CN112220443A - Self-adaptive signal noise reduction eye axial length measuring method - Google Patents
Self-adaptive signal noise reduction eye axial length measuring method Download PDFInfo
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Abstract
The invention provides a method and a device for measuring the axial length of a self-adaptive signal noise reduction eye, comprising the following steps: performing normalization processing on an illumination intensity signal acquired based on a Tyman Green interference system; carrying out recursive smooth filtering processing on the illumination intensity signal; correcting the peak value point of the filtered illumination intensity signal; and calculating the length of the eye axis according to the filtered illumination intensity signal. The method and the device for measuring the eye axis length provided by the invention have low requirement on hardware and high accuracy, and can meet the requirements of different application scenes.
Description
Technical Field
The invention relates to the technical field of eye measurement equipment, in particular to a self-adaptive signal noise reduction eye axial length measurement method.
Background
An avalanche photodiode (hereinafter, referred to as APD) is a photoelectric device based on an internal photoelectric effect. The avalanche photodiode has the functions of internal gain and amplification, and one photon can generate dozens or even hundreds of pairs of photo-generated electron-hole pairs, thereby playing the role of amplifying optical power. The avalanche photodiode operates under reverse bias. Under a certain range of reverse bias voltage, the higher the bias voltage is, the more photo-generated electron-hole pairs are generated, namely, the avalanche effect occurs, and the signal current is amplified.
At present, in an eye axis length measurement method implemented by using a coherent light interference principle, after light intensity data is acquired by a tayman green interference system based on an APD, filtering and noise reduction processing needs to be performed on a current signal (light intensity signal) acquired by the APD, so as to extract an interference signal, and further calculate an eye axis length.
Disclosure of Invention
In view of the above problems, the present invention aims to provide an adaptive signal noise reduction eye axial length measurement method.
The purpose of the invention is realized by adopting the following technical scheme:
in a first aspect, a method for measuring an axial length of an adaptive signal noise reduction eye is provided, which is applied to a data processing module, and includes the following steps:
s20, performing normalization processing on the illumination intensity signal acquired based on the Taemann Green interference system, wherein the abscissa of the illumination intensity signal represents the signal length, the signal length corresponds to the movement distance of a reference arm in the Taemann Green interference system, and the ordinate represents the illumination intensity of the signal;
s30 performs recursive smoothing filtering on the illumination intensity signal, including: traversing the illumination intensity signal by adopting a window with a set size, calculating a local signal standard deviation in the window, and amplifying the signal at the current traversing position and finishing signal updating when the local signal standard deviation meets a set condition; outputting a current illumination intensity signal after traversing;
s40 judging whether the current light intensity signal reaches the steady state, when the signal does not reach the steady state, returning to S30, and carrying out a new round of recursive smooth filtering processing on the current light intensity signal; when the signal reaches a steady state, outputting the current illumination intensity signal as a filtered illumination intensity signal;
s60 calculates an eye axis length from the filtered illumination intensity signal.
In one embodiment, step S30 includes: and when the standard deviation of the local signals in the window is larger than a set threshold value, amplifying the signals at the current traversal position.
In one embodiment, step S40 further includes:
when the signal reaches a steady state, performing wavelet threshold filtering processing on the current illumination intensity signal, and outputting the illumination intensity signal after the wavelet threshold filtering processing as a filtered illumination intensity signal.
In one embodiment, the step S40 of determining whether the current illumination intensity signal reaches a steady state specifically includes:
acquiring a peak point of a current illumination intensity signal, and marking the peak point as a stable state when a difference value between a coordinate of a certain peak point and a coordinate of an adjacent peak point is within a set standard range; and when the ratio of the peak value marked as the steady state in the illumination intensity signal is greater than a set threshold value, judging that the illumination intensity signal reaches the steady state.
In one embodiment, step S40 is followed by:
s50 peak point correcting the filtered illumination intensity signal, including: and carrying out backward difference calculation on the filtered illumination intensity signal to detect a peak point in the signal, calibrating, comparing the peak point with the signal mean value of the local range of n adjacent periods, and rejecting the peak point when the peak point is smaller than the mean value of the local range.
