U.S. patent application number 17/010417 was filed with the patent office on 2020-12-24 for miniature wide-angle imaging lens.
The applicant listed for this patent is ImmerVision, Inc.. Invention is credited to Pierre KONEN, Pascale NINI, Jocelyn Parent, Patrice ROULET, Simon THIBAULT, Hu ZHANG.
Application Number | 20200400920 17/010417 |
Document ID | / |
Family ID | 1000005073658 |
Filed Date | 2020-12-24 |
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United States Patent
Application |
20200400920 |
Kind Code |
A1 |
Parent; Jocelyn ; et
al. |
December 24, 2020 |
MINIATURE WIDE-ANGLE IMAGING LENS
Abstract
A miniature wide-angle imaging lens has a miniaturization ratio,
of a total track length from the center of a first surface to a
focal plane by an image circle diameter, with a value less than
3.0. The imaging lens includes, starting from an object side of the
lens, a first group of at least three optical elements, a second
group including an aperture stop and an optical element immediately
in front of or behind the aperture stop, and a third group of at
least two optical elements.
Inventors: |
Parent; Jocelyn; (Montreal,
CA) ; THIBAULT; Simon; (Quebec City, CA) ;
ROULET; Patrice; (Montreal, CA) ; ZHANG; Hu;
(Montreal, CA) ; NINI; Pascale; (Montreal, CA)
; KONEN; Pierre; (Saint-Bruno, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ImmerVision, Inc. |
Montreal |
|
CA |
|
|
Family ID: |
1000005073658 |
Appl. No.: |
17/010417 |
Filed: |
September 2, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16432180 |
Jun 5, 2019 |
10795120 |
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17010417 |
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15384900 |
Dec 20, 2016 |
10353173 |
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16432180 |
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62298795 |
Feb 23, 2016 |
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62387409 |
Dec 23, 2015 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02B 9/64 20130101; G02B
5/208 20130101; G02B 9/62 20130101; G02B 13/0045 20130101; G02B
13/06 20130101; G02B 13/001 20130101; G02B 5/005 20130101 |
International
Class: |
G02B 13/00 20060101
G02B013/00; G02B 13/06 20060101 G02B013/06; G02B 9/62 20060101
G02B009/62; G02B 5/00 20060101 G02B005/00; G02B 5/20 20060101
G02B005/20; G02B 9/64 20060101 G02B009/64 |
Claims
1. A miniature wide-angle optical apparatus comprising: a
light-receiving first surface; a focal plane; and a non-linear
targeted resolution to intentionally create a zone in an image
captured by the miniature wide-angle optical apparatus with a lower
or higher object to image magnification compared to linear targeted
resolution, the lower or higher object to image magnification being
used to compensate, at least in part, for a lower image quality due
to at least one of a drop of relative illumination or a drop of MTF
in a zone of the image, an opening angle of light entering the
optical apparatus being over 100.degree..
2. The miniature wide-angle optical apparatus of claim 1, wherein
the optical apparatus is configured to create a resulting image
with a constant image quality across a whole field of view.
3. The miniature wide-angle optical apparatus of claim 1, wherein a
targeted resolution curve has a change of direction near an edge of
a field of view.
4. The miniature wide-angle optical apparatus of claim 1, wherein
an angle of chief-rays reaching the focal plane is over 20.degree.
from an optical axis of the optical apparatus.
5. The miniature wide-angle optical apparatus of claim 1, further
comprising a plurality of optical elements, at least one of the
plurality of optical elements defining the first surface.
6. The miniature wide-angle optical apparatus of claim 5, wherein
at least one of the optical elements is made of glass.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation application of U.S.
patent application Ser. No. 16/432,180, filed Jun. 5, 2019,
entitled "Miniature Wide-Angle Imaging Lens," currently pending,
which is a continuation application of U.S. patent application Ser.
No. 15/384,900, filed Dec. 20, 2016, entitled "Miniature Wide-Angle
Imaging Lens," now U.S. Pat. No. 10,353,173, which claims the
benefit of U.S. Provisional Patent Application No. 62/387,409,
filed Dec. 23, 2015, entitled "Miniature wide-angle imaging lens,"
now expired, and U.S. Provisional Patent Application No.
62/298,795, filed Feb. 23, 2016, entitled "Miniature wide-angle
imaging lens," now expired, the entire contents of all of which are
incorporated by reference herein.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to optical lenses and more
particularly to miniature lenses having a wide-angle field of
view.
