We address freeform aplanatic designs both as solutions of a differential system of equations and as limiting cases of SMS designs. We conclude that, in general, freeform aplanatic systems need at least 3 optical-surfaces with illustrative examples.
Axisymmetric aplanatic systems have been used in the past for solar concentrators and condensers (Gordon et. al, 2010).
It is well know that such a system must be stigmatic and satisfy the Abbe sine condition. This problem is well known
(Schwarzschild, 1905) to be solvable with two aspherics when the system has rotational symmetry.
However, some of those axisymmetric solutions have intrinsically shading losses when using mirrors, which can be
prevented if freeform optical surfaces are used (Benitez, 2007).
In this paper, we explore the design of freeform surfaces to obtain full aplanatic systems. Here we prove that a rigorous
solution to the general non-symmetric problem needs at least three free form surfaces, which are solutions of a system of
partial differential equations (PDE). We also present the PDEs for a three surface full aplanat. The examples considered
have one plane of symmetry, where a consistent 2D solution is used as boundary condition for the 3D problem. We have
used the x-y polynomial representations for all the surfaces, and the iterative algorithm formulated for solving the above
said PDE has shown very fast convergence.
Freeform optical surfaces have been in much demand recently due to improved techniques in their manufacturability and design methodology, and the degrees of freedom it gives the designers. Specifically in the case of off-axis mirror systems, freeform surfaces can considerably reduce the number of surfaces and compensate for some of the higher order aberrations as well, which improves the overall system performance. In this paper, we explore the design of freeform surfaces to obtain full aplanatic mirror systems, i.e., free of spherical aberration and circular coma of all orders. It is well know that such a system must be stigmatic and satisfy the Abbe sine condition. This problem is well known (Schwarzschild, 1905) to be solvable with two aspheric when the system has rotational symmetry. Here we prove that a rigorous solution to the general non-symmetric problem needs at least three free form surfaces, which are solutions of a system of partial differential equations. The examples considered have one plane of symmetry, where a consistent 2D solution is used as boundary condition for the 3D problem. We have used the x-y polynomial representations for all the surfaces used, and the iterative algorithm formulated for solving the above mentioned partial differential equations has shown very fast convergence.
Axisymmetric aplanatic concentrators have been used in the past for solar concentrators and condensers (Gordon et. al, 2010). It is well know that such a system must be stigmatic and satisfy the Abbe sine condition. This problem is well known (Schwarzschild, 1905) to be solvable with two aspherics when the system has rotational symmetry. However, some of those axisymmetric solutions have intrinsically shading losses when using mirrors, which can be prevented if freeform optical surfaces are used (Benitez, 2007). In this paper, we explore the design of freeform surfaces to obtain full aplanatic systems. Here we prove that a rigorous solution to the general non-symmetric problem needs at least three free form surfaces, which are solutions of a system of partial differential equations (PDE). We also present the PDEs for a three surface full aplanat. The examples considered have one plane of symmetry, where a consistent 2D solution is used as boundary condition for the 3D problem. We have used the x-y polynomial representations for all the surfaces, and the iterative algorithm formulated for solving the above said PDE has shown very fast convergence.
In this work, we demonstrate how it is possible to sharply image multiple object points. The Simultaneous Multiple Surface (SMS) design method has usually been presented as a method to couple N wave-front pairs with N surfaces, but recent findings show that when using N surfaces, we can obtain M image points when N<M under certain conditions. We present the evolution of SMS method, from its basics, to imaging two object points through one surface, the transition from two to three objet points obtained by increasing the parallelism, and getting to the designs of six surfaces imaging up to eight object points. These designs are limited with the condition that the surfaces cannot be placed at the aperture stop. In the process of maximizing the object points to sharp image, we try to exhaust the degrees of freedom of aspherics and free-forms. We conjecture that maximal SMS designs are very close to a good solution, hence using them as a starting point for the optimization will lead us faster to a final optical system. We suggest here different optimization strategies which combined with the SMS method are proven to give the best solution. Through the example of imaging with the high aspect ratio, we compare the results obtained optimizing the rotational lens and using a combination of SMS method and optimization, showing that the second approach is giving significantly smaller value of overall RMS spot diameter.
