element 19 according to the invention for an embodiment of the device according to the invention without a lens device.
  • FIG. 7B shows a variant of the device 2 ′′ according to the invention, in which the lens 13, the delay element 16 and the second mirror 17 are replaced by the delay element 19 in comparison to the device 2 from FIG. 2.
  • FIG. 7A shows the detail VII A Figure 7B.
  • the delay element 19 is curved, it has a stepped first surface 19.1 with first surface sections 19.3 and a continuously curved second surface 19.2.
  • the radius of curvature of the first surface sections 19.3 and the second surface 19.2 corresponds in each case to the distance from the point of incidence 11 of the main beam 5.3 on the first mirror 10.
  • the main beam 5.3 hits the second surface 19.2 and the respective one perpendicular to the pivoting angle of the first mirror 10 Surface section 19.3, so that it therefore does not experience any deflection.
  • the second mirror device is formed by a reflective coating 20 on the first surface 19.1.
  • the delay element 19 consists of a carrier 19.4 with a constant thickness T, to which a step body in the form of a plastic strip 19.5 with the stepped first surface 19.1 has been applied and fastened to produce the delay lines with different optical delays.
  • the gradation of the plastic strip 19.5 was generated as described above before applying it to the carrier 19.4 by a known impression technique.
  • plastic strip 19.5 was initially manufactured as a planar element. The curved shape was only impressed on the carrier 19.4 when it was used, using its elastic properties. However, it goes without saying that the plastic strip can also be produced in the corresponding curved shape in other variants.
  • the present invention has been described above using an example of an OCT system.
  • the device according to the invention can be used not only in connection with such OCT applications but also in connection with so-called low coherence interferometry (LCI) or any other interferometry-based optical measurement or imaging method.
  • LCDI low coherence interferometry

Abstract

L'invention concerne un dispositif servant à ajuster le retard optique dans un trajet optique, notamment dans un trajet optique de référence d'un interféromètre OCT. Ce dispositif comprend une première unité miroir (10) pouvant pivoter au moins dans un premier plan de pivotement autour d'un premier axe de pivotement, servant à dévier de manière sélective des rayons du trajet optique sur une première ligne à retard sélectionnée parmi un certain nombre de premières lignes à retard présentant différents retards optiques. Les premières lignes à retard sont formées dans au moins un élément à retard (16) qui présente au moins une première surface (16.1) étagée dans une première direction, servant à faire varier le retard optique.
PCT/EP2004/010312 2003-09-16 2004-09-15 Dispositif servant a ajuster le retard optique dans un trajet optique WO2005033624A1 (fr)

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DE10343028.8 2003-09-16
DE2003143028 DE10343028A1 (de) 2003-09-16 2003-09-16 Vorrichtung zum Verstellen der optischen Verzögerung in einem Strahlengang

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WO2006054116A3 (fr) * 2004-11-18 2006-10-12 Sira Ltd Dispositif, procede et sonde d'interferences
WO2007039267A3 (fr) * 2005-10-05 2007-10-11 Zeiss Carl Meditec Ag Tomographie par coherence optique destinee a la mesure de la longueur de l'oeil
DE102009022958A1 (de) 2009-05-28 2010-12-02 Carl Zeiss Meditec Ag Vorrichtung und Verfahren zur optischen Messung von Relativabständen
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WO1997032182A1 (fr) * 1996-02-27 1997-09-04 Massachusetts Institute Of Technology Procede et appareil permettant d'effectuer des mesures optiques a l'aide d'un endoscope, un catheter ou un fil de guidage d'imagerie a fibre optique
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WO2006054116A3 (fr) * 2004-11-18 2006-10-12 Sira Ltd Dispositif, procede et sonde d'interferences
US7859682B2 (en) 2004-11-18 2010-12-28 Michelson Diagnostics Limited Optical interference apparatus
WO2007039267A3 (fr) * 2005-10-05 2007-10-11 Zeiss Carl Meditec Ag Tomographie par coherence optique destinee a la mesure de la longueur de l'oeil
US7400410B2 (en) 2005-10-05 2008-07-15 Carl Zeiss Meditec, Inc. Optical coherence tomography for eye-length measurement
US7480059B2 (en) 2005-10-05 2009-01-20 Carl Zeiss Meditec, Inc. Optical coherence tomography for eye-length measurement
US8427654B2 (en) 2006-06-20 2013-04-23 Carl Zeiss Meditec, Inc. Spectral domain optical coherence tomography system
US8705048B2 (en) 2006-06-20 2014-04-22 Carl Zeiss Meditec, Inc. Spectral domain optical coherence tomography system
US9372067B2 (en) 2006-06-20 2016-06-21 Carl Zeiss Meditec, Inc. Spectral domain optical coherence tomography system
DE102009022958A1 (de) 2009-05-28 2010-12-02 Carl Zeiss Meditec Ag Vorrichtung und Verfahren zur optischen Messung von Relativabständen

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