Optical Pickup Research Articles

Integral Imaging Pickup Method With Extended Depth-of-Field by Gradient-Amplitude Modulation

One of the major drawbacks of the three-dimensional (3D) integral imaging (II) is the limited depth-of-field (DOF). One approach to enhance the DOF is applying the amplitude-modulating method on the microlens arrays. However, the conventional amplitude-modulating methods usually suffer some collateral effects such as lateral resolution reductions or contrast reversals. In this paper, we propose a gradient-amplitude-modulating (GAM) method to enhance the DOF of the II pickup system when recording large-depth 3D scenes. This method is practical and not accompanied by any obvious lateral resolution deteriorations or contrast reversals. Experimental results obtained from the optical pickup process and computational reconstruction process finally demonstrate the feasibility of the proposed method.

Position alignment of laser beam spots in optical disc drives using cross-correlation

Optical pickup unit (OPU) is a data read/write head in optical disc drives, and precision orientation angle adjustment of a diffraction grating (GT) is an important process in OPU manufacturing for aligning laser beam spots on the same data track of an optical disc. This paper proposes a new method for detecting alignment of laser beam spots for utilization in automation of the GT adjustment process. While a conventional method uses complicated and expensive image processing techniques to an eye diagram of a data radio frequency (RF) signal, the proposed method measures the cross-correlation of two binary signals corresponding to two of the laser beam spots in consideration of the geometric relationship between the laser beam spots and data tracks. The proposed method is not only so simple as to be implemented using a digital logic circuit but also tolerant to poor signal condition due to radial off-track run-out and disc rotational speed error. A FPGA-based implementation of the proposed method is presented, and experimental results are provided to show its validity1.

Optical imaging module for astigmatic detection system.

In this paper, an optical imaging module design for an astigmatic detection system (ADS) is presented. The module is based on a commercial optical pickup unit (OPU) and it contains a coaxial illuminant for illuminating a specimen. Furthermore, the imaging module facilitates viewing the specimen and the detection laser spot of the ADS with a lateral resolution of approximately 1 μm without requiring the removal of an element of the OPU. Two polarizers and one infrared filter are used to eliminate stray laser light in the OPU and stray light produced by the illuminant. Imaging modules designed for digital versatile disks (DVDs) and Blu-ray DVDs were demonstrated. Furthermore, the module can be used for imaging a small cantilever with approximate dimensions of 2 μm (width) × 5 μm (length), and therefore, it has the potential to be used in high-speed atomic force microscopy.

An integrated one-chip-sensor system for microRNA quantitative analysis based on digital droplet polymerase chain reaction

A silicon microfluidic chip was developed for microRNA (miRNA) quantitative analysis. It performs sequentially reverse transcription and polymerase chain reaction in a digital droplet format. Individual processes take place on different cavities, and reagent and sample mixing is carried out on a chip, prior to entering each compartment. The droplets are generated on a T-junction channel before the polymerase chain reaction step. Also, a miniaturized fluorescence detector was developed, based on an optical pick-up head of digital versatile disc (DVD) and a micro-photomultiplier tube. The chip integrated in the detection system was tested using synthetic miRNA with known concentrations, ranging from 300 to 3,000 templates/µL. Results proved the functionality of the system.

High density holographic versatile disc (HVD) system using collinear technologies

Collinear Holography was proposed by OPTWARE Corporation, in which the information and reference beams were aligned co-axially and modulated by the same SLM. With this unique configuration the optical pickup can be designed as small as the DVD's, and can be placed on one side of the recording disc. A 2-dimensional digital page data format was used and the shift-multiplexing method was employed to increased recording density of HVD. As the servo technology is being introduced to control the objective lens to be maintained precisely to the disc in the recording and the reconstructing process, a vibration isolator is no longer necessary. In HVD, the pre-formatted meta-data reflective layer was used for the focus/tracking servo and reading address information, and the dichroic mirror layer was used for detecting holographic recording information without interfering with the preformatted information. Experimental and theoretical studies suggest that the holographic material is very effective to increased recording density of the system. HVD will be compatible with existing disc storage systems, like CD and DVD, and enable us to expand its applications into other optical information storage systems.