In one embodiment, the step S60 includes, according to the filtered illumination intensity signal:
and acquiring corresponding signal length information according to the peak point coordinate position of the filtered illumination intensity signal, and calculating the length of the eye axis according to the acquired signal length information.
In one embodiment, the method further comprises:
s10, collecting an illumination intensity signal, wherein the collected illumination intensity signal is an illumination intensity signal collected based on a Thyman Green interference system, and an APD collection illumination intensity signal is arranged in the Thyman Green interference system.
In a second aspect, an adaptive signal noise reduction eye axial length measuring device is provided, which comprises a receiving module and a data processing module; wherein the content of the first and second substances,
the receiving module is used for receiving an illumination intensity signal acquired based on the Tyman Green interference system; the abscissa of the illumination intensity signal corresponds to the movement distance of a reference arm in the Tayman Green interference system, and the ordinate represents the illumination intensity of the signal;
the data processing module is configured to execute the adaptive signal noise reduction eye axis length measurement method provided in any one of the first 6 implementation manners in the aspect, and output an eye axis length measurement result.
In one embodiment, the apparatus further comprises a detection module comprising a Taemann Green interference system, wherein the APD is configured to collect the illumination intensity signal.
The invention has the beneficial effects that:
1) the adaptive signal noise reduction eye axis length measuring method provided by the invention can perform adaptive filtering processing according to the state of the illumination intensity signal, can adapt to the illumination intensity signals collected under different instruments and different parameter conditions to perform filtering processing, and has a good filtering effect.
2) Through iterative recursive smooth filtering processing, the signal which may be an interference point can be amplified, meanwhile, noise is effectively inhibited, and the performance of the signal is improved.
3) Error points near the interference points can be effectively filtered through self-adaptive peak point correction, and the accuracy of interference signal measurement is further improved.
4) The method and the device for measuring the eye axis length have low requirement on hardware and high accuracy, and can meet the requirements of different application scenes.
Drawings
The invention is further illustrated by means of the attached drawings, but the embodiments in the drawings do not constitute any limitation to the invention, and for a person skilled in the art, other drawings can be obtained on the basis of the following drawings without inventive effort.
FIG. 1 is a flow chart of an adaptive signal noise reduction eye axis length measuring method of the present invention;
FIG. 2 is a schematic diagram of an optical path of a detecting device according to an embodiment of the present invention;
FIG. 3 is a block diagram of a detection device according to an embodiment of the present invention;
fig. 4 is a structural diagram of a detection device according to an embodiment of the present invention.
Detailed Description
The invention is further described in connection with the following application scenarios.
Referring to fig. 1, a method for measuring the axial length of an adaptive signal noise reduction eye is shown, which comprises the following steps:
s10, collecting an illumination intensity signal, wherein the collected illumination intensity signal is an illumination intensity signal collected based on a Thyman Green interference system, and an APD collection illumination intensity signal is arranged in the Thyman Green interference system.
In one embodiment, the illumination intensity signal collected by the APD is fed back as an electrical signal to determine the intensity of the light intensity.
The abscissa of the illumination intensity signal represents the signal length, which corresponds to the movement distance of the reference arm in the Tayman Green interference system, and the ordinate represents the illumination intensity of the signal.
In a scenario, the abscissa of the illumination intensity may be represented as a displacement distance of the reference arm, and in a process of uniform movement of the reference arm, the APD acquisition module synchronously outputs an illumination intensity signal acquired by the APD acquisition module at a set sampling frequency, so that the abscissa of the illumination intensity corresponds to displacement information of the reference arm.
In one scenario, the abscissa of the illumination intensity is represented as time information, and the time information is combined with the uniform movement speed of the reference arm, so that the translation information of the reference arm can be converted.
Collecting coherent light signals through a collecting module based on a Tyman Green interference system, wherein the abscissa of the obtained illumination intensity signals corresponds to the displacement of a reference arm in the Tyman Green interference system, and the ordinate represents the size of the illumination intensity reflected by the amplitude; and meanwhile, an APD is arranged in the Tyman Green interference system and is used as a coherent light signal in a receiver acquisition system, and the coherent light signal is output to a data processing module in the form of a current signal.
S20 normalizes the acquired light intensity signal.
