CN107960979B

CN107960979B - Xerophthalmia detects illumination imaging system

Info

Publication number: CN107960979B
Application number: CN201711479540.2A
Authority: CN
Inventors: 董月芳; 朱海龙; 付威威; 刘敏; 周哲
Original assignee: Suzhou Institute of Biomedical Engineering and Technology of CAS
Current assignee: Suzhou Institute of Biomedical Engineering and Technology of CAS
Priority date: 2017-12-29
Filing date: 2017-12-29
Publication date: 2020-09-29
Anticipated expiration: 2037-12-29
Also published as: CN107960979A

Abstract

The invention discloses a xerophthalmia detection illumination imaging system, which comprises: a Placido plate comprising a plurality of black and white concentric rings; the illumination optical system is arranged on the rear surface of the Placido plate and comprises a plurality of groups of LED units which are annularly arranged, and the Placido plate is projected to the tear film; and the imaging optical system receives the Placido disc projection drawing on the tear film and sequentially comprises an imaging objective lens and a CCD camera along an imaging optical path. The invention can collect a series of pictures from complete to rupture of the tear film on the surface of the eye of the examinee in a non-invasive way, and then the pictures are processed by an image algorithm, so that the rupture time of the tear film can be obtained, and whether the rupture time of the tear film of the examinee is abnormal or not can be judged.

Description

Xerophthalmia detects illumination imaging system

Technical Field

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

Background

The xerophthalmia, also known as keratoconjunctival xerosis, has common symptoms of dry eyes, easy tiredness, itchy eyes, foreign body sensation, burning sensation, viscous secretion, fear of wind, photophobia, sensitivity to external stimulation and the like, has the prevalence rate of the xerophthalmia in China of about 21 to 33.7 percent, has the current annual rising trend of the incidence rate of the xerophthalmia in the world, and has developed into a common disease and a frequently encountered disease which endanger health. Dry eye will continue to increase with the widespread use of electronic screens, environmental degradation, abuse of eye drops, wear of contact lenses, and the like. The main reason causing dry eye is abnormal rupture of the tear film on the surface of eyes, and related research articles show that the tear film rupture time of patients with dry eye is usually less than 10s, and the tear film rupture time of normal eyes is usually 10-45 s. The tear film rupture time is an important index for judging whether the patient has dry eye, so that accurate and effective detection of tear film rupture time is of great significance for examination of dry eye.

Conventional dry eye syndrome examination methods include: slit lamp examination, Tear secretion tests (Schirmer I and II tests), Tear film Break-up Time (BUT) test, eye surface vital stain test, Tear osmolarity test, Lactoferrin content determination (Lactoferrin, LF) test, Tear ferning test, conjunctival blot cytology examination, serology examination, and the like. The traditional method for evaluating the tear film stability is invasive tear film break-up time (IBUT), and has the limitations of large variability, low repeatability, easy influence from the outside and the like.

Disclosure of Invention

An object of the present invention is to solve at least the above problems and/or disadvantages and to provide at least the advantages described hereinafter.

It is still another object of the present invention to provide a dry eye syndrome detecting illumination imaging system, which can acquire a series of pictures from complete to rupture of the tear film on the surface of the eye of the examinee in a non-invasive manner, and then the pictures are processed by an image algorithm to obtain the rupture time of the tear film, so as to determine whether the rupture time of the tear film 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:

the Placido disc comprises a plurality of black and white concentric rings, wherein white is a light-transmitting part, and black is a light-proof part;

the illumination optical system is arranged on the rear surface of the Placido plate and comprises a plurality of groups of LED units which are annularly arranged, black and white stripes on the Placido plate are projected to the tear film, and the LED lamp beads are annularly arranged to obviously improve the light homogenizing effect of illumination;

and the imaging optical system receives the Placido disc projection drawing on the tear film and sequentially comprises an imaging objective lens and a CCD camera along an imaging optical path.