Development of a Compact Atomic Force Microscope Based on an Optical Pickup Head

Abstract: To develop a compact and cost-effective atomic force microscope (AFM), this paper proposes to utilize components of an optical pickup head of a CD/DVD player. One of the voice coil motors and the astigmatic detection system of the optical pickup head are employed to provide vertical actuation of an AFM cantilever and to measure its deflection. A flexure is installed on the optical pickup head to reduce the influence of ground vibrations and to change its actuator sensitivity for better AFM imaging. The feasibility of the proposed system is experimentally shown by recording a topography image of a standard calibration grating.

Evolutionary Learning of Classifiers for Disk Discrimination

A novel disk discrimination approach with two levels of classification is proposed. The optical pickup head is controlled to emit the digital versatile disk laser followed by the compact disk laser during the process of being pulled in from the neutral position toward the optical disk. Four features are measured and analyzed based on the reflected signals from the optical disk. Two levels of classifications are designed for the disk discrimination using these four features. A supervised learning approach based on the evolutionary ellipsoid classification algorithm is utilized to learn the classifiers and optimize the classifier parameterizations. Six different disk types have been successfully discriminated using the proposed approach.

A 3D nano-resolution scanning probe for measurement of small structures with high aspect ratio

A tactile 3D scanning probe based on differential detection of astigmatic focus error is developed using commercial DVD optical pick-ups as sensing elements, and proposed for measurement of small structures with aspect ratio up to 30:1. The conflict between resolution and lateral size of the probe is resolved by a design of parallel kinematic flexible suspension with vertical and orthogonal layout of sensing elements, and common mode interference is significantly suppressed by differential detection of astigmatic focus error signals. Experimental results show that the displacement resolution of the probe is up to 1nm with a ϕ3mm probing ball and a 150mm long stylus. It is therefore concluded that the probe proposed is a solution for measurement of structures with high aspect ratio with high precision and low cost.

Restoration of the near-diffraction-limited response size at heterodyne detection of microholograms, distorted by spherical aberration.

Spherical aberrations (SAs) are an important factor in limiting the number of recording layers in a multilayer microholographic data storage scheme. This paper discusses the effect of the restoration of the response size, which makes it possible to decrease considerably the requirement of accuracy for the SA correction of the optical pickup system. The restoration occurs at the heterodyne detection of microholograms distorted by aberrations. The effect of restoring is demonstrated experimentally. A study of the dependence of the microholograms' lateral and longitudinal sizes on the medium depth in which they were formed was carried out. To measure the longitudinal size, a special material containing submicron microspheres was used. The size of the microhologram distorted by aberrations was then compared with the response size obtained at detection. In the last step, a conclusion about the restoration of the response size is made. The multilayer microholograms recording was carried out in iron-doped lithium niobate at a depth range from 70 to 520μm. A mathematical model of the microholograms' recording-reading was developed. This model makes it possible to give a qualitative explanation of the processes leading to the restoration of the near-diffraction-limited response size.

Blu-ray based optomagnetic aptasensor for detection of small molecules.

This paper describes an aptamer-based optomagnetic biosensor for detection of a small molecule based on target binding-induced inhibition of magnetic nanoparticle (MNP) clustering. For the detection of a target small molecule, two mutually exclusive binding reactions (aptamer-target binding and aptamer-DNA linker hybridization) are designed. An aptamer specific to the target and a DNA linker complementary to a part of the aptamer sequence are immobilized onto separate MNPs. Hybridization of the DNA linker and the aptamer induces formation of MNP clusters. The target-to-aptamer binding on MNPs prior to the addition of linker-functionalized MNPs significantly hinders the hybridization reaction, thus reducing the degree of MNP clustering. The clustering state, which is thus related to the target concentration, is then quantitatively determined by an optomagnetic readout technique that provides the hydrodynamic size distribution of MNPs and their clusters. A commercial Blu-ray optical pickup unit is used for optical signal acquisition, which enables the establishment of a low-cost and miniaturized biosensing platform. Experimental results show that the degree of MNP clustering correlates well with the concentration of a target small molecule, adenosine triphosphate (ATP) in this work, in the range between 10µM and 10mM. This successful proof-of-concept indicates that our optomagnetic aptasensor can be further developed as a low-cost biosensing platform for detection of small molecule biomarkers in an out-of-lab setting.