The illumination intensity signals are subjected to normalization processing, so that subsequent detection of signal peak points and interference signal positions is facilitated, and meanwhile, the illumination intensity signals collected under different conditions and parameters are normalized during filtering processing so as to adapt to filtering processing.
S30 performs recursive smoothing filtering on the illumination intensity signal, including: traversing the illumination intensity signal by adopting a window with a set size, calculating a local signal standard deviation in the window, and amplifying the signal at the current traversing position and finishing signal updating when the local signal standard deviation meets a set condition; and outputting a current illumination intensity signal after traversing.
In one embodiment, step S30 includes: and when the standard deviation of the local signals in the window is larger than a set threshold value, amplifying the signals at the current traversal position.
In a scene, when the standard deviation of a local signal in a window is detected to be larger than a set threshold value, performing exponential amplification or multiple amplification processing on the signal corresponding to the central position of the window, and replacing the original value in the signal with the amplified signal to finish one-time updating of the signal position; the updated window continues to traverse forwards until the traversal filtering processing of the whole illumination intensity signal is completed; through the amplification filtering processing, the condition that weak signals are easily submerged by noise under the condition that the signal-to-noise ratio of the signals is low is improved.
According to the embodiment, the self-adaptive filtering processing can be performed according to the state of the signal, the characteristic part in the illumination intensity signal is effectively highlighted and amplified, and a foundation is laid for measurement and calculation according to the illumination intensity signal.
S40 judging whether the current light intensity signal reaches the steady state, when the signal does not reach the steady state, returning to S30, and carrying out a new round of recursive smooth filtering processing on the current light intensity signal; and when the signal reaches a stable state, outputting the current illumination intensity signal as the filtered illumination intensity signal.
In one embodiment, step S40 further includes:
when the signal reaches a steady state, performing wavelet threshold filtering processing on the current illumination intensity signal, and outputting the illumination intensity signal after the wavelet threshold filtering processing as a filtered illumination intensity signal.
And performing wavelet soft threshold filtering processing on the illumination intensity signal after the steady state again, so that noise interference in the signal can be further removed, and the quality of the signal is further improved.
In one embodiment, the step S40 of determining whether the current illumination intensity signal reaches a steady state specifically includes:
acquiring a peak point of a current illumination intensity signal, and marking the peak point as a stable state when a difference value between a coordinate of a certain peak point and a coordinate of an adjacent peak point is within a set standard range; and when the ratio of the peak value marked as the steady state in the illumination intensity signal is greater than a set threshold value, judging that the illumination intensity signal reaches the steady state.
In a scene, when checking whether the current illumination intensity signal reaches a steady state, detecting each peak point in the signal according to a set peak point detection method, acquiring coordinate information corresponding to each peak point, further detecting the coordinate difference of adjacent peak points, and if the horizontal coordinate difference between a certain peak point and the adjacent peak point is within a set range, judging that part of the peak point signal reaches the steady state; and meanwhile, acquiring a steady-state ratio according to the proportion of the part of the signal reaching the steady state in the whole signal, and judging that the signal reaches the steady state when the steady-state ratio is greater than a set threshold value.
In one scenario, the setting range of the coordinate difference between adjacent peak points may be set according to the sampling frequency of the illumination intensity signal; and reasonably setting a judgment range for judging whether the peak point is stable or not according to the sampling frequency of the signal, the theoretical range of adjacent peak points and a proper allowable error range.
In one scenario, the decision range is plus or minus 10 ranges of the theoretical mean of the peak point interval.
The iteration times for amplifying the signals are limited by judging the steady-state ratio, so that the iteration times for amplifying the signals can be accurately limited while the characteristic points of the signals are ensured to be amplified remarkably, the condition of filtering transition or insufficient filtering of the signals is effectively avoided, and the information of interference signals is enhanced.
In step S40, a peak point is corresponding to each signal period in the illumination intensity signal; by judging the distance between the peak points, whether the amplification filtering degree of the signals reaches the standard or not can be accurately detected, and the signal-to-noise ratio of the illumination intensity signals can be increased and the characteristic parts of the signals can be highlighted through repeated recursive smooth filtering processing.
S50 peak point correcting the filtered illumination intensity signal, including: and carrying out backward difference calculation on the filtered illumination intensity signal to detect a peak point in the signal, calibrating, comparing the peak point with the signal mean value of the local range of n adjacent periods, and rejecting the peak point when the peak point is smaller than the mean value of the local range.
