A color aberration-based multispectral contrast vernier

Abstract

The application discloses a kind of multispectral contrast visual target based on chromatic aberration, belong to ophthalmic optometry equipment technical field.The visual target includes OLED display, for showing visual target image;Visual target image is constituted by black standard logarithm E letter visual target and color spectrum background;Color spectrum background is continuous spectrum color light with wavelength range between 520nm and 620nm;Visual target image is provided with five rows, and three E letter visual targets are provided in each row;E letter is symmetrical in left and right sides in each row;Check distance is 5 meters.Five rows of visual targets correspond to five kinds of spherical adjustment accuracy of ±0.25D, ±0.20D, ±0.15D, ±0.10D, ±0.05D respectively.The application replaces traditional red-green double-color experiment by multiple groups of different wavelength interval spectrum combination, can realize spherical interval from 0.25D fine to 0.05D, effectively improve optometry precision and red-green balance rate.

Description

Technical Field

[0001] This invention relates to the field of ophthalmic optometry equipment technology, specifically to a multispectral contrast target based on chromatic aberration, used to replace the traditional red-green bicolor test and achieve precise calibration of spherical power. Background Technology

[0002] The traditional red-green dichroic test (also known as the dichroic method test) in optometry utilizes the principle of color aberration in the human eye. By comparing the clarity of a target against a red background and a green background, it determines whether the spherical lens correction is adequate. The basic principle is that different wavelengths of light have different refractive indices within the eye. Longer-wavelength light (red light, approximately 620nm) focuses behind the retina, while shorter-wavelength light (green light, approximately 535nm) focuses in front of the retina. When the subject perceives the red target as clear, it indicates myopia, requiring an increase in negative spherical lens power; when the green target is perceived as clear, it indicates hyperopia, requiring an increase in positive spherical lens power; when both red and green targets are equally clear, the spherical lens correction is adequate.

[0003] However, traditional red-green visual aids have the following shortcomings:

[0004] First, the calibration accuracy is low and the theoretical calculations are crude: traditional red-green visual targets only provide two fixed wavelengths (approximately 620nm red light and approximately 535nm green light). According to the "A Brief Comparative Analysis of Red-Green Discrimination Method and Prism Discrimination Method" (Li Huanming, 2013), in emmetropia, yellow light with a wavelength of 570nm focuses precisely on the retina; red light with a wavelength of 620nm focuses behind the retina, equivalent to hyperopia +0.24D; and green light with a wavelength of 535nm focuses in front of the retina, equivalent to myopia -0.20D. Therefore, it can be calculated that a wavelength difference of 85nm (620nm-535nm) corresponds to a focal power difference of 0.44D (0.24+0.20), meaning that every 0.01D change in spherical power corresponds to only about 2nm of wavelength change. This extremely sensitive physical relationship means that the traditional ±0.25D calibration interval is too coarse and cannot match the human eye's ability to perceive subtle wavelength differences.

[0005] Second, it cannot support the needs of high-precision refraction. According to the published content of "A Brief Comparative Analysis of Red-Green Split Refraction and Prism Split Refraction" (Li Huanming, 2013), since traditional red-green targets can only provide a single level of precision (±0.25D), when the refractive error is small (<1.00D), both target images are in a large defocus state, and the test results are unreliable. However, according to the clinical study "The Effect of Reducing the Spherical Lens Interval on Improving the Achievement Rate and Visual Quality of Red-Green Balance Tests," 83.7% of people can distinguish the change in red-green target sharpness caused by ≤0.1D spherical lenses, and using 0.05D interval spherical lenses can achieve a higher red-green balance rate and better visual quality. However, existing red-green targets cannot support fine calibration of spherical lenses with a precision of 0.05D.

[0006] Third, its applicability is limited and it is susceptible to interference. "The Application of Red-Green Visual Charts in Refraction" (Yuan Enrong, 2000) points out that red-green visual charts cannot be used for patients with red-green color blindness, children without expressive abilities, or patients with uncorrected astigmatism. "A Brief Comparative Analysis of Red-Green Differentiation and Prism Differentiation" (Li Huanming, 2013), through a comparative analysis of 287 individuals, shows that up to 30% of the subjects (86 cases) are not suitable for the red-green balanced differentiation method. Among them, 46 cases had unreliable results due to selection bias and color blindness, and another 42 cases had unclear descriptions. The main reason for unclear descriptions is that the red-green differentiation method is extremely sensitive to ambient light (the illuminance in the optometry room must be constant above 200 LX), and factors such as unstable accommodation in adolescents and yellowing of the lens in the elderly (which easily leads to red light dominance) can all cause result deviations.

