CN114366019B - System and method for measuring eyeball parameters - Google Patents
System and method for measuring eyeball parameters Download PDFInfo
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Abstract
The invention provides a system and a method for measuring eyeball parameters, which comprises the following steps: the low coherence measurement unit is used for obtaining a low coherence interference signal spectrum related to the thickness of each tissue in the eye axis direction of the eyeball to be measured, and the low coherence interference signal spectrum comprises a plurality of interference peaks; the long coherence measurement unit is used for obtaining a long coherence interference signal spectrum with approximate equal amplitude; an interference signal synchronization unit for synchronizing the low coherence measurement unit and the long coherence measurement unit; the eyeball imaging unit is used for acquiring a surface image of an eyeball to be detected; the signal processing and control unit is respectively electrically connected with the low coherence measurement unit, the long coherence measurement unit and the eyeball imaging unit, and measures the distance between low coherence interference peaks in the low coherence interference signal spectrum according to the long coherence interference signal spectrum so as to obtain eyeball parameters in the eye axis direction of the eyeball to be measured; and simultaneously, analyzing the surface image of the eyeball to be detected according to a digital image processing technology to obtain the transverse eyeball parameters of the eyeball to be detected.
Description
Technical Field
The invention relates to the technical field of optical measurement, in particular to a system and a method for measuring eyeball parameters.
Background
Many clinical ophthalmic diseases such as glaucoma, myopia, cataract and the like can cause the change of parameters of an eyeball, and at present, the total myopia rate of children and teenagers in China in 2018 is 53.6% according to the data display of the national health committee. The myopia degree is positively correlated with the length of the axis of the eye, and is an important basis for distinguishing true myopia from pseudomyopia. Monitoring the axial length of the eyes of children and teenagers helps to prevent and treat myopia and its related ophthalmic diseases. Meanwhile, with the continuous development of science and technology, the cataract surgery mode is gradually changed from the traditional resurgence surgery into the refractive surgery with better effect, but 20% -40% of cataract patients still have the prediction refractive power error larger than +/-0.50D in China after surgery, the measurement of the length of the eye axis is a key factor influencing the error, the accurate measurement of eyeball parameters before surgery is more and more important, and the accuracy of the measurement of the length of the eye axis closely influences the refractive error after surgery.
The cornea and the pupil are also important components of the human eye, the cornea is a transparent refraction medium in front of the human eye and provides about 70 percent of refractive power for the human eye, and the measurement of the curvature of the cornea can not only guide the corneal diopter correction operation and judge whether the human eye has astigmatism, but also provide scientific basis for people to wear a corneal contact lens; the size of the pupil diameter can be used as the basis for judging eye diseases and can also indirectly reflect the change process of human physiology and psychology. Therefore, it is important to obtain accurate parameters of the eyeball, such as axial length, corneal thickness, anterior chamber depth, lens thickness, corneal curvature, pupil diameter, etc., in the process of preventing, diagnosing and treating ophthalmic diseases.
The existing eyeball parameter measuring means are divided into an ultrasonic measuring method and an optical measuring method according to different technologies. The ultrasonic measurement method has the advantages of low price and convenient carrying, but because of the factors of low resolution, need of contact detection and complex operation, the ocular surface anesthesia is needed before measurement, the pressure of the contact angle membrane of the measurement probe influences the measurement result, the measurement precision is low, and the cornea is easily damaged and infected. Meanwhile, the measurement result is easily influenced by the subjectivity of an operator and only can realize the measurement of parameters in the visual axis direction of the eyeball, namely the length of the visual axis, the thickness of the cornea and the like; in contrast, the optical measurement method has the advantages of non-contact, high precision, simple operation and the like, the accuracy and the repeatability of the measurement result are superior to those of the ultrasonic measurement method, and meanwhile, some limitations in the ultrasonic measurement method, such as susceptibility, are avoided. The traditional optical measurement method mainly measures the length of an eye axis through time domain optical coherence tomography, and the one-dimensional optical imaging biological measurement method has the limitations of slow scanning rate, incapability of fixing vision, capability of only realizing measurement of parameters in the eye visual axis direction and the like.
In view of the above, there is a need for a system and method that can simultaneously measure axial and lateral parameters of an eyeball.
Disclosure of Invention
The invention aims to provide a system and a method for measuring eyeball parameters, which solve the problem that the conventional eyeball parameter measuring means cannot measure axial parameters and transverse parameters of eyeballs at the same time.
In order to achieve the above object, the present invention provides an eyeball parameter measurement system, comprising:
the low coherence measurement unit is used for obtaining a low coherence interference signal spectrum related to the thickness of each tissue in the eye axis direction of the eyeball to be measured, and the low coherence interference signal spectrum comprises a plurality of interference peaks;
the long coherence measurement unit is used for obtaining a long coherence interference signal spectrum with approximate equal amplitude;
an interference signal synchronization unit for synchronizing the low coherence measurement unit and the long coherence measurement unit;
the eyeball imaging unit is used for acquiring a surface image of an eyeball to be detected;
the signal processing and control unit is respectively and electrically connected with the low coherence measuring unit, the long coherence measuring unit and the eyeball imaging unit; the signal processing and control unit is used for: measuring the distance between low coherent interference peaks in the low coherent interference signal spectrum according to the long coherent interference signal spectrum, and calculating eyeball parameters in the eyeball axis direction to be detected according to the distance; and analyzing the surface image of the eyeball to be detected according to a digital image processing technology to obtain the transverse eyeball parameters of the eyeball to be detected.
