CN107960979B - An illumination imaging system for dry eye detection - Google Patents

Abstract

The invention discloses an illumination imaging system for detecting dry eye, comprising: a Placido disc, which includes several black and white concentric rings; an illumination optical system, which is arranged on the rear surface of the Placido disc, and the illumination optical system Including several groups of LED units arranged in a ring shape, the Placido disc is projected to the tear film; an imaging optical system, which receives the projection map of the Placido disc on the tear film, along the imaging optical path, the imaging optical system sequentially includes imaging Objective and CCD camera. The invention can collect a series of pictures of the tear film on the eye surface of the examinee from completeness to rupture in a non-invasive manner, and then post-process the image algorithm to obtain the tear film rupture time, thereby judging the examinee Whether the tear film break-up time is abnormal or not, the technical solution of the present invention can not only reduce the pain of the patient, but also improve the stability and accuracy of the detection result.

Description

An illumination imaging system for dry eye detection

technical field

The present invention relates to the field of optical detection. More particularly, the present invention relates to an illumination imaging system for dry eye detection.

Background technique

Dry eye syndrome, also known as keratoconjunctiva xerosis, common symptoms include dry eyes, easy fatigue, itchy eyes, foreign body sensation, burning sensation, thick secretions, fear of wind, photophobia, and sensitivity to external stimuli. The prevalence of dry eye is about 21%-33.7%. At present, the incidence of dry eye in the world is increasing year by year, and it has developed into a common and frequently-occurring disease that endangers health. With the widespread use of electronic screens, environmental degradation, the abuse of eye drops, and the wearing of contact lenses, dry eye syndrome will continue to increase. The main cause of dry eye syndrome is the abnormal rupture of the tear film on the ocular surface. Relevant research articles show that the tear film rupture time of dry eye patients is usually less than 10s, and the tear film rupture time of normal people is generally 10-45s. The breakup time of tear film is an important indicator to judge whether there is dry eye disease, so accurate and effective detection of tear film breakup time is of great significance for the examination of dry eye disease.

Traditional dry eye examination methods include slit lamp examination, tear secretion test (Schirmer I and II test), tear break-up time (BUT) test, ocular surface biopsy, and tear osmolarity measurement. Test, lactoferrin content determination (Lactoferrin, LF) test, tear fern-like change test, conjunctival imprint cytology, serology and so on. These traditional methods for evaluating tear film stability are invasive tear break-up time (IBUT), which have limitations such as large variability, low repeatability, and susceptibility to external influences.

SUMMARY OF THE INVENTION

SUMMARY OF THE INVENTION An object of the present invention is to address at least the above-mentioned problems and/or disadvantages and to provide at least the advantages that will be described hereinafter.

Another object of the present invention is to provide an illumination imaging system for the detection of dry eye syndrome, which can collect a series of pictures of the tear film on the eye surface of the examinee from intact to ruptured in a non-invasive manner, and then process the image through an image algorithm, namely, The tear film break-up time can be obtained, so that it can be judged whether the tear film break-up time of the examinee is abnormal.

To achieve these objects and other advantages in accordance with the present invention, there is provided a dry eye detection illumination imaging system comprising:

Placido disc, which includes several black and white concentric rings, wherein white is the light-transmitting part, and black is the opaque part;

The illumination optical system is arranged on the rear surface of the Placido disc, the illumination optical system comprises several groups of LED units arranged in a ring shape, and the black and white stripes on the Placido disc are projected onto the tear film, wherein the LED lamp beads are annular The arrangement can significantly improve the uniform light effect of lighting;

An imaging optical system, which receives the projection image of the Placido disc on the tear film, along the imaging optical path, the imaging optical system sequentially includes an imaging objective lens and a CCD camera.

Preferably, an acrylic light diffusion plate is further arranged between the illumination optical system and the Placido disc, so as to further improve the uniform diffusion of the illumination light source. The illumination of a uniform light source can make the black and white stripes in the Placido disc form concentric rings of light and dark, improving the contrast of imaging.

Preferably, the distance between the illumination optical system and the acrylic light diffusion plate is 7-15 cm, so as to achieve the optimal diffusion effect for the LED light source.