Preferably, an acrylic light diffusion plate is further disposed between the illumination optical system and the Placido plate to further improve uniform diffusion of the illumination light source. The illumination of the uniform light source can enable black and white stripes in the Placido plate to form concentric rings with alternate light and shade, and the contrast of imaging is improved.

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

Preferably, the Placido plate is of an ellipsoidal design to improve the brightness of the image formed by the CCD unit.

Preferably, the illumination optical system comprises four sets of LED units arranged in a ring shape to achieve uniform dispersion of the illumination intensity.

Preferably, each group of LED units consists of LED lamp beads arranged at equal intervals, and the LED lamp beads are infrared LED lamp beads with the wavelength of 850 nm. Because image acquisition is continuous long-time collection during xerophthalmia detection, in order to reduce the stimulation to people's eyes, the infrared LED lamp pearl that selects the wavelength to be 850 nm.

Preferably, the divergence angle of the infrared LED lamp beads is 150 degrees, so that the brightness uniformity of Placido disc imaging is ensured.

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

Preferably, wherein, along the imaging optical path, the imaging objective sequentially comprises: a first plano-convex lens with its convex surface facing the object; a concave lens; a convex lens; a second plano-convex lens with its convex surface facing the object; the imaging objective lens can effectively correct aberrations such as spherical aberration, astigmatism, field curvature and the like through the combination of 5 lens units, and the imaging quality is improved;

the diaphragm is arranged between the first plano-convex lens and the concave lens and close to the position of the concave lens, and the lens of the concave lens close to the diaphragm bends to the diaphragm, so that the deflection angle of the chief ray is as small as possible, and the correction of off-axis aberration is facilitated.

Preferably, the concave lens and the convex lens are glued together to correct chromatic aberration, wherein the cemented lens can be made of glass material with larger chromatic aberration, and axial chromatic aberration can be effectively reduced.

The invention at least comprises the following beneficial effects:

(1) the technical scheme of the application adopts a Placido disc-based non-invasive testing method, so that the pain of a patient can be reduced, and the stability and accuracy of a detection result are improved;

(2) the photo optical system disclosed by the application document adopts an LED annular arrangement design, and a plurality of groups of LED units and lamp beads in the LED units are reasonably arranged, so that the uniform divergence of an illumination light source can be obviously improved, and the contrast of adjacent black and white stripes in Placido disc imaging is improved;

(3) the objective lens in the imaging optical system can effectively correct aberrations such as spherical aberration, astigmatism, field curvature and the like through the combination of 5 lens units, and the concave lens and the convex lens are glued together to correct chromatic aberration, so that the imaging quality is obviously improved.

Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention.

Drawings

FIG. 1 is a schematic diagram of a dry eye detection illumination imaging system in accordance with an embodiment of the present invention;

FIG. 2 is a schematic diagram of an LED unit in an annular arrangement in an illumination optical system according to another embodiment of the present invention;

FIG. 3 is a schematic view of the structure of an objective lens in another example imaging optical system of the present invention;

FIG. 4 is a schematic diagram of a spot-column for verification of an imaging optical system using zemax software in another embodiment of the present invention;

FIG. 5 is a plot of modulation transfer function (MFT) for verification of an imaging optical system using zemax software in another example of the invention;

FIG. 6 is a graph of field curvature distortion for verification of an imaging optical system using zemax software in another embodiment of the present invention;

FIG. 7 is a wave aberration diagram for verification of an imaging optical system using zemax software in another example of the invention;

figure 8 is a projection image of a tear film on the surface of a human eye using a dry eye detection illumination imaging system in another embodiment of the invention.

In the figure: 1-Placido plate; 2-an illumination optical system; 3-tear film; 4-an imaging objective lens; 5-a CCD camera; 6-acrylic light diffuser plate; 21-LED lamp beads; 41-a first plano-convex lens 41; a 42-concave lens; 43-convex lens; 44-a second plano-convex lens; 45-meniscus lens; 46-diaphragm.

