JP2005198851A - Interference type ocular metering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an interference type ocular metering device where optical interference is sufficiently utilized by a low-output and low-coherent light source by automatically, speedily and properly setting an alignment and an working distance. <P>SOLUTION: The device is provided with: a measurement light irradiation optical system 2 having a measurement light source 11 and an object lens 12; a reference optical system 3 which reflects and returns a part of light from the measurement light source 11 as reference light; an optical separator 4 which separates and sends the light to an eye to be tested E and the reference optical system 3; an interference measurement optical system 5 which receives measurement light reflected by the eye to be tested and the reference light to measure the prescribed dimension of the eye to be tested E based on the interference of both of the light; a working distance detection mechanism 6 for detecting the working distance; an alignment optical system 7 for positioning the optical axis 2a of the device 1 with respect to the vertex of the eye to be tested; and a controller 8 for controlling moving and working of the working distance detection mechanism 6 and the alignment optical system 7. The controller 8 commands working of each optical system based on alignment detection information obtained by the alignment optical system 7 and working distance detection information obtained by the working distance detection mechanism 6. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an interference type eye measurement apparatus. More particularly, the present invention relates to an interferometric eye measurement apparatus that measures a distance between parts such as a corneal thickness by causing reflected light from a reference eye light to interfere with reference light.

Conventionally, various interference-type ophthalmic measurement devices that use interference between a plurality of reflected lights that reflect the same light at a plurality of locations, that is, a device that measures the size of a predetermined portion in an eye to be examined (for example, Patent Document 1, Patent Document 2, Patent Document 3 and Patent Document 3).
JP-A-2-4310 JP-A-2-297332 Japanese Patent Laid-Open No. 3-1111027 However, the content disclosed in these documents is a basic configuration for executing the principle of measuring the distance between predetermined sites in the eye to be examined using light interference. . Therefore, automatic measurement, such as the configuration of the device for quickly positioning and measuring the device relative to the eye to be examined while the eye does not move, the configuration of the device that causes sufficient optical interference with low output and low coherent light, etc. An apparatus for performing the above is not disclosed.

  In order to execute the measurement method disclosed in the above-mentioned prior art document, an optical interference optical system is mounted on a conventionally known slit lamp, and all of the measurement is forced to be performed manually by an inspector.

  On the other hand, as a practical device, it is desirable to use a low-output light source from the viewpoint of cost and safety.

  In view of the current situation described above, the present invention automatically determines an appropriate alignment and working distance, so that even if a low-power, low-coherent light source is used, the light interference is sufficiently utilized between each part of the eye to be examined. The object is to provide an interferometric eye measurement device capable of measuring dimensions (for example, corneal thickness).

The interferometric eye measurement device of the present invention is
A measurement light irradiation optical system having a measurement light source for irradiating the eye to be examined with low-coherent measurement light, and an objective lens;
A reference optical system that reflects part of the measurement light as reference light and returns it to the original; and
A light separator that separates and transmits measurement light from the measurement light source to the eye to be examined and the reference optical system;
An interference measurement optical system that receives the measurement light reflected by the eye to be examined and the reference light, and measures a predetermined dimension in the eye to be examined based on interference between the measurement light and the reference light;
A working distance detection mechanism having a focusing light projection optical system that projects focused light onto the eye to be examined, and a focus detection optical system that detects the working distance by detecting the focused light reflected by the eye to be examined;
An alignment optical system for aligning the device with the apex of the eye by irradiating the front part of the eye with illumination light from the front and detecting the image of the corneal reflection light;
A control device for controlling the movement and operation of the working distance detection mechanism and the alignment optical system,
The control device is configured to command the operation of each of the optical systems based on the alignment detection information by the alignment optical system and the working distance detection information by the working distance detection mechanism.

  An interference type eye measurement device in which the working distance detected by the working distance detection mechanism is set within a predetermined range is preferable.

  The predetermined range of the working distance is the distance from the position on the basis of the position of the objective lens to the corneal surface of the eye to be examined, and an interferometric eye measuring device that is 20 to 35 mm is preferable.

  An interferometric eye measurement device in which the predetermined range of the working distance is 25 to 30 mm is more preferable.

  According to the present invention, quick and appropriate alignment and working distance can be automatically determined, and light interference can be sufficiently utilized even when a low-power and low-coherent light source is used.

