CN1720857A - Human eye aberration and corneal surface shape measuring system based on micro-prism array shack-Hartmann wavefront sensor - Google Patents

Abstract

The invention discloses a human eye aberration and corneal surface shape measuring system based on a micro-prism array shack-Hartmann wavefront sensor, which consists of a pupil or corneal illumination light source, a spectroscope, a pupil imaging objective lens, a CCD, a beacon light source, a beacon light collimation system, a caliber control device, a reflector, a front group focusing objective lens, a rear group focusing objective lens, a caliber matching system, a shack-Hartmann wavefront sensor based on a micro-prism array, a target system, a computer and an additional measuring lens, can realize two functions of measuring human eye aberration and corneal surface shape, is convenient and easy to switch, can obtain low-grade and high-grade aberration data and corneal surface shape data of human eyes at one time, is convenient to know the characteristics and the relation among the whole aberration, the corneal aberration and the internal aberration of the human eyes, and avoids errors caused by adopting different instruments to respectively measure the human eye aberration and the corneal aberration in the prior art, more accurate and sufficient diagnosis data can be provided for medical clinics.

Description

Human eye aberration and corneal surface measurement system based on microprism array Shack-Hartmann wavefront sensor

Technical field

The invention relates to a human eye aberration and corneal surface shape measurement system based on a microprism array Shack-Hartmann wavefront sensor, which uses the same instrument and can simultaneously realize human eye aberration measurement and human corneal measurement. Optical system for surface profile measurement.

Background technique

The monochromatic aberrations of the human eye, such as defocus, astigmatism, etc., and some higher-order aberrations, such as coma, spherical aberration, etc., will lead to the reduction of retinal imaging quality and the decline of subjective visual experience. The Shaker-Hartmann human eye aberration measurement system is commonly used in the measurement of low-level and high-level aberrations of the human eye, and fundus retinal imaging technology. The main feature of this type of measurement system is that it uses a Shack-Hartmann wavefront sensor based on a microlens array (“Visual Performance after correcting the monochromatic and chromatic aberrations of the eye” Geun-Young Yoon and DavidR.Williams, J. Opt.Soc.Am.A/Vol.19, No.2/February). At present, a new type of Hartmann wavefront sensor based on microprism array has been successfully invented (see Chinese patent application No. 03126430.1 and 200310100168.1), which has a simple and stable structure. Sensor technology can simplify installation, adjustment and reduce production costs. In terms of human eye aberration measurement, the Shack-Hartmann wavefront sensor based on microprism array can also measure the low-level and high-level aberrations of the human eye non-invasively. Several national patents have been applied for applications such as high-order aberration correction and visual simulation (see Chinese patent application numbers 03126431.X, 200410009116.8 and 200410009043.2).

In addition to the measurement of the overall aberration of the human eye, scientists have also begun to pay attention to some special structures of the human eye, such as the characteristics of the cornea and lens and their independent optical surfaces. This information is very important for understanding the optical properties of the various structures of the human eye and the interaction between them. Orthokeratology in ophthalmic surgery corrects the overall aberration of the human eye by correcting the shape of the cornea. Therefore, it is not only necessary to understand the overall aberration of the human eye, but also to measure the corneal surface shape and aberration, and to analyze the aberration of the human eye. The relationship between the overall aberration and the corneal aberration, and the relative balance between the corneal aberration and the internal aberration of the human eye can provide more accurate and sufficient data for clinical medicine.

At present, some experimental institutions have begun to study the use of projection-based corneal topography measurement systems, such as laser interferometers, or reflection-based corneal topography measurement systems, such as keratometers, videokeratoscopes, etc. to measure corneal topography. Corneal aberration, and the technology of measuring the overall aberration of the human eye with the Shack-Hartmann wavefront sensor. However, two different instruments are used to measure the corneal topography and the human eye aberration, and they have different visual reference axes in the measurement, which leads to errors in the calculation of corneal aberration and the calculation of the internal aberration of the human eye, as shown in the literature (“ Videokeratoscope-line-of-sight misalignment and its effect on measurements of corneal and internal coular aberrations”, J.Opt.Soc.Am.A19, 657-669, 2002).

Contents of the invention

The technical solution provided by the present invention is to provide a human eye aberration sensor based on a microprism array Shack-Hartmann wavefront sensor that can measure both the overall aberration of the human eye and the corneal surface shape at the same time. And corneal surface measurement system, it uses the same instrument to measure the human eye aberration and corneal surface shape, and can obtain the low-level, high-level aberration data and corneal aberration data of the human eye at one time, which is convenient for understanding the overall image of the human eye Aberration, corneal aberration, and internal aberration of the human eye and their characteristics and the relationship between the three; at the same time, errors caused by using different instruments to measure the aberration of the human eye and corneal aberration in the prior art are avoided.