Optionally, the low coherence measurement unit comprises:
the broadband light source is electrically connected with the signal processing and controlling unit and is used for sending broadband light signals;
the guide light source is electrically connected with the signal processing and control unit and is used for sending out a guide light signal;
the input end of the first single-mode fiber coupler is respectively connected with the broadband light source and the guide light source, and the output end of the first single-mode fiber coupler outputs a coupled optical signal;
the second single-mode fiber coupler is connected with the output end of the first single-mode fiber coupler and is used for dividing the coupled optical signal into a low-coherence reference optical signal, a low-coherence zero optical signal and a low-coherence sample optical signal; the low-coherence reference optical signal returns to the second single-mode optical fiber coupler after being subjected to optical signal delay by the interference signal synchronization unit; the low-coherence zero-point optical signal is reflected back to the second single-mode fiber coupler through the Faraday mirror and interferes with the returned low-coherence reference optical signal to generate a reference zero-point interference signal; the low-coherence sample optical signal returns to the second single-mode optical fiber coupler after being reflected by each tissue interface of the eyeball to be detected, and interferes with the returned low-coherence reference optical signal to generate a reference sample interference signal;
and the balance photoelectric detector is connected with the second single-mode fiber coupler, receives the reference zero interference signal and the reference sample interference signal, respectively converts the reference zero interference signal and the reference sample interference signal into electric signals and transmits the electric signals to the signal processing and control unit.
Optionally, the low coherence measurement unit further comprises: the first polarization controller, the optical fiber wavelength division multiplexer and the optical fiber collimator are sequentially arranged on a low-coherence reference optical signal optical path;
the first optical fiber matcher and the Faraday mirror are sequentially arranged on a low-coherence zero-point optical signal optical path;
the second polarization controller, the second optical fiber matcher and the eyeball focus tracking module are sequentially arranged on the optical signal path of the low-coherence sample.
Optionally, the eyeball focus tracking module comprises:
the focusing lens control system comprises a servo motor and a focusing lens arranged on the servo motor, wherein the servo motor is in control connection with the signal processing and control unit, and the servo motor is used for driving the focusing lens to move axially.
Optionally, the long coherence measurement unit comprises:
the narrow-band light source is electrically connected with the signal processing and controlling unit and is used for emitting a narrow-band light signal;
the third single-mode fiber coupler is connected with the output end of the narrow-band light source and is used for splitting the narrow-band light signal into a long coherent reference light signal and a long coherent measurement light signal; the long coherent reference optical signal returns to the third single-mode fiber coupler through the reflecting film; the long coherent measurement optical signal is delayed by the interference signal synchronization unit, returns to the third single-mode fiber coupler and interferes with the returned long coherent reference optical signal to generate a reference measurement interference signal;
and the Si photoelectric detector is connected with the third single-mode fiber coupler, receives the reference measurement interference signal, converts the reference measurement interference signal into an electric signal and transmits the electric signal to the signal processing and control unit.
Optionally, the long coherence measuring unit further comprises: a reflective film disposed on an optical path of the long coherent reference light signal;
and the optical fiber wavelength division multiplexer and the optical fiber collimator are sequentially arranged on the optical path of the long coherence measurement optical signal.
Optionally, the interference signal synchronization unit includes: the device comprises a base, a rotating disc, a direct current brushless disc type motor, a plurality of adjusting frames, a plurality of hollow roof prism reflectors and a plane reflector;
the rotating disk and the direct current brushless disk type motor are both arranged on the base, and the rotating disk is arranged on the direct current brushless disk type motor; the direct current brushless disk type motor is in control connection with the signal processing and control unit and is used for driving the rotating disk to rotate;
the plurality of adjusting frames are uniformly fixed on the rotating disc, the plurality of hollow roof prism reflectors are respectively arranged on the plurality of adjusting frames, and the hollow roof prisms are used for refracting incident optical signals;
the plane mirror is arranged on the base and used for reflecting incident optical signals.
Optionally, the eyeball imaging unit comprises:
the illumination plate is in control connection with the signal processing and control unit through an illumination plate control circuit and is used for generating imaging light and irradiating the imaging light on the eyeball to be detected;
the spectroscope and the imaging objective lens are sequentially arranged on a light path of light reflected by the eyeball to be detected and are used for generating a surface image of the eyeball to be detected on the imaging objective lens;
and the image sensor is arranged in parallel with the imaging objective lens and electrically connected with the signal processing and control unit, and is used for collecting the surface image of the eyeball to be detected.
