Eye axis length measuring device based on DMD dynamic optical path adjustment

Abstract

The invention discloses an eye axis length measuring device based on DMD dynamic optical path adjustment, which comprises an eye axis length measuring device body, a coaxial interference optical module, a signal processing module, a power supply module and a man-machine interaction module, a 850nm near-infrared low-coherence light source, a beam combining piece, a first relay lens, a first light splitting piece, a second relay lens, a second light splitting piece and an objective lens on the eye axis length measuring device are connected in series on the same straight line, a body of the eye axis length measuring device screens effective signals of retina reflection through a peak value extraction algorithm, interference of reflection of anterior surface tissues such as cornea and crystalline lens is avoided, and the measurement accuracy of the eye axis length measuring device is improved. The measurement error is reduced by more than or equal to 40%, a fixation lamp and a measurement light path point are designed in a synthetic manner, a fixation target point is superposed with a measurement light incidence point, the light path coaxiality is ensured to be less than or equal to + / -0.05 mm, the measurement precision is greatly improved, the cornea injury risk is avoided, the comfort of a detected person is high, no mechanical moving part exists, the vibration resistance is high, a commercial module is selected as a core device, and the production cost is reduced compared with that of a traditional OCT.

Description

Technical Field

[0001] This invention relates to the field of axial length measurement technology, specifically to an axial length measurement device based on DMD dynamic optical path adjustment. Background Technology

[0002] Axial length is a key indicator for assessing eye development and diagnosing eye diseases. Current measurement techniques mainly include contact A-mode ultrasound and optical coherence tomography (OCT). A-mode ultrasound is prone to causing discomfort to the examinee, and its measurement accuracy is greatly affected by the operation. OCT uses a mechanically moving reference arm to adjust the optical path, which has drawbacks such as mechanical wear, slow response, weak vibration resistance, large equipment size, and high cost.

[0003] Currently, there is no axial length measurement scheme that uses DMD as the core optical path adjustment component and combines a low-coherence optical interference signal peak extraction algorithm with a fixation lamp-measurement optical path point synthesis design. Traditional techniques cannot accurately guide the eyeball to fixation and are prone to measurement errors due to insufficient optical path coaxiality. Therefore, an improved technology is urgently needed to solve this problem in the existing technology. Summary of the Invention

[0004] The purpose of this invention is to provide an axial length measurement device that uses a peak extraction algorithm to screen effective retinal reflection signals, avoids interference from reflections from anterior surface tissues such as the cornea and lens, reduces measurement error by ≥40%, and integrates the fixation lamp and measurement light path point to achieve coincidence between the fixation target point and the incident point of the measurement light, ensuring optical path coaxiality ≤±0.05mm, significantly improving measurement accuracy, eliminating the risk of corneal damage, providing high patient comfort, eliminating mechanical moving parts, having strong vibration resistance, and using commercially available modules for core components, thus reducing production costs compared to traditional OCT. This invention aims to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: an axial length measuring device based on DMD dynamic optical path adjustment, comprising an axial length measuring device body, a coaxial interference optical module, a signal processing module, a power supply module, and a human-computer interaction module. The axial length measuring device body is provided with an 850nm near-infrared low coherence light source, a beam combiner, a relay lens one, a beam splitter one, a relay lens two, a beam splitter two, and an objective lens. The 850nm near-infrared low coherence light source, the beam combiner, the relay lens one, the beam splitter one, the relay lens two, the beam splitter two, and the objective lens are connected in series on the same straight line. An LED fixed-view light is provided below the bundle combiner sheet; Below the first beam splitter, a DMD objective lens, a DMD unit, and a TIR prism are provided. The TIR prism is located directly below the DMD objective lens, and the DMD unit and the TIR prism are arranged on the same horizontal line. Below the second beam splitter, a third beam splitter, a focusing lens, and a detector are provided.

[0006] Preferably, a projection lens is provided between the TIR prism and the beam splitter, and the TIR prism, projection lens, and beam splitter are arranged on the same straight line.

[0007] Preferably, both the 850nm near-infrared low-coherence light source and the LED fixed-view lamp are equipped with detectors.

[0008] Preferably, the LED fixed-view lamp is coaxial with the measurement optical path after being reflected by a semi-transparent and semi-reflective mirror. The LED fixed-view lamp is a 650nm visible red LED with a brightness of 80mcd, a spot diameter of 0.5-1mm, a power supply voltage of 5V DC, and shares a power supply with the main control board.

