WO2014125063A1

WO2014125063A1 - Arrangement and method for automatically lighting fundus images

Info

Publication number: WO2014125063A1
Application number: PCT/EP2014/052893
Authority: WO
Inventors: Thomas Mohr; Björn ROSSBERGER; Tobias Schmitt-Manderbach; Wolfgang Grau
Original assignee: Carl Zeiss Meditec Ag
Priority date: 2013-02-15
Filing date: 2014-02-14
Publication date: 2014-08-21
Also published as: DE102013002827A1

Abstract

In order to produce an arrangement and a method for automatically lighting fundus images, by means of which a local maximum in the fundus image is evaluated in order to obtain significantly better image quality while simultaneously optimising lighting control, an image sensor (13) is proposed, which is connected to a control and evaluation unit (16) in order to determine and transmit a maximum intensity of a fundus image and which has a spatial minimum resolution of pixels and a very high image frequency. In order to automatically light fundus images, a local maximum in the fundus image is evaluated by the spatially-resolving image sensor (13) in repetition after the capture of a movement field of the eye, and the control and evaluation unit (16) determines a point in time for deactivating a lighting unit (1) from the data flow of the maximum intensities.

Description

Arrangement and method for automatic exposure of fundus images

The invention relates to an arrangement and a method for automatic exposure of Fundusaufnahmen for

Fundus cameras for observation, examination, diagnosis and therapy of an ocular fundus, if the fundus image contains a very high dynamic, very dark and very bright areas.

It is known that in the observation, examination and diagnosis of the ocular fundus of a patient with a fundus camera the problem arises that the

existing automatic exposure measures only an areal integral value for the entire fundus image and that upon reaching a threshold value the illumination, e.g. a flash lamp is turned off. This principle is disadvantageous if the fundus image contains a very high dynamic, very bright and very dark areas. The dynamics of a fundus image gives the ratio of the highest and the lowest in the image

Intensities. The integration over the entire picture of a fund of very high dynamics then includes

Reaching the threshold value overshadowed areas and these lead to a poorer image quality. That is why it is precisely in ophthalmology for the examinations of the eye, associated with the imaging of individual

Eye sections important, especially at

Single frames with a high dynamic both all

Structures are clearly displayed and at the same time easily recognizable. From the prior art, therefore, a variety of technical solutions are known to this

To achieve conditions for a very good picture quality. Thus, from DE 10 2007 046 210 AI an arrangement and a Method for generating images with an extended dynamics known by having at least one beam splitter,

in particular with an asymmetrical division ratio, and at least two image sensors are mirrored into at least one beam splitter in a common imaging beam path. From DE 10 2009 030 467 AI a device and a method for recording highly dynamic fundus and slit images at very low illumination intensity is also known by the device, a second opto-electronic sensor array and a

additional beam splitter for dividing the light reflected from the eye. Both opto-electronic sensor arrays pick up the light reflected from the eye and direct the output signals to the evaluation unit.

Based on this prior art, the present invention seeks to provide an arrangement and a method for automatic exposure of Fundusaufnahmen, by which a local maximum in the fundus image is evaluated in order to obtain a much better picture quality, with a simple and inexpensive arrangement to

automatic exposure and easy operation while optimizing the exposure control.

This object is achieved by an arrangement having the features specified in claim 1 and by a method having the features specified in claim 9. Preferred developments and refinements are the subject of the dependent

Claims .

According to the invention, the arrangement for automatic

Exposure of Fundusaufnahmen an image sensor connected to a control and evaluation unit with a local Minimum resolution of pixels and a very high

Frame rate on, with a rating of a

characteristic value (e.g., one or more local maximum intensities) in the fundus image and the

Control and evaluation unit the data stream of

characteristic values (e.g., the maximum intensities) are compared to a threshold value and, when the threshold value is exceeded, a signal for switching off a

Lighting unit generated. In contrast to the known automatic exposure, which measures only a flat integral value for the entire fundus image, the arrangement according to the invention for automatic exposure enables a better image quality, since the fundus images no longer have any overexposed areas.