In the above embodiment, the noise peak point near the interference position in the illumination intensity signal is further removed; the peak points existing near two interference signals corresponding to the ocular surface and the fundus of the eyeball are removed, the number of the peak points which are misjudged as the interference signals in the subsequent calculation of the axial length of the eye is reduced, most of noise of the illumination intensity signals can be filtered through the recursive smooth filtering processing in S30, but error points around effective signal points (interference signals) cannot be effectively removed, so the error peak points near the effective signals are further removed through the correction of the peak points, and the filtering performance for the illumination intensity signals is indirectly improved.
S60 calculates an eye axis length from the filtered illumination intensity signal.
In one embodiment, the step S60 includes, according to the filtered illumination intensity signal:
and acquiring corresponding signal length information according to the peak point coordinate position of the filtered illumination intensity signal, and calculating the length of the eye axis according to the acquired signal length information.
In one embodiment, based on the remaining calibrated peak points in step S50, the peak point coordinate positions corresponding to the (two) interference signals in the illumination intensity signal are obtained from the set theoretical range of the eye axis length by combining the amplitudes of the peak points, and the eye axis length is further calculated according to the coordinate distance between the interference signals and the peak points.
In one scenario, since in step S50, only the peak point with the highest amplitude is retained for the peak points near the interference signal, and the remaining peak points with smaller amplitudes are eliminated under the influence of the peak point with the highest amplitude. Therefore, when the interference signals corresponding to the eye chart and the eye fundus are obtained, the signal amplitude is set to be larger than a certain proportion or a certain value, the distance between two obtained peak points is used as a screening condition according to the theoretical range of the axial length of the human eyes, and the accurate position of the interference signals can be accurately obtained.
In one scene, the abscissa of the illumination intensity signal corresponds to the displacement information of the reference arm, the position of the interference signal in the signal is obtained by obtaining the peak point of the filtered illumination intensity signal, and the eye axis length is obtained by multiplying the coordinate distance of the peak point by the refractive index of the eye structure.
In one embodiment, as a reference, the adaptive signal noise reduction eye axis length measurement method provided above is configured such that the sampling frequency of the illumination intensity signal is set as follows: the 2MHz, reference arm moving speed is: 0.110736m/s, i.e., the time spacing information between adjacent signal samples, is: 0.5 mu s; setting the width of a filtering processing window as follows: 10; the set standard deviation judgment threshold is as follows: 4.0.
based on the self-adaptive signal noise reduction eye axial length measuring method, a self-adaptive signal noise reduction eye axial length measuring device is also provided, and comprises a detection module, a receiving module and a data processing module; wherein the content of the first and second substances,
the detection module comprises a Thyman Green interference system, wherein an APD is arranged in the Thyman Green interference system to acquire an illumination intensity signal; the system is used for collecting an illumination intensity signal; the abscissa of the illumination intensity signal corresponds to the movement distance of a reference arm in the Tayman Green interference system, and the ordinate represents the illumination intensity of the signal;
the receiving module is used for receiving an illumination intensity signal acquired based on the Tyman Green interference system;
the data processing module is used for executing the adaptive signal noise reduction eye axial length measuring method provided by any one of the above adaptive signal noise reduction eye axial length measuring methods, and outputting an eye axial length measuring result.
In one embodiment, the detection module employs a Taemann Green interferometer, wherein the illumination intensity signal is collected with an APD as a receiver.
In an embodiment, the detection module may also adopt a detection device based on the tayman green interference system, wherein the schematic diagram of the optical path of the detection device is shown in fig. 2;
the eyepiece 4 is used for aligning with the eyeball part of a user, the laser emitter 7 emits laser to the second corner stack prism 11, the second corner stack prism 11 is divided into laser A and laser B, after the laser B reaches the first corner stack prism 10, the first corner stack prism 10 corrects and reflects the laser B, the laser B is reflected from the first corner stack prism 10 back to the second corner stack prism 11 and converged with the laser A to form laser C, the laser C is reflected from the second corner stack prism 11 to the first light splitting prism 2, the first light splitting prism 2 divides the laser C into laser D and laser E, the laser D is reflected to the surface of the eyeball of the user, the laser E is reflected to the second light splitting prism 3 and divided into laser F and laser G, the laser F passes through the reflector 5 and reaches the infrared camera 6, the infrared camera 6 is used for observing the position of a reflection point of the laser D after the laser D strikes the surface of the eyeball so as to adjust the device to enable the laser D to strike the center position of the pupil of the eyeball, the laser light G is reflected to APD 16; and collecting an illumination intensity signal through the APD and sending the illumination intensity signal to the data processing module.