The technical solution of the present invention is: human eye aberration and corneal surface shape measurement system based on the microprism array Shack-Hartmann wavefront sensor: it consists of pupil or corneal illumination light source, beam splitter (positioned at the front of the human eye, reflecting Part of the beacon light enters the pupil imaging system, and the transmitted light enters the measurement optical path), pupil imaging objective lens, CCD detector, beacon light source, beacon light collimation system, aperture control device, mirror (located in the aperture control device and focusing system Between), the front group focusing objective lens, the rear group focusing objective lens, the beam splitter (located between the focusing system and the beacon light collimation system), the aperture matching system, the mirror (located in the aperture matching system), based on microprism The Shaker-Hartmann wavefront sensor of the array, the beam splitter (located between the focusing system and the target system), the target system, the computer and the additional measurement lens are composed.

The described Shack-Hartmann wavefront sensor based on the microprism array mainly consists of a microprism array of a sawtooth phase grating structure, a Fourier lens (or imaging lens) and a photoelectric coupling device (such as a CCD detector), wherein the Fourier The lens (or imaging lens) is close to the microprism array, and the photoelectric coupling device is located on the focal plane of the Fourier lens (or imaging lens).

The principle of the present invention is: on the basis of the human eye aberration Shack-Hartmann measuring instrument based on the microprism array (see Chinese invention patent application number 03126431.X), through a caliber control device, change the human eye aberration The incident aperture of the beacon light in the instrument (from a thin beam to a wide beam), and an additional measuring lens, through the axial adjustment of the measuring lens, focuses the beacon light of the wide beam to the inner focal point of the corneal surface, and passes through the front surface of the cornea The reflection is collimated into parallel light by the additional measuring lens, and then enters the human eye aberration measuring instrument to realize the measurement of the surface shape of the human cornea. However, when the existing Shaker-Hartmann human eye aberration measuring instrument based on microprism arrays measures the overall aberration of the human eye, it uses a beam of thin beams to enter the eye from the pupil, and after being converged by the human eye, A spot of light is formed on the fundus, scattered by the fundus and emitted from the pupil, and the wavefront error of this beam of light is measured by the Shack-Hartmann wavefront sensor based on the microprism array, which is the aberration of the human eye. The invention reforms the existing Shaker-Hartmann human eye aberration measuring instrument based on the microprism array, and can realize the measurement of the corneal surface shape and the overall aberration of the human eye on the same system.

The described human eye aberration Shack-Hartmann wavefront sensor based on the microprism mirror array mainly consists of a microprism array of a sawtooth phase grating structure, a Fourier lens (or an imaging objective lens) and a photoelectric coupling device (such as a CCD detection device), wherein the Fourier lens (or imaging lens) is close to the microprism array, and the photoelectric coupling device is located on the focal plane of the Fourier lens (or imaging lens).

A confocal filter diaphragm is added to the field diaphragm surface or the real image surface of the field diaphragm, and the confocal filter diaphragm is placed at the common focal point of the front group and rear group lenses of the aperture matching system or the front group of the focusing system The common focal point of the lens and the rear lens group.

The beneficial effect of the present invention compared with the prior art: the present invention couples the function of measuring the surface shape of the human eye to the Shack-Hartmann human eye aberrometer based on the microprism array, and through additional optical parts, It can not only realize the measurement of human eye aberration, but also realize the measurement of corneal surface shape, avoiding the error caused by using different instruments for measurement. The structure of the system is simple, and the switching between the functions of human eye aberration measurement and corneal surface shape measurement is convenient and easy to operate. The surface shape and the overall aberration data of the human eye help to understand the optical characteristics of the human cornea, corneal aberration and the internal aberration of the human eye, and the way of aberration balance between them. Surgery, etc. provide more accurate and sufficient basis for diagnosis.

Description of drawings

Fig. 1 is a functional block diagram of the system structure of the present invention. The system works under the state of human eye aberration measurement, and the beam path is shown in the shaded part (fine beam aperture) in the figure; when the corneal surface measurement function is used, the system works under the wide beam aperture shown in the figure;

Fig. 2 is a schematic diagram of the principle of measuring corneal surface shape with an additional measuring lens in the present invention;

FIG. 3 is a schematic diagram of the human eye aberration Shack-Hartmann wavefront sensor based on the microprism mirror array of the present invention.