An advantageous embodiment is seen in that for imaging a small field on the first

Image sensor for capturing all for exposure

relevant retinal areas a second image sensor is provided. To image the fundus image at first

Image sensor and the second image sensor in a common imaging beam path, a beam splitter is provided, to the image sensors a different respectively

having asymmetrical division ratio. Of the

In this case, the beam splitter has a small division ratio to the first image sensor and a large division ratio to the second image sensor, so that thereby

different radiation energies in the reflected and transmitted light are made possible with little effort. The first image sensor further preferably has a spectral sensitivity of blue to infrared.

Furthermore, it is advantageous that the first image sensor is provided for optimizing the exposure control, such that both a minimum intensity of the fundus image and the integral of all intensities are read out for optimizing the exposure control, or for optimizing the exposure control, in particular for

Minimum exposures are selectively selected dark ones

Considered areas of the fundus image.

A preferred development is seen in that the first image sensor is provided as a preview camera from a certain resolution of pixels. The preview camera preferably generates a live image for user display and for continuous control of the positioning of the fundus camera relative to the patient's eye.

It is also advantageously provided that the evaluation and control unit is coupled to the lighting unit such that upon reaching a threshold value, the lighting unit can be switched off very quickly.

Preferred embodiments of the illumination unit of a fundus camera are e.g. a slit lamp, a flash lamp or LEDs. It should be noted that when using a flash lamp, an LED or a laser, a maximum

Period from the pixel evaluation to turning off the lighting unit of preferably 50ys is needed.

It can also be provided according to the invention to use only one image sensor, via its internal

Control the exposure measurement and recording the fundus image is controlled sequentially or alternately. In this case, can be dispensed with the beam splitter.

Furthermore, in addition to the intensity also with this linked or separately determined other local or integral photometric parameters such as minimum / maximum ratio of intensity or similar are used as characteristic values to generate the signal for switching off the

To create lighting unit.

The inventive method for the automatic exposure of Fundusaufnahmen with a very high dynamics in

Fundus image provides by means of the arrangement according to the invention, that the spatially resolving first image sensor in

Repeats picks up a motion field of the eye and determines a local area that has the highest intensity. Subsequently, the maximum intensity is determined for this area and there is a comparison of the determined maximum intensity with a predetermined threshold.

The calculation of an optimized exposure time or a switch-off time of the illumination then takes place from the determined maximum intensity or else with this associated other local or integral

photometric parameters such as minimum / maximum ratio of intensity or the like

By emitting a signal to the illumination unit then the shutdown of the illumination unit and the transmission of the optimally illuminated fundus image to the evaluation and control unit and a display unit.

The invention will be explained in more detail with reference to an embodiment schematically shown in a drawing.

It shows:

Fig. 1 shows an inventive embodiment of the

automatic exposure of fundus images. FIG. 1 shows, in a schematic representation, an imaging beam path according to the invention for the automatic exposure of fundus images for fundus cameras for classical retina examinations of a patient's eye.

That of a lighting unit 1 of a fundus camera, e.g. a slit lamp, a flash lamp or LEDs

emitted illumination beam for illuminating a

7 of an eye 8 eye background for a direct

Observation or a recording will be in one

Illumination beam path 2 via a lens 3, a

Hole mirror 4 and an ophthalmoscope lens 5 through a pupil 6 on the ocular fundus 7 of the eye to be examined 8 shown as a luminous field through which the

Ocular fundus 7 is evenly illuminated. The light reflected from the fundus 7 of the eye 8 is imaged by the pupil 6 over the

Ophthalmoscope lens 5 to form an intermediate image through the aperture of the perforated mirror 4 and a the

