U.S. patent application number 17/219654 was filed with the patent office on 2021-11-04 for system and method for inspecting optical power and thickness of ophthalmic lenses immersed in a solution.
The applicant listed for this patent is EMAGE VISION PTE. LTD.. Invention is credited to Santosh Singh Elangbam, Ya'akob Bin Mohamed, Sergey Smorgon.
Application Number | 20210341353 17/219654 |
Document ID | / |
Family ID | 1000005712587 |
Filed Date | 2021-11-04 |
United States Patent
Application |
20210341353 |
Kind Code |
A1 |
Smorgon; Sergey ; et
al. |
November 4, 2021 |
SYSTEM AND METHOD FOR INSPECTING OPTICAL POWER AND THICKNESS OF
OPHTHALMIC LENSES IMMERSED IN A SOLUTION
Abstract
A system for producing a high contrast image of an ophthalmic
lens under inspection, comprising: top camera to view ophthalmic
lens through lens module; motorized mechanism for positioning top
camera at two pre-programmed positions; three illumination modules;
said illumination modules focusing light through ophthalmic lens
under inspection, thereby producing a high contrast image of
features of ophthalmic lens; wherein ophthalmic lens is contained
within cuvette with optical power of positive of ten; said cuvette
mounted with two optical windows, one of them being vertical and
other at an angle; said cuvette having transparent bottom glass
suitably designed to position ophthalmic lens under inspection;
said cuvette designed to be filled with saline solution; accurately
calibrated test object positioned to achieve image of ophthalmic
lens overlaid with image of pattern present on test object;
additional illumination source comprising laser diode; and second
camera to view ophthalmic lens through slanted optical lens
module.
Inventors: |
Smorgon; Sergey; (Singapore,
SG) ; Mohamed; Ya'akob Bin; (Singapore, SG) ;
Elangbam; Santosh Singh; (Singapore, SG) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
EMAGE VISION PTE. LTD. |
SINGAPORE |
|
SG |
|
|
Family ID: |
1000005712587 |
Appl. No.: |
17/219654 |
Filed: |
March 31, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
16375061 |
Apr 4, 2019 |
10976217 |
|
|
17219654 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01M 11/0228 20130101;
G01M 11/0235 20130101; G01M 11/0264 20130101; G01M 11/0278
20130101; G01M 11/0207 20130101; G01M 11/0214 20130101 |
International
Class: |
G01M 11/02 20060101
G01M011/02 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 19, 2018 |
SG |
SG10201803290V |
Claims
1. A system for producing a high contrast image of an ophthalmic
lens under inspection, comprising: a) a Top camera to view the
ophthalmic lens through a lens module; b) Motorized mechanism for
positioning the Top camera at two pre-programmed positions; c)
three illumination modules; d) said illumination modules focusing
light through the ophthalmic lens under inspection, thereby
producing a high contrast image of the features of the ophthalmic
lens; e) wherein the ophthalmic lens is contained within a cuvette
with an optical power of positive of Ten; f) said cuvette mounted
with two optical windows, one of them being vertical and the other
at an angle; g) said cuvette having a transparent bottom glass
suitably designed to position the ophthalmic lens under inspection;
h) said cuvette designed to be filled with Saline solution; i) an
accurately calibrated test object positioned to achieve an image of
the ophthalmic lens overlaid with the image of the pattern present
on the test object; j) an additional illumination source comprising
a laser diode; and h) a second camera to view the ophthalmic lens
through a slanted optical lens module.
2. A system according to claim 1, further comprising a focusing
lens.
3. A system according to claim 1, further comprising a set of beam
splitters.
4. A method for inspecting defects of an ophthalmic lens, the
method comprising the steps of: moving the Top camera to a second
position; providing an inspection cuvette designed with an optical
power of positive ten, comprising an optically transparent bottom
glass having a concave inner surface containing the ophthalmic lens
immersed in a liquid, and positioning the inspection cuvette in the
optical axis of the Top camera; providing a separate set of
illumination sources and a Top camera for receiving illumination
having passed through ophthalmic lens contained in the inspection
cuvette to produce multiple enhanced images of the defects in the
Ophthalmic lens; inspecting for defects such as scratches, tears
and air bubbles within the Ophthalmic lens; and removing the lens
if the size of the defects detected in the Ophthalmic lens is
beyond a predetermined size.