Detailed ways

As shown in Figure 1, the present invention consists of pupil or corneal illumination light source 2, beam splitter 3, pupil imaging objective lens 4, CCD 5, beacon light source 6, beacon light collimation system 7, aperture control device 8, mirror 9, Beam splitter 10, front group focusing objective lens 11, rear group focusing objective lens 12, beam splitter 13, aperture matching system 14, mirror 15, confocal filter diaphragm 16, Shack-Hartmann wave based on microprism array Front sensor 17, target system 18, computer 19, and additional measuring lens 20 are made up, and wherein, pupil or cornea illuminating light source (2) is positioned at human eye side front; Additional measuring lens (20) is close to human eye, and its focal point and corneal curved surface The focal points coincide; the beam splitter (3) is located in front of the human eye, the pupil imaging objective lens is located in the reflection direction of the beam splitter (3), and the CCD (5) is located on the focal plane of the pupil imaging objective lens; the beacon light source (6), the beacon light standard The straight system (7), the aperture control device (8), the reflector (9), the beam splitter (10), the front group focusing objective lens (11), the rear group focusing objective lens (12), and the beam splitter (3) Beacon light input optical path; beam splitter (13) and target system (18) are placed in front of the beam splitter (10); the aperture matching system (14) is located in the beam reflection direction of the beam splitter (13), and the mirror (15) is located at In the optical path of the aperture matching system (14); the Shack-Hartmann wavefront sensor (17) based on the microprism array is located at the optical path exit of the aperture matching system (14); the computer (19) is to the CCD (5) and the microprism-based Shaker-Hartmann wavefront sensors (17) of the array apply control signals and perform data processing.

Pupil among the present invention or cornea illuminating light source can be near-infrared light-emitting diode; Beacon light source wherein can be LD semiconductor laser; Aperture control device 8 wherein can be a rotating beacon device; Utilize 8 to make the beam aperture by it variable small, can provide the thin beam needed for human eye aberration measurement; use 8 to make the beam aperture passing through it larger, and then can release the wide beam required for corneal surface measurement; the additional measurement lens 20 has a good aberration-elimination design, It also has a two-dimensional adjustment mechanism in the direction of the vertical optical axis and along the axis, which can adapt to the curvature of the cornea of different individuals, and adjust the beacon light to the inner focus of the cornea as shown in Figure 2. Or move out to realize switching between different functional states.

The system can work under the two functions of corneal surface measurement and human eye aberration measurement, which are described in detail as follows:

When the system is working under the function of corneal surface measurement, the pupil alignment is first performed, and the pupil of the measured human eye is illuminated by the illumination source 2, reflected by the beam splitter 3, and the pupil of the measured human eye 1 is imaged by the pupil imaging objective lens 4 On the CCD 5 target surface, the video signal output by the CCD 5 is input to the video acquisition card in the computer 19, and is displayed on the computer monitor in real time. Adjust the position of the instrument so that the center of the pupil of the measured human eye 1 is located at the center of the optical axis of the instrument, and then the subject's eyes pass through the focusing system composed of the beam splitter 3, the front group focusing objective lens 11 and the rear group focusing objective lens 12. The mirror 10 and the beam splitter 13 observe an infinitely distant target in the target system 18 . After the alignment is completed, the beacon light is emitted by the beacon light source 6, collimated by the beacon light collimation system 7, and the aperture control device 8 is released to the Datong light aperture, so that the beacon light becomes a wide beam, and passes through the reflector After being reflected by 9, it is reflected by the beam splitter 10, passes through the focusing system, passes through the beam splitter 3, and passes through the additional measurement lens 20 to adjust the additional measurement lens so that the beacon light is focused on the inner focal point of the cornea. The reflected light from the front surface of the cornea is collimated by the additional measurement lens 20 to become a parallel beam, passes through the beam splitter 3 and the focusing system, then passes through the beam splitter 10, is reflected by the beam splitter 13, and enters the aperture matching system 14 and the mirror 15 , the outgoing light enters the Shack-Hartmann wavefront sensor 17 based on the microprism array, and the Shack-Hartmann wavefront sensor 17 inputs the video signal output by the CCD into the computer 19, and the computer 19 calculates the measured human eye 1 The shape of the cornea. The real focal plane of the aperture matching system 14, or the common focal point of the front group lens 11 and the rear group lens 12 of the focusing system is provided with a confocal filter diaphragm 16, which only reflects light through the front surface of the cornea and can filter out the system stray light in the .