Hole mirror 4 subordinate lens 9 on a in the optical axis of an imaging beam path 10th

arranged on and ausschwenkbaren, obliquely, dichroic trained beam splitter 11 out, for example, as a splitter mirror with an asymmetrical division ratio of the reflection to the transmission

is trained. That of the eye 8 through the

Ophthalmoscope lens 5 incident light is through the

Beam splitter 11 preferably with an asymmetrical division ratio of, for example, 5-10% via an upstream objective 12 to a first image sensor 13 and preferably with a single-ended

Division ratio of, for example, 90-95% via an upstream lens 14 to a second image sensor 15 passed. The division ratio between the image sensors 13 and 15 is dimensioned such that for the second Image sensor 15 only the minimum necessary light for

reliable evaluation of the maximum and minimum

Intensities is decoupled. The second image sensor 15 must meet the requirements of the ophthalmological

Application, for example a minimum resolution,

Color fidelity and a minimum dynamics meet. The first

Image sensor 13 must have a minimum resolution of about 30x30 pixels as well as the ones described

Evaluation modalities, for example a short one

Exposure time and can then at this

Resolution can also be used as a preview camera.

An evaluation and control unit 16 provides both the

Exposure times of the image sensors 13 and 15 for the

Shots of the frames asymmetrically and reads even after recording the frames from the image sensors 13 and 15 and transmits them to a no closer

shown, known computer, which monitors and adjusts the evaluation and control unit 16 and the evaluation and control unit 16, the exposure times for the

Image sensors 13 and 15 pretends. On the one hand a

accelerated measurement and on the other hand a

To reduce patient stress by reading the sensors quickly, the selection of sensors is very important. In this embodiment, preferably for the image sensor 13 is a sensor with measurement in several

Sectors. The arrows shown in the beam path indicate the real intermediate images. To adjust the picture quality of automatic exposure of

To improve fundus images, the known, areal integral image sensor 15 is supplemented by an image sensor 13, which has, for example, in this embodiment, a local minimum resolution of preferably 30x30 pixels. The first image sensor 13 preferably operates at a very high image frequency of at least 1 kHz and ascertains temporally pixels with maximum intensity and outputs this maximum intensity in the following process steps:

the spatially resolving image sensor 13 records in repetitions a motion field of the eye 8, then the determination of a local area, which is the highest

Has intensity and determination of the maximum

Intensity for this area. By comparing the determined maximum intensity with a predetermined threshold value, a calculation of an optimized one takes place

Exposure time or a shutdown time of the

Lighting from the determined maximum intensity, and the emission of a signal to the lighting unit 1 for switching off the lighting unit 1 or the

Transmission of the optimally exposed fundus image to the evaluation and control unit 16 and a known display unit, not shown.

To optimize the exposure control, both a minimum intensity and the integral of all

Intensities are read and for minimum exposures selected dark areas of the fundus image are considered. The evaluation and control unit 16 is set up so that it has the overall picture with a high

Dynamics determined and this to a closer

transmitted known computer, wherein the evaluation and control unit 16 from the data stream of the maximum intensities determines a threshold, so that the diagnostic and therapeutic examinations are interrupted by the control and evaluation unit 16 by the

Lighting unit 1, for example, a flash lamp is turned off. When using a flash lamp, an LED or a laser is thereby a maximum period of the

Pixel evaluation until the lighting unit is switched off by preferably 50ys.

The invention is not limited to the

Embodiment, but is applied in the

Setup variable. It also includes in particular

Variations made by combining features described in connection with the present invention

can be formed optical elements. All mentioned in the foregoing description and removable from the drawing features are further components of

Invention, even if they are not particularly highlighted and mentioned in the claims.

In this case, only one image sensor can be provided, which can also be combined together with the evaluation and control unit in a housing.

In addition to the maximum intensity, it is also possible to use other local or integral photometric parameters associated therewith or separately, such as minimum / maximum ratio of the intensity or the like. be used as characteristic values for the evaluation.

