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.
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.
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 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.
Conventional image restoration technique generally uses one point-spread function (PSF) corresponding to an object
distance (OD) and a viewing angle (VA) in filter design. However, for those imaging systems, which concern a better
balance or a new tradeoff of image restoration within a range of ODs or VAs, the conventional design might be
insufficient to give satisfactory results. In this paper, an extension of the minimum mean square error (MMSE) method is
proposed. The proposed method defines a cost function as a linear combination of multiple mean square errors (MSEs).
Each MSE is for measuring the restoration performance at a specific OD and VA and can be computed from the restored
image and its correspondent target image. Since the MSEs for different ODs are lumped into one cost function, the filter
solved can provide a better balance in restoration compared with the conventional design. The method is applied to an
extended depth-of-field (EDoF) imaging system and computer simulations are performed to verify its effectiveness.
Due to the application of mobile phone lens, the clear image for the different object distance from infinity to close-up
creates a new bargaining. We found that wave-front coding applied to extend the depth of field may solve this problem.
By means of using cubic phase mask (CPM), the blurred point-spread function (PSF) is substantially invariant to defocus.
Thus, the ideal hyperfocal distance condition can be satisfied as long as the constant blurred image can eventually be recovered by a simple digital signal processing. In this paper, we propose a different design method of computational imaging lens for mobile phone up to ideal depth of field based on PSF focus invariance. Because of the difficulty for comparing the similarity to different PSFs, we define a new metric, of correlation, to evaluate and optimize the PSF similarity. Besides, by means of adding the
anti-symmetric free form phase plate at aperture stop and using the correlation and Strehl ratio as the two major optimization operands, we can get the optimum phase plate surface to achieve the required extended depth of field (EDoF). The resulted PSF on focal plane is significantly invariant to object distance varying from infinity to 10cm.