  An interference type eye measurement device according to an embodiment of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a schematic plan view showing an embodiment of the interference-type eye measurement apparatus of the present invention, and mainly shows the equipment and the optical path. 2 is a cross-sectional view taken along the line II-II in FIG. 1, showing a side surface of a part of the optical system (a focusing light projection optical system and a focusing detection optical system described later) in FIG. 3 is a view taken along the line III-III in FIG. 1, showing a side surface of a part of the optical system (an alignment optical system described later) in FIG.

  An interferometric eye measurement device (hereinafter simply referred to as “device”) 1 shown in FIG. 1 includes a measurement light irradiation optical system 2 having a measurement light source 11 and an objective lens 12 for irradiating the eye E with interference measurement light. The reference optical system 3 having a reference mirror 13 that reflects a part of the measurement light from the measurement light source 11 as reference light, the optical path 2a to the eye E to be measured from the measurement light source 11, and the reference optical system 3 An optical separator 4 for separating and transmitting to the optical path 3a, and an interference light receiving sensor 14 for receiving the measurement light reflected by the eye E and the reference light and detecting the interference between the measurement light and the reference light. And an interference measurement optical system 5. As the measurement light source 11, not a laser beam but a super luminescent diode (referred to as SLD) that emits high-luminance and low-coherent light is used. A non-polarizing beam splitter is used as the light separator 4.

  The apparatus 1 further detects the focused light projection optical system 15 that projects the focused light onto the eye E from the oblique front and the focused light reflected by the eye E from the diagonal front of the eye E. By operating the working distance detecting mechanism 6 having the focus detection optical system 16 for detecting the working distance by irradiating the front eye part of the eye E with illumination light from the front and detecting the image of the cornea reflected light An alignment optical system 7 for positioning the apparatus 1 with respect to the vertex E of the eye to be examined, and a control device 8 for controlling the movement and operation of the working distance detection mechanism 6 and the alignment optical system 7 are provided. In addition, a fixation lamp 9 for fixing the visual axis of the eye to be examined in a fixed direction by fixing the eye E to be examined is provided. A forehead and a chin stand (not shown) are installed on the surface of the apparatus 1 facing the subject. The subject presses the forehead against the forehead and fixes the face by placing the chin on the chin stand.

  The optical systems 2, 3, 4, 5, 7, 15, and 16 are all installed on a triaxial mount 10 that can move in the XYZ triaxial directions.

  The measurement light irradiation optical system 2 includes a collimation lens 19 that converts the measurement light from the low coherence measurement light source 11 into a parallel light beam, a projection-side condensing lens 20, a first pinhole member 21 for removing noise, A projection-side magnifying lens 22 for converting the light that has passed through the pinhole of the one pinhole member 21 into a parallel light beam is guided to the light separator 4 through the measurement light that has passed therethrough.

  One measurement light separated by the light separator 4 is converged on the eye E by the objective lens 12, and the other measurement light separated is sent to the reference optical system 3 as described later. The measurement light from the measurement light source 11 is made into a parallel light flux between the collimation lens 19 and the projection side condensing lens 20 and between the projection side magnifying lens 22 and the objective lens 12. The reason why the lens denoted by reference numeral 22 is referred to as a magnifying lens is that the width of the parallel light beam emitted from the collimation lens 19 is a parallel light beam enlarged by the projection side magnifying lens 22. Reference numeral 23 denotes a mirror for bending the optical path of the measurement light irradiation optical system 2 and is installed as necessary. The measurement light reflected by the eye E returns to the light separator 4 as parallel light by passing through the objective lens 12 through the same optical path.

  The reference optical system 3 includes a mask member 24. The mask member 24 converts the other measurement light separated by the light separator 4 through the window 24 a into a light beam having a predetermined diameter and sends it to the reference mirror 13. The light beam that has passed through the window 24 a of the mask member 24 is reflected by the reference mirror 13, passes through the same optical path 3 a, passes through the window 24 a of the mask member 24, and returns to the light separator 4. This light is called reference light. The reference light is a parallel light beam. The reference mirror 13 is configured to be movable along the optical path 3 a of the reference optical system 3. The light interference is measured by detecting the phase matching state of the measurement light and the reference light while moving the reference mirror 13 in the direction of the optical axis 3a.