[0003] For most applications requiring wide-angle imaging, larger
lens constructions having a miniaturization ratio (i.e., a total
track length over an image circle diameter) greater than 3.0 are
often used. However, for consumer applications, especially with
mobile devices, the trend is that the lens thicknesses are becoming
thinner while the sensor sizes are becoming larger. Accordingly, a
new kind of wide-angle lenses with a miniaturization ratio less
than 3.0 are required.
[0004] Previously suggested miniature wide-angle lenses, such as
that described in "Consumer electronic optics: how small can a lens
be: the case of panomorph lenses" published in "Proc. SPIE 9192,
Current Developments in Lens Design and Optical Engineering XV,
91920H," or as in U.S. Pat. No. 8,248,715 or U.S. Pat. App. Pub.
Nos. 2014/0029115, 2013/0308206, 2014/0226222, 2014/0285906,
2015/0253542, 2015/0268446 or 2012/0212839 were designed for
previous generations of sensors having smaller sizes and larger
pixels. These lenses had lower performance requirements, especially
regarding image quality and aperture size. For these existing lens
constructions, a total of three to six optical elements were enough
to meet the required performances for these sensors. For the
existing wide-angle 6-element lenses, a symmetric construction
using 3 elements in front of the stop and 3 elements behind the
stop has been used. However, with new larger sensors and smaller
pixels, more complex wide-angle lens constructions using six
elements with asymmetric constructions around the stop or using
seven or more elements must be designed to achieve the required
performances.
[0005] One of the challenges to achieve good imaging performance
over the whole field of view of a miniature wide-angle lens is the
change of relative illumination from the center to the edge of the
field of view. In wide-angle lenses, the relative illumination is
usually maximum in the center and drops continuously toward the
edge of the field of view. The consequence of lower illumination
toward the edge is a lower image quality at the edge due to
increased diffraction effects and additional sensor noise at the
edges.
[0006] Another challenge to achieve good imaging performance over
the whole field of view of a miniature wide-angle lens is a drop of
the modulation transfer function (MTF) from the center to the edge
of the field of view. In wide-angle lenses, the image MTF is
usually maximum in the center and drops continuously toward the
edge of the field of view. The consequence of lower MTF toward the
edge is a lower image quality at the edge.
BRIEF SUMMARY OF THE INVENTION
[0007] To overcome all the previously mentioned issues, embodiments
of the current invention describe miniature wide-angle imaging
lenses having a miniaturization ratio (i.e., total track length
from the center of the first surface to the focal plane over the
image circle diameter) having a value less than 3.0 while
maintaining a good balance between image quality parameters,
including MTF, relative illumination, and resolution. The imaging
lens construction, in order from the object space to the image
space, preferably includes a first group of elements, a second
group of elements, and a third group of elements.
[0008] The first group of elements, preferably including all the
elements in front of the second group, has a negative optical power
in the paraxial region and preferably includes at least three
optical lenses. Of these at least three optical lenses, the first
lens on the object side is generally a negative meniscus lens with
a surface on the object side and accepting light from an opening
angle of at least 100.degree. and generally between 120.degree. to
280.degree..
[0009] The second group of elements preferably includes an aperture
stop and a single optical lens immediately in front of or behind
the aperture stop. The single optical lens of the second group is
preferably a positive lens.
[0010] The third group of elements preferably includes at least two
optical lenses after the second group. Of these at least two
optical lenses, there is generally at least one positive element
and at least one negative element. The last lens element on the
image side has a surface on the image side transmitting light to an
opening angle of at least 40.degree..
[0011] In an embodiment of the current invention, the miniature
optical lens has six optical elements, split as three, one, and two
elements respectively for the first, second, and third groups. In
another embodiment of the current invention, the miniature optical
lens has seven optical elements in it, split as three, one, and
three elements respectively for the first, second, third groups. In
another embodiment of the current invention, the miniature optical
lens has eight optical elements in it, split as four, one, and
three elements respectively for the first, second and third
groups.
[0012] In some embodiments of the current invention, the targeted
resolution curve of the miniature wide-angle lens is configured to
offset, at least in part, the drop of relative illumination from
the miniature wide-angle lens by increasing the number of pixels
imaged in the zone where the relative illumination is lower.