Detailed Description

The present invention is further described in detail below with reference to the attached drawings so that those skilled in the art can implement the invention by referring to the description text.

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

FIGS. 1-2 illustrate one implementation form according to the present invention, including: .

A Placido plate 1 which comprises a plurality of black and white concentric rings;

the illumination optical system 2 is arranged on the rear surface of the Placido plate, comprises a plurality of groups of LED units which are annularly arranged, and projects the Placido plate to the tear film 3;

and the imaging optical system receives the Placido disc projection drawing on the tear film and sequentially comprises an imaging objective lens 4 and a CCD camera 5 along an imaging optical path.

In the technical scheme, the LED illumination optical system illuminates the Placido plate, projects an image of the Placido plate with alternate black and white stripes onto a tear film of a human eye, then reflects the light through the tear film, and images a surface image of the tear film on the CCD camera through the imaging objective lens. When the tear film on the surface of the human eye is complete and has no rupture, the black and white rings on the tear film on the surface of the human eye collected by the CCD camera are complete coaxial circles, and when the tear film on the surface of the human eye is ruptured and distorted. A series of pictures from complete to rupture of the tear film on the surface of the eye of the examinee are acquired by a CCD camera, and the tear film rupture time can be obtained through the subsequent processing of an image algorithm, so that whether the tear film rupture time of the examinee is abnormal or not can be judged.

In another example, an acrylic light diffuser plate 6 is further disposed between the illumination optical system and the Placido plate to further improve the diffusion uniformity of the illumination light source. Also, this manner is merely an illustration of a preferred example, but not limited thereto. In the implementation of the invention, the aspect of the diffusion device of the illumination optical system can be implemented according to the requirements of users.

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 plate is of an ellipsoidal design, and this approach is merely illustrative of a preferred example, but not limiting.

In another example, referring to fig. 2, the illumination optical system includes four sets of LED units arranged in a ring shape. Also, this manner is merely an illustration of a preferred example, but not limited thereto. In the implementation of the present invention, different aspects of the illumination optical system can be implemented according to the user's needs.

In the above example, each group of LED units is composed of LED bulbs 21 arranged at equal intervals, and the LED bulbs are infrared LED bulbs 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, the arrangement distance between the four groups of annular LED units from the inner ring to the outer ring is 1: 1-1.5: 0.3 to 0.7.

The illumination optical system of the embodiment is adopted to illuminate the Placido plate, the center of the plate is taken as the center of a circle, illumination values are measured by a spectrometer at intervals of 90 degrees on the front surface (the side close to human eyes) of each white ring, illumination values of 44 points are obtained, the measured data are shown in table 1, the uniformity of the illumination values obtained by calculation of the table 1 is 88.8 percent, and the fact shows that the illumination optical system of the embodiment can be adopted to uniformly illuminate the rear surface of the Placido plate, and meets the imaging requirements of a subsequent system.

TABLE 1 Placido plate actual measurement illuminance value

In another example, with reference to fig. 3, the imaging objective 4 comprises in sequence: a first plano-convex lens 41 with its convex surface facing the object; a concave lens 42; a convex lens 43; a second plano-convex lens 44 with its convex surface facing the object; a meniscus mirror 45 with its convex surface facing the object;

wherein, the diaphragm 46 is arranged between the first plano-convex lens and the concave lens and is close to the position of the concave lens.

Also, this manner is merely an illustration of a preferred example, but not limited thereto. When the invention is implemented, different modes of the imaging objective lens can be implemented according to the requirements of users.

In the above example, referring to fig. 3, the concave lens and the convex lens are cemented together. Also, this manner is merely an illustration of a preferred example, but not limited thereto.