  In the interference measurement optical system 5, the measurement light reflected by the eye E and the reference light reflected by the reference mirror 13 and incident from the reference optical system 3 are superposed in the light separator 4. Both the reference light and the reflected measurement light are parallel light beams. Then, the interference measurement optical system 5 converges the hot mirror 17 that bends the optical path 5a, the second pinhole member 25 for noise removal, and the superimposed light flux into the pinhole of the second pinhole member 25. And a detection side reduction lens 27 for making the light beam that has passed through the pinhole parallel light. The interference light receiving sensor 14 receives the light beam transmitted through these optical elements 17, 25, 26 and 27. The light flux between the light separator 4 and the detection-side condensing lens 26 and between the detection-side reduction lens 27 and the interference light-receiving sensor 14 is a parallel light flux. The reason why the lens denoted by reference numeral 27 is referred to as a reduction lens is that the width of the parallel light beam from the light separator 4 is a parallel light beam reduced by the detection side reduction lens 27. The reason for contracting the light beam is to increase the light density and facilitate the detection of interference by the interference light receiving sensor 14. In order to obtain interference between the measurement light and the reference light, the light beam cross-section of the measurement light must have a shape that covers the reference light in the range of the mask window 24a.

  An APD (avalanche photodiode) is used as the interference light receiving sensor 14. By moving the reference mirror along the optical axis 3a of the reference optical system, the reflected measurement light from each part of the eye to be inspected and the reference light interfere with each other. Therefore, the interference light receiving sensor 14 determines the intensity of the received light. This interference is detected. A control device 8 is connected to the interference light receiving sensor 14, and the control device 8 measures a distance using a low coherence light interferometry. Reference numeral 28 denotes a mirror for bending the optical path 5a of the interference measurement optical system 5, and is installed as necessary.

  As shown in FIGS. 1 and 2, in the working distance detection mechanism 6, the optical path 15 a of the focused light projection optical system 15 and the optical path 16 a of the focus detection optical system 16 intersect (intersection point is indicated by a symbol C). Thus, they are arranged at a predetermined angle. The focused light projection optical system 15 includes an infrared LED 29 as a focused light source, and includes a condenser lens 30, a target slit 31, and a projection lens 32 toward the eye E along the optical axis 15a. ing. The focus detection optical system 16 is for detecting the focused light reflected at the apex of the eye E, has a detection sensor 33 such as a PSD (Position Sensitive Detector), and the eye to be examined on the optical axis 16a. An imaging lens 34 and a visible light cut filter 35 are provided on the E side. A control device 8 is connected to the working distance detection mechanism 6, and the control device 8 positions the device 1 in the Z direction with respect to the eye E using the focusing optical systems 15 and 16. That is, the control device 8 moves the triaxial mount 10 back and forth with respect to the eye to be examined. When the intersection C of the optical axes 15a and 16a coincides with the apex of the eye E, the focus detection optical system 16 detects the focus, and the control device 8 determines that the working distance has been detected. Reference numeral 36 denotes a mirror for bending the optical path of the interference measurement optical system 5 and is installed as necessary.

  As shown in FIGS. 1 and 3, the alignment optical system 7 positions the apparatus 1 in the XY directions with respect to the eye E, and a red LED 37 as a light source of alignment index light that irradiates the anterior eye portion of the eye to be examined. And a projection lens 38 on the optical axis 7a. Then, the alignment index light is applied to the anterior segment of the eye E through the hot mirror 39 and the half mirror 40. The alignment optical system 7 has a CCD 41 as an alignment sensor that receives a bright spot (Purkinje image) as a reflection image of the alignment light source 37 from the eye to be examined. The reflected image (reflected light) passes through the hot mirror 17 (FIG. 1) and reaches the CCD 41 through the half mirror 40 and the detection lens 42 arranged along the optical axis 7a. The controller 8 is connected to the alignment optical system 7. Based on this Purkinje image, the control device 8 moves the triaxial mount 10 in the X and Y directions (moves each optical system in the X and Y directions) to make the alignment optical axis 7a coincide with the apex of the cornea. That is, as shown in FIG. 4, the Purkinje image P generated in the anterior segment being photographed is guided to a predetermined range (within a circle T having a predetermined diameter) at the center of the anterior segment. The center of the anterior segment image is the apex of the cornea. If the Purkinje image falls within this circle T, it is determined that alignment has been achieved.