[0009] Preferably, the signal processing module inside the main body of the axial length measuring device adopts an FPGA+MCU integrated architecture and has a built-in low coherence optical interference signal peak extraction algorithm. In the peak extraction algorithm, the peak selection threshold is 5 times the baseline noise, and only interference signal peaks with intensity greater than this threshold are retained. The MCU is based on the optical path difference corresponding to the effective peak value, and the formula for calculating the optical path difference is: ΔL = λ × Δφ / (4π) The axial length of the eye is inverted based on the refractive index of the eyeball tissue of 1.336, with a measurement accuracy of ≤±100μm and repeatability of ≤33μm.

[0010] Preferably, the human-computer interaction module on the main body of the axial length measuring device includes an OLED display screen and a 3-button operation panel, which supports one-button measurement, automatic calibration and data export.

[0011] Compared with the prior art, the beneficial effects of the present invention are: (1) When the subject gazes at the LED fixed light spot, the visual axis of the eyeball automatically coincides with the incident direction of the measurement light, ensuring that the sample light is transmitted in a straight line along the eye axis, eliminating the optical path deviation caused by eyeball deviation from a physical level, and playing the role of coaxial guidance. (2) Clear coaxial target points can significantly reduce physiological eye saccades and micro-tremors in subjects, avoid retinal reflex position drift, ensure stable interference signal peak, and play a role in eye movement inhibition. (3) The peak extraction algorithm is used to screen the effective signal of retinal reflection, avoiding the interference of the reflection of the anterior surface tissues such as cornea and lens, reducing the measurement error by ≥40%. The fixation lamp and the measurement light path point are designed to coincide, ensuring that the fixation target point and the measurement light incident point coincide, ensuring that the optical path coaxiality is ≤±0.05mm, greatly improving the measurement accuracy, eliminating the risk of corneal damage, providing high patient comfort, eliminating mechanical moving parts, and having strong vibration resistance. The core components are commercial modules, reducing the production cost compared to traditional OCT. (4) The main body of the axial length measuring device filters the effective signal of retinal reflection through peak extraction algorithm to avoid interference from the reflection of anterior surface tissues such as cornea and lens, reducing the measurement error by ≥40%. The fixation lamp and the measurement light path point are designed to coincide, ensuring that the fixation target point and the measurement light incident point coincide, ensuring that the optical path coaxiality is ≤±0.05mm, greatly improving the measurement accuracy, eliminating the risk of corneal damage, providing high comfort for the examinee, eliminating mechanical moving parts, and having strong vibration resistance. The core components are commercial modules, reducing the production cost compared to traditional OCT. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the axial length measuring device of the present invention.

[0013] In the figure: 1. Main body of the axial length measuring device; 2. 850nm near-infrared low coherence light source; 3. Beam combiner; 4. Relay lens one; 5. Beam splitter one; 6. Relay lens two; 7. Beam splitter two; 8. Objective lens; 9. LED fixation lamp; 10. DMD objective lens; 11. DMD unit; 12. TIR prism; 13. Projection lens; 14. Beam splitter three; 15. Focusing lens; 16. Detector. Detailed Implementation

[0014] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0015] Please see Figure 1 This invention provides a technical solution: an axial length measurement device based on DMD dynamic optical path adjustment, comprising an axial length measurement device body 1, a coaxial interference optics module, a signal processing module, a power supply module, and a human-computer interaction module. The axial length measurement device body 1 is equipped with an 850nm near-infrared low coherence light source 2, a beam combiner 3, a relay lens 4, a beam splitter 5, a relay lens 6, a beam splitter 7, and an objective lens 8. The 850nm near-infrared low coherence light source 2, the beam combiner 3, the relay lens 4, the beam splitter 5, the relay lens 6, the beam splitter 7, and the objective lens 8 are connected in series on the same straight line.

[0016] An LED fixed-view light 9 is provided below the bundle 3.

[0017] Below the beam splitter 5, a DMD objective lens 10, a DMD unit 11, and a TIR prism 12 are provided. The TIR prism 12 is located directly below the DMD objective lens 10. The DMD unit 11 and the TIR prism 12 are arranged on the same horizontal line. The DMD unit is a DLP9000 series VGA-level DMD unit.

[0018] The main body 1 of the axial length measuring device uses a 10000mAh lithium battery and a USB-C fast charging module, supporting continuous measurement ≥500 times.

[0019] Below the second beam splitter 7, there is a third beam splitter 14, a focusing lens 15, and a detector 16.

[0020] A projection lens 13 is provided between the TIR prism 12 and the beam splitter 14, and the TIR prism 12, the projection lens 13, and the beam splitter 14 are arranged on the same straight line.