In another aspect, the present invention further provides a method for measuring eyeball parameters, applying the measurement system as described above, including the following steps:
obtaining a low coherence interference signal spectrum related to the thickness of each tissue in the eye axis direction of an eyeball to be detected by using a low coherence measurement unit, wherein the low coherence interference signal spectrum comprises a plurality of interference peaks;
obtaining a long coherent interference signal spectrum with approximate equal amplitude by using a long coherent measurement unit;
acquiring a surface image of an eyeball to be detected by using an eyeball imaging unit;
measuring the distance between low coherence interference peaks in the low coherence interference signal spectrum according to the long coherence interference signal spectrum, and calculating eyeball parameters in the direction of the eyeball axis to be detected according to the distance;
and analyzing the surface image of the eyeball to be measured according to a digital image processing technology, and measuring to obtain the transverse eyeball parameters of the eyeball to be measured.
Optionally, the measuring method further comprises: synchronizing the low coherence measurement unit and the long coherence measurement unit with an interference signal synchronization unit.
According to the specific invention content provided by the invention, the invention discloses the following technical effects:
the invention provides a system and a method for measuring eyeball parameters, which comprises the following steps: the low coherence measurement unit is used for obtaining a low coherence interference signal spectrum related to the thickness of each tissue in the eye axis direction of the eyeball to be measured, and the low coherence interference signal spectrum comprises a plurality of interference peaks; the long coherence measurement unit is used for obtaining a long coherence interference signal spectrum with approximate equal amplitude; an interference signal synchronization unit that synchronizes the low coherence measurement unit and the long coherence measurement unit; the eyeball imaging unit is used for acquiring a surface image of an eyeball to be detected; the signal processing and control unit is respectively electrically connected with the low coherence measurement unit, the long coherence measurement unit and the eyeball imaging unit, and measures the distance between low coherence interference peaks in a low coherence interference signal spectrum according to the long coherence interference signal spectrum so as to obtain eyeball parameters in the eye axis direction of the eyeball to be measured; and analyzing the surface image of the eyeball to be detected according to a digital image processing technology to obtain the transverse eyeball parameters of the eyeball to be detected. The measuring system and the measuring method provided by the invention adopt an optical interferometry to measure the parameters of the eyeball to be measured in the visual axis direction, and simultaneously measure the transverse parameters of the eyeball to be measured according to the imaging principle and the digital image processing technology.
In addition, because the low coherence measurement unit and the long coherence measurement unit are synchronized through a rotary optical delay line, interference signals generated by the low coherence measurement unit and the long coherence measurement unit have synchronism, the distance between two adjacent weak coherence interference peaks can be obtained through an interference ranging method, namely, the periodicity of the long coherence interference signal between two adjacent low coherence interference peaks is calculated, and further, the thickness information of each tissue layer in the visual axis direction of the human eye can be accurately obtained.
Furthermore, the Faraday mirror is adopted in the optical path of the interference system, so that the change of the polarization state caused by thermal disturbance and mechanical disturbance in the optical fiber can be reduced to the greatest extent, the control of the polarization state of the interference system is facilitated, and the interference signal intensity and the signal-to-noise ratio of a measurement result are improved.
Furthermore, the invention adopts a rotary optical delay line, controls the hollow roof prism reflector on the rotating disc to rotate through the direct-current brushless disc type motor, changes the optical path of the reference optical path, realizes the scanning of different layers of human eyes, and obtains the thickness information of each layer in the visual axis direction of the human eyes through one-time scanning; the hollow roof ridge prism reflector consists of two right-angle prisms and a rectangular substrate, has extremely high surface flatness and good optical performance, and has excellent light transmission and extremely low fluorescence intensity in the whole spectral range. Meanwhile, the inclined planes of the right-angle prisms are plated with silver films with metal protection layers, the high reflectivity is achieved in visible light and near infrared wave bands, the inclined planes of the two prisms are oppositely arranged, and the dihedral angle is 90 degrees. The hollow roof prism reflector can reflect light incident to the inclined edge of the prism from the outside, and the hollow roof prism reflector is different from a plane reflector in that reflected light is still parallel to incident light, so that the influence of light beam interference is avoided. Moreover, the direct-current brushless disk type motor adopted by the invention is provided with a built-in encoder and is used for accurate displacement calibration; the motor has the characteristics of compact structure, high dynamic, high efficiency and stable operation, and the disc structure provides convenience for the connection of the motor and the base.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required in the embodiments will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a block diagram of a system for measuring eyeball parameters, provided in embodiment 1 of the present invention;
fig. 2 is a flowchart of a method for measuring eyeball parameters, according to embodiment 2 of the present invention;
fig. 3 is a schematic structural diagram of an eyeball parameter measurement system provided in embodiment 3 of the present invention;
fig. 4 is a schematic structural diagram of a rotating optical delay line according to embodiment 3 of the present invention;
fig. 5 is a schematic structural diagram of an eyeball focus tracking module according to embodiment 3 of the present invention;
fig. 6 is a structural diagram of different tissue interfaces in the visual axis direction and the transverse direction of an eyeball in the measurement method provided in embodiment 3;
fig. 7 (a) is a spectrum of a low coherence interference signal generated by a low coherence measurement unit provided in embodiment 3 of the present invention;
fig. 7 (b) is a spectrum of a long coherence interference signal generated by the long coherence measurement unit provided in embodiment 3 of the present invention;
fig. 8 is a schematic diagram of measuring the distance between interference peaks of each interface in the visual axis direction of the eyeball tissue according to the long coherent interference signal in the measurement method provided in embodiment 3 of the present invention.