Referring to fig. 3-7, the imaging system of this example was validated using zemax software in which four fields of view were selected with object half heights of 0mm, 4.5mm, 6.3mm, and 9mm, respectively. As shown in fig. 4, the root mean square (RMS value) of the diffuse spots is smaller than the ccd pixel size of 5.5um in each field, and each value approaches the airy disc size; FIG. 5 shows the MTF curve for the system, where it can be seen that the full field MTF value is greater than 0.4 at a spatial frequency value of 91lp/mm, and the MTF curve approaches the diffraction limit; FIG. 6 is a distortion diagram of the field curvature of the system, and it can be seen from the diagram that the field curvature is not greater than 0.04mm at the maximum of the full field of view, and the maximum distortion of the full field of view is not greater than 0.8%; FIG. 7 is a wave aberration diagram of the system where the peak-to-valley ratio at 9mm of maximum field of view is 0.17 wavelengths, less than the Rayleigh criterion 0.25 wavelengths. From the above, the system has good imaging quality and meets the design requirements.

In another example, the invention is further described in conjunction with the specific application of the embodiments of the present document to the detection of tear film on the surface of the human eye:

referring to fig. 8, the projection picture of the Placido ring on the eye surface collected by the dry eye syndrome detection imaging system prepared by the technical scheme is a regular concentric circle, and the projection picture of the Placido ring on the eye surface is a regular concentric circle, so that the brightness uniformity of the Placido ring on the tear film surface is better, and the projection picture of the Placido plate on the tear film surface with good quality is obtained.

The number of apparatuses and the scale of the process described herein are intended to simplify the description of the present invention. Applications, modifications and variations of 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 invention, a series of pictures from complete to broken tear film on the surface of the eye of the examinee can be acquired in a non-invasive manner, so that the pain of the patient can be reduced, and the stability and the accuracy of the detection result can be improved.

While embodiments of the invention have been disclosed above, it is not intended to be limited to the uses set forth in the specification and examples. It can be applied to all kinds of fields suitable for the present invention. Additional modifications will readily occur to those skilled in the art. It is therefore intended that the invention not be limited to the exact details and illustrations described and illustrated herein, but fall within the scope of the appended claims and equivalents thereof.

Claims

1. A dry eye detection illumination imaging system, comprising:

a Placido plate comprising a plurality of black and white concentric rings;

illumination optical system, it locates Placido dish rear surface, illumination optical system includes that four groups are the LED unit of annular arrangement, along inner circle to outer lane, the interval of arranging of four groups of annular LED units is 1: [ 1-1.5 ]: [ 0.3-0.7 ] to ensure uniform divergence of illumination intensity, the illumination optical system projecting the Placido plate to the tear film;

an acrylic light diffusion plate is further arranged between the illumination optical system and the Placido plate to improve the diffusion uniformity of the illumination light source LED unit;

the imaging optical system receives a Placido disc projection drawing on the tear film and sequentially comprises an imaging objective lens and a CCD camera along an imaging optical path;

the Placido disc is designed in an ellipsoidal shape to improve the imaging brightness of the CCD camera;

each group of LED units consists of LED lamp beads arranged at equal intervals, the LED lamp beads are infrared LED lamp beads with the wavelength of 850nm, and the divergence angle of the infrared LED lamp beads is 150 degrees so as to ensure the brightness uniformity of Placido disc imaging;

along the imaging light path, the imaging objective lens sequentially comprises: a first plano-convex lens with its convex surface facing the object; a concave lens; a convex lens; a second plano-convex lens with its convex surface facing the object; and a meniscus mirror with its convex surface facing the object; aberrations such as spherical aberration, astigmatism and field curvature can be effectively corrected through the combination of the 5 lens units;

the diaphragm is arranged between the first plano-convex lens and the concave lens and is close to the position of the concave lens; the lens of the concave lens close to the diaphragm is bent to the diaphragm, so that the deflection angle of the main light ray is as small as possible, and the correction of off-axis aberration is facilitated;

the concave and convex lenses are cemented together to correct chromatic aberration.

2. The dry eye detection illumination imaging system of claim 1, wherein a distance between the illumination optical system and the acrylic light diffuser plate is 7-15 cm.