Meanwhile, in combination with the optical principle of the device, the application also provides a specific structure of the detection device, as shown in fig. 3 and 4, the detection device comprises a base 1, wherein a first light splitting prism 2 and a second angle stack prism 11 which are used for refracting and dispersing laser are arranged on the base 1;
the base 1 is also provided with a laser emitter 7 for emitting laser, a magnetic grid ruler 8 for acquiring displacement data, an APD16 for receiving laser energy data and a moving component for driving the first corner cube prism 10;
the moving component is connected with the first corner-stack prism 10 to form a reference arm part in the Taemann Green interference system;
in an optional embodiment, the moving assembly comprises a sliding plate 17, a supporting plate 18 and a first fixing plate 19, the supporting plate 18 is provided with a driving motor 12, a gear is sleeved on an output shaft of the driving motor 12, the lower end surface of the sliding plate 17 is slidably connected with the base 1, the side wall of the sliding plate 17 is provided with a rack 13, and the rack 13 is meshed with the gear;
the slide plate 17 is also vertically provided with a first corner stack prism 10 and a position control baffle plate 14;
first fixed plate 19 and base 1 mutually perpendicular, first fixed plate 19 is provided with two, is provided with photoelectric switch 15 on the first fixed plate 19, is provided with the recess that can hold position control separation blade 14 on the photoelectric switch 15, and two recesses and position control separation blade 14 are same linear arrangement along slide 17 slip direction, and two photoelectric switches 15 all are connected with driving motor 12 electricity.
Wherein, the base 1 is also provided with an ocular 4, a reflector 5 and an infrared camera 6, wherein the ocular 4 forms a measuring arm (sample arm) part of the Tyman Green interference system;
the emitting head of the laser emitter 7 faces the second corner cube prism 11;
the first corner cube prism 10 and the second corner cube prism 11 are oppositely arranged and are positioned on the same horizontal plane;
the second corner cube prism 11 and the first beam splitter prism 2 are oppositely arranged and are positioned on the same horizontal plane;
the first beam splitter prism 2 and the ocular lens 4 are oppositely arranged and are positioned on the same horizontal plane;
the second beam splitter prism 3 is arranged above the first beam splitter prism 2;
the reflector 5 is arranged above the second beam splitter prism 3;
the infrared camera 6 and the reflector 5 are oppositely arranged and positioned on the same horizontal plane, and the lens of the infrared camera 6 faces the reflector 5;
the APD16 and the second beam splitting prism 3 are oppositely arranged.
The measuring process of the detection device is as follows: an output shaft on the driving motor 12 drives a gear to rotate, the rotation of the gear drives the rotating rack 13 to move, so that the sliding plate 17 and the position control barrier 14 are displaced, when the position control barrier 14 moves into a groove of one photoelectric switch 15, the photoelectric switch 15 detects that light emitted in the groove is shielded by the position control barrier 14, the photoelectric switch 15 controls the driving motor 12 to rotate reversely at the moment, and when the position control barrier 14 moves to the other photoelectric switch 15, the driving motor 12 stops operating by applying the same principle; the movement of the first angular stack prism 10 is realized through the method, the APD16 can acquire laser G intensity signals reflected by different positions of an eyeball through the movement of the first angular stack prism 10, the APD16 sends the acquired laser G intensity signals at each moment (position) to the data processing module through serial port communication, and the eye axis length is calculated through the self-adaptive signal noise reduction eye axis length measuring method.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the protection scope of the present invention, although the present invention is described in detail with reference to the preferred embodiments, it should be analyzed by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.