Preferably, the Placido disk is designed in an ellipsoid shape, so as to improve the imaging brightness of the CCD unit.

Preferably, the illumination optical system includes four groups of LED units arranged in a ring, so as to achieve uniform dispersion of the illumination light intensity.

Preferably, each group of LED units is composed of LED lamp beads arranged at equal intervals, and the LED lamp beads are infrared LED lamp beads with a wavelength of 850 nm. Since the image acquisition in the detection of dry eye is continuous and long-term, in order to reduce the stimulation to the human eye, the infrared LED lamp beads with a wavelength of 850nm are selected.

Preferably, the divergence angle of the infrared LED lamp bead is 150°, so as to ensure the uniformity of the brightness of the imaging of the Placido disk.

Preferably, from the inner ring to the outer ring, the arrangement spacing between the four groups of annular LED units is 1:1-1.5:0.3-0.7, so as to ensure the uniform divergence of the illuminating light intensity.

Preferably, along the imaging optical path, the imaging objective lens sequentially includes: a first plano-convex lens whose convex surface faces the object side; a concave lens; a convex lens; a second plano-convex lens whose convex surface faces the object side; and a meniscus mirror whose convex surface is Facing the object, the imaging objective lens can effectively correct aberrations such as spherical aberration, astigmatism and field curvature through the combination of 5 lens units, and improve the imaging quality;

The diaphragm is arranged between the first plano-convex lens and the concave lens and is close to the concave lens, and the lens of the concave lens close to the diaphragm is bent toward the diaphragm, so that the declination angle of the chief ray is as small as possible, which is conducive to the correction of off-axis aberrations.

Preferably, the concave lens and the convex lens are cemented together to correct chromatic aberration, wherein the cemented lens can be selected from a glass material with a larger chromatic aberration, which can effectively reduce axial chromatic aberration.

The present invention includes at least the following beneficial effects:

(1) The technical solution of the present application adopts the non-invasive testing method based on the Placido disc, which can not only reduce the pain of the patient, but also improve the stability and accuracy of the testing result;

(2) The photo optical system of this application document adopts the LED ring arrangement design, and the reasonable arrangement of several groups of LED units and the lamp beads therein can significantly improve the uniform divergence of the illumination light source, and improve the adjacent black and white stripes in the Placido disk imaging. the contrast;

(3) The objective lens in the imaging optical system of this application can effectively correct aberrations such as spherical aberration, astigmatism and field curvature through the combination of 5 lens units, and the concave lens and convex lens are cemented together to correct chromatic aberration and significantly improve the image quality.

Other advantages, objects, and features of the present invention will appear in part from the description that follows, and in part will be appreciated by those skilled in the art from the study and practice of the invention.

Description of drawings

1 is a schematic structural diagram of an illumination imaging system for dry eye detection in an example of the present invention;

2 is a schematic structural diagram of LED units arranged in a ring shape in another example of an illumination optical system of the present invention;

3 is a schematic structural diagram of an objective lens in another example imaging optical system of the present invention;

FIG. 4 is a schematic diagram of a dot sequence for verifying the imaging optical system using zemax software in another example of the present invention;

Fig. 5 is the modulation transfer function (MFT) diagram that adopts zemax software to verify the imaging optical system in another example of the present invention;

Fig. 6 is the field curvature distortion diagram that adopts zemax software to verify the imaging optical system in another example of the present invention;

Fig. 7 is the wave aberration diagram that adopts zemax software to verify the imaging optical system in another example of the present invention;

FIG. 8 is a projection imaging diagram of the tear film on the surface of the human eye using the dry eye syndrome detection illumination imaging system in another example of the present invention.

In the figure: 1-Placido disk; 2-Illumination optical system; 3-Tear film; 4-Image objective lens; 5-CCD camera; 6-Acrylic light diffusion plate; 21-LED lamp beads; 41-First plano-convex lens 41; 42-concave lens; 43-convex lens; 44-second plano-convex lens; 45-meniscus; 46-diaphragm.