5. A method for determination of lens thickness of an ophthalmic
lens the method comprising the steps of: providing an inspection
cuvette designed with an optical power of positive ten, comprising
an optically transparent bottom glass designed to have an optical
power of positive ten, having a concave inner surface containing
the ophthalmic lens immersed in a liquid, and positioning the
inspection cuvette in the optical axis of the Top camera; providing
a single laser illumination source and a second camera for
receiving illumination directed by a set of beam deflectors and
having passed through focusing lens and ophthalmic lens contained
in the inspection cuvette, to produce a laser beam scattered image
formed by the reflected rays, and measuring the distance between
the two extremes of reflected rays of light.
6. The method according to claim 5, further comprising the steps
of: providing an inspection cuvette designed with an optical power
of positive ten, comprising an optically transparent glass bottom
having a concave inner surface containing the ophthalmic lens
immersed in a liquid, and positioning the inspection cuvette in the
optical axis of the imaging module; providing a single laser
illumination source and a second camera for receiving illumination
directed by a set of beam deflectors and having passed through
focusing lens and ophthalmic lens contained in the inspection
cuvette, to produce a laser beam scattered image formed by the
reflected rays, and measuring the distance between the two extremes
of reflected rays of light; and creating a chart (Length in pixels
vs thickness) of measurements between the two extremes of the
scattered laser beams of several pre-selected lenses of known
thickness, to be used as a reference for determining the lens
thickness of subsequent ophthalmic lenses to be inspected.
7. The method according to claim 6, further comprising the steps
of: providing an inspection cuvette designed with an optical power
of positive ten, comprising an optically transparent bottom glass
having a concave inner surface containing the ophthalmic lens
immersed in a liquid, and positioning the inspection cuvette in the
optical axis of the second camera; providing a single laser
illumination source and a second camera for receiving illumination
directed by a set of beam splitters and having passed through
focusing lens and ophthalmic lens contained in the liquid filled
inspection cuvette, to produce a laser beam scattered image formed
by the reflected rays, and measuring the distance between the two
extremes of reflected rays of light; and removing and segregating
the ophthalmic lens from the Cuvette after determining the optical
thickness of the lens under inspection, based on the chart plotted
for Length in pixels vs thickness.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of copending U.S. patent
application Ser. No. 16/375,061, entitled "SYSTEM AND METHOD FOR
INSPECTING OPTICAL POWER AND THICKNESS OF OPHTHALMIC LENSES
IMMERSED IN A SOLUTION" and filed on Apr. 4, 2019, which claims
priority to, and the benefit of, Singapore Patent Application No.
10201803290V, filed on Apr. 19, 2018, each of which is incorporated
by reference as if set forth herein in its entirety.
FIELD OF THE INVENTION
[0002] The present invention relates to an apparatus and method for
measuring optical power of Ophthalmic lenses. More specifically,
the present invention relates to an apparatus and method to measure
the optical power of contact lenses, which can be suitably
integrated into an automated manufacturing system.
BACKGROUND OF THE INVENTION
[0003] A number of prior art measuring systems exist in which the
optical power and other characteristics of ophthalmic lenses are
measured at local points on the ophthalmic lens. Commercial
instruments for performing optical power measurements that use
probing beams combined with dynamic positioning to measure optical
power of the lens are available. However these instruments cannot
be integrated into high speed automated manufacturing systems
because of the time required to inspect each lens, making them
unsuitable for such a purpose. Ophthalmic lenses are manufactured
to suit different types of eye characteristics. The lenses need to
be appropriately categorized and segregated before distribution
according to their optical power.