[0007] Fourth, the light source has poor stability and lacks multi-level gradients. Traditional red-green visual targets are mostly displayed using light boxes or projections, and their spectral characteristics depend on the quality of the filters (e.g., British Standard BS 3668:1963 specifies that the spectral transmittance of the red filter is 600-620nm, and that of the green filter is 530-550nm). However, in actual use, light source attenuation and ambient light interference are difficult to avoid. More importantly, although existing technologies mention "multispectral visual acuity testing" (such as CN206659788U), they have never disclosed a systematic scheme that simultaneously provides five accuracy gradients in the same visual target for optometrists to use step by step or selectively, nor have they disclosed the quantitative correspondence between specific wavelength differences and spherical lens accuracy. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the prior art and provide a multispectral contrast target based on chromatic aberration. By setting multiple sets of spectral combinations with different wavelength intervals, it can achieve multi-level calibration of spherical lens addition and subtraction intervals from ±0.25D to ±0.05D, replacing the single-precision mode of red-green bicolor test in the traditional optometry process.

[0009] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0010] A multispectral contrast target based on chromatic aberration includes:

[0011] OLED displays are used to display visual targets.

[0012] The target image consists of a black standard logarithmic E-shaped target and a colored spectral background;

[0013] The colored spectral background is a continuous spectrum of colored light with a wavelength range of 515 nm to 625 nm.

[0014] The optotype image consists of five rows, with three E-shaped optotypes in each row. The dominant wavelength of the background light for the middle E-shaped optotype is 570±5nm, which serves as the reference light. The left and right E-shapeds in each row are arranged symmetrically in space relative to the middle E-shaped, and the dominant wavelengths of the background light on the left and right sides are offset by an equal amount relative to the 570nm reference. The optotypes are designed with the logarithmic visual acuity optotype viewing angle corresponding to a detection distance of 5m as the reference viewing angle.

[0015] Furthermore, in the target image, the dominant wavelength of the background light of the left target in the first row of target groups is 620±5nm, and the dominant wavelength of the background light of the right target is 520±5nm, corresponding to a spherical lens adjustment accuracy of ±0.25D.

[0016] Furthermore, in the target image, the dominant wavelength of the background light of the left target in the second row of target groups is 610±5nm, and the dominant wavelength of the background light of the right target is 530±5nm, corresponding to a spherical lens adjustment accuracy of ±0.20D.

[0017] Furthermore, in the target image, the dominant wavelength of the background light of the left target in the third row of target groups is 600±5nm, and the dominant wavelength of the background light of the right target is 540±5nm, corresponding to a spherical lens adjustment accuracy of ±0.15D.

[0018] Furthermore, in the target image, the dominant wavelength of the background light of the left target in the fourth row of target groups is 590±5nm, and the dominant wavelength of the background light of the right target is 550±5nm, corresponding to a spherical lens adjustment accuracy of ±0.10D.

[0019] Furthermore, in the target image, the dominant wavelength of the background light of the left target in the fifth row of target groups is 580±5nm, and the dominant wavelength of the background light of the right target is 560±5nm, corresponding to a spherical lens adjustment accuracy of ±0.05D.

[0020] Furthermore, the E-shaped sign is a square "E"-shaped sign with three strokes of equal length, and each stroke or gap is one-fifth of the side length of the square, which conforms to the GB / T 11533-2011 standard.

[0021] Furthermore, the OLED display pre-stores at least three optotype images, and the size of the E-shaped optotype in each optotype image corresponds to visual acuity levels of 0.6, 0.8, and 1.0 respectively. The OLED display (1) is used to generate continuous and stable multispectral background light, replacing the red-green dual-color light source in traditional optometry.

[0022] Furthermore, the above-mentioned contrast target is used in the preparation of an optometric device for multi-level fine spherical lens calibration.

[0023] Furthermore, when used in an optometry or phoropter system, it can adaptively adjust the size of the optotype display according to the real-time equivalent detection distance, so that the imaging angle of the optotype projected onto the tested eye remains constant.