  As shown in FIG. 1, the optical axis 7 a that reaches the eye E of the alignment optical system 7 passes through the intersection C. As a result of the in-focus detection by the in-focus light projection optical system 15 and the in-focus detection optical system 16 and the alignment by the alignment optical system 7 being performed in parallel, the working distance is detected. . That is, the detection of the working distance by the control device 8 using the working distance detection mechanism 6 and the alignment optical system 7 is achieved by the cooperation of the focusing operation and the alignment operation. Specifically, the triaxial mount 10 is advanced toward the eye E (Z direction). When the Purkinje image can be detected by the alignment optical system 7, the triaxial mount 10 is displaced in the X direction and the Y direction to perform alignment. While maintaining the alignment, that is, while maintaining the alignment optical axis 7a within a predetermined range of the corneal apex (within the circle T in the alignment screen 43 shown in FIG. 4), the triaxial mount 10 is displaced in the Z direction. When the intersection C reaches the corneal apex of the eye E to be examined, this focused light is detected by the detection sensor 33. That is, the working distance is detected. Based on the detection signal from the detection sensor 33 at this time, for example, the control device 8 causes the measurement light source 11 of the measurement light irradiation optical system 2 to emit light, displaces the reference mirror 13, and causes the interference light receiving sensor 14 to emit interference light. Receive light.

  The working distance is a separation distance between the surface of the eye to be examined (corneal apex) and the distal end surface of the objective lens 12 of the apparatus 1 that is determined in advance. The position of the device 1 that is separated from the eye E by this working distance is called the working position. The distance between the apex of the cornea and the front end surface of the objective lens 12 is made substantially equal to the focal length of the objective lens 12, but the focal length of the objective lens 12 is determined by the conditions described later. Specifically, this working distance is a distance determined based on the distance between the apex of the cornea and the distal end surface of the objective lens 12 (approximate to the focal length of the objective lens 12). For the sake of convenience, the working distance is generally a dimension obtained by subtracting the thickness of the objective lens support member from the focal length of the objective lens 12. That is, as a general definition, it is a separation distance between a portion of the apparatus closest to the eye E to be examined and the corneal apex of the eye to be examined. However, for easy understanding, in the following description, the distance between the apex of the cornea and the distal end surface of the objective lens 12 (distance approximate to the focal length of the objective lens 12) is referred to as a working distance. In the present apparatus 1, this working distance is set to one of the ranges of 20 to 35 mm (for example, 28 mm). Preferably, it may be set within a range of 25 to 30 mm.

  The working distance setting range (20 to 35 mm) of the device 1 is determined from the following reasons and conditions. These will be described with reference to FIG.

  First, no matter how accurately the above-described alignment is performed, fixation eye movements with high frequency and minute amplitude are usually generated in the eye to be examined. Furthermore, in order to provide a realistic apparatus that can be handled easily and meet the demand as an industrial product, it is necessary to provide not only the alignment accuracy but also provide each necessary performance in a balanced manner. Therefore, it is necessary to consider a realistic error in alignment. Furthermore, it is necessary to set an upper limit for the output of the measurement light source 11 in order to reduce the cost and the safety of the subject. It is preferable to select a commercially available product having a small output.

  FIG. 5A shows a state in which the optical axis 2a of the apparatus 1 is at the apex of the cornea (correctly aligned) and the working distance is also matched. That is, there is no position shift of the eye to be examined due to fixation fine movement, there is no alignment error of the apparatus 1, and the apparatus optical axis coincides with the apex of the cornea. The symbol DL is the optical axis of the apparatus 1 (specifically, the optical axis 2a of the measurement light irradiation optical system), and the symbol EL is the eye optical axis. Reference symbol L1 is the peripheral light at the upper end in the drawing of the light beam emitted from the objective lens to the eye E. The emission angle of the upper peripheral light (angle formed with the optical axis DL of the device 1) is indicated by reference sign θ1. Reference sign L2 is a light beam incident on the apparatus 1 of the above-mentioned peripheral light at the upper end of the light (measurement light) reflected by the eye E, and its incident angle to the apparatus 1 is denoted by reference sign θ2. As shown in the figure, if the alignment and the working distance are accurately made and there is no deviation, θ1 = θ2, and the measurement light emitted from the objective lens 12 is reflected by the eye E to be examined and is symmetrical with respect to the optical axis DL of the apparatus 1 Return on the objective lens 12 in the same range as the emission range.

  As is clear when referring also to FIG. 1, the reference numeral D <b> 1 in the drawing indicates the cross-sectional diameter of the irradiated light beam. As described above, since the measurement light source 11 with a small output is used, it is necessary to suppress the decrease in the light density caused by the light beam expansion by the magnifying lens 22 as much as possible, so that D1 cannot be increased. That is, D1 is the maximum allowable diameter determined from the minimum light density of the irradiation light, and if the beam width of the measurement light is widened beyond this D1, the light density is lowered, so the interference light receiving sensor 14 makes a clear determination. It cannot be done.