[0004] In light of the above, there is need for an automated system
or apparatus and method to accurately and reliably measure the
optical power of the lens within a fraction of a second, so as to
be able to integrate the apparatus into automated manufacturing
systems.
SUMMARY OF THE INVENTION
[0005] To achieve this end, an embodiment of the invention
comprises: A high resolution imaging device to capture the image of
the contact lens; a positioning mechanism to move the Camera to a
first position using a motorised mechanism; enabling the test
object LED based light head to effectively illuminate the glass
target and capture an image of the glass target as seen through an
empty cuvette filled with Saline solution;
[0006] It is an object of the present invention to provide an
apparatus and method for inspecting the optical power of the
contact lens. The process begins by moving the Top camera to the
first position and capturing an image of the Test object through a
contact lens with zero optical power and the cuvette filled with
Saline solution. This image is subsequently used as a reference
image. Subsequently calibration of the Top camera 14 is carried out
using the reference image by measuring and tabulating the distance
between adjacent dots preferably in X, Y and Z direction using a
set of software algorithms; loading a contact lens with optical
power into the cuvette; enabling the test object light head to
illuminate the lens under inspection and capture an image of the
glass target as seen through the contact lens suspended in the
Saline solution; measuring the distance between all adjacent dots
with the optical zone in X, Y and Z direction; using the distance
value to determine the optical power of the lens; and a display
means for displaying and notifying a result judged by the software
program. The result may also be communicated via electronic means
to enable integration to third party equipment.
[0007] It is further an object of the present invention to provide
an apparatus and method to inspect for defects such as tear, cuts,
voids, bubbles, mold flash and foreign material within a contact
lens comprising: A high resolution imaging device to capture the
image of the contact lens; a positioning mechanism to move the
Camera to a second position using a motorised mechanism; enabling
multiple illumination modules at different times to effectively
highlight various defects in the contact lenses; capturing multiple
images under different illuminating conditions; analysing the
images using multiple set of software algorithms to detect and
identify the defective contact lenses; and communicating the
results of the inspection to the host machine to remove the
defective lenses.
[0008] It is further an object of the present invention to provide
an apparatus and method to inspect for the thickness of the contact
lens comprising; A second high resolution imaging device mounted at
an angle to the contact lens under inspection; enabling the laser
diode base illumination module; capture an image of the contact
lens with the second camera; analysing the image using a separate
set of algorithms to measure the thickness of the lens; and
communicating the results of the inspection to the host machine to
take further steps such as segregating lenses of different
thickness.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] A complete understanding of the present invention may be
gained by considering the following detailed description together
with the accompanying drawings, in which:
[0010] FIG. 1 shows, in pictorial form, a preferred embodiment of a
first aspect of the present invention which is apparatus for
measuring the optical power, identifying defects such as cuts,
tears, voids, bubbles, mold flash and foreign material and the
thickness of ophthalmic lenses. The apparatus comprises of three
different parts 100, 200 & 300. Module 100 comprises the
cameras and the objectives & 200 comprises the complex
illumination module along with the necessary lenses and prisms to
guide and focus the illumination towards the contact lens and 300
is a specially designed cuvette in which the contact lens under
inspection is loaded and two optical windows that allows the
vertical camera and the slant camera to view and capture the image
of the contact lens; specially designed cuvette is filled with
Saline solution;
[0011] FIG. 2 shows, a sample of a precision glass based
calibration target available from any optics accessories
supplier;
[0012] FIG. 3 shows, an enlarged view of the area enclosed by the
box 41 in the precision glass target. The distance between a pair
of dots, and the diameter of the every adjacent dot is measured and
stored as calibration data;
[0013] FIG. 4, shows an illustration of an image of the precision
target object with cuvette filled with Saline solution captured
through a contact lens with a zero optical power contact lens
positioned in the cuvette;
[0014] FIG. 4a, shows an enlarged view of the area enclosed by the
box in FIG. 4;
[0015] FIG. 5, shows an illustration of an image of the precision
target object as seen through a positive power contact lens located
in the cuvette filled with Saline solution;
[0016] FIG. 5a, shows an enlarged view of the area enclosed by the
box in FIG. 5;
[0017] FIG. 6, shows an illustration of an image of the precision
target object as seen through a negative power contact lens located
in the cuvette filled with Saline solution;
[0018] FIG. 6a, shows an enlarged view of the area enclosed by the
box in FIG. 6;
[0019] FIG. 7, shows an illustration of a drawing showing three
adjacent dots of a positive power lens and a negative power lens,
superimposed on three adjacent dots of the glass target.