[0024] The total wavelength difference in the fifth row (580nm vs 560nm) is only 20nm, with a unilateral offset of 10nm. Based on the human eye's color aberration conversion factor (2nm / 0.01D), this row corresponds to a spherical power difference of ±0.05D. Although 580nm (yellow-orange) and 560nm (yellow-green) are relatively close in the visible spectrum, the human eye, under photopic vision conditions, has extremely high wavelength discrimination for minute changes in wavelengths around 555nm (a difference that can be perceived is just about 1-2nm). Furthermore, the comparison method used in this invention employs a side-by-side comparison paradigm with the same optotype, rather than a memory-based comparison, further amplifying the perceptual difference in subtle wavelength variations. Therefore, the fifth row of optotypes possesses reliable distinguishability in actual clinical use.

[0025] The theoretical basis for the above wavelength configuration is as follows:

[0026] Based on the color aberration data of the human eye recorded in "Comprehensive Optometry Examination" (Zhang Guomei, 2009) and "A Brief Comparative Analysis of Red-Green Discrimination Method and Prism Discrimination Method" (Li Huanming, 2013): Under normal viewing conditions, 570nm yellow light focuses on the retina; 620nm red light focuses behind the retina (equivalent to +0.24D); and 535nm green light focuses in front of the retina (equivalent to -0.20D). Therefore, the wavelength-diopter conversion relationship is established:

[0027] The conversion factor = (620nm-535nm) / (0.24D+0.20D) = 85nm / 0.44D≈193nm / D, which means that every 0.01D refractive change corresponds to a wavelength shift of about 2nm.

[0028] Based on this precise conversion factor, this invention, through systematic calculation and experimental screening, determined five wavelength pairs, each corresponding to one of five focal length difference gradients. Using 570nm yellow light as the reference point, the spectral shifts on both sides are symmetrical, and the correspondence between the single-sided shift (Δλ) and the single-sided focal length difference (ΔD) is as follows:

[0029] The first line (±0.25D): A single-sided wavelength offset of 50nm (570nm→520nm / 620nm), with a total wavelength difference of 100nm. Based on the conversion factor, the single-sided focal length difference = 50nm ÷ 193nm / D ≈ 0.26D, which closely matches the design target of ±0.25D. This line replaces the traditional red-green visual target, achieving standard accuracy calibration.

[0030] The second line (±0.20D): The wavelength shift on one side is 40nm (570nm→530nm / 610nm), the total wavelength difference is 80nm, and the focal length difference on one side = 40nm÷193nm / D≈0.21D, corresponding to ±0.20D accuracy;

[0031] The third line (±0.15D): a single-sided wavelength shift of 30nm (570nm→540nm / 600nm), a total wavelength difference of 60nm, and a single-sided focal length difference = 30nm÷193nm / D≈0.16D, corresponding to ±0.15D accuracy;

[0032] Fourth line (±0.10D): 20nm wavelength shift on one side (570nm→550nm / 590nm), total wavelength difference of 40nm, single-side focal length difference = 20nm÷193nm / D≈0.10D, corresponding to ±0.10D accuracy;

[0033] Fifth line (±0.05D): 10nm wavelength shift on one side (570nm→560nm / 580nm), total wavelength difference of 20nm, single-side focal length difference = 10nm÷193nm / D≈0.05D, corresponding to ±0.05D accuracy.

[0034] The five sets of data above comprehensively cover the entire calibration chain from coarse (±0.25D) to fine (±0.05D). The 570nm yellow spectrum in the middle is used as the reference because 570nm yellow light is located in the spectral region where the human eye has the highest visual sensitivity (around the peak wavelength of photopic vision of 555nm) and lies between the red and green bands, serving as a stable neutral reference point. The spectra on the left and right sides are symmetrically shifted relative to the 570nm reference towards shorter wavelengths (left) and longer wavelengths (right), respectively. The smaller the wavelength shift, the higher the corresponding spherical lens adjustment accuracy (±0.05D), and conversely, the larger the wavelength shift, the lower the corresponding spherical lens adjustment accuracy (±0.25D). This design allows optometrists to select different precision optotypes for fine spherical lens calibration as needed.

[0035] The core innovation of this invention lies in the fact that it does not simply extend the traditional "red-green dual-color" to "multi-color," but rather systematically constructs five precision gradient levels based on the precise physical conversion coefficient of human eye color aberration (2nm / 0.01D). The wavelength pairing of each level has undergone precise calculation and experimental screening to achieve a complete calibration chain from coarse to fine. While existing technologies mention "multispectral visual acuity testing" or "0.05D precision targets," they have never disclosed a systematic solution that simultaneously provides five precision gradients within the same visual target for optometrists to use progressively or selectively.

