Optical system for light measurement of an eye fund

• US 4,253,744 A
• Filed: 05/07/1979
• Issued: 03/03/1981
• Est. Priority Date: 05/12/1978
• Status: Expired due to Term

• Current Assignee: Minolta Camera Kabushiki Kaisha
• Original Assignee: Minolta Camera Kabushiki Kaisha
• Inventors: Sawa, Seiji
• Primary Examiner(s): SACHER, PAUL
• Application Number:
  US06/036,311
• Time in Patent Office: 666 Days
• Field of Search: 351/6, 351/7, 351/16, 354/62, 128/666, 128/645, 128/745, 128/687
• US Class Current: 351/211
• CPC Class Codes: A61B 3/13 Ophthalmic microscopes
• CPC Class Codes: A61B 5/02216 Ophthalmodynamometers

Abstract

In a light measuring optical system for use in measurement of pulse waves in the artery at the eye fundus or oxygen saturation in the artery blood at the eye fundus, light for illuminating the eye fundus is converged on the surface of the cornea of the eye to be measured and enters the interior of the eye through a small area within the pupil. Light reflected at the surface of the cornea is converged and blocked at its converging position while the light reflected from the eye fundus is allowed to pass by the light blocking member and reach a photocell. Coupled with the photocell is an electric circuit which transmits AC component of photocell output when DC component of the same assumes its minimum value.

Claims

1. An eye fund measuring system for illuminating the fundus of an eye to be measured and measuring the light reflected from the fundus, comprising:

a light source having a small light emitting area;

a first converging means for converging the light from the light source on a surface of the eye;

a second converging means for converging the light reflected at the surface of the eye;

a photoelectric element for detecting the light from the eye fundus;

a light blocking means for blocking the light reflected at the surface of the eye at the position where the surface reflected light is converged by said second converging means, said light blocking means allowing the light from the eye fundus to pass by to said photoelectric element; and

a responsive means responsive to the output of said photoelectric element to provide a measurement of the light contacting the photoelectric element.

2. An eye fundus measuring system as claimed in claim 1 wherein said light source includes a lamp and a restricting member for restricting the cross sectional area of the light ray emitted from the lamp and passing through the restricting member.

3. An eye fundus measuring system as claimed in claim 1 further comprising a reflector disposed between the eye and said photoelectric element for directing the light from said light source to the eye, said reflector being so constructed as to allow passage of the light from the eye fundus to said photoelectric element.

6. An eye fundus measuring system as claimed in claim 1 wherein said responsive means includes an electric high pass filter for passing a high frequency component of the output of said photoelectric element, an electric low pass filter for pass a low frequency component of the output and gate means for transmitting said high frequency component therethrough when the low frequency component assumes its minimum value.

7. An eye fundus measuring system as claimed in claim 6 wherein said responsive means includes an indicator responsive to the high frequency component transmitted by said gate means.

4. An eye fundus measuring system as claimed in claim 4 wherein said reflector includes a semi-transparent mirror.

5. An eye fundus measuring system as claimed in claim 4 wherein said reflector includes a total reflection mirror, and said second converging means includes a first converging lens for converging the light reflected at the eye surface on said total reflection mirror, and a second converging lens for converging the light reflected by said total reflection mirror on the eye surface, said second converging lens also functioning as said second converging means, with said total reflection mirror functioning as said light blocking means.

8. An improved eye fund optical measuring system for providing a continuous measurement of the condition of blood in the eye fundus by measuring the light reflected from the eye fundus, comprising;

a light source at a finite distance from a position at which an eye of a patient is to be measured;

first means for converging the light from the light source at a focal point substantially coincident with the exterior surface of the cornea of the eye, and having a cross-sectional area considerably smaller than the pupil area of the patient'"'"'s eye;

second means for converging both the light reflected from the cornea and the light reflected from the eye fundus at separate focal points;

means for eliminating the further progressive transmission of the cornea reflected light, located at substantially the focal point of the reflected cornea light, while permitting the transmission of the reflected light from the eye fundus, and

means for measuring the reflected eye fundus light.

9. The invention of claim 8 wherein the means for measuring the reflected eye fundus light includes filter means for providing a high frequency signal and a low frequency signal from the measured light and gate means responsive to a predetermined value of the low frequency signal to provide a measurement of the condition of the patient'"'"'s blood with the high frequency signal.