[0021] The beam splitter splits the probe light into sample light and reference light. The sample light enters the eye along the axial direction and returns via the retina. The reference light enters the DMD unit 11. Through micromirror ±12° bistable angle switching and 2×2 pixel grouping timing modulation, continuous optical path adjustment of 15mm-30mm is achieved. The single micromirror switching speed is ≤15μs. The two beams converge at the beam splitter, and an effective interference signal is generated only when the optical path difference is less than the coherence length of the light source.

[0022] Both the 850nm near-infrared low-coherence light source 2 and the LED fixed-view lamp 9 are equipped with detectors 16.

[0023] The LED fixed-view lamp 9 is coaxial with the measurement light path after being reflected by a semi-transparent mirror. The LED fixed-view lamp 9 is a 650nm visible red LED with a brightness of 80mcd, a light spot diameter of 0.5-1mm, and a power supply voltage of 5V DC, sharing the power supply with the main control board. The LED fixed-view lamp 9 is installed on the front right side of the housing and is coaxial with the measurement light path through a semi-transparent mirror. The light emission target point of the LED fixed-view lamp 9 is completely coincident with the incident point of the 850nm measurement light after being reflected by the semi-transparent mirror, forming a coaxial guiding structure of "the gaze target point = the incident point of the measurement light".

[0024] When the subject focuses on the LED fixation lamp spot 9, the visual axis of the eyeball automatically aligns with the incident direction of the measurement light, ensuring that the sample light is transmitted in a straight line along the eye axis. This eliminates the optical path deviation caused by eyeball deviation from a physical perspective and plays a coaxial guiding role.

[0025] Clear coaxial target points can significantly reduce physiological saccades and micro-tremors in subjects, avoid retinal reflex position drift, ensure stable interference signal peaks, and play a role in eye movement inhibition.

[0026] A unified gaze standard ensures consistent optical path coaxiality across multiple measurements, improving measurement repeatability (≤25μm).

[0027] The signal processing module inside the main body 1 of the axial length measuring device adopts an FPGA+MCU integrated architecture and has a built-in low coherence optical interference signal peak extraction algorithm. In the peak extraction algorithm, the peak selection threshold is 5 times the baseline noise, and only interference signal peaks with intensity greater than this threshold are retained. The MCU is based on the optical path difference corresponding to the effective peak value, and the formula for calculating the optical path difference is: ΔL = λ × Δφ / (4π) The axial length of the eye is inverted based on the refractive index of the eyeball tissue of 1.336, with a measurement accuracy of ≤±100μm and repeatability of ≤33μm.

[0028] The signal processing module adopts an FPGA+MCU integrated architecture and has a built-in low-coherence optical interference signal peak extraction algorithm. The FPGA controls the DMD to perform a full-range optical path scan of 15mm-30mm in 10μs steps, while the InGaAs detector synchronously acquires the light intensity data of the interference signal.

[0029] Baseline noise caused by ambient stray light and detector dark current is removed, while retaining the effective interference signal.

[0030] Extract the light intensity peak of the interference signal, and retain only the peak signal with an intensity greater than the threshold (preset to be 5 times the baseline noise). This peak corresponds to the optical path difference matching point between the retinal reflected light and the reference light.

[0031] It filters weak signals (light intensity below the threshold) reflected by anterior surface tissues such as the cornea and lens, retaining only the effective peak value of retinal reflection.

[0032] The MCU calculates the optical path difference based on the optical path difference corresponding to the effective peak value, using the formula ΔL=λ×Δφ / (4π). Then, it inverts the axial length of the eye based on the refractive index of the eye tissue (1.336). The measurement accuracy is ≤±100μm and the repeatability is ≤33μm.

[0033] The human-computer interaction module on the main body 1 of the axial length measuring device includes an OLED display screen and a 3-button operation panel, which supports one-button measurement, automatic calibration and data export.

[0034] The specific implementation process of the main body 1 of the axial length measurement device: After power-on, the FPGA completes the DMD parameter configuration, the detector collects and subtracts the background noise, sets the peak screening threshold, and at the same time, the fixation lamp 9 is started. The coaxial target point is synthesized with the measurement optical path through the semi-transparent and semi-reflective mirror, and the coaxiality calibration is ≤ ±0.05mm.

[0035] The subject gazes at the coaxial target point formed by the fixation lamp and the measurement optical path, keeping the eyeball still. At this time, the incident direction of the sample light automatically coincides with the eye axis, and the optical path is scanned and the signal is acquired. When the measurement key is pressed, the FPGA controls the DMD to perform a full-range optical path scan of 15mm-30mm, and the detector synchronously acquires the interference signal.

