Optical coherence tomography (OCT) technique is an extremely powerful tool to detect numerous ophthalmological disorders, such as retinal disorder, and can be applied on other fields. Thus, many OCT systems are developed. For assessment of the skin textures, a cross-sectional (B-scan) spectra domain OCT system is better than an en-face one. However, this kind of commercial OCT system is not available. We designed a brand-new probe of commercial OCT system for evaluating skin texture without destroying the original instrument and it can be restored in 5 minutes. This modification of OCT system retains the advantages of commercial instrument, such as reliable, stable, and safe. Furthermore, the structural changes in aging skin are easily obtained by means of our probe, including larger pores, thinning of the dermis, collagen volume loss, vessel atrophy and flattening of dermal-epidermal junction. We can use this OCT technique in the field of cosmetic medicine such as detecting the skin textures and skin care product effect followup.
We designed and assembled a portable 3-D miniature microscopic image system with the size of 35x35x105 mm3 . By integrating a microlens array (MLA) into the optical train of a handheld microscope, the biological specimen’s image will be captured for ease of use in a single shot. With the light field raw data and program, the focal plane can be changed digitally and the 3-D image can be reconstructed after the image was taken. To localize an object in a 3-D volume, an automated data analysis algorithm to precisely distinguish profundity position is needed. The ability to create focal stacks from a single image allows moving or specimens to be recorded. Applying light field microscope algorithm to these focal stacks, a set of cross sections will be produced, which can be visualized using 3-D rendering. Furthermore, we have developed a series of design rules in order to enhance the pixel using efficiency and reduce the crosstalk between each microlens for obtain good image quality. In this paper, we demonstrate a handheld light field microscope (HLFM) to distinguish two different color fluorescence particles separated by a cover glass in a 600um range, show its focal stacks, and 3-D position.
Merit function with higher efficiency is helpful for lens design, especially in hybrid imaging system. Although different
merit functions have been proposed in recent years, for example, Fisher information, Hilbert space angle, mean square
error (MSE) based on optical transfer function, intermediate or restored image, structure similarity, correlation or
statistical properties from point spread function (PSF). But it is still an unanswered question that which merit function is
best for optimization in hybrid imaging system. So, a novel approach which is based on finite impulse response of hybrid
imaging system is proposed. And several merit functions, blur MSE, PSF similarity, modulation transfer function (MTF)
area and volume are evaluated by present method. The results show that performance of merit function is not only
affected by noise, sampling ratio. But the effect of restoration filter should be also considered. Finally, compare with PSF
similarity, blur MTF in area and volume; blur MSE provide much stable results in hybrid imaging system, which means
it could be an optimized merit function in hybrid imaging system.
Extended depth of field (EDoF) technology can be applied to imaging systems by merging phase-coding design and
digital signal processing. This paper presents an application of EDoF to the microscope platform and shows the
capability to capture EDoF images in a single shot. Ultra-precision machining conditions for a phase-coding component
were compared the peak-to-valley (P-V) error of the cubic surface with the performance of the EDoF. For the phase
variation is very small for this phase plate, determining the optimal cutting condition at which the quality of phase plate
is stabilized is very important. Therefore, the single point diamond turning (SPDT) was used to manufacture the optical
components for its high precision. And the results are as following, the accuracy of non-symmetric phase plate found
between 0.4 μm and 1μm had better performance of the EDoF image. Overall, the depth of field of the new objective
could be increased more than five times compared to an objective having no such phase plate. The purpose of this study
is to compare the relationship between PV error of phase plate surface and imaging restoration quality, which maybe a
good benchmark in this field.
Computational imaging has been using for depth of field extension, distance estimation and depth map for stereo imaging
and displaying with great successfully, which are realized by using special designed imaging lens and optimized image
post-processing algorithm. Several special coding structures have been presented, like cubic, generalized cubic,
logarithmic, exponential, polynomial, spherical and others. And different image post-processing algorithms like Wiener
filter, SVD method, wavelet transform, minimum mean square error method and others are applied to achieve
jointly-optimization. Although most of studies have shown excellent invariant of optical transfer function for imaging lens,
but such invariance will be unsatisfied when manufacturing errors are considered. In this paper, we present a method to
consider behavior of tolerance in computational imaging system from pure optical to optical - digital, which means lens
and image post-processing are both included. An axial irradiance equalization phase coded imaging system is illustrated
for tolerance sensitivity by using similarity of point spread function (PSF), Strehl ratio (SR), and root mean square error
(RMSE) of restored images. Finally, we compare differences between presented method and Zemax.
This paper presents a mobile phone imaging module with extended depth of focus (EDoF) by using axial irradiance
equalization (AIE) phase coding. From radiation energy transfer along optical axis with constant irradiance, the focal
depth enhancement solution is acquired. We introduce the axial irradiance equalization phase coding to design a two-element
2-megapixel mobile phone lens for trade off focus-like aberrations such as field curvature, astigmatism and
longitudinal chromatic defocus. The design results produce modulation transfer functions (MTF) and phase transfer
functions (PTF) with substantially similar characteristics at different field and defocus positions within Nyquist pass
band. Besides, the measurement results are shown. Simultaneously, the design results and measurement results are
compared. Next, for the EDoF mobile phone camera imaging system, we present a digital decoding design method and
calculate a minimum mean square error (MMSE) filter. Then, the filter is applied to correct the substantially similar blur
image. Last, the blur and de-blur images are demonstrated.