Claims (9)
1. A self-adaptive signal noise reduction eye axial length measuring method is applied to a data processing module and is characterized by comprising the following steps:
s20, performing normalization processing on the illumination intensity signal acquired based on the Taemann Green interference system, wherein the abscissa of the illumination intensity signal represents the signal length, the signal length corresponds to the movement distance of a reference arm in the Taemann Green interference system, and the ordinate represents the illumination intensity of the signal;
s30 performs recursive smoothing filtering on the illumination intensity signal, including: traversing the illumination intensity signal by adopting a window with a set size, calculating a local signal standard deviation in the window, and amplifying the signal at the current traversing position and finishing signal updating when the local signal standard deviation meets a set condition; outputting a current illumination intensity signal after traversing;
s40 judging whether the current light intensity signal reaches the steady state, when the signal does not reach the steady state, returning to S30, and carrying out a new round of recursive smooth filtering processing on the current light intensity signal; when the signal reaches a steady state, outputting the current illumination intensity signal as a filtered illumination intensity signal;
s60 calculates an eye axis length from the filtered illumination intensity signal.
2. The adaptive signal noise reduction eye axis length measurement method according to claim 1, wherein the step S30 includes: and when the standard deviation of the local signals in the window is larger than a set threshold value, amplifying the signals at the current traversal position.
3. The adaptive signal noise reduction eye axis length measurement method according to claim 1, wherein the step S40 further includes:
when the signal reaches a steady state, performing wavelet threshold filtering processing on the current illumination intensity signal, and outputting the illumination intensity signal after the wavelet threshold filtering processing as the filtered illumination intensity signal.
4. The method for measuring the axial length of the adaptive signal noise reduction eye according to claim 1, wherein the step S40 of determining whether the current illumination intensity signal reaches a steady state specifically includes:
acquiring a peak point of a current illumination intensity signal, and marking the peak point as a stable state when a difference value between a coordinate of a certain peak point and a coordinate of an adjacent peak point is within a set standard range; and when the ratio of the peak value marked as the steady state in the illumination intensity signal is greater than a set threshold value, judging that the illumination intensity signal reaches the steady state.
5. The adaptive signal noise reduction eye axis length measuring method according to claim 1, further comprising, after step S40:
s50 peak point correcting the filtered illumination intensity signal, including: and carrying out backward difference calculation on the filtered illumination intensity signal to detect a peak point in the signal, calibrating, comparing the peak point with the signal mean value of the local range of n adjacent periods, and rejecting the peak point when the peak point is smaller than the mean value of the local range.
6. The method for measuring the axial length of the adaptive signal noise reduction eye according to claim 5, wherein the step S60 includes, according to the filtered illumination intensity signal:
and acquiring corresponding signal length information according to the peak point coordinate position of the filtered illumination intensity signal, and calculating the length of the eye axis according to the acquired signal length information.
7. The adaptive signal noise reduction eye axis length measurement method of claim 1, further comprising:
s10, collecting an illumination intensity signal, wherein the collected illumination intensity signal is an illumination intensity signal collected based on a Thyman Green interference system, and an APD collection illumination intensity signal is arranged in the Thyman Green interference system.
8. The self-adaptive signal noise reduction eye axial length measuring device is characterized by comprising a receiving module and a processing module; wherein the content of the first and second substances,
the receiving module is used for receiving an illumination intensity signal acquired based on the Tyman Green interference system; the abscissa of the illumination intensity signal corresponds to the movement distance of a reference arm in the Tayman Green interference system, and the ordinate represents the illumination intensity of the signal;
the processing module is used for executing the adaptive signal noise reduction eye axis length measuring method of any one of the claims 1 to 6 and outputting the eye axis length measuring result.
9. The adaptive signal denoising eye axis length measuring device of claim 1, further comprising a detection module comprising the Taemann Green interference system, wherein the Taemann Green interference system is configured with APDs to collect illumination intensity signals.
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| CN117406046A (en) * | 2023-12-14 | 2024-01-16 | 凯恩茨(福州)工业有限公司 | Partial discharge detection device |
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| CN117406046A (en) * | 2023-12-14 | 2024-01-16 | 凯恩茨(福州)工业有限公司 | Partial discharge detection device |
| CN117406046B (en) * | 2023-12-14 | 2024-03-08 | 凯恩茨(福州)工业有限公司 | Partial discharge detection device |
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Application publication date: 20210115 |
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