After the measurement of the corneal surface shape is completed, the system can work under the function of measuring the overall aberration of the human eye: change the aperture of the aperture control device 8 to make the beacon light into a thin beam, and move the additional measurement lens 20 out of the system outside. The same as the corneal surface measurement procedure, first pupil alignment is carried out, and the pupil of the measured human eye 1 is illuminated by the pupil or the corneal lighting source 2, reflected by the beam splitter 3, and the pupil of the measured human eye 1 is imaged on the CCD by the pupil imaging objective lens 4 5 on the target surface, then the video signal output by the CCD 5 is input to the video capture card in the computer 19, which is displayed on the computer monitor in real time. Adjust the position of the instrument so that the center of the pupil of the measured human eye 1 is located at the center of the optical axis of the instrument, and then the subject's eyes pass through the focusing system composed of the beam splitter 3, the front group focusing objective lens 11 and the rear group focusing objective lens 12. The mirror 10 and the beam splitter 13 observe an infinitely distant target in the target system 18, and adjust the focusing system so that the target is clearly imaged in the fundus. After the alignment and focus adjustment are completed, the beacon light emitted by the beacon light source 6 and collimated by the beacon light collimation system 7 becomes a thin beam through the aperture control device 8, is reflected by the reflector 9, and then Reflected by the beam splitter 10, pass through the focusing system, and finally pass through the beam splitter 3, and enter the measured human eye 1; the beacon light scattered by the fundus of the measured human eye 1 passes through the beam splitter 3 and the focusing system, and then passes through the beam splitter The mirror 10 is reflected by the beam splitter 13 and enters the aperture matching system 14 and the reflector 15, and the outgoing light enters the Shack-Hartmann wavefront sensor 17 based on the microprism array, and the sensor 17 inputs the video signal output by the CCD into the computer 19 , the aberration of the human eye 1 to be measured is calculated by the computer 19 . Now, at the real focal plane of the aperture matching system 14, or the confocal filter diaphragm 16 at the common focal point of the front group lens 11 and the rear group lens 12 of the focusing system, only allow the scattered light of the fundus to pass through, so that the Corneal stray light filtering.

As shown in Fig. 3, the Shack-Hartmann wavefront sensor based on the microprism array is mainly composed of a microprism array 31 with a sawtooth phase grating structure, a Fourier lens (or imaging lens) 32 and a photoelectric coupling device (such as a CCD detector). ) 33, wherein the Fourier lens (or imaging lens) 32 is close to the microprism array 31, and the photocoupler device 33 is located on the focal plane of the Fourier lens (or imaging lens) 31.

The working principle of the human eye aberration Hartmann sensor based on the microprism array is: after the incident light beam passes through the microprism array 31, the light beams of each sub-aperture produce corresponding phase changes respectively, and pass through the Fourier lens ( or imaging lens) 32 imaging, and its light intensity distribution is detected by a photocoupler device 33 located on the focal plane of the Fourier lens (or imaging lens), and the light intensity distribution contains the phase information generated by the two-dimensional zigzag phase grating array. The phase changes produced by the sub-apertures are different, so a spot array is formed on the focal plane of the Fourier lens (or imaging lens), and the entire beam aperture is evenly divided. The spot array generated by standard plane wave incidence will be saved as calibration data.

When a wavefront with a certain aberration is incident, each local inclined plane wave produces a new additional phase to the two-dimensional zigzag phase grating in its sub-aperture, and the phase change will be reflected in the spot position of the focal plane of the Fourier lens (or imaging lens) Offset on.

The light spot signal received by the photoelectric coupling device 33 can be processed by a computer, using the centroid algorithm: the position (xi _, y _i ) of the light spot is calculated by the formula ①, and the wavefront error information of the full aperture is detected:

$x_i=\frac{\underset{m=1}{\overset{m}{\mathrm{\Σ}}}\underset{\mathrm{no}=1}{\overset{N}{\mathrm{\Σ}}}{x}_{\mathrm{nm}}{I}_{\mathrm{nm}}}{\underset{m=1}{\overset{m}{\mathrm{\Σ}}}\underset{\mathrm{no}=1}{\overset{N}{\mathrm{\Σ}}}{I}_{\mathrm{nm}}},{\mathrm{the\; y}}_i=\frac{\underset{m=1}{\overset{m}{\mathrm{\Σ}}}\underset{\mathrm{no}=1}{\overset{N}{\mathrm{\Σ}}}{\mathrm{the\; y}}_{\mathrm{nm}}{I}_{\mathrm{nm}}}{\underset{m=1}{\overset{m}{\mathrm{\Σ}}}\underset{\mathrm{no}=1}{\overset{N}{\mathrm{\Σ}}}{I}_{\mathrm{nm}}}$ ①