[0013] In some other embodiments of the current invention, the
targeted resolution curve of the miniature wide-angle lens is
configured to offset, at least in part, the drop of MTF from the
miniature wide-angle lens by increasing the number of pixels imaged
in the zone where the MTF is lower.
[0014] In some other embodiments of the current invention, the
targeted resolution curve of the miniature wide-angle lens is
configured as the optimal curve to produce the highest relative
illumination and MTF values combination and hence produce the
optimal image quality for the whole lens plus camera system.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0015] The foregoing summary, as well as the following detailed
description of a preferred embodiment of the invention, will be
better understood when read in conjunction with the appended
drawings. For the purpose of illustration, there is shown in the
drawings an embodiment which is presently preferred. It should be
understood, however, that the invention is not limited to the
precise arrangements and instrumentalities shown.
[0016] In the drawings:
[0017] FIG. 1 is a first preferred embodiment of a miniature
wide-angle lens with six total lens elements;
[0018] FIG. 2 is a second preferred embodiment of a miniature
wide-angle lens with seven total lens elements;
[0019] FIG. 3 is third preferred embodiment of a miniature
wide-angle lens with eight total lens elements;
[0020] FIG. 4 is an example of a typical relative illumination
curve of a miniature wide-angle lens;
[0021] FIG. 5 is an example of a typical MTF curve of a miniature
wide-angle lens;
[0022] FIG. 6 is an example of a targeted resolution curve used to
at least partially compensate the relative illumination or at least
partially compensate the MTF according to certain embodiments of
the present invention; and
[0023] FIG. 7 is an example of a targeted resolution curve chosen
to produce the highest relative illumination in the whole field of
view while keeping the highest MTF according to certain embodiments
of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0024] Certain terminology is used in the following description for
convenience only and is not limiting. The words "right", "left",
"lower", and "upper" designate directions in the drawings to which
reference is made. The words "inwardly" and "outwardly" refer to
directions toward and away from, respectively, the geometric center
of the device and designated parts thereof. The terminology
includes the above-listed words, derivatives thereof, and words of
similar import. Additionally, the words "a" and "an", as used in
the claims and in the corresponding portions of the specification,
mean "at least one."
[0025] FIG. 1 shows a first embodiment of the present invention
with an optical layout for a design having six optical elements in
an asymmetric configuration around the stop, having four optical
elements before the stop and two optical elements after the stop.
The lens 100 is comprised of the three groups 110, 112 and 114. In
this embodiment of the miniature wide-angle lens 100, the first
group 110 from the object space is made of lenses 120, 121 and 122.
The first group has a negative total optical power. The second
group 112 includes an aperture stop 124 and a single positive lens
123. The second group 112 has positive optical power. In this
embodiment of the miniature wide-angle lens 100, the third group
114 has two optical elements 125, 126 and has a negative total
optical power.
[0026] Light entering the miniature lens 100 hits a first surface
of element 120 from all directions between an upper angle 130 and a
lower angle 134. In this example embodiment of FIG. 1, a total
field of view around the central field 132 of the lens 100 is
180.degree., but any total field of view over 100.degree. can be
considered as a wide-angle lens according to the present
invention.
[0027] The light then passes through all the elements 120, 121,
122, of the first group 110, the single lens 123 and the aperture
stop 124 of the second group 112, and the elements 125 and 126 of
the third group 114 to reach an IR filter and image sensor 127.
More specifically, the light beam from direction 130 reaches the
sensor 127 at position 144, the light from direction 132 reaches
the sensor 127 at position 142, and the light from direction 134
reaches the sensor 127 at position 140. For all beams of light 130,
132 and 134, the chief-ray is defined as the middle ray of the
three rays drawn because it passes through the center of the
aperture stop 124. In this example embodiment, the angle of the
cone of light formed by the chief-rays reaching the sensor plane at
positions 140 and 144 is over 40.degree. to minimize the dimensions
of the lens 100. When measured with respect to the chief-ray
reaching the sensor 127 at position 142, which represents the
optical axis of the lens 100, the chief-ray angle of the extreme
rays reaching the sensor at position 140 or 144 are over
20.degree..
[0028] The lens 100 has a total track length 150, which is a
measure from the first surface on the object side of lens 120 to
the image sensor 127, and forms an image having a diameter 160,
which is a distance on the sensor 127 between the position 140 and
the position 144 where the light beams from the lower and the upper
fields 130, 134 reach the sensor 127. The miniaturization ratio is
calculated by dividing the total track length 150 over the
footprint diameter 160 and is less than 3.0 for any miniature lens
according to the present invention and could even be less than 2.0
for an extreme miniature lens.