[0020] FIG. 8, shows a chart demonstrating the relation between the
optical power of contact lenses and the distance between two
selected dots within the optical zone of a contact lens with
optical power.
[0021] FIG. 9 is an illustration of the sub-system extracted from
FIG. 1, which is used to measure the thickness of the contact
lens.
[0022] FIG. 10 is an image of the laser beam emitted by laser diode
light head 47 in FIG. 1 as viewed by the camera 20 in FIG. 9 with
no contact lens present in the cuvette.
[0023] FIG. 11 is an image of the laser beam emitted by laser diode
light head 47 in FIG. 1 as viewed by the camera 20 in FIG. 9 with a
thin contact lens present in the cuvette.
[0024] FIG. 12 is an image of the laser beam emitted by laser diode
light head 47 in FIG. 1 as viewed by the camera 20 in FIG. 9 with a
thicker contact lens present in the cuvette.
[0025] FIG. 13 is an illustration of a chart used as a reference to
compute the thickness of the contact lens after measuring the
length of the scattered laser beam Y1 in FIG. 11 and Y2 in FIG.
12.
DETAILED DESCRIPTION
[0026] FIG. 1 shows, in pictorial form, an embodiment of a first
aspect of the present invention which is apparatus for measuring
the optical power, thickness and various other defects such as
bubbles, scratches, contaminants & edge defects of contact
lenses. The embodiment consists of two main parts.
[0027] The first part is as follows. The camera and lens module 100
is made up of a Top camera 14 mounted vertically and driven by a
motorized mechanism 10 to position the camera 14 at different
positions 11 and 12 in the vertical axis. The camera 14 is suitably
integrated to the lens module 16. The second camera 20 mounted at
an angle is suitably integrated to the lens module 22. The flat
window 18 and side inclined window 24 enable image capture of the
contact lens 30 by cameras 14 and 20 respectively. First position
12 of camera 14 is preferably used to inspect the optical power of
the contact lens and the second position 11 of camera 14 is
preferably used to inspect for defects such as bubbles, scratches,
contaminants & edge defects.
[0028] The second part 200 is a complex illumination module and
comprises several illumination modules that are utilized in various
combinations, to illuminate certain specific defects in the contact
lenses.
[0029] The illumination module 44 is enabled only for optical power
measurements and for the purpose of calibrating the inspection
system using the test object 43. The beam splitters 41 and 42
directs the Bright field illumination from 49 towards the contact
lens 30 that is suspended in Saline solution in Cuvette 32 and
suitably positioned on bottom glass 35.
[0030] The beam splitters 41 and 42 also directs illumination from
Test object illumination module 44 towards the contact lens 30
which is suspended in Saline solution in Cuvette 32 and suitably
positioned on bottom glass 35. The Test object 43 is positioned
between the Target object illumination module 44 and the beam
splitter 42 to enable Top camera 14 to capture the image of the
test object. The test object is preferably a precision glass object
on which a pattern of precisely sized dots are imprinted as shown
in FIG. 2. The test object shown in FIG. 2 is a typical glass
target available from many optics accessories supplier and FIG. 3
shows a enlarged representation of two adjacent dots imprinted on
the glass object of FIG. 2 The glass target 43 maybe of several
types, one of which is shown in FIG. 2. The lens 40 works as a
focusing lens to focus all the light towards the cuvette.