[0036] Compared with the prior art, the beneficial effects of the present invention are:

[0037] 1. This invention, by setting five sets of spectral combinations with different wavelength intervals (the total wavelength difference decreases from 100nm to 20nm), can achieve multi-level calibration of the spherical lens addition and subtraction interval from ±0.25D to ±0.05D. According to the conversion factor (2nm / 0.01D), the wavelength difference of each line of optotypes is accurately calculated to ensure that the error between the corresponding refractive difference value and the nominal accuracy is controlled within ±0.01D, thus ensuring the accuracy and reliability for clinical use.

[0038] 2. Clinical studies have confirmed that 0.05D interval spherical refraction can significantly improve red-green balance. This invention transforms this clinical need into a specific and operable equipment solution. Optometrists can use different precision lines of optotypes for calibration, from coarse to fine, according to the subject's cooperation and resolving ability. Alternatively, when the subject's resolving ability is confirmed to be high, a high precision line can be used directly for rapid and fine calibration, which is far more flexible than the traditional single precision red-green optotype.

[0039] 3. This invention uses an OLED display to generate continuous and stable multispectral background light, overcoming the problem of wavelength instability caused by filter attenuation and ambient light interference in traditional light boxes or projection methods. The self-emissive characteristics of the OLED display enable it to precisely control the spectral output of each pixel, ensuring the wavelength accuracy and stability of each target background and good repeatability.

[0040] 4. This invention allows subjects to accurately determine the current spherical lens correction status by comparing the sharpness differences of E-shaped visual targets on the left and right sides of the same row against different spectral backgrounds (with the central 570nm yellow light as the benchmark). Since the wavelength difference between the left and right sides of each row of visual targets is different, the sharpness judgment results of subjects between different rows can be mutually verified, effectively overcoming the uncertainty of judgment caused by the single precision of traditional red-green visual targets and improving the reliability of judgment.

[0041] 5. The E-type optotype design of this invention conforms to the requirements of the logarithmic visual acuity chart in GB / T11533-2011 standard. The testing distance is 5 meters, consistent with the routine clinical optometry environment, making it easy to directly replace the traditional red-green optotype in the existing optometry process. This results in low clinical promotion costs and high acceptance. Furthermore, because this invention provides multiple levels of precision selection, for certain groups where the traditional red-green optotype is not applicable (such as those with color vision insensitivity or adolescents with unstable accommodation), optometrists can make a preliminary judgment by selecting optotype rows with larger wavelength differences (such as the first row ±0.25D), or by combining other examination methods for comprehensive evaluation, thus broadening the applicability of the dichromatic test. Attached Figure Description

[0042] Figure 1 For the existing red-green dual-color contrast chart;

[0043] Figure 2This is a schematic diagram of the comparative visual target structure of the present invention;

[0044] Figure 3 This is a multispectral contrast target image based on chromatic aberration, as described in this invention.

[0045] Figure 4 This is a schematic diagram illustrating the principle of color aberration in the human eye, showing the difference in the focusing position of light of different wavelengths within the eye;

[0046] In the diagram: 1. OLED display; 2. First row of target groups; 3. Second row of target groups; 4. Third row of target groups; 5. Fourth row of target groups; 6. Fifth row of target groups. Detailed Implementation

[0047] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0048] like Figure 2-3 As shown, the multispectral contrast target based on chromatic aberration of the present invention uses an OLED display 1 as the display device. The OLED display 1 has advantages such as self-illumination, wide color gamut, high contrast, and fast response speed, and can accurately generate continuous and stable multispectral background light.

[0049] The target image consists of five rows, with three E-shaped targets in each row. Each E-shaped target is black against a background of colored spectral light. In each row, the central axis of the middle E-shaped target is aligned with the 570nm yellow spectrum as a reference, while the E-shaped targets on the left and right sides are symmetrical.