Description of the symbols:
1: a broadband light source; 2: a guiding light source; 3: a narrow band light source; 4: a Si photodetector; 5: a balanced photodetector; 6:2 × 1 single mode fiber coupler; 7:3 × 3 single mode fiber coupler; 8: a fiber wavelength division multiplexer; 9:2 × 2 single-mode fiber couplers; 10: an optical fiber collimator; 11: a rotating optical delay line; 12: a plane mirror; 13: a first double-paddle optical fiber polarization controller; 14: a second double-oar fiber polarization controller; 15: a first optical fiber matcher; 16: a Faraday mirror; 17: a second optical fiber matcher; 18: a focusing lens; 19: a stepping motor; 20: a beam splitter; 21: an imaging objective lens; 22: a CMOS;23: a lighting panel; 24: a human eye to be detected; 25: a lighting panel control circuit; 26: a power supply module; 27: a signal processing and control unit; 28: a laser driving module; 29: a computer; 30: a base; 31: rotating the disc; 32: a hollow roof prism reflector; 33: a DC brushless disk motor; 34: an adjusting frame; 35: an imaging unit; 36: human eye optical system model.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention aims to provide a system and a method for measuring eyeball parameters, which solve the problem that the conventional eyeball parameter measuring means cannot measure axial parameters and transverse parameters of eyeballs at the same time.
In order to make the aforementioned objects, features and advantages of the present invention more comprehensible, the present invention is described in detail with reference to the accompanying drawings and the detailed description thereof.
Example 1:
as shown in fig. 1, the present invention provides an eyeball parameter measurement system, which includes:
the low coherence measurement unit is used for obtaining a low coherence interference signal spectrum related to the thickness of each tissue in the eye axis direction of the eyeball to be measured, and the low coherence interference signal spectrum comprises a plurality of interference peaks;
the long coherence measurement unit is used for obtaining a long coherence interference signal spectrum with approximate equal amplitude;
an interference signal synchronization unit for synchronizing the low coherence measurement unit and the long coherence measurement unit;
the eyeball imaging unit is used for acquiring a surface image of an eyeball to be detected;
the signal processing and control unit is respectively and electrically connected with the low coherence measuring unit, the long coherence measuring unit and the eyeball imaging unit; the signal processing and control unit is used for: measuring the distance between low coherence interference peaks in the low coherence interference signal spectrum according to the long coherence interference signal spectrum, and calculating eyeball parameters in the direction of the eyeball axis to be detected according to the distance; and analyzing the surface image of the eyeball to be detected according to a digital image processing technology to obtain the transverse eyeball parameters of the eyeball to be detected.
In order to improve the anti-interference performance of the system and the convenience of an optical path, single-film optical fiber coupling is adopted in the optical path part, and the single-film optical fiber is used as a conducting medium of the optical path; in order to adjust the optical path, a He-Ne laser is adopted as the guide light in the low-coherence system, and the light emitted by the He-Ne laser and the low-coherence light emitted by the SLED broadband light source enter the system after passing through a fiber coupler. In particular, the low coherence measurement unit comprises in turn:
the broadband light source is selected from the SLED broadband light source, is electrically connected with the signal processing and control unit and is used for emitting broadband light signals;
a guiding light source, which is selected from a He-Ne laser in the embodiment and is electrically connected with the signal processing and controlling unit and used for sending out a guiding light signal;
a first single-mode fiber coupler, in this embodiment, a 2 × 1 single-mode fiber coupler is selected, two input ends of the 2 × 1 single-mode fiber coupler are respectively connected to the broadband light source and the guiding light source, and an output end of the first single-mode fiber coupler outputs a coupled optical signal;
a second single-mode fiber coupler, in this embodiment, a 3 × 3 single-mode fiber coupler is selected, connected to the output end of the first single-mode fiber coupler, and configured to divide the coupled optical signal into a low-coherence reference optical signal, a low-coherence zero-point optical signal, and a low-coherence sample optical signal; the low-coherence reference optical signal returns to the second single-mode optical fiber coupler after being subjected to optical signal delay by the interference signal synchronization unit; the low-coherence zero-point optical signal is reflected back to the second single-mode fiber coupler through the Faraday mirror and interferes with the returned low-coherence reference optical signal to generate a reference zero-point interference signal; the low-coherence sample optical signal returns to the second single-mode optical fiber coupler after being reflected by each tissue interface of the eyeball to be detected, and interferes with the returned low-coherence reference optical signal to generate a reference sample interference signal;
and the balance photoelectric detector is connected with the second single-mode fiber coupler, receives the reference zero interference signal and the reference sample interference signal, converts the reference zero interference signal and the reference sample interference signal into electric signals respectively, and transmits the electric signals to the signal processing and control unit.