[0029] FIG. 2 shows an embodiment of the present invention with an
optical layout for a design having seven optical elements. The lens
200 is comprised of the three groups 210, 212 and 214. In this
embodiment of the miniature wide-angle lens 200, the first group
210 from the object space is made of lenses 220, 221, and 222. The
first group 210 has a negative total optical power. The second
group 212 includes the aperture stop 223 and a single positive lens
224. The second group 212 has positive optical power. In this
embodiment of the miniature wide-angle lens 200, the third group
214 has three optical elements 225, 226, 227 and has a negative
total optical power.
[0030] Light entering the miniature lens 200 hits the first surface
of element 220 from all directions between the upper angle 230 and
the lower angle 234. In this example embodiment of FIG. 2, the
total field of view around the central field 232 is 180.degree.,
but any total field of view over 100.degree. can be considered as a
wide-angle lens according to the present invention.
[0031] The light then passes through all the elements 220, 221, 222
of the first group 210, the aperture stop 223 and positive lens 224
of the second group 212, and the elements 225, 226 and 227 of the
third group 214 to reach the IR filter and image sensor 228. More
specifically, the light beam from direction 230 reaches the sensor
at position 244, the light from direction 232 reaches the sensor at
position 242, and the light from direction 234 reaches the sensor
at position 240. In this example, an angle of the cone of light
formed by the chief-rays reaching the sensor plane at positions 240
and 244 is over 40.degree. to minimize the dimensions of the lens
200. When measured with respect to the chief ray reaching the
sensor 228 at position 242, which represents the optical axis of
the lens 200, the chief-ray angle of the extreme rays is over
20.degree..
[0032] The lens 200 has a total track length 250, which is a
measure from the first surface on the object side of lens 220 to
the image sensor 228 and forms an image having a diameter 260,
which is the distance on the sensor between the position 240 and
the position 244 where the light beams from the upper and the lower
fields 230, 234 reach the sensor. The miniaturization ratio is
calculated by dividing the total track length 250 over the
footprint diameter 260 and is less than 3.0 for any miniature lens
according to the present invention, and could even be less than 2.0
for an extreme miniature lens.
[0033] FIG. 3 shows an embodiment of the present invention with an
optical layout for a design having eight optical elements. The lens
is comprised of the three groups 310, 312 and 314. In this
embodiment of the miniature wide-angle lens, the first group 310
from the object space is made of lenses 320, 321, 322 and 323. The
first group has a negative total optical power. The second group
312 includes the aperture stop 324 and a single positive lens 325.
The second group 312 has positive optical power. In this embodiment
of the miniature wide-angle lens 300, the third group 314 has three
optical elements 326, 327, 328 and has a negative total optical
power.
[0034] Light entering the miniature lens 300 hit the first surface
of element 320 from all directions between the upper angle 330 and
the lower angle 334. In this example embodiment of FIG. 3, the
total field of view around the central field 332 is 180.degree.,
but any total field of view over 100.degree. can be considered as a
wide-angle lens according to the present invention.
[0035] The light then passes through all the elements 320, 321,
322, 323 of the first group 310, the aperture stop 324 and lens 325
of the second group 312, and the elements 326, 327 and 328 of the
third group 314 to reach the IR filter and image sensor 329. More
specifically, the light beam from direction 330 reaches the sensor
329 at position 344, the light from direction 332 reaches the
sensor 329 at position 342, and the light from direction 334
reaches the sensor 329 at position 340. In this example, the angle
of the cone of light formed by the chief-rays reaching the sensor
plane at positions 340 and 344 is over 40.degree. to minimize the
dimensions of the lens. When measured with respect to the chief ray
reaching the sensor at position 342, which represents the optical
axis of the lens, the chief-ray angle of the extreme rays is over
20.degree..
[0036] The lens has a total track length 350, which is a measure
from the first surface on the object side of lens 320 to the image
sensor 329, and forms an image having a diameter 360 which is a
distance on the sensor 329 between the position 340 and the
position 344 where the light beams from the upper and the lower
fields 330, 334 reach the sensor. The miniaturization ratio is
calculated by dividing the total track length 250 over the
footprint diameter 260 and is less than 3.0 for any miniature lens
according to the present invention and could even be less than 2.0
for an extreme miniature lens.