Analysis of behavior of focusing error signals generated by astigmatic method when a focused spot moves beyond the radius of a land-groove-type optical disk

We theoretically calculate behaviors of focusing error signals generated by an astigmatic method in a land-groove-type optical disk. The focusing error signal from the land does not coincide with that from the groove. This behavior is enhanced when a focused spot of an optical pickup moves beyond the radius of the optical disk. A gain difference between the slope sensitivities of focusing error signals from the land and the groove is an important factor with respect to stable focusing servo control. In our calculation, the format of digital versatile disc-random access memory (DVD-RAM) is adopted as the land-groove-type optical disk model, and the dependences of the gain difference on various factors are investigated. The gain difference strongly depends on the optical intensity distribution of the laser beam in the optical pickup. The calculation method and results in this paper will be reflected in newly developed land-groove-type optical disks.

Note: Compact and light displacement sensor for a precision measurement system in large motion.

We developed a compact and light displacement sensor applicable to systems that require wide range motions of its sensing device. The proposed sensor utilized the optical pickup unit of the optical disk drive, which has been used applied to atomic force microscopy (AFM) because of its compactness and lightness as well as its high performance. We modified the structure of optical pickup unit and made the compact sensor driver attachable to a probe head of AFM to make large rotation. The feasibilities of the developed sensor for a general probe-moving measurement device and for probe-rotating AFM were verified. Moreover, a simple and precise measurement of alignment between centers of rotator and probe tip in probe-rotation AFM was experimentally demonstrated using the developed sensor.

Cell depth imaging by point laser scanning fluorescence microscopy with an optical disk pickup head

A compact, cost-effective, and position-addressable digital laser scanning microscopy (DLSM) instrument is made using a commercially available Blu-ray disc read-only memory (BD-ROM) pickup head. Fluorescent cell images captured by DLSM have resolutions of 0.38 µm. Because of the position-addressable function, multispectral fluorescence cell images are captured using the same sample slide with different excitation laser sources. Specially designed objective lenses with the same working distance as the image-capturing beam are used for the different excitation laser sources. By accurately controlling the tilting angles of the sample slide or by moving the collimator lens of the image-capturing beam, the fluorescence cell images along different depth positions of the sample are obtained. Thus, z-section images with micrometer-depth resolutions are achievable.

Extended depth-of-field in integral-imaging pickup process based on amplitude-modulated sensor arrays

We implement a depth-of-field (DOF) extending pickup experiment of integral imaging based on amplitude-modulated sensor arrays (SAs). By implementing the amplitude-modulating technique on the SA in the optical pickup process, we can modulate the light intensity distribution in the imaging space. Therefore, the central maximum of the Airy pattern becomes narrower and the DOF is enlarged. The experimental results obtained from the optical pickup process and the computational reconstruction process demonstrate the effectiveness of the DOF extending method. We present that the DOF extending pickup method is more suitable for enhancing the DOF of three-dimensional scenes with small depth ranges.

Guitar pickups and the plucked string

This demonstration will use optical, magnetic, and piezoelectric guitar pickups to measure time signals and frequency spectra for the displacement, velocity, and force (measured at the bridge) of a plucked and struck guitar string. For the plucked string, experimental observations of the displacement and velocity of a point on the string agree very well with theory. Frequency spectra also agree well with theoretical predictions and highlight the differences in timbre between the audio signals obtained with each pickup. The demonstration will briefly discuss theoretical time signals and frequency spectra for a point on a plucked string, show measured time signals and frequency spectra from the various pickups, and compare audible examples of the sounds from the pickups for a plucked string. For the struck string, a simple theory approximates the basic shape of the string displacement and velocity, but dispersion effects in the string and the reality of the hammer-string interaction are evident in the measured string response. If time permits, a demonstration of the sound and spectrum of a compound string will be included.

High density collinear holographic data storage system

Holographic data storage system (HDSS) has been a good candidate for a volumetric recording technology, due to their large storage capacities and high transfer rates, and have been researched for tens of years after the principle of holography was first proposed. However, these systems, called conventional 2-axis holography, still have essential issues for commercialization of products. Collinear HDSS, in which the information and reference beams are modulated co-axially by the same spatial light modulator (SLM), as a new read/write method for HDSS are very promising. With this unique configuration, the optical pickup can be designed as small as DVDs, and can be placed on one side of the recording media (disc). In the disc structure, the preformatted reflective layer is used for the focus/tracking servo and reading address information, and a dichroic mirror layer is used for detecting holographic recording information without interfering with the preformatted information. A 2-dimensional digital page data format is used and the shift-multiplexing method is employed to increase recording density. As servo technologies are being introduced to control the objective lens to be maintained precisely to the disc in the recording and reconstructing process, a vibration isolator is no longer necessary. Collinear holography can produce a small, practical HDSS more easily than conventional 2-axis holography. In this paper, we introduced the principle of the collinear holography and its media structure of disc. Some results of experimental and theoretical studies suggest that it is a very effective method. We also discussed some methods to increase the recording density and data transfer rates of collinear holography.