Reference sign list

1 lighting unit

2 illumination beam path

3 Objective

4 hole mirror

5 ophthalmoscope lens

6 pupil of the eye

7 eye background

8 eye

9 Objective

10 imaging beam path

11 beam splitter

12 upstream lens

13 first image sensor

14 upstream lens

15 second image sensor

16 evaluation and control unit

Claims

claims

Arrangement for automatic exposure of

Fundus images for fundus cameras for observation, examination, diagnosis and therapy of a

Fundus images for fundus images that contain a very high level of dynamics, including one

Illumination beam path with an illumination optics for illuminating the fundus, one

Observation beam path leading from the fundus of the eye via an observation optics to a

Detector for imaging the light reflected by the eye, preferably a beam splitter and at least one image sensor and a control and evaluation unit,

characterized,

in that an image sensor (13) connected to a control and evaluation unit (16) for detecting and outputting a characteristic value (for example a maximum intensity) of a fundus image is a localized image sensor

Minimum resolution of pixels and a very high

In the case of an automatic exposure of fundus images with an evaluation of the characteristic values (z, B, of a local maximum in the fundus image), the control and evaluation unit (16) derives from the data stream of the characteristic values (for example maximum intensities) a time for

Shutdown of a lighting unit (1) determined.

Arrangement for automatic exposure of

Fundus shots according to claim 1,

characterized,

for imaging the fundus image onto the first image sensor (13) and a second image sensor (15) in FIG a common imaging beam path (10) a beam splitter (11) is provided, wherein the

Beam splitter (11) to the image sensors (13,15) a different respectively unbalanced

Dividing ratio has.

3. Arrangement for automatic exposure of

Fundus photographs according to claim 1 and 2,

characterized,

in that the beam splitter (11) has a small division ratio to the image sensor (13) and a large division ratio to the image sensor (15).

4. Arrangement for automatic exposure of

Fundus photographs according to one of claims 1 to 3, characterized

that the image sensor (13) has a spectral

Sensitivity from blue to infrared.

5. Arrangement for automatic exposure of

Fundus photographs according to one of claims 1 to 4, characterized

that the image sensor (13) from a resolution of about 30x30 pixels is also provided as a preview camera.

6. Arrangement for automatic exposure of

Fundus photographs according to one of the preceding

Claims,

characterized,

in that the image sensor (13) optimizes the

Exposure control a minimum intensity

read out.

7. Arrangement for automatic exposure of

Fundus photographs according to one of claims 1 to 6, characterized

in that the evaluation and control unit (16) is coupled to the lighting unit (1), such that upon reaching a threshold value, the

Lighting unit (1) can be switched off.

8. Arrangement for automatic exposure of

Fundus photographs according to one of claims 1 to 7, characterized

when using a flash lamp, an LED or a laser, a maximum period of time

Pixel evaluation until the shutdown of the

Lighting unit of preferably 50ys is needed.

9. Method for automatic exposure of

Fundus images with a very high dynamics in the

Fundus image for observation, examination and for

Diagnosis of an ocular fundus, with one

Illumination optics, an imaging optics, preferably a beam splitter, at least one image sensor (13) and an evaluation and control unit (16)

characterized by the following steps:

Recording of a movement field of the eye by the spatially resolving first image sensor (13) in

Repetition and detection of a local area that has the highest intensity,

Determine the maximum intensity for this

Area,

Comparison of the determined maximum intensity with a predetermined threshold, Calculation of an optimized exposure time or a switch-off time of the illumination from the determined maximum intensity,

Emitting a signal to the lighting unit (1) for switching off the lighting unit (1),

Transmission of the optimally illuminated fundus image to the evaluation and control unit (16) and a

Display unit.

10. The method according to claim 9,

characterized,

In order to optimize the exposure control, both a minimum intensity and the integral of all intensities are read out.

11. The method according to claim 9 and 10,

characterized,

that to optimize the exposure control

specifically targeted for minimum exposures

selected dark areas of the fundus image

to be viewed as.