In the formula, m=1～M, n=1～N is that the sub-aperture maps to the corresponding pixel area on the photosensitive target surface 34 of the photocoupler device 33, and _{1 nm} is the (n, m)th on the photosensitive target surface 34 of the photocoupler device 33 ) the signal received by the pixel, x _nm and y _nm are the x-coordinate and y-coordinate of the (n, m)th pixel respectively.

Then calculate the wavefront slope g _xi and g _yi of the incident wavefront according to formula ②:

$g_{\mathrm{xi}}=\frac{\mathrm{\Δx}}{\mathrm{\λf}}=\frac{x_i-x_o}{\mathrm{\λf}},g_{\mathrm{yi}}=\frac{\mathrm{\Δy}}{\mathrm{\λf}}=\frac{{\mathrm{the\; y}}_i-{\mathrm{the\; y}}_o}{\mathrm{\λf}}$ ②

In the formula, (x ₀ , y ₀ ) is the reference position of the center of the spot obtained by calibrating the Hartmann sensor with a standard plane wave; when the Hartmann sensor detects wavefront distortion, the center of the spot is shifted to ( _xi , y _i ), completing the Hartmann sensor Signal detection by a Terman wavefront sensor.

Claims (5)

1. The human eye aberration and corneal surface measurement system based on the microprism array Shack-Hartmann wavefront sensor is characterized in that: it consists of a pupil or cornea lighting source (2), a beam splitter (3), and a pupil imaging Objective lens (4), CCD (5), beacon light source (6), beacon light collimation system (7), aperture control device (8), reflector (9), beam splitter (10), front group focusing Objective lens (11), rear group focusing objective lens (12), beam splitter (13), aperture matching system (14), mirror (15), Shaker-Hartmann wavefront sensor based on microprism array (17) , target system (18), computer (19) and additional measuring lens (20), wherein, pupil or corneal illumination light source (2) is positioned at human eye side front; Additional measuring lens (20) is close to human eye, and its focal point and cornea The focal points in the curved surface overlap; the beam splitter (3) is located in front of the human eye, the pupil imaging objective lens is located in the reflection direction of the beam splitter (3), and the CCD (5) is located on the focal plane of the pupil imaging objective lens; the beacon light source (6), the beacon Light collimation system (7), aperture control device (8), mirror (9), beam splitter (10), front group focusing objective lens (11), rear group focusing objective lens (12), beam splitter (3) Together form the beacon light input optical path; the beam splitter (13) and the target system (18) are placed in front of the beam splitter (10); the aperture matching system (14) is located in the beam reflection direction of the beam splitter (13), and the mirror (15 ) is located in the optical path of the aperture matching system (14); the Shack-Hartmann wavefront sensor (17) based on the microprism array is located at the optical path exit of the aperture matching system (14). 2. The human eye aberration and corneal surface measurement system based on the microprism array Shaker-Hartmann wavefront sensor according to claim 1, characterized in that: the microprism array-based Shaker-Hartmann wavefront sensor is characterized in that: The Hartmann wavefront sensor is mainly composed of a microprism array with a zigzag phase grating structure, a Fourier lens (or imaging lens) and a photoelectric coupling device (such as a CCD detector), where the Fourier lens (or imaging lens) is close to the microprism array , the photocoupler is located on the focal plane of the Fourier lens (or imaging lens). 3. The human eye aberration and corneal surface measurement system based on the microprism array Shaker-Hartmann wavefront sensor according to claim 1, characterized in that: the beacon light beam is changed by the aperture control device (8) caliber. 4. The human eye aberration and corneal surface measurement system based on the microprism array Shack-Hartmann wavefront sensor according to claim 1, characterized in that: the system field of view diaphragm surface or the field of view diaphragm is real The image plane is also provided with a confocal filter diaphragm (16). 5. The human eye aberration and corneal surface measurement system based on the microprism array Shack-Hartmann wavefront sensor according to claim 4, characterized in that: the confocal filter diaphragm (16) is set It is located at the common focal point of the front lens group and the rear lens group of the aperture matching system (14) or at the common focal point of the front lens group (11) and the rear lens group (12) of the focusing system.

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