Pinhole Array Research Articles

Spirally-patterned pinhole arrays for long-term fluorescence cell imaging.

Fluorescence cell imaging using a fluorescence microscope is an extensively used technique to examine the cell nucleus, internal structures, and other cellular molecules with fluorescence response time and intensity. However, it is difficult to perform high resolution cell imaging for a long period of time with this technique due to necrosis and apoptosis depending on the type and subcellular location of the damage caused by phototoxicity. A large number of studies have been performed to resolve this problem, but researchers have struggled to meet the challenge between cellular viability and image resolution. In this study, we employ a specially designed disc to reduce cell damage by controlling total fluorescence exposure time without deterioration of the image resolution. This approach has many advantages such as, the apparatus is simple, cost-effective, and easily integrated into the optical pathway through a conventional fluorescence microscope.

Design and Development of a High Performance Pinhole Array Dual Head SPECT Using Monte Carlo Simulation

Design and Development of a High Performance Pinhole Array Dual Head SPECT Using Monte Carlo Simulation

Computational Approach to Color Overlapped Integral Imaging for Depth Estimation

A computational approach to depth estimations using a color over lapped integral imaging system is presented. The proposed imaging system acquires multiple color images simultaneously through a single lens with an array of multiple pinholes that are distributed around the optical axis. This paper proposes a computational model of the relationship between the real distance of an object and the disparity among different color images. The proposed model can serve as a computational basis of a single camera-based depth estimation.

3D image encoding in FT domain based on CGII algorithm

We propose a three-dimensional (3D) image encoding in Fourier transform (FT) domain by the combined use of the computer-generated integral imaging (CGII) and cellular automata (CA) transform. In the 3D image encryption process, the rays information emitting from 3D image through a pinhole array and recorded by a two-dimensional (2D) pickup device. The recorded information is known as 2D elemental image array (EIA) which is the demagnified images of different perspectives of the 3D image. The recorded 2D EIA is encoded by using the CA transform and random phase mask encoding method. The advantages of this proposed method can not only increase the resolution of the reconstructed plane images, but also greatly improve the robustness compared with conventional methods. We present the experimental results to verify the performance of our proposed encryption method.

Common-path on-axis Fresnel holography based on a pinhole array plate.

A common-path and on-axis configuration for improving the resolution power of a lensless Fresnel holographic imaging system is proposed. In this configuration, a pinhole array plate (PAP) is inserted between the object and the recording plane. We demonstrated that the complex amplitude of the object wave can be directly extracted from a single Fresnel hologram of the object wave sampled by the PAP, and the numerical aperture of the effective imaging system can be increased because of the diffraction effect of the pinhole array. It may provide one approach for improving the capabilities of digital holography available for a wide range of wavelengths from far-infrared to x-ray and electron beams.

Effect of Thickness of Pinhole Array on Viewing Angle of Integral Imaging Display

A parameter design of a pinhole array is one of the most important keys to design an integral imaging (II) display using pinhole array. The relationship between the thickness of the pinhole array and the viewing angle of the II display is studied, and the maximal value of the thickness is also obtained. When the thickness of the pinhole array is greater than the maximal value, the viewing angle of the II display is decreased with increasing the thickness of the pinhole array. A prototype of the II display using pinhole array is developed, and the experimental results agree well with the theory.

Investigating high speed phenomena in laser plasma interactions using dilation x-ray imager (invited).

The DIlation X-ray Imager (DIXI) is a new, high-speed x-ray framing camera at the National Ignition Facility (NIF) sensitive to x-rays in the range of ≈2-17 keV. DIXI uses the pulse-dilation technique to achieve a temporal resolution of less than 10 ps, a ≈10× improvement over conventional framing cameras currently employed on the NIF (≈100 ps resolution), and otherwise only attainable with 1D streaked imaging. The pulse-dilation technique utilizes a voltage ramp to impart a velocity gradient on the signal-bearing electrons. The temporal response, spatial resolution, and x-ray sensitivity of DIXI are characterized with a short x-ray impulse generated using the COMET laser facility at Lawrence Livermore National Laboratory. At the NIF a pinhole array at 10 cm from target chamber center (tcc) projects images onto the photocathode situated outside the NIF chamber wall with a magnification of ≈64×. DIXI will provide important capabilities for warm-dense-matter physics, high-energy-density science, and inertial confinement fusion, adding important capabilities to temporally resolve hot-spot formation, x-ray emission, fuel motion, and mix levels in the hot-spot at neutron yields of up to 10(17). We present characterization data as well as first results on electron-transport phenomena in buried-layer foil experiments.