[0037] In some embodiments of the present invention, all of the
elements inside the miniature wide-angle lenses are made of plastic
materials in part to ease the mass-production or lower the costs.
In some other embodiments of the present invention, the miniature
wide-angle lens consist of at least one glass element to improve
the optical performances of the miniature wide-angle lens or to
increase the rigidity of when the glass element is the first
element.
[0038] FIG. 4 shows a typical relative illumination curve 400 for a
miniature wide-angle lens according to embodiments of the present
invention. The exact values of the relative illumination with
respect to the field of view vary between each embodiment of the
present invention, but the overall shape having a value around 100%
at 0.degree. shown at center 410 and under 80% at the maximum field
angle shown at position 420 is present in all families of miniature
wide-angle lenses according to the present invention.
[0039] FIG. 5 shows a typical sagittal MTF curve 500 and tangential
MTF curve 505 for a miniature wide-angle lens according to
embodiments of the present invention. The exact values of the MTF
with respect to the field of view vary between each embodiment of
the present invention and also vary according to the spatial
frequency at which the MTF is calculated, but the overall shape
having a higher value at 0.degree. shown at center 510 than at the
edge shown at position 520 is present in all families of miniature
wide-angle lenses according to the present invention.
[0040] FIG. 6 shows an example targeted resolution curve 600 for a
miniature wide-angle lens according to embodiments of the present
invention where the targeted resolution is non-linear and a higher
number of pixels per degree is intentionally present in a part of
the image. In some embodiments of the miniature wide-angle, the
shape of the targeted resolution curve is intentionally designed to
compensate for the drop of relative illumination seen in FIG. 4. In
some other embodiments of the miniature wide-angle lens, the shape
of the targeted resolution is intentionally designed to compensate
for the drop of MTF seen in FIG. 5. In the zone where the
resolution is higher, there are more pixels of the sensors used to
image a given angle of the object space. By having more imaging
pixels in this zone, this compensates for the lower image quality
in this zone either due to the lower relative illumination or the
lower MTF. The final resulting image can then be processed to
create a resulting image with constant image quality across the
whole field of view.
[0041] FIG. 7 shows another example embodiment of a non-linear
targeted resolution curve 700 for a miniature wide-angle lens
according to the present invention. The targeted resolution curve
is chosen to have an upward curve between the center resolution
value 710 and a maximum 712 (number of pixels/degree), followed by
a downward curve between the maximum 712 and a region near the edge
of the field of view around position 714. This downward curve
between maximum value 712 and position 714 allows the lens system
to have a higher relative illumination value toward the edge of the
field of view by having a lower object to image magnification ratio
in that region and hence redirecting the same quantity of light
from an object to a smaller region in the image with more
illumination.
[0042] In some embodiments of a miniature wide-angle lens according
to the present invention, the resolution curve has a change of
direction at the edge of the field of view 716. This change of
direction is an upward trend if it is preceded by a downward trend
and it is a downward trend if it is preceded by an upward trend.
This change of direction allows for a closer value of resolution in
pixels/degree in the center 710 and at the edge 716, creating the
best balance of MTF between the center 710 and the edge 716.
[0043] Combined together, the downward curve between maximum value
712 and position 714 allowing higher relative illumination and the
change of direction in the curve between position 714 and edge
provides 716 the best image quality on the lens and camera system.
The more balanced relative illumination creates less sensor noise
in the images due do illumination differences and less difference
of diffraction effects on the image quality due to the variable f/#
across the field of view. For the more balanced MTF, thanks to the
change of direction between position 614 and edge 616, it is
directly related to the image quality of the lens.
[0044] All of the above are figures and examples of miniatures
wide-angle lenses. They are examples of families of constructions
having three groups and at least six optical elements. Furthermore,
the miniature wide-angle lenses can be optimized according to a
function which at least includes the relative illumination, the
resolution and the MTF. Similar constructions are possible and the
three examples presented should not limit the scope and spirit of
the present invention. It will be appreciated by those skilled in
the art that changes could be made to the embodiments described
above without departing from the broad inventive concept thereof.
It is understood, therefore, that this invention is not limited to
the particular embodiments disclosed, but it is intended to cover
modifications within the spirit and scope of the present invention
as defined by the appended claims.
* * * * *