  Reference numeral D2 denotes a diameter limited by the mask window 24a after the D1 in FIG. 1 is separated by the light separator 4, and indicates a range centering on the apparatus optical axis DL. The measurement light reflected and returned by the eye E is collimated by the objective lens 12 and reaches the light separator 4. Here, the measurement light is reflected by the reference mirror 13 and overlaps only with the reference light that has passed through the window 24a to cause interference. In other words, only the measurement light reflected by the eye E is returned to the range of D2 in the objective lens 12 and interferes with the reference light.

  FIG. 5 (b) shows a state in which fixation micromotion of the eye E and an alignment error of the apparatus 1 occur, and the apparatus optical axis 2a deviates from the eye axis EL. In this way, the fixation eye E constantly undergoes fixation fine movement and there is an error in the alignment of the apparatus 1, so that the reflection direction of the measurement light on the eye E changes rapidly. Since the surface of the eye E to be examined is a spherical surface, the reflected light (measurement light) L2 greatly deviates from the device optical axis DL when the eye optical axis EL to be examined and the device optical axis DL are shifted. However, this figure shows a state in which the corneal reflection light (measurement light) returns to the allowable range D2 in the objective lens 12. In the figure, reference numeral NL indicates a normal line at a reflection point in the eye to be examined.

  FIG. 5 (c) also shows a state in which the alignment deviates from the corneal apex due to fixation fine movement and an allowable maximum error in alignment. In this figure, the limit state of the optical axis deviation is shown, and if it deviates further, the corneal reflection measurement light deviates from D2. As a result, the measurement light that can be interfered is less than the range of D2, and the intensity of the light due to the interference is also reduced. This is because the intensity of interference is determined by the phase matching between the measurement light returning from the eye to be examined and the reference light, and the measurement light overlapping the entire area D2 of the reference light.

  FIG. 5D shows a state in which the measurement light deviates from D2 in the objective lens 12 because it is not yet aligned. In this state, there is no interference between the measurement light and the reference light, and measurement is impossible.

  Since D2 is determined by the shape of the mask window 24a, it can be large or small. However, there are limitations for the following reasons.

  If the light beam is enlarged by the magnifying lens 22 in order to increase D2, the light density is lowered, so that clear measurement becomes difficult. Moreover, as can be seen from FIGS. 5B and 5C, if D2 is set to be large, reflected measurement light easily deviates from D2 unless the alignment tolerance is reduced accordingly. However, as described above, eye movements occur in the eye to be examined, and there is a limit to the accuracy of alignment. Therefore, it is difficult to increase D2.

  On the other hand, if D2 is reduced, the tolerance of alignment can be increased. However, since reducing D2 means reducing the mask window 24a, the amount of reference light is reduced, making clear measurement difficult. Although it is conceivable to reduce the focal lengths of the projection-side condenser lens 20 and the projection-side magnifying lens 22 in order to increase the amount of reference light while reducing the window 24a, there is no effect because D1 is also reduced. As described above, the size of D2 is limited.

  In addition, there is a limit to the setting of the working distance (selection of the objective lens). This will be described with reference to FIG. When the working distance is set small (selecting a lens having a small focal length) with D1 and D2 unchanged, the objective lens 12 is relatively moved closer to the eye E in FIG. In the 12th plane, L2 enters the inside of D2. However, the increase in θ2 increases as θ1 increases beyond that. Therefore, the smaller the working distance is, the more in the direction in which fixation micromotion and alignment errors are absorbed and made ineffective. However, since the focal length of the objective lens has to be reduced, the F value is disadvantageous. Furthermore, setting the working distance small means that the distal end of the apparatus, such as the objective lens holding part, approaches the eye to be examined, which gives a fear to the subject. Therefore, there is a limit to reducing the working distance. This lower limit is 20 mm, preferably 25 mm.

  On the other hand, when the working distance is set large (selecting a lens with a large focal length) with D1 and D2 unchanged, the objective lens 12 is relatively away from the eye E, so that L2 is D2 on the lens 12 surface. This is the outward direction (advantageous direction). However, since the degree of decrease of θ2 increases as θ1 becomes smaller than that, the above advantage is negated. That is, the rate of measurement light that can interfere is reduced. Therefore, an upper limit is set for the working distance. This upper limit is 35 mm, preferably 30 mm.