Reconstruction of 2D x-ray radiographs at the National Ignition Facility using pinhole tomography (invited).

Two-dimensional radiographs of imploding fusion capsules are obtained at the National Ignition Facility by projection through a pinhole array onto a time-gated framing camera. Parallax among images in the image array makes it possible to distinguish contributions from the capsule and from the backlighter, permitting correction of backlighter non-uniformities within the capsule radiograph. Furthermore, precise determination of the imaging system geometry and implosion velocity enables combination of multiple images to reduce signal-to-noise and discover new capsule features.

Light intensity and SNR improvement for high-resolution optical imaging via time multiplexed pinhole arrays.

In this paper, we present a novel method for pinhole optics with variable pinhole arrays. The imaging system is based on a time multiplexing method using variable and moving pinhole arrays. The improved resolution and signal-to-noise ratio are achieved with improved light intensity in the same exposure time, compared with that of a one-pinhole system. This new configuration preserves the advantages of pinhole optics while solving the resolution limitation problem and the long exposure time of such systems. The system also can be used as an addition to several existing optical systems, which use visible and invisible light and x-ray systems.

Design of x-ray diagnostic beam line for a synchrotron radiation source and measurement results

Indus-2 is a 2.5GeV synchrotron radiation source (SRS) operational at the Raja Ramanna Centre for Advanced Technology (RRCAT) in India. We have designed, developed and commissioned x-ray diagnostic beam line (X-DBL) at the Indus-2. It is based on pinhole array imaging (8–18keV). We have derived new equations for online measurements of source position and emission angle with pinhole array optics. Measured values are compared with the measurements at an independent x-ray beam position monitor (staggered pair blade monitor) installed in the X-DBL. The measured values are close to the theoretical expected values within ±12µm (or ±1.5μrad) for sufficiently wide range of the beam movements. So, beside the beam size and the beam emittance, online information for the vertical position and angle is also used in the orbit steering. In this paper, the various design considerations of the X-DBL and online measurement results are presented.

A 3D image encryption technique using computer-generated integral imaging and cellular automata transform

A novel three-dimensional (3D) image encryption approach by using the computer-generated integral imaging and cellular automata transform (CAT) is proposed, in which, the two-dimensional (2D) elemental image array (EIA) digitally recorded by light rays coming from the 3D image is mapped inversely through the virtual pinhole array according to the ray-tracing theory. Next, the encrypted image is generated by using the 2D CAT scrambling transform for the 2D EIA. The reconstructed process is carried out by using the modified computational integral-imaging reconstruction (CIIR) technique; the depth-dependent plane images are reconstructed on the output plane. The reconstructed 3D image quality of the proposed scheme can be greatly improved, because the proposed encryption scheme carries out in a computer which can avoid the light diffraction caused by optical device CIIR, and solves blur problem caused by CIIR by using the pixel-averaging algorithm. Furthermore, the CAT-based encryption algorithm is an error-free encryption method; CAT as an orthogonal transformation offers considerable simplicity in the calculation of the transform coefficient, that is, it can improve the quality of the reconstructed image by reducing energy loss compared with the traditional complicated transform process. To show the effectiveness of the proposed scheme, we perform computational experiments. Experimental results show that the proposed scheme outperforms conventional encryption methods.