In a further configuration, the low coherence measurement unit further includes: the first polarization controller, the optical fiber wavelength division multiplexer and the optical fiber collimator are sequentially arranged on a low-coherence reference optical signal optical path;
the first optical fiber matcher and the Faraday mirror are sequentially arranged on a low-coherence zero-point optical signal optical path;
the second polarization controller, the second optical fiber matcher and the eyeball focus tracking module are sequentially arranged on the optical signal path of the low-coherence sample.
Because measuring light is in the transmission of people's eye, the absorption characteristic that the eye tissue was to the light leads to the decay of light signal, makes each tissue interface reflection signal of people's eye reduce, is unfavorable for interference signal's collection, consequently, utilizes servo motor and focusing lens to design eyeball focus and has tracked the module, and eyeball focus is tracked the module and includes:
the focusing lens control system comprises a servo motor and a focusing lens arranged on the servo motor, wherein the servo motor is in control connection with the signal processing and control unit, and the servo motor is used for driving the focusing lens to move axially.
In order to distinguish from a low coherence measurement unit and satisfy a requirement that a coherence length is larger than an amount of variation in optical path length of an interference signal synchronization unit, the long coherence measurement unit includes:
the narrow-band light source is electrically connected with the signal processing and controlling unit and is used for emitting a narrow-band light signal;
a third single-mode fiber coupler, in this embodiment, a 2 × 2 single-mode fiber coupler is selected, connected to the output end of the narrowband light source, and configured to split the narrowband optical signal into a long coherent reference optical signal and a long coherent measurement optical signal; the long coherent reference optical signal passes through the reflecting film and returns to a third single-mode fiber coupler; the long coherent measurement optical signal is delayed by the interference signal synchronization unit 3, returns to the third single-mode fiber coupler, interferes with the returned long coherent reference optical signal, and generates a reference measurement interference signal;
and the Si photoelectric detector is connected with the third single-mode fiber coupler, receives the reference measurement interference signal, converts the reference measurement interference signal into an electric signal and transmits the electric signal to the signal processing and control unit.
In a further aspect, the long coherence measuring unit further includes: a reflective film disposed on an optical path of the long coherent reference light signal;
and the optical fiber wavelength division multiplexer and the optical fiber collimator are sequentially arranged on the optical path of the long-coherence measurement optical signal.
Optionally, the interference signal synchronization unit includes: the device comprises a base, a rotating disc, a direct current brushless disc type motor, a plurality of adjusting frames, a plurality of hollow roof prism reflectors and a plane reflector;
the rotating disk and the direct current brushless disk type motor are both arranged on the base, and the rotating disk is arranged on the direct current brushless disk type motor; the direct current brushless disk type motor is in control connection with the signal processing and control unit and is used for driving the rotating disk to rotate;
the plurality of adjusting frames are uniformly fixed on the rotating disc, the plurality of hollow roof prism reflectors are respectively arranged on the plurality of adjusting frames, and the hollow roof prisms are used for refracting incident optical signals;
the plane mirror is arranged on the base and used for reflecting incident optical signals.
Be convenient for gather the surface image of the eyeball that awaits measuring, eyeball imaging unit includes:
the illumination plate is in control connection with the signal processing and control unit through an illumination plate control circuit and is used for generating imaging light and irradiating the imaging light on the eyeball to be detected;
the spectroscope and the imaging objective lens are sequentially arranged on a light path of light reflected by the eyeball to be detected and are used for generating a surface image of the eyeball to be detected on the imaging objective lens;
and the image sensor is arranged in parallel with the imaging objective lens and electrically connected with the signal processing and control unit, and is used for collecting the surface image of the eyeball to be detected.
Example 2:
as shown in fig. 2, the present invention also provides an eyeball parameter measurement method corresponding to the eyeball parameter measurement system of the embodiment 1, the measurement system of the embodiment 1 is applied, and the method comprises the following steps:
s1, obtaining a low coherence interference signal spectrum related to the thickness of each tissue in the eye axis direction of an eyeball to be detected by using a low coherence measurement unit, wherein the low coherence interference signal spectrum comprises a plurality of interference peaks;
s2, obtaining a long coherent interference signal spectrum with approximate equal amplitude by using a long coherent measurement unit;
s3, obtaining a surface image of the eyeball to be detected by using the eyeball imaging unit;
s4, measuring the distance between low coherence interference peaks in the low coherence interference signal spectrum according to the long coherence interference signal spectrum, and calculating eyeball parameters in the eyeball axis direction to be detected according to the distance;
and S5, analyzing the surface image of the eyeball to be measured according to the digital image processing technology, and measuring to obtain the transverse eyeball parameters of the eyeball to be measured.