  For the above reasons and conditions, a working distance of 20 to 35 mm is appropriate, and 25 to 30 mm is more preferable. In this way, the reasonable working distance can be reduced by taking into account the safety and availability of the subject by adopting a low-power measurement light source, and reducing the cost and alignment required time by relaxing the alignment accuracy of the device. The range is set as a result of realizing shortening or the like. The objective lens may be selected so that the working distance falls within the above range, and the specifications of the peripheral elements may be determined accordingly. The apparatus 1 configured as described above automatically moves the apparatus 1 to the operation position by the operation of the triaxial mount 10, the working distance detection mechanism 6, and the alignment optical system 7 by the control device 8. When the working distance is detected, the control device 8 automatically activates the measurement light irradiation optical system 2, the reference optical system 3, and the interference measurement optical system 5, and uses the low-coherent optical interferometry to detect the eye E. The distance of the predetermined part of is measured.

  According to the present invention, by automatically determining an appropriate alignment and working distance, light interference can be sufficiently utilized even when a low-output and low-coherent light source is used. Therefore, it is possible to provide an interference type eye measurement apparatus capable of measuring dimensions such as corneal thickness quickly and accurately at a relatively low cost.

It is a schematic plan view which shows one Embodiment of the interference type eye measuring device of this invention, and has mainly shown the apparatus and the optical path. It is the II-II arrow directional view of FIG. 1 which shows the side surface of the focusing light projection optical system in FIG. 1, and a focusing detection optical system. It is the III-III arrow directional view of FIG. 1 which shows the side surface of the alignment optical system in FIG. It is explanatory drawing which shows the alignment operation | movement by the control apparatus in FIG. FIG. 5A is a schematic plan view showing an embodiment of the interference type eye measurement device of the present invention, and FIG. 1B is a schematic side view thereof.

Explanation of symbols

1 device (interference eye measurement device)
2 Measurement light irradiation optical system 2a Optical path of measurement light irradiation optical system 3 Reference optical system 3a Optical path of reference optical system 4 Optical separator 5 Interference measurement optical system 5a Optical path of interference measurement optical system 6 Working distance detection Mechanism 7 Alignment optical system 7a Optical path (of alignment optical system) 8 Control device 9 Fixation lamp 10 Triaxial mount 11 Measurement light source 12 Objective lens 13 Reference mirror 14 Interference light receiving sensor 15 Focus light projection optical system 16 Focus detection optical system DESCRIPTION OF SYMBOLS 17 Hot mirror 19 Collimation lens 20 Projection side condensing lens 21 1st pinhole member 22 Projection side expansion lens 23 Mirror 24 Mask member 25 Second pinhole member 26 Detection side condensing lens 27 Detection side reduction lens 28 Mirror 29 Infrared LED (focusing light source)
30 condenser lens 31 index slit 32 projection lens 33 detection sensor 34 imaging lens 35 visible light cut filter 36 mirror 37 infrared LED (alignment light source)
38 projection lens 39 hot mirror 40 half mirror 41 (for alignment) CCD
42 Detection lens 43 Alignment screen C Optical axis intersection of working distance detection mechanism E Eye to be examined NL (on the surface of eye to be examined) P P Purkinje image

Claims (4)

A measurement light irradiation optical system having a measurement light source for irradiating the eye to be examined with low-coherent measurement light, and an objective lens;
A reference optical system that reflects part of the measurement light as reference light and returns it to the original; and
A light separator that separates and transmits measurement light from the measurement light source to the eye to be examined and the reference optical system;
An interference measurement optical system that receives the measurement light reflected by the eye to be examined and the reference light, and measures a predetermined dimension in the eye to be examined based on interference between the measurement light and the reference light;
A working distance detection mechanism having a focusing light projection optical system that projects focused light onto the eye to be examined, and a focus detection optical system that detects the working distance by detecting the focused light reflected by the eye to be examined;
An alignment optical system for aligning the device with the apex of the eye by irradiating the front part of the eye with illumination light from the front and detecting the image of the corneal reflection light;
A control device for controlling the movement and operation of the working distance detection mechanism and the alignment optical system,
An interference-type eye measurement device configured to instruct the operation of each optical system based on alignment detection information by an alignment optical system and working distance detection information by a working distance detection mechanism.   The interference type eye measurement apparatus according to claim 1, wherein the working distance detected by the working distance detection mechanism is set within a predetermined range.   The interferometric eye measurement apparatus according to claim 2, wherein the predetermined range of the working distance is a distance from a position relative to the position of the objective lens to a corneal surface of the eye to be examined, and is 20 to 35 mm. The interferometric eye measurement apparatus according to claim 3, wherein the predetermined range of the working distance is 25 to 30 mm.

Images