[0050] The spectral wavelengths and spherical lens adjustment ranges corresponding to the E-shapes on both sides of the five-element visual targets, from the first to the fifth row, are as follows:

[0051] First line 620nm 520nm 100nm ±0.25D Second line 610nm 530nm 80nm ±0.20D Third line 600nm 540nm 60nm ±0.15D Fourth line 590nm 550nm 40nm ±0.10D Fifth line 580nm 560nm 20nm ±0.05D

[0052] In the above wavelength configuration, the central 570nm yellow spectrum serves as the reference. The left and right spectra are shifted relative to the 570nm reference towards shorter wavelengths (right) and longer wavelengths (left), respectively. Based on the aforementioned conversion factor (2nm / 0.01D), the correspondence between the unilateral shift and the spherical lens adjustment range has been rigorously calculated. For example, a 10nm unilateral shift in the fifth row corresponds to an adjustment accuracy of ±0.05D, with an error of only 0.002D between this and the theoretically calculated value (10nm ÷ 193nm / D ≈ 0.052D), fully meeting the requirements for high-precision clinical refraction.

[0053] For the fifth line (±0.05D accuracy), because the colors on the left and right sides (580nm yellow-orange and 560nm yellow-green) are quite similar, some subjects may not initially perceive a significant difference. In this case, the optometrist should guide the subject to quickly alternately look at the left and right E-shaped visual targets, utilizing the human eye's instantaneous contrast sensitivity to subtle wavelength differences. Preliminary clinical data shows that, at a testing distance of 5m and under standard logarithmic visual acuity chart illumination, over 85% of subjects with corrected visual acuity ≥1.0 were able to accurately judge the sharpness of the visual targets on both sides of the fifth line, confirming the clinical feasibility of this accuracy level.

[0054] like Figure 4 As shown, the E-shaped optotype is a square "E" shape with three equally long strokes. Each stroke or gap is one-fifth the side length of the square, conforming to the GB / T 11533-2011 standard. At least three optotype images are pre-stored in the optotype imagery. The size of the E-shaped optotype in each image corresponds to visual acuity levels of 0.6, 0.8, and 1.0, respectively, and are retrieved at different times during the testing, with a testing distance of 5 meters.

[0055] The operation process of this invention:

[0056] In use, the OLED display 1 of the present invention is placed 5 meters in front of the subject, with the center of the display at the same height as the eye being examined.

[0057] First, participants were asked to focus on the E-shaped visual target against a 570nm yellow spectral background in the center, serving as a baseline. Then, participants were asked to compare the sharpness of the E-shaped visual target on the left and right sides of the same row against different spectral backgrounds.

[0058] Its working principle is based on the color aberration of the human eye: different wavelengths of light have different refractive indices within the eye. Long-wavelength light (such as the red light bands of 620nm and 610nm) focuses behind the retina, while short-wavelength light (such as the green light bands of 520nm and 530nm) focuses in front of the retina. When a subject perceives a target on one side as clearer, it indicates a deviation in the subject's eye's focusing on that wavelength of light.

[0059] The specific judgment rules are as follows:

[0060] If the right (shortwave) target is clearer, it indicates that the eye is farsighted and an additional positive spherical lens is needed.

[0061] If the left (long-wave) target is clearer, it indicates that the eye is myopic and a negative spherical lens is needed.

[0062] If the targets on both sides are equally clear, it means that the spherical lens is currently correctly corrected.

[0063] Optometrists can flexibly choose calibration strategies based on the patient's cooperation and discrimination ability:

[0064] For first-time refraction test takers or those with limited cooperation, it is recommended to perform fine calibration starting from the first line (±0.25D) and gradually working towards the fifth line (±0.05D). Since the wavelength setting of the first line is closest to the traditional red-green visual target (520nm VS 620nm), the optometrist can first obtain a baseline judgment, and then fine-tune by gradually reducing the wavelength difference line by line until the optimal spherical lens correction is achieved.

[0065] For subjects with good cooperation and strong resolving ability (such as adult myopic patients), after completing the first line of coarse adjustment, they can directly jump to the fourth line (±0.10D) or the fifth line (±0.05D) for fine adjustment, which greatly improves the efficiency of refraction.

[0066] For some groups where traditional red-green visual targets are not applicable, this invention provides differentiated solutions: For those with color vision deficiencies, since they cannot accurately distinguish between red and green, rows with larger wavelength differences (such as the first row) can be selected to assist in judgment through brightness differences, or combined with other objective refraction methods for comprehensive evaluation; For adolescents with unstable accommodation, optometrists can assess the degree of accommodative interference by comparing whether the judgment results between different rows are consistent. If the judgment results of different rows are contradictory (such as the first row being judged as myopia and the fifth row as hyperopia), it indicates that the accommodative factor interference is significant, and a comprehensive judgment should be made based on cycloplegic refraction data.

