IL110618A

IL110618A - Device for testing optical elements

Info

Publication number: IL110618A
Application number: IL11061894A
Authority: IL
Inventors: Shmuel Liran; Amit Stekel; Moshe Lapidot
Original assignee: Optomic Techn Corp Ltd
Priority date: 1994-08-10
Filing date: 1994-08-10
Publication date: 1996-12-05
Also published as: WO1996005503A1; AU3344395A; IL110618A0

Description

DEVICE FOR TESTING OPTICAL ELEMENTS OF INVENTION The invention relates to a system and method for the rapid inspection of optical elements devoid of optical The inspection reveals the presence of defects of the transparent inspected such as surface flaws and also Internal such as Bubbles or BACKGROUND OF THE INVENTION There exist a wide variety of devices which are intended for the inspection of optical and especially optically active elements such as optical lenses and the Most of these are based on the scanning of the and on the detection of any external or internal generally by observing light scattering resulting from such Patent is based on of the and detection of light refracted by Patent relates to a device for detecting defects of ophthalmic and this is based on the passage of a narrow beam of light through the lens and detecting due to scattering By by an array of photodetectors arranged around the edge of the which would not be reached by ght in the absence of such According to this patent the lens surface is scanned by the narrow light and means are provided for quantitizing the results of such SUMMARY OF THE INVENTIO There is provided a system for the rapid inspection of optical elements devoid of optical There is also provided a method for effecting such inspections and for the evaluation of the The system of the invention is Based on the provision of an illuminating Beam which passes via a rela lens and through the optical element to Be such a lens of sunglasses or any other element devoid of optical there being provided a diffusing screen with a central dark circular and an imaging lens on the axis of the relay lens and optical so that the image of the dark circular area prevents direct light from the light source from reaching the imaging Only light scattered by any defects of the examined optical element reaches this lens and is discerned and Generally the imaging lens is part of a video but other such as any CCD array or the may Be This field results in that light scattered by surface defects or internal such as parent defects and the reach the imaging lens and such is indicative of such defects and their Means can Be provided for automatically evaluating the location and severity of defects of the optical and criteria can be provided for discarding any optical element which is of a qualtity inferior to that predetermined By such The invention also provided a method for the inspection of transparent optical elements devoid of optical which comprises illuminating the optical element by a beam a relay lens where the light beam from the light source passes via a diffusing screen with a central dark circular area and imaging the diffusing screen on an imaging so that the dark circular area blacks out any direct light from the light source to the imaging scattered by defects of the optical element reaching the imaging and through it suitable detection providing information on the presence or aBsence of defects and their OF THE PREFERRED EMBODIMENT The invention illustrated by way of example only with reference to the enclosed schematical perspective view illustrating the principles of a system of the As shown in the for the rapid inspection of optical element which is devoid of optical comprises in bination a light source 11 in front of which there is located a diffusing screen with a central dark circular area so that light from source 11 is diffused through screen 12 and passes through a relay lens and through said optical element onto imaging lens 16 which may be part of a video camera The light passes the diffusing screen 12 has a gradually varying and covers a wide solid The light beam passes via relay lens and this results in the focus ng of the circular dark area 13 at the aperture plane and the dimensions are such that the image of the circular area 13 covers entirely the entrance pupil of the imaging lens The path of light from the light source illustrates the principle the rays 19 which emerge from the contour of 13 reach the contour of the image of this dark area at the aperture plane 18 of lens Light rays 20 which emerge from the diffusing screen 12 in pass via relay lens and converge as shown by 21 to test point 22 of tested lens and are scattered in the direction shown by Light rays 20 are blocked by dark area 13 so that they converge from the relay lens 14 1n the direction 24 to test point of the element 15 which illuminated by a wide solid angle of of from about 1 degree to about 40 except for the narrow solid angle in the 1 degree the direction normal to the components at the location of the test 22 there a defect of the optical element the result is a scattering of light part of which the imaging lens there is formed an image on the surface of lens which represents such 4 Various types of defects are sensitive to different angles of and thus it is important to provide a wide range of illumination nation is defined as the angle between the surface normal of the test and the specific of impinging on the surface Most of the flaws are detectable when at a small angle of and such are easily attainable by the system of the It is one of the constraints of the system that a narrow depth of field is A possible source of errors is reflections in the There exist two main the first is an internal reflection between the two surfaces of the relay lens and the second is reflection between relay lens 14 and test object A small tilt of the relay lens 14 serves to resolve this problem by deflecting various reflections away from the optical axis of the lens 16 and camera This will not influence direct rays except for negligible distortions of the image area insufficientOCRQuality

Claims

« 110618/2 CLAIMS ί

1. , A method for the rapid inspection of optical elements devoid of optical power, which comprises illuminating such an optical element with a wide angle optical beam, originating from a strong light source, which is first passed -via a diffusing screen and a relay lens, said diffusing screen having a central dark circular area, there being arranged on the optical axis of the system an imaging lens, which is masked out from direct illumination due to the said central dark area said imaging lens receiving only signals resulting from external or internal defects of the examined optical element, evaluating such signals in order to determine whether the optical element can be used or is to be discarded. t

2. , A method according to claim 1, where the optical element is a lens devoid of optical power.

3. A method according to claim 1 or 2, where the light beam illuminating the optical element has a solid angle of from about 1 to about 40 degrees, in the direction normal to the surface of the optical element.

4. A method according to any of claims 1 to 3 where the relay lens tilted at a small angle respective the optical axis of the system. 110618/2

5. A system for the rapid examination and grading of optical elements devoid of optical power to detect and evaluate surface and internal defects, which comprises, arranges along an optical axis, a sequence of a source of light, a diffusing screen, at the center of which there is provided a dark circular area, a relay lens, the optical element to be tested, an imaging lens which is shielded from direct illumination by said dark circular area, and which is reached only by light scattered by imperfections of the optical element and means, for evaluating such light signals coining via the imaging lens arranged after the relay lens.