Progress of super-resolution near-field structure and its application in optical data storage

The era of big data has necessitated the use of ultra-high density optical storage devices. Super-resolution near-field structure (super-RENS), which has successfully surpassed the fundamental optical diffraction limit, is one of the promising next generation high-density optical storage technologies. This technology combines the traditional super-resolution optical disk with a near-field structure, and has the advantages of structural simplicity, strong practicability, and, more importantly, compatibility with the current optical storage pickup. The mask layer in super-RENS functions as the key to realizing super- resolution. Development of suitable materials and stack designs has greatly been improved in the last decade. This paper described several types of super-RENS, such as aperture-type, light scattering center-type, bubble-type, and other types (e.g., WOx and ZnO), particularly the newly proposed super-RENS technology and research achievements. The paper also reviews the applications of super-RENS in high-density optical data storage in recent years. After analyzing and comparing various types of super-RENS technology, the paper proposes the aperture- type based on the mechanism of nonlinear optics as the most suitable candidate for practical applications in the near future.

Quantification of rolling circle amplified DNA using magnetic nanobeads and a Blu-ray optical pick-up unit.

We present the first implementation of a Blu-ray optical pickup unit (OPU) for the high-performance low-cost readout of a homogeneous assay in a multichamber microfluidic disc with a chamber thickness of 600 μm. The assay relies on optical measurements of the dynamics of magnetic nanobeads in an oscillating magnetic field applied along the light propagation direction. The laser light provided by the OPU is transmitted through the sample chamber and reflected back onto the photo detector array of the OPU via a mirror. Spectra of the 2nd harmonic photo detector signal vs. the frequency of the applied magnetic field show a characteristic peak due to freely rotating magnetic nanobeads. Beads bound to ~1 μm coils of DNA formed off-chip by padlock probe recognition and rolling circle amplification show a different dynamics and the intensity of the characteristic peak decreases. We have determined the optimum magnetic bead concentration to 0.1mg/mL and have measured the response vs. concentration of DNA coils formed from Escherichia Coli. We have found a limit of detection of 10 pM and a dynamic range of about two orders of magnitude, which is comparable to the performance obtained using costly and bulky laboratory equipment. The presented device leverages on the advanced but low-cost technology of Blu-ray OPUs to provide a low-cost and high-performance magnetic bead-based readout of homogeneous bioassays. The device is highly flexible and we have demonstrated its use on microfluidic chambers in a disc with a thickness compatible with current optical media mass-production facilities.

Color image encryption using a high-quality elemental image array

In this paper, we present a color image encoding algorithm by combined use of the high-quality elemental image array (EIA) and the pseudo-random mask. To overcome low resolution drawbacks in widely used optical pickup system, in our scheme, the pseudo-inverse filter is introduced to improve this problem. In the cryptosystem, the proposed scheme provides high security because of the high key space of cellular automata. Meanwhile, the hologram-like attribute of the EIA can significantly improve the robustness of the encrypted image against some common image processing attacks. Experiments and analysis have both demonstrated the feasibility and efficiency of the image encryption algorithm.

A Compact and Low-Cost Optical Pickup Head-Based Optical Microscope

An optical pickup head (OPH) is a compact and low-cost but of high-precision optical system. In the past, it has been used for much scientific research besides optical disc storage, in particular, for the length-related measurements. In this paper, we propose a compact and low-cost OPH-based optical microscope (OM). A CMOS sensor disassembled from the web camera is fixed below the fold mirror of the OPH. The revised structure is simple and low cost but without permanently altering the original structure of the OPH. The user can choose operation modes of either the OPH or OM by a simple switching. We estimated that the optical magnification of the OM is 15.5X. The experimentally measured resolution of the OM is ~2 μm for the visible light, and it achieved diffraction limit for narrow-band light source. From the results of optical simulation, the main factor deteriorating the resolution is chromatic aberration. Astigmatic aberration is not important. Some plant cells investigation results using the microscope are also demonstrated in this paper.