[0031] The illumination modules 46, 48 and 49 are used individually
or in a predetermined combination to enhance defects such as tear,
cuts, voids, bubbles, mold flash and foreign material within the
contact lens. Beam splitters 45 and 41 direct the light emitted by
illumination modules 46, 48 and 49 and beam splitters 42 and 41
direct the light emitted by 47 and 44 towards the contact lens 30
which is suitably positioned on bottom glass 35.
[0032] The third part 300 is the contact lens cuvette 32 wherein
the Contact lens 30 to be inspected is positioned. The cuvette 32
is filled by saline and contact lens 30 and is suitably positioned
on bottom glass 35 are placed in the Saline solution 37. The
container also comprises of a flat window 18 and side inclined
window 24 for the camera 14 and 20 respectively.
[0033] The functionality of each the first part 100, second part
200 and third part 300 is such that each can be separately used
with different apparatus. Further, whilst the thickness measurement
and power measurement are described herein as operating together to
form the first part 100, these two may be used with other
apparatus. It follows that the various aspects of the invention
include the following, which may be used as separate components for
other applications, used in various combinations or together as an
assembly of functional components, as described herein: [0034] The
power measurement & defect detection system (14, 16, 18);
[0035] The thickness measurement system (20, 22, 24); [0036] The
glass target 43, and; [0037] The illumination module 200.
[0038] The method of inspection for optical power relies on the
average distance between a set of pre-selected dots of the captured
image of different contact lens with different optical power. To
enable the measurement of negative power lenses the cuvette is
designed to have an optical power above 10 above zero optical power
so any contact lenses with optical power from negative 10 to
positive 10 can be measured. As a test object, round dots are
chosen because position of image center of such object can be
measured even with a significant defocusing.
[0039] The illumination modules used to inspect for contact lens
defects such as tear, cuts, voids, bubbles, mold flash and foreign
material are a bright field illuminator 49, a Dark field
illuminator 46 and a Single Spot illuminator 48. The Laser Diode
illuminator 47 is enabled only for measuring thickness of the
contact lens.
[0040] The Single spot illumination from 48 is directed towards the
contact lens 30 suspended in saline solution in cuvette 32, by beam
splitters 45 and 41. The lens 40 is used to focus all the different
illuminations towards the cuvette. The Laser Diode illumination 47
is utilized for measuring thickness of the contact lens.
[0041] FIG. 2 shows a sample of a glass target 43 with several dots
precisely imprinted on a precision glass target. The glass target
and the printed pattern may change according to the requirements of
inspection characteristics.
[0042] FIG. 3 shows an enlarged view of two printed dots 56 on
target 43 of FIG. 1. In the calibration process, images of known
powered lenses are used for capturing images and the average
distances across the preselected set of dots are plotted to arrive
at the chart in FIG. 8.
[0043] FIG. 4 shows a image of the glass target as captured by the
Top camera 14 located in the first position and a zero power
contact lens mounted in the cuvette. FIG. 4a is an enlarged image
of the box in FIG. 4. The distance 60 between the center of dots d1
and d2 is measured and stored in a table. The process is repeated
for a set of 18 to 20 dots selected from the optical area 65. The
preselected set of dots (determined at the time of calibration) is
adjacent to each other and maybe in the horizontal, vertical or
angular direction as long as they fall within the optical area 65.
FIG. 5 is the image of the same target glass 43 in FIG. 1 captured
with a contact lens with positive optical power placed in the
cuvette and with the Top camera 14 in the first position. FIG. 5a
is an enlarged image of the box in FIG. 5. The process of measuring
the distance 70 between two adjacent dots d3 and d4 and repeating
the process for the preselected set of dots (determined at the time
of calibration) located within the optical area of the contact lens
is executed and the results tabulated.
[0044] FIG. 6 is the image of the same target glass 43 in FIG. 1
captured with a contact lens with negative optical power placed in
the cuvette and with the Top camera 14 in the first position. FIG.
6a is an enlarged image of the box in FIG. 6. The process of
measuring the distance 80 between two adjacent dots d5 and d6 and
repeating the process for the preselected set of dots (determined
at the time of calibration) located within the optical area of the
contact lens is executed and the results tabulated.