Detailed ways

The present invention will be further described in detail below with reference to the accompanying drawings, so that those skilled in the art can implement it with reference to the description.

It should be understood that terms such as "having", "comprising" and "including" as used herein do not assign the presence or addition of one or more other elements or combinations thereof.

Figures 1-2 show an implementation form according to the present invention, which includes: .

Placido disc 1, which includes several black and white concentric rings;

Illumination optical system 2, which is arranged on the rear surface of the Placido disc, the illumination optical system includes several groups of LED units arranged in a ring shape, and projects the Placido disc to the tear film 3;

The imaging optical system, which receives the projection image of the Placido disc on the tear film, along the imaging optical path, the imaging optical system sequentially includes an imaging objective lens 4 and a CCD camera 5 .

In this technical solution, the LED illumination optical system illuminates the Placido disc, and projects the image of the Placido disc with black and white stripes onto the tear film, and then the light is reflected by the tear film and passes through the imaging objective lens to image the tear film surface image on the tear film. on the CCD camera. When the tear film on the surface of the human eye is intact without rupture, the black and white circles on the tear film on the surface of the human eye captured by the CCD camera are complete coaxial circles. When the tear film on the surface of the human eye is ruptured, The black and white rings on the human tear film captured by the CCD camera are broken and distorted. According to a series of pictures of the tear film on the subject's eye surface from completeness to rupture, collected by the CCD camera, and then processed by the image algorithm, the tear film rupture time can be obtained, so that the tear film rupture time of the examinee can be judged. Is it abnormal.

In another example, an acrylic light diffusion plate 6 is further provided between the illumination optical system and the Placido disc, so as to further improve the diffusion uniformity of the illumination light source. Moreover, this method is only an illustration of a preferred example, but not limited thereto. When implementing the present invention, the aspect of the illumination optical system diffusion device can be implemented according to the needs of the user.

In another example, the distance between the illumination optical system and the acrylic light diffusion plate is 7-15 cm.

In another example, the Placido disc has an ellipsoidal design, and this approach is merely an illustration of a preferred example, but not limited thereto.

In another example, referring to FIG. 2 , the illumination optical system includes four groups of LED units arranged in a ring shape. Moreover, this method is only an illustration of a preferred example, but not limited thereto. When implementing the present invention, different aspects of the illumination optical system can be implemented according to user requirements.

In the above example, each group of LED units is composed of LED lamp beads 21 arranged at equal intervals, and the LED lamp beads are infrared LED lamp beads with a wavelength of 850 nm.

In the above example, the divergence angle of the infrared LED lamp bead is 150°.

In the above example, along the inner ring to the outer ring, the arrangement spacing between the four groups of annular LED units is 1:1-1.5:0.3-0.7.

Using the illumination optical system of this example to illuminate the Placido disc, take the center of the disc as the center of the circle, measure the illuminance value with a spectrometer every 90° on the front surface of each white ring (the side close to the human eye), and obtain the illuminance of 44 points. The measured data are shown in Table 1. The uniformity of the illuminance value calculated from Table 1 is 88.8%, which indicates that the illumination optical system design of this example can uniformly illuminate the rear surface of the Placido disc to meet the imaging requirements of the rear system.

Table 1 Measured illuminance value of Placido plate

In another example, referring to FIG. 3 , the imaging objective lens 4 sequentially includes: a first plano-convex lens 41 whose convex surface faces the object side; a concave lens 42 ; a convex lens 43 ; a second plano-convex lens 44 whose convex surface faces the object side; a meniscus Mirror 45, whose convex surface faces the object side;

The diaphragm 46 is disposed between the first plano-convex lens and the concave lens and is close to the concave lens.

Moreover, this method is only an illustration of a preferred example, but not limited thereto. When implementing the present invention, different aspects of the imaging objective lens can be implemented according to user requirements.

In the above example, referring to FIG. 3 , the concave lens and the convex lens are cemented together. Moreover, this method is only an illustration of a preferred example, but not limited thereto.