Computational imaging technology can capture extra information at the sensor and can be used for various photographic
applications, including imaging with extended depth of field or depth extraction for 3D applications. The depth
estimation from a single captured photograph can be achieved through a phase coded lens and image processing. In this
paper, we propose a new method to design a phase coded lens, using a blur metric (BM) as the design criterion. Matlab
and Zemax are used for the co-optimization of optical coding and digital image process. The purpose of the design is to
find a curve for which the BM changes continuously and seriously within a distance range. We verified our approach by
simulation, and got a axial symmetric phase mask as the coded lens. By using a pseudo-random pattern which contains
uniform black and white patches as the input image, and the on-axis point spread function (PSF) calculated from Zemax,
we can evaluate the BM of the simulated image which is convoluted by the pseudo-random pattern and PSF. In order to
ensure the BM curve evaluated from the on-axis PSF represents the result of the whole field of view, the PSF is also
optimized to get high off-axis similarity.
Computational imaging technology can modify the acquisition process to capture extra information at the sensor that can
be used for various photographic applications, including imaging with extended depth of field, refocusing photographs
after the image is taken or depth extraction for 3D applications. In this paper, we propose a generalized phase coded
imaging which involves encoding of the captured light and post-capture decoding for improved features and
performance. Phase coded optics utilizes optics to purposely encode specific object information in a more efficient way,
which is the most flexible and cost effective solution for correcting optical aberrations or any other optical functions.
Practically any shape can be generated on any lens surface for shaping the point spread function of the lens module to
achieve desired image results. Phase coded optics is a more general scheme than previous proposed for finding the
optimal solutions in digital imaging systems and has proven to be an enabling technology to the imaging problem. Some
of the possible applications based on this technique are also investigated in this paper.
This paper proposes a digital image restoration algorithm for phase-coded imaging systems. In order to extend the depth-of-
field (Dof), an imaging system equipped with a properly designed phase-coded lens can achieve an approximately
constant point spread function (PSF) for a wide range of depths. In general, a phase-coded imaging system produces
blurred intermediate images and requires subsequent restoration processing to generate clear images. For low-computational
consumer applications, the kernel size of the restoration filter is a major concern. To fit for practical
applications, a pyramid-based restoration algorithm is proposed in which we decompose the intermediate image into the
form of Laplacian pyramid and perform restoration over each level individually. This approach provides the flexibility in
filter design to maintain manufacturing specification. On the other hand, image noise may seriously degrade the
performance of the restored images. To deal with this problem, we propose a Pyramid-Based Adaptive Restoration
(PBAR) method, which restores the intermediate image with an adaptive noise suppression module to improve the
performance of the phase-coded imaging system for Dof extension.
This paper develops a digital decoding design for the imaging system with phase coded lens. The phase coded lens is
employed to extend the depth of filed (DoF), and the proposed design is used to restore the special-purpose blur caused
by the lens. Since in practice the imaging system inevitably contains manufacturing inaccuracy, it is often difficult to
obtain precise point spread function (PSF) for image restoration. To deal with this problem, we develop a flow for
designing filters without PSF information. The imaging system first takes a shot of a well-designed test chart to have a
blur image of the chart. This blur image is then corrected by using the perspective transformation. We use both of the
image of the test chart and the corrected blur image to calculate a minimum mean square error (MMSE) filter, so that the
blur image processed by the filter can be very alike to the test chart image. The filter is applied to other images captured
by the imaging system in order to verify its effectiveness in reducing the blur and for showing the capability of extending
the DoF of the integrated system.
A novel design of a phase coded depth-sensing camera is presented. A rotational symmetric phase mask is designed to
discriminate the point spread functions (PSF) from different scene distances. The depth information can then be
computationally obtained from a single captured photograph through a phase coded lens. The PSF must be carefully
optimized at off-axis angles in order to create a restored image which is sharp over the required field of view. In this
paper, a phase coded depth camera with a focal length 10.82mm, sensor size 2mm and F-number 5 is designed.
Simulation data is exchanged between Matlab and Zemax for co-optimization of optical coding and digital decoding
process. The simulation result shows that coarse depth information is investigated for object distance from 513 mm to
A novel design of a wavefront coded compact camera system with liquid lens is presented. The point spread function
must remain practically constant over a wide range of defocus in order to create an image which is sharp over a large
depth of field. Therefore, the trade-off between the effect of extended depth of field and reduction in the signal to noise
ratio of the restored image become critical. By combining liquid lens and wavefront coding, the system can deliver much
greater depth of field without the restoration problems caused by the similarity of point spread function. This could
improve the overall image performance.
A compact zoom lens design for cell phone is presented. A three groups lens system with five lens element is designed
for cell phone camera with 3M pixels and 2.5~3X optical zoom. The first lens is a negative lens with a concave surface
facing the object so that, when used for a long focal length, the rear principle plane is moved forwards to shorten the total
length of the lens. A positive lens group composed of three lens elements is arranged at the second lens group. By
control the optical power of the second lens group, the distortion can be reduced and also shortens the moving distance
of the second lens group while zooming. The fifth lens in the third lens group is a positive lens to control the incident
angle entering the photosensitive element. It is used for focusing when the object distance has changed.
In this paper, an analytic procedure has been developed for the root cause identification of the lens module decentration. By analyzing the lens module according to a predetermined analysis process to generate analysis parameters corresponding to the lens module, and measured performance data can then be compared with these simulated data for validation. This can reveals very valuable information to help fine tune the injection mold.
An integrated process for design and manufacturing of lens modules is proposed. A high end compact zoom lens is designed and analytic procedure has been developed for the root cause identification of the lens decentration.
Axial and lateral compensators are used for zoom systems tolerancing to improve the manufacturability of high zoom ratio lenses. An investigation into the tolerance distribution for various zoom ratios, and compensation conditions and corresponding performance is presented. A flexible method is applied to a rear focusing four-groups 10X zoom to demonstrate the effectiveness of different compensators.