핀홀어레이를 이용한 슈퍼 멀티-뷰 3D 디스플레이

본 논문에서는 핀홀어레이를 사용한 완전시차 3D 방식의 초다시점 디스플레이를 제안한다. 이는 시점 이미지를 화면에 나타내는 디스플레이 장치, 완전시차의 구현을 위한 핀홀어레이, 시점 영상들을 동공에 동시에 투영시키기 위한 이미징 렌즈로 구성된다. 제안된 방법은 관찰자에게 수평 및 수직 시차가 동시에 제공되는 초다시점 디스플레이 방법이다. 이에 대한 파라미터들의 분석과 시뮬레이션을 통해 수정체 렌즈의 초점 거리만을 조절함에 따라, 망막에 분포하는 빛들의 분포 및 조도 변화를 확인하였으며, 수정체 렌즈가 이미징 렌즈를 통해 생성된 3D 이미지의 깊이면에 초점을 맺을 때에 가장 선명한 영상이 획득됨을 확인하였다. In this paper a Super Multi-view display method using a pinhole array with full parallax was proposed. The proposed method was simulated and its parameters analyzed. Also, the distribution and irradiance of light through each pinhole on the retina receiver, according to the change of crystalline lens focal length, were found by simulation. As a result, an image free of blurring was obtained while the crystalline lens focused on the depth plane of the three-dimensional image created by the imaging lens.

Single order soft X-ray diffraction with quasi-random radius pinhole array spectroscopic photon sieves

A novel single order diffraction grating in the soft X-ray region, called quasi-random radius pinhole array spectroscopic photon sieves (QRSPS), is proposed in this paper. This new grating is composed of pinholes on a substrate, whose radii are quasi-random, while their centers are regular. Analysis proves that its transmittance function across the grating bar is similar to that of sinusoidal transmission gratings. Simulation results show that the QRSPS can suppress higher-order diffraction effectively. And the QRSPS would still retain its characteristic of single order diffraction when we take the effect of X-ray penetration into account. These properties indicate that the QRSPS can be used in the soft X-ray spectra measurement.

An improved cellular automata-based digital image watermarking scheme combining the use of pixel-wise masking and 3D integral imaging

A three-dimensional (3D) watermark integral imaging-based watermarking algorithm operating in the cellular automata (CA) domain is presented. Instead of using conventional two-dimensional (2D) watermarking, in this proposed method, an elemental image array (EIA) obtained by recording the rays emanating from a 3D watermark through a pinhole array is used as a watermark to be embedded into the coefficients of CA-transformed pattern. A series of depth-dependent 3D plane images can be reconstructed by the volumetric computational reconstruction (VCR) technique. The embedded 2D EIA is composed of many elemental images possessing their own perspectives of the 3D watermark. The hologram-like 3D properties of the 2D EIA can make a robust reconstruction of the watermark available even though the embedded watermark data may be damaged by image-processing attacks. To embed the watermark imperceptibly, a masking model is introduced to adapt the watermark embedding strength by exploiting the characteristics of the human vision system. In addition, a CA transform with various CA bases and rule numbers can provide many transform planes for watermark embedding. To demonstrate the usefulness of the proposed method, we carry out preliminary experiments and present the experimental results.

Light f ield head-mounted display with correct focus cue using micro structure array

A new type of light field display is proposed using a head-mounted display (HMD) and a micro structure array (MSA, lens array or pinhole array). Each rendering point emits abundant rays from different directions into the viewer’s pupil, and at one time the dense light field is generated inside the exit pupil of the HMD through the eyepiece. Therefore, the proposed method not only solves the problem of accommodation and convergence conflict in a traditional HMD, but also drastically reduces the huge data in real three-dimensional (3D) display. To demonstrate the proposed method, a prototype is developed, which is capable of giving the observer a real perception of depth.