In order to make the interference signals generated by the low coherence measuring unit and the long coherence measuring unit synchronous, the distance between low coherence interference peaks can be calculated by adopting an interference ranging method, and the low coherence measuring unit and the long coherence measuring unit are synchronized by using an interference signal synchronizing unit.
Example 3:
as shown in fig. 3, a specific example is used in this embodiment to describe and verify the effect achieved by the measurement method provided by the present invention in detail.
Selecting SLED broadband light source 1 with wavelength of 1060nm and bandwidth of 3dB of 60nm, certainly using broadband light source meeting requirements, after the low coherent light emitted by SLED broadband light source 1 and the guide light emitted by He-Ne laser 2 pass through 2 × 1 single-mode optical fiber coupler 6, and then pass through 3 × 3 single-mode optical fiber coupler 7 to be divided into a measuring light source reference light path, a measuring light source zero light path and a measuring light source sample light path; wherein, the light path of the measurement light source sample passes through the first double-oar optical fiber polarization controller 13 and the second optical fiber matcher 17, then passes through the movable focusing lens 18, and then is focused to each interface of eye tissues and returns; a reference light path of a measurement light source enters the optical fiber collimator 10 after passing through the optical fiber wavelength division multiplexer 8 of the second double-paddle optical fiber polarization controller 14, light emitted by the optical fiber collimator 10 enters the rotary optical delay line 11, the structure of the rotary optical delay line is shown in figure 4, the light emitted by the optical fiber collimator 10 passes through a hollow ridge prism reflector 32 distributed on the rotary optical delay line 11 and then is emitted to a plane reflector 12 installed on a base 30, light reflected by the plane reflector 12 returns according to an original light path and interferes with light reflected by each interface of human eye tissues in a 3 x 3 single-mode optical fiber coupler 7, and an interference signal is received by a balance photoelectric detector 5; a first optical fiber matcher 15 and a Faraday mirror 16 are arranged on a zero-point light path of the measuring light source, incident light is reflected by the Faraday mirror 16, reflected light returns according to an original light path, interference is generated in the 3 × 3 single-mode fiber coupler 7 with light returned by a reference light path of the measuring light source, and interference signals are received by the balance photoelectric detector 5; the interference signal received by the balance detector 5 is subjected to signal processing by the signal processing and control unit 27 and then output to the computer 29.
The long coherent light source adopts a narrow-band light source 3, and in order to be separated from the low coherent light source and meet the requirement that the coherent length is larger than the optical path variation of the optical delay line, a DFB laser with the wavelength of 1310nm and the bandwidth of 1.1GHz is selected; the light emitted by the narrow-band light source 3 is divided into a measuring light path and a reference light path of a long coherent interference system by the 2 x 2 single-mode fiber coupler 9, wherein the reference light path is reflected back to the 2 x 2 single-mode fiber coupler 9 by a reflection film at the end of a single-mode fiber, the measuring light path enters the rotary optical delay line 11 by the fiber wavelength division multiplexer 8 and the fiber collimator 10, passes through the hollow roof prism reflector 32 distributed on the rotary optical delay line 11 and then is emitted to the plane reflector 12 arranged on the base 30, the light reflected by the plane reflector 12 returns according to the original light path, the reflected light and the return light of the reference light path interfere in the 2 x 2 single-mode fiber coupler 9, the interference signal is received by the Si photoelectric detector 4, the interference signal received by the detector is processed by the signal processing and controller 27, and a sine wave with approximately equal amplitude is formed after the signal processing.
The imaging unit 35 comprises an illuminating plate 23, a spectroscope 20, an imaging objective lens 21, a CMOS module 22 and a human eye 24 to be measured, wherein the illuminating plate 23 is connected with an illuminating plate control circuit 25, the illuminating plate control circuit 25 controls a light source of the illuminating plate, light emitted by the illuminating plate irradiates the human eye 24 to be measured, the light reflected by the cornea of the human eye is split by the spectroscope 20 to form an image on the imaging objective lens 21, a human eye image is collected by the CMOS module 22 and is transmitted to the signal processing and control device 27 and the computer 29, and the measurement of transverse parameters such as eyeball cornea curvature and the like is realized through a digital image processing technology and an interference distance measuring technology.
The low coherence measurement unit and the long coherence measurement unit share one rotary optical delay line 11, and the generated interference signals have synchronism, so that the distance between two adjacent weak coherence interference peaks can be obtained by calculating the periodicity of the long coherence interference signal between two adjacent low coherence interference peaks by an interference ranging method, and further the thickness information of each tissue layer in the visual axis direction of the human eye can be obtained.