This paper describes the design of a 3-5microns 26:1 zoom with a focal length extender capability that increases NFOV
focal length by 1.75x. Mechanical restrictions for a payload envelope will be considered as well as cold stop efficiency
issues.
In this work, two SMS algorithms are presented for an objective design with different selected ray-bundles: three
meridian ray-bundles (3M) and one meridian and two skew ray-bundles (1M-2S), the latter from pin hole point of view,
provides a better sampling of the phase space. Results obtained with different algorithms will be compared.
While multichannel configurations are well established for non-imaging applications, they have not been used yet
for imaging applications. In this paper we present for the first time some of multichannel designs for imaging
systems. The multichannel comprises discontinuous optical sections which are called channels. The phase-space
representation of the bundle of rays going from the object to the image is discontinuous between channels. This
phase-space ray-bundle flow is divided in as many paths as channels there are but it is a single wavefront both at the
source and the target. Typically, these multichannel systems are at least formed by three optical surfaces: two of
them have discontinuities (either in the shape or in the shape derivative) while the last is a smooth one. Optical
surfaces discontinuities cause at the phase space the wave front split in separate paths. The number of discontinuities
is the same in the two first surfaces: Each channel is defined by the smooth surfaces in between discontinuities, so
the surfaces forming each separate channel are all smooth. Aplanatic multichannel designs are also shown and used
to explain the design procedure.
In this work, two SMS algorithms are presented for an objective design with different selected ray-bundles: three meridian ray-bundles (3M) and one meridian and two skew ray-bundles (1M-2S), the latter from pin hole point of view, provides a better sampling of the phase space. Results obtained with different algorithms will be compared.
Two new optical structures are designed using the Simultaneous Multiple Surfaces (SMS) method, comprised of 2
reflecting surfaces and 2 refracting surfaces, 800mm focal length, f/8 (aperture diameter 100 mm) and 1.180 diagonal
field of view in the SWIR band. The lens surfaces are rotational symmetric and calculated to have good control of
non-paraxial rays. We have achieved designs with excellent performance, and with total system length of less than 60 mm.
Lately the short-wave infrared (SWIR) has become very important due to the recent appearance on the market of
the small detectors with a large focal plane array. Military applications for SWIR cameras include handheld and
airborne systems with long range detection requirements, but where volume and weight restrictions must be
considered. In this paper we present three different designs of telephoto objectives that have been designed
according to three different methods. Firstly the conventional method where the starting point of the design is an
existing design. Secondly we will face design starting from the design of an aplanatic system. And finally the
simultaneous multiple surfaces (SMS) method, where the starting point is the input wavefronts that we choose.
The designs are compared in terms of optical performance, volume, weight and manufacturability. Because the
objectives have been designed for the SWIR waveband, the color correction has important implications in the
choice of glass that will be discussed in detail.
In this work, we propose two new optical structures, using the Simultaneous Multiple Surfaces (SMS) method,
comprised of 2 reflecting surfaces and 2 refracting surfaces, 800mm focal length, f/8 (aperture diameter 100 mm)
and 1.18° diagonal field of view in the SWIR band. The lens surfaces are rotational symmetric and calculated to have
good control of non-paraxial rays. We have achieved designs with excellent performance, and with total system
length of less than 60 mm.
Using the Simultaneous Multiple Surface method in 2D (SMS2D), we present a
fast catadioptric objective with a wide field of view (125°×96°designed for a microbolometer
detector with 640×480 pixels and 25 microns pixel pitch.
New ultra-thin optical designs are presented. They are formed by optical sections (called channels) working in parallel
(multichanneling) to provide the desired optical function. The phase-space representation of the bundle of rays going
from the source to the target is discontinuous between channels. This phase-space ray-bundle flow is divided in as many
branches as channels there are but it is a single trunk at the source and at the target. Typically, these multichannel
devices are at least formed by three optical surfaces: two of them have discontinuities (in the shape or in the shape
derivative) while the last one is smooth. The discontinuities of the optical surfaces are causing the separation of the flow
in branches (in the phase space). The number of discontinuities is the same in the two first surfaces: Each channel is
defined by the smooth surfaces in between discontinuities, so the surfaces forming each separate channel are all smooth.