High security and robust optical image encryption approach based on computer-generated integral imaging pickup and iterative back-projection techniques

In this paper, a novel optical image encryption algorithm by combining the use of computer-generated integral imaging (CGII) pickup technique and iterative back-projection (IBP) technique is proposed. In this scheme, a color image to be encrypted which is firstly segregated into three channels: red, green, and blue. Each of these three channels is independently captured by using a virtual pinhole array and be computationally transformed as a sub-image array. Then, each of these three sub-image arrays are scrambled by the Fibonacci transformation (FT) algorithm, respectively. These three scrambled sub-image arrays are encrypted by the hybrid cellular automata (HCA), respectively. Ultimately, these three encrypted images are combined to produce the colored encrypted image. In the reconstruction process, because the computational integral imaging reconstruction (CIIR) is a pixel-overlapping reconstruction technique, the interference of the adjacent pixels will decrease the quality of the reconstructed image. To address this problem, we introduce an image super-resolution reconstruction technique, the image can be computationally reconstructed by the IBP technique. Some numerical simulations are made to test the validity and the capability of the proposed image encryption algorithm.

이중 현미경 구조를 이용한 마이크로 렌즈 및 핀홀 어레이 기반 병렬 공초점 시스템

The three-dimensional measurement method of confocal systems is a spot scanning method which has a high resolution and good illumination efficiency. However, conventional confocal systems had a weak point in that it has to perform XY axis scanning to achieve FOV (Field of View) vision through spot scanning. There are some methods to improve this problem involving the use of a galvano mirror [1], pin-hole array, etc. Therefore, in this paper we propose a method to improve a parallel mode confocal system using a micro-lens and pin-hole array in a dual microscope configuration. We made an area scan possible by using a combination MLA (Micro Lens Array) and pin-hole array, and used an objective lens to improve the light transmittance and signal-to-noise ratio. Additionally, we made it possible to change the objective lens so that it is possible to select a lens considering the reflection characteristic of the measuring object and proper magnification. We did an experiment using 5X, 2.3X objective lens, and did a calibration of height using a VLSI calibration target.

Dual-view integral imaging three-dimensional display

In this paper, we propose a dual-view integral imaging (DVII) three-dimensional (3D) display that presents different 3D images in the left and right viewing directions simultaneously. The DVII 3D display consists of a display panel and a microlens array, and its elemental image array (EIA) is composed of two sub-EIAs. The sub-EIAs captured for two different 3D scenes are responsible for two different 3D images in the left-view and right-view integral imaging 3D displays, respectively. A prototype of the DVII 3D display using a pinhole array is developed, and good results are obtained.

High-optical-efficiency integral imaging display based on gradient-aperture pinhole array

widths are gradually increased from both sides to the middle in the horizontal and vertical directions. The principle of the proposed II display is shown in Fig. 3. Suppose that L is the viewing distance between the gradient-aperture pinhole array and the observer, g is the gap between the gradient-aperture pinhole array and the display panel, p is the pitch of the gradient-aperture pinhole array, D is the width of the viewing zone, and W is the aperture width of a conventional pinhole. M and N are the numbers of the elemental images in the horizontal and vertical directions, respectively. Hi and Vj denote the horizontal and vertical widths of the pinhole which is in the i-th column and j-th row, respectively. i is a positive integer which is greater than or equal to 1 and less than or equal to M, and j is a positive integer which is greater than or equal to 1 and less than or equal to N. As shown in Fig. 3, we can see that when L is constant, the viewing angle of the proposed II display is only determined by D. When the gradient-aperture pinhole array and the display panel are fixed, D is only determined by the solid lines emitted from the leftmost and rightmost pinholes. Therefore, the horizontal viewing angle of the proposed II display is only determined by the solid lines emitted from the leftmost and rightmost pinholes. When the horizontal viewing angle of the proposed II display is equal to that of the conventional II display, the relationship between H1 and W can be determined as H 1 ¼ W:

Beyond Young’s experiment: time-domain correlation measurement in a pinhole array

Time-domain analysis of field correlations provided by the interferogram from a nonredundant pinhole array is performed. It is shown that the described single measurement is identically equal to a series of Young's two-pinhole experiments. Proper postmeasurement analysis, taking into account the finite coherence time of the source, results in a sampling of the spatial-temporal coherence function.