[0045] FIG. 7 is a pictorial representation of the process of
measuring the power of the different contact lenses shown in FIGS.
4, 5 & 6. For the purpose of easy understanding the drawing
shown in FIG. 7 refers to 3 dots, though more number of dots can be
used to measure the distances. x1 and x2 refers to distances
between three dots selected from FIG. 4 that represents the image
of the glass target with no contact lens loaded in the cuvette. y1
and y2 refers to distances between three dots selected from FIG. 5
that represents the image of the glass target with a positive power
contact lens loaded in the cuvette. z1 and z2 refers to distances
between three dots selected from FIG. 6 that represents the image
of the glass target with a negative power contact lens loaded in
the cuvette. Taking the averages of x1 and x2, y1 and y2 and z1 and
z2 will result in x, y and z.
[0046] Distances x, y and z are plotted and with the calibration
chart in FIG. 8 to determine the power of the contact lens under
inspection. The results are subsequently relayed to the integrated
system for further action.
[0047] Any changes in the fundamental configuration of the
inspection apparatus will require a calibration process to be
redone to arrive at a new calibration chart such as the one in FIG.
8. The change can include but not limited to the position of focus,
the type of saline solution, a change or modification in the
position of any of the optical elements of the inspection system
such as the Camera resolution, Camera position, Camera lens,
cuvette material or its configuration, Glass target configuration,
illumination intensity, illumination pattern, Glass target
position, Prism configuration or position and a combination of any
of the above.
[0048] In FIG. 9, the sub-system of the apparatus shown in FIG. 1
highlights the modules used to measure the contact lens thickness.
The sub-system constitutes the Camera 20 suitably integrated to the
optical lens 22 and the side inclined window 24. The camera 20
captures the image of the contact lens 30 which is suspended in
saline solution in the cuvette 32 and suitably positioned on bottom
glass 35. The contact lens 30 is illuminated by a laser beam 39
emitted by the laser diode illumination module 47 of FIG. 1, and
subsequently guided by beam splitters 42 and 41 as shown in FIG. 1.
The principle behind the measurement of thickness relies on the
laser light 39 being scattered by contact lens material and its
surfaces 33 and 34 indicated in FIG. 9. For the purpose of
understanding, a single ray scattered from the two surfaces of the
contact lens is shown in the FIG. 9. When the laser beam 39 is
incident on the contact lens 30 of FIG. 9, the laser rays scatter
in different directions. The scattering of the laser light is
directly proportional to the thickness of the contact lens. The
distance 38 measured between the scattered rays 36 and 37,
represents a proportional value of the thickness of the contact
lens 30. As evident the smaller the distance 38, the smaller is the
thickness of the contact lens. The distance 38 is shown as Y1 and
Y2 in FIG. 11 and FIG. 12 respectively and is measured in pixels. A
relatively higher distance 38, represents a thicker contact lens. A
pre-configured chart FIG. 13 showing proportional thickness values
which are directly proportional to the distances 38 in FIG. 9, is
created and subsequently used to determine the thickness value of
the contact lens under inspection. For calibration purposes, an
image of an empty cuvette (no contact lens present) is shown in
FIG. 10. The chart is created by capturing images of n number of
contact lenses with known thickness values and subsequently
measuring the distance Y1, Y2 . . . Yn in the captured images. The
values Y1, Y2 . . . Yn are then used to create a chart such as the
one shown in FIG. 13. The refractive index of the saline solution,
and the effect of the cuvette are considered during the creating of
the table to determine thickness of the contact lenses. Any change
in the liquid or power of the cuvette holder, will require a new
calibration chart such as the one shown in FIG. 13 will have to be
created. Due to the low divergence characteristics of the laser
beam, the distance 38 in FIG. 9, translates to a fairly accurate
value of the thickness of the contact lens.
[0049] Many modifications and variations of the present invention
can be achieved without departing from its spirit and scope, as it
will become to one skilled in the art. The embodiments described
herein as offered by way of example only and the invention should
not be construed as limited in its scope.
* * * * *