Referring to Figures 3 to 7, use the zemax software to verify the imaging system of this example. In the zemax software, four fields of view are selected, which are 0mm, 4.5mm, 6.3mm, and 9mm, respectively. As shown in Figure 4, the root mean square (RMS value) of the diffuse spot is smaller than the CCD pixel size of 5.5um in each field of view, and each value is close to the Airy disk size; Figure 5 shows the MTF curve of the system, It can be seen from the figure that the MTF value of the full field of view is greater than 0.4 at the spatial frequency value of 91lp/mm, and the MTF curve is close to the diffraction limit; Figure 6 is the system field curvature distortion diagram. It can be seen from the figure that the field curvature is The maximum point of the full field of view is not more than 0.04mm, and the maximum distortion of the full field of view is not more than 0.8%; Figure 7 is the wave aberration diagram of the system. 0.25 wavelengths. It can be seen from the above that the system has good imaging quality and meets the design requirements.

In another example, the present invention is further elaborated in conjunction with the specific application of the technical solution of the present application in the detection of tear film on the surface of the human eye:

Referring to Fig. 8, the projection picture on the tear film collected by the dry eye detection imaging system prepared by this technical solution is a regular concentric circle, and the projection picture of the Placido ring on the visible ocular surface is a regular concentric circle, thus it can be seen that the tear film surface The brightness uniformity of the ring is relatively good, and the projection map of the Placido disk on the surface of the tear film of good quality is obtained.

The number of apparatuses and processing scales described here are intended to simplify the description of the present invention. Applications, modifications and variations to the dry eye detection illumination imaging system of the present invention will be apparent to those skilled in the art.

As described above, according to the present invention, a series of pictures of the tear film on the eye surface of the examinee from intact to rupture can be collected in a non-invasive manner, which can not only reduce the pain of the patient, but also improve the stability and accuracy of the detection result .

Although embodiments of the present invention have been disclosed above, they are not limited to the applications set forth in the specification and embodiments. It can be fully adapted to various fields suitable for the present invention. Additional modifications can readily be implemented by those skilled in the art. Therefore, the invention is not to be limited to the specific details and illustrations herein shown and described, without departing from the general concept defined by the appended claims and the scope of equivalents.

Claims (2)

1. a dry eye detection illumination imaging system, is characterized in that, comprises: Placido disc, which includes several black and white concentric rings; An illumination optical system, which is arranged on the rear surface of the Placido disc, the illumination optical system includes four groups of LED units arranged in a ring shape, and from the inner ring to the outer ring, the arrangement spacing of the four groups of ring LED units is 1: [ 1 to 1.5]: [0.3 to 0.7] to ensure the uniform divergence of the illumination light intensity, the illumination optical system projects the Placido disc to the tear film; An acrylic light diffusion plate is also arranged between the illumination optical system and the Placido disc to improve the diffusion uniformity of the illumination light source LED unit; an imaging optical system, which receives the projection image of the Placido disc on the tear film, along the imaging optical path, the imaging optical system sequentially includes an imaging objective lens and a CCD camera; Described Placido disc is ellipsoid design to improve the brightness of CCD camera imaging; Each group of the LED units is composed of LED lamp beads arranged at equal intervals. The LED lamp beads are infrared LED lamp beads with a wavelength of 850 nm. The divergence angle of the infrared LED lamp beads is 150° to ensure the brightness of the Placido disk imaging. homogeneity; Along the imaging optical path, the imaging objective lens sequentially includes: a first plano-convex lens with its convex surface facing the object side; a concave lens; a convex lens; a second plano-convex lens with its convex surface facing the object side; and a meniscus mirror with its convex surface facing the object side; The combination of lens units can effectively correct aberrations such as spherical aberration, astigmatism and field curvature; Wherein, the diaphragm is arranged between the first plano-convex lens and the concave lens and is close to the concave lens; the lens of the concave lens close to the diaphragm is bent toward the diaphragm, so that the declination angle of the chief ray is as small as possible, which is conducive to the correction of off-axis aberrations; The concave and convex lenses are cemented together to correct chromatic aberration. 2 . The illumination imaging system for dry eye disease detection according to claim 1 , wherein the distance between the illumination optical system and the acrylic light diffusion plate is 7-15 cm. 3 .

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