No diffractive analysis is done.
Using the Simultaneous Multiple Surface method in 2D (SMS2D), we present a fast catadioptric objective with a wide
field of view (125°×96°) designed for a microbolometer detector with 640×480 pixels and 25 microns pixel pitch
Keywords: Infrared lens design, thermal imaging, Schwarzschild configuration, SMS2D, wide field of view, driving
cameras, panoramic systems
Using the Simultaneous Multiple Surface method in 2D (SMS2D), we present a fast catadioptric objective with a wide
field of view (125°×96°) designed for a microbolometer detector with 640×480 pixels and 25 microns pixel pitch.
New ultra-thin optical designs are presented that comprise discontinuous optical sections (called channels) working in
parallel (multichanneling) to provide the desired optical function. Aplanatic (a particular case of SMS-design)
multichannel designs are also shown and used to explain more easily the design procedure. Typically, these multichannel
devices are at least formed by three optical surfaces: one of them has discontinuities in the shape, a second one may have
discontinuities in its derivative while the third one is smooth. The number of discontinuities is the same in the two first
surfaces: Each channel is defined by the smooth surfaces in between the discontinuities, so that the surfaces forming
each separate channel are all smooth. No diffractive effects are considered.
The Simultaneous Multiple Surfaces (SMS) was developed as a design method in Nonimaging Optics during the 90s.
Later, the method was extended for designing Imaging Optics. We present an overview of the method applied to imaging
optics in planar (2D) geometry and compare the results with more classical designs based on achieving aplanatism of
different orders. These classical designs are also viewed as particular cases of SMS designs. Systems with up to 4
aspheric surfaces are shown.
The SMS design strategy is shown to perform always better than the classical design (in terms of image quality).
Moreover, the SMS method is a direct method, i.e., it is not based in multi-parametric optimization techniques. This
gives the SMS method an additional interest since it can be used for exploring solutions where the multiparameter
techniques can get lost because of the multiple local minima.
Wavefront coding (WFC) is a powerful hybrid optical-numerical technique for increasing the depth of
focus of imaging systems. There is a low cost solution that uses decentred lenses inducing coma as an
adjustable and removable phase element. This coding has been proven useful for IR systems. However
these systems usually have several configurations with multiple fields of view. Unless the detector is
uncooled, the f/number of the system is maintained for all configurations thus entrance pupil size changes
for each one. As a result, the coding coma changes accordingly. This paper presents an approach to
maintain the same amount of coma for dual field of view (DFOV) systems.
Wavefront coding (WFC) is a powerful hybrid optical-numerical technique for increasing the depth of focus of imaging
systems. It is based on two components: (1) an optical phase element that codifies the wavefront, and (2) a numerical
deconvolution algorithm that reconstructs the image. Traditionally, some sophisticated optical WFC designs have been
used to obtain approximate focus-invariant point spread functions (PSFs). Instead, we present a simple and low cost
solution, implemented on infrared (IR) cameras, which uses a decentred lens inducing coma as an adjustable and
removable phase element. We have used an advanced deconvolution algorithm for the image reconstruction, which is
very robust against high noise levels. These features allow its application to low cost imaging systems. We show
encouraging preliminary results based on realistic simulations using optical PSFs and noise power spectral density (PSD)
laboratory models of two IR imaging systems. Without induced optical phase, the reconstruction algorithm improves the
image quality in all cases, but it performs poorly when there are both in and out-of-focus objects in the scene. When
using our coding/decoding scheme with low-noise detectors, the proposed solution provides high quality and robust
recovery even for severe defocus. As sensor noise increases, the image suffers a graceful degradation, its quality being
still acceptable even when using highly noisy sensors, such as microbolometers. We have experienced that the amount of
induced coma is a key design parameter: while it only slightly affects the in-focus image quality, it is determinant for the
final depth of focus.
The performance of bi-spectral diffractive lenses for MWIR and LWIR is shown. The effect of ghost light produced by
third order will enhance the importance of the reference wavelength (λ0) in the design of the diffractive surface.
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