[0036] The MCU executes a peak extraction algorithm to filter out interference signals, extract the effective peak value of retinal reflection, calculate the axial length of the eye, and display it on the OLED screen; the time for a single measurement is ≤100ms.

[0037] Press the calibration button, and the device will call the built-in standard optical path data to complete the self-test without the need for an external standard sample. At the same time, it will calibrate the coaxiality of the fixed lamp and the measuring optical path to ensure long-term accuracy.

[0038] The axial length measurement device accurately filters the effective retinal reflection signal through a low-coherence optical interference signal peak extraction algorithm. Combined with the fixation lamp and the measurement optical path point synthesis design, it ensures that the optical path is coaxial, thus achieving high-precision and portable axial length measurement.

[0039] The main body 1 of this axial length measurement device uses a peak extraction algorithm to filter effective signals from retinal reflection, avoiding interference from reflections from anterior surface tissues such as the cornea and lens, reducing measurement error by ≥40%. The fixation lamp and measurement light path point are designed to coincide, ensuring that the fixation target point and the incident point of the measurement light coincide, guaranteeing optical path coaxiality ≤±0.05mm, significantly improving measurement accuracy, eliminating the risk of corneal damage, providing high patient comfort, eliminating mechanical moving parts, and having strong vibration resistance. The core components use commercial modules, reducing production costs compared to traditional OCT.

[0040] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An axial length measurement device based on DMD dynamic optical path adjustment, comprising an axial length measurement device body (1), a coaxial interference optical module, a signal processing module, a power supply module, and a human-computer interaction module, characterized in that: The main body (1) of the axial length measuring device is provided with an 850nm near-infrared low coherence light source (2), a beam combiner (3), a relay lens one (4), a beam splitter one (5), a relay lens two (6), a beam splitter two (7), and an objective lens (8). The 850nm near-infrared low coherence light source (2), the beam combiner (3), the relay lens one (4), the beam splitter one (5), the relay lens two (6), the beam splitter two (7), and the objective lens (8) are connected in series on the same straight line. An LED fixed-view lamp (9) is provided below the bundled sheet (3); Below the beam splitter (5) are a DMD objective lens (10), a DMD unit (11), and a TIR prism (12). The TIR prism (12) is located directly below the DMD objective lens (10), and the DMD unit (11) and the TIR prism (12) are located on the same horizontal line. Below the second beam splitter (7) are a third beam splitter (14), a focusing lens (15), and a detector (16).

2. The axial length measuring device based on DMD dynamic optical path adjustment according to claim 1, characterized in that: The TIR prism (12) and the beam splitter (14) are fitted with a projection lens (13), and the TIR prism (12), projection lens (13), and beam splitter (14) are arranged on the same straight line.

3. The axial length measuring device based on DMD dynamic optical path adjustment according to claim 1, characterized in that: The 850nm near-infrared low coherence light source (2) and the LED fixed-view lamp (9) are both equipped with detectors (16).

4. The axial length measuring device based on DMD dynamic optical path adjustment according to claim 1, characterized in that: The LED fixed-view lamp (9) is coaxial with the measurement optical path after being reflected by a semi-transparent and semi-reflective mirror. The LED fixed-view lamp (9) is a 650nm visible red LED with a brightness of 80mcd, a spot diameter of 0.5-1mm, a power supply voltage of 5V DC, and shares the power supply with the main control board.

5. The axial length measuring device based on DMD dynamic optical path adjustment according to claim 1, characterized in that: The signal processing module inside the main body (1) of the axial length measuring device adopts an FPGA+MCU integrated architecture and has a built-in low coherence optical interference signal peak extraction algorithm. In the peak extraction algorithm, the peak screening threshold is 5 times the baseline noise, and only interference signal peaks with intensity greater than the threshold are retained. The MCU is based on the optical path difference corresponding to the effective peak value, and the formula for calculating the optical path difference is: ΔL = λ × Δφ / (4π) The axial length of the eye is inverted based on the refractive index of the eyeball tissue of 1.336, with a measurement accuracy of ≤±100μm and repeatability of ≤33μm.

6. The axial length measuring device based on DMD dynamic optical path adjustment according to claim 1, characterized in that: The human-computer interaction module on the main body (1) of the axial length measuring device includes an OLED display screen and a 3-key operation panel, which supports one-key measurement, automatic calibration and data export.

Images