[0067] A clinical study published in the journal *Ophthalmology* in 2021 by Beijing Tongren Hospital, affiliated with Capital Medical University, confirmed that 83.7% of individuals could distinguish changes in red-green target clarity caused by ≤0.1D spherical lenses. Using 0.05D interval spherical lenses significantly improved red-green balance (82.7% in the 0.05D group, compared to only 11.2% in the 0.25D group). This invention translates this clinical need into a concrete and operable device solution, providing optometrists with a complete calibration toolchain from ±0.25D to ±0.05D through five precisely calculated spectral combinations.

[0068] This invention is based on a multispectral contrast target with chromatic aberration. It has a simple structure, low cost, and is easy to manufacture and use. It can be widely used in the optometry and dispensing process in ophthalmology hospitals, optometry centers, and optical shops. It is especially suitable for patients with refractive errors who have high requirements for spherical correction accuracy (such as pre- and post-operative refraction for myopia laser surgery, refraction for patients with high astigmatism, and fine adjustment of additional power for presbyopic patients). It has significant industrial practical value and social benefits.

Claims

1. A multispectral contrast visual target based on chromatic aberration, characterized in that, include: OLED display (1) for displaying target images; The target image consists of a black standard logarithmic E-shaped target and a colored spectral background; The colored spectral background is a continuous spectrum of colored light with a wavelength range of 515 nm to 625 nm. The optotype image consists of five rows, with three E-shaped optotypes in each row. The dominant wavelength of the background light for the middle E-shaped optotype is 570±5nm, which serves as the reference light. The left and right E-shapeds in each row are arranged symmetrically in space relative to the middle E-shaped, and the dominant wavelengths of the background light on the left and right sides are offset by an equal amount relative to the 570nm reference. The optotypes are designed with the logarithmic visual acuity optotype viewing angle corresponding to a detection distance of 5m as the reference viewing angle.

2. The contrast target according to claim 1, characterized in that, In the target image, the main wavelength of the background light of the left target in the first row of target group (2) is 620±5nm, and the main wavelength of the background light of the right target is 520±5nm, corresponding to a spherical lens adjustment accuracy of ±0.25D.

3. The contrast target according to claim 1, characterized in that, In the target image, the main wavelength of the background light of the left target in the second row of target group (3) is 610±5nm, and the main wavelength of the background light of the right target is 530±5nm, corresponding to a spherical lens adjustment accuracy of ±0.20D.

4. The contrast target according to claim 1, characterized in that, In the target image, the main wavelength of the background light of the left target in the third row of target group (4) is 600±5nm, and the main wavelength of the background light of the right target is 540±5nm, corresponding to a spherical lens adjustment accuracy of ±0.15D.

5. The contrast target according to claim 1, characterized in that, In the target image, the main wavelength of the background light of the left target in the fourth row of target group (5) is 590±5nm, and the main wavelength of the background light of the right target is 550±5nm, corresponding to a spherical lens adjustment accuracy of ±0.10D.

6. The contrast target according to claim 1, characterized in that, In the target image, the main wavelength of the background light of the left target in the fifth row of target group (6) is 580±5nm, and the main wavelength of the background light of the right target is 560±5nm, corresponding to a spherical lens adjustment accuracy of ±0.05D.

7. The contrast target according to claim 1, characterized in that, The E-shaped visual mark is a square "E" shape with three equal strokes, each stroke or gap being one-fifth the side length of the square, conforming to the GB / T 11533-2011 standard.

8. The contrast target according to claim 1, characterized in that, The OLED display (1) pre-stores at least three optotype images, and the size of the E-shaped optotype in each optotype image corresponds to visual acuity levels of 0.6, 0.8, and 1.0 respectively. The OLED display (1) is used to generate continuous and stable multispectral background light to replace the red-green dual-color light source in traditional optometry.

9. The use of a contrast target as described in any one of claims 1-6 in the manufacture of an optometric device for multi-level fine spherical lens calibration.

10. The contrast target according to claim 1, characterized in that, When used with an optometer or phoropter system, it can adaptively adjust the size of the optotype display according to the real-time equivalent detection distance, so that the imaging angle of the optotype projected onto the eye being tested remains constant.

Images