In the system, an optical interference method, an interference distance measuring method and a digital image processing technology are adopted, and an eyeball focus tracking module is designed, as shown in fig. 5, the eyeball focus tracking module comprises a focusing lens 18, a servo motor 19 and an eye optical system model 36, in the embodiment, the eye optical system model 36 is a human eye 24 to be measured, wherein the focusing lens 18 is movable, the servo motor 19 is controlled to axially move at a set speed through a signal processing and controller 27, and the distance between the focusing lens 18 and incident light of a second optical fiber matcher 17 is controlled, so that the purpose of adjusting the focusing of the incident light on each layer of human eye tissue is achieved, and further, the interference signal intensity and the system signal-to-noise ratio are improved. The signal-to-noise ratio and the measurement precision of the system are improved; the rotary optical delay line designed by the hollow roof prism reflector and the direct-current disc type brushless motor improves the measurement speed of the system.
FIG. 6 is a view showing the structure of different tissue interfaces in the visual axis direction and the transverse direction of the eyeball; where AL eye axis length, CCT is corneal thickness, AD is anterior chamber depth, LT is lens thickness, VT is vitreous thickness, PD is pupil diameter, WTW is white-to-white distance, and K is corneal curvature.
Fig. 7 shows an interference signal spectrum generated by the measurement system provided in the present embodiment, in which fig. 7 (a) is a long coherent interference waveform generated by a long coherent measurement unit, an output waveform is approximate to a sine waveform with equal amplitude due to a narrow spectral line width of a light source adopted by the long coherent measurement unit, and fig. 7 (b) is an interference waveform of each tissue layer in the visual axis direction of the eyeball generated by a low coherent measurement unit acquired by an oscilloscope, and amplitudes of the generated interference signals are different because intensities of reflected signals of the tissue layers are different. FIG. 8 is a schematic diagram of measuring the distance between the interference peaks of the interfaces in the visual axis direction of the eyeball tissue according to the long coherent interference signal.
Portions of the technology may be considered "articles of manufacture" or "articles of manufacture" in the form of executable code and/or associated data embodied in or carried out by a computer readable medium. Tangible, non-transitory storage media may include memory or storage for use by any computer, processor, or similar device or associated module. For example, various semiconductor memories, tape drives, disk drives, or any similar device capable of providing a storage function for software.
All or a portion of the software may sometimes communicate over a network, such as the internet or other communication network. Such communication may load software from one computer device or processor to another. For example: from a server or host computer of the video object detection device to a hardware platform of a computer environment, or other computer environment implementing a system, or similar functionality related to providing information needed for object detection. Thus, another medium capable of transferring software elements may also be used as a physical connection between local devices, such as optical, electrical, electromagnetic waves, etc., propagating through cables, optical cables, air, etc. The physical medium used for the carrier wave, such as an electric, wireless or optical cable or the like, may also be considered as the medium carrying the software. As used herein, unless limited to a tangible "storage" medium, other terms referring to a computer or machine "readable medium" refer to media that participate in the execution of any instructions by a processor.
The principles and embodiments of the present invention have been described herein using specific examples, which are provided only to help understand the method and the core concept of the present invention; it will be understood by those skilled in the art that the above-described modules or steps of the present invention may be implemented by a general-purpose computer device, and alternatively, they may be implemented by program code executable by a computing device, such that they may be stored in a storage device and executed by the computing device, or separately fabricated into individual integrated circuit modules, or multiple modules or steps thereof may be fabricated into a single integrated circuit module. The present invention is not limited to any specific combination of hardware and software.
Meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.
Claims (6)
1. A system for measuring an eye globe parameter, the system comprising:
the low coherence measurement unit is used for obtaining a low coherence interference signal spectrum related to the thickness of each tissue in the eye axis direction of the eyeball to be measured, and the low coherence interference signal spectrum comprises a plurality of interference peaks;
the long coherence measurement unit is used for obtaining a long coherence interference signal spectrum with approximate equal amplitude;
an interference signal synchronization unit for synchronizing the low coherence measurement unit and the long coherence measurement unit; the interference signal synchronization unit includes: the device comprises a base, a rotating disc, a direct current brushless disc type motor, a plurality of adjusting frames, a plurality of hollow roof prism reflectors and a plane reflector;
the rotating disk and the direct current brushless disk type motor are both arranged on the base, and the rotating disk is arranged on the direct current brushless disk type motor; the direct current brushless disk type motor is in control connection with the signal processing and control unit and is used for driving the rotating disk to rotate;
the plurality of adjusting frames are uniformly fixed on the rotating disc, the plurality of hollow roof prism reflectors are respectively arranged on the plurality of adjusting frames, and the hollow roof prism reflectors are used for refracting incident optical signals; the hollow roof prism reflector is composed of two right-angle prisms and a rectangular substrate, has extremely high surface flatness and good optical performance, and has high reflectivity in visible light and near infrared bands due to the fact that the silver film with a metal protective layer is plated on the inclined surface of the right-angle prism;
the plane mirror is arranged on the base and used for reflecting incident optical signals;
the eyeball imaging unit is used for acquiring a surface image of an eyeball to be detected;
the signal processing and control unit is respectively and electrically connected with the low coherence measurement unit, the long coherence measurement unit and the eyeball imaging unit; the signal processing and control unit is used for: measuring the distance between low coherence interference peaks in the low coherence interference signal spectrum according to the long coherence interference signal spectrum, and calculating eyeball parameters in the direction of the eyeball axis to be detected according to the distance; analyzing the surface image of the eyeball to be detected according to a digital image processing technology to obtain the transverse eyeball parameter of the eyeball to be detected;
the low coherence measurement unit includes:
the broadband light source is electrically connected with the signal processing and controlling unit and is used for sending broadband light signals;
the guide light source is electrically connected with the signal processing and control unit and is used for sending out a guide light signal; a He-Ne laser is used as a guide light source;
the input end of the first single-mode fiber coupler is respectively connected with the broadband light source and the guide light source, and the output end of the first single-mode fiber coupler outputs a coupled optical signal;
the second single-mode fiber coupler is connected with the output end of the first single-mode fiber coupler and is used for dividing the coupled optical signal into a low-coherence reference optical signal, a low-coherence zero-point optical signal and a low-coherence sample optical signal; the low-coherence reference optical signal returns to the second single-mode optical fiber coupler after being subjected to optical signal delay by the interference signal synchronization unit; the low-coherence zero-point optical signal is reflected back to the second single-mode fiber coupler through the Faraday mirror and interferes with the returned low-coherence reference optical signal to generate a reference zero-point interference signal; the low-coherence sample optical signal returns to the second single-mode fiber coupler after being reflected by each tissue interface of the eyeball to be detected, and interferes with the returned low-coherence reference optical signal to generate a reference sample interference signal;
the balance photoelectric detector is connected with the second single-mode fiber coupler, receives the reference zero interference signal and the reference sample interference signal, respectively converts the reference zero interference signal and the reference sample interference signal into electric signals and transmits the electric signals to the signal processing and control unit;
the low coherence measurement unit further comprises: the first polarization controller, the optical fiber wavelength division multiplexer and the optical fiber collimator are sequentially arranged on a low-coherence reference optical signal optical path;
the first optical fiber matcher and the Faraday mirror are sequentially arranged on a low-coherence zero-point optical signal optical path;
the second polarization controller, the second optical fiber matcher and the eyeball focus tracking module are sequentially arranged on the optical signal path of the low-coherence sample.
2. The measurement system of claim 1, wherein the eye focus tracking module comprises:
the servo motor is in control connection with the signal processing and control unit, and the servo motor is used for driving the focusing lens to move axially.
3. The measurement system of claim 1, wherein the long coherence measurement unit comprises:
a reflective film disposed on an optical path of the long coherent reference light signal;
the optical fiber wavelength division multiplexer and the optical fiber collimator are sequentially arranged on the optical path of the long coherence measurement optical signal;
the narrow-band light source is electrically connected with the signal processing and controlling unit and is used for emitting a narrow-band light signal;
the third single-mode fiber coupler is connected with the output end of the narrow-band light source and is used for splitting the narrow-band light signal into a long coherent reference light signal and a long coherent measurement light signal; the long coherent reference optical signal returns to the third single-mode fiber coupler through the reflecting film; the long coherent measurement optical signal returns to the third single-mode optical fiber coupler after being subjected to optical signal delay through the interference signal synchronization unit, and interferes with the returned long coherent reference optical signal to generate a reference measurement interference signal;
and the Si photoelectric detector is connected with the third single-mode fiber coupler, receives the reference measurement interference signal, converts the reference measurement interference signal into an electric signal and transmits the electric signal to the signal processing and control unit.
4. The measurement system of claim 1, wherein the eye imaging unit comprises:
the illumination plate is in control connection with the signal processing and control unit through an illumination plate control circuit and is used for generating imaging light and irradiating the imaging light on the eyeball to be detected;
the spectroscope and the imaging objective lens are sequentially arranged on a light path of light reflected by the eyeball to be detected and are used for generating a surface image of the eyeball to be detected on the imaging objective lens;
and the image sensor is arranged in parallel with the imaging objective lens and electrically connected with the signal processing and control unit, and is used for collecting the surface image of the eyeball to be detected.
5. A method for measuring parameters of the eye, using a measuring system according to any of claims 1-4, wherein the method comprises:
obtaining a low coherence interference signal spectrum related to the thickness of each tissue in the eye axis direction of an eyeball to be detected by using a low coherence measurement unit, wherein the low coherence interference signal spectrum comprises a plurality of interference peaks;
obtaining a long coherent interference signal spectrum with approximate equal amplitude by using a long coherent measurement unit;
acquiring a surface image of an eyeball to be detected by using an eyeball imaging unit;
measuring the distance between low coherence interference peaks in the low coherence interference signal spectrum according to the long coherence interference signal spectrum, and calculating eyeball parameters in the direction of the eyeball axis to be detected according to the distance;
and analyzing the surface image of the eyeball to be measured according to a digital image processing technology, and measuring to obtain the transverse eyeball parameters of the eyeball to be measured.
6. The measurement method according to claim 5, further comprising:
synchronizing the low coherence measurement unit and the long coherence measurement unit with an interference signal synchronization unit.
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