Conventional Charge-coupled Device Camera Research Articles

Coincidence detection of spatially correlated photon pairs with a monolithic time-resolving detector array.

We demonstrate coincidence measurements of spatially entangled photons by means of a multi-pixel based detection array. The sensor, originally developed for positron emission tomography applications, is a fully digital 8×16 silicon photomultiplier array allowing not only photon counting but also per-pixel time stamping of the arrived photons with an effective resolution of 265 ps. Together with a frame rate of 500 kfps, this property exceeds the capabilities of conventional charge-coupled device cameras which have become of growing interest for the detection of transversely correlated photon pairs. The sensor is used to measure a second-order correlation function for various non-collinear configurations of entangled photons generated by spontaneous parametric down-conversion. The experimental results are compared to theory.

Performance of a direct detection camera for off-axis electron holography

The performance of a direct detection camera (DDC) is evaluated in the context of off-axis electron holographic experiments in a transmission electron microscope. Its performance is also compared directly with that of a conventional charge-coupled device (CCD) camera. The DDC evaluated here can be operated either by the detection of individual electron events (counting mode) or by the effective integration of many such events during a given exposure time (linear mode). It is demonstrated that the improved modulation transfer functions and detective quantum efficiencies of both modes of the DDC give rise to significant benefits over the conventional CCD cameras, specifically, a significant improvement in the visibility of the holographic fringes and a reduction of the statistical error in the phase of the reconstructed electron wave function. The DDC's linear mode, which can handle higher dose rates, allows optimisation of the dose rate to achieve the best phase resolution for a wide variety of experimental conditions. For suitable conditions, the counting mode can potentially utilise a significantly lower dose to achieve a phase resolution that is comparable to that achieved using the linear mode. The use of multiple holograms and correlation techniques to increase the total dose in counting mode is also demonstrated.

A high-density ternary barcode detection system employing a stable fixed-period delay method

A fixed-period delay method is proposed to increase the detection range and detection stability of a ternary barcode detection system. The system combines an envelope differential detection technique containing nonlinear filtering and a fixed-period delay to detect the barcode over a longer range and at higher scanning speeds while being simple and capable of handling a large amount of information. The system was demonstrated with its miniaturized circuit, and it was established that the detection range of the system for a minimum bar width W = 0.25 mm was 1.8 times that of the conventional count-latch envelope differential technique because of the stable delay achieved by a shift register and the noise suppression by a nonlinear filter. In addition, the system operated at a maximum scanning speed of 8.3 times that of conventional charge-coupled device cameras under the practical detection range for W = 0.3 mm. This system is expected to facilitate the real-time identification of goods on production lines and in automated warehouses.

A rotatable electron spectrometer for multicoincidence experiments

We have developed a rotatable hemispherical spectrometer with good energy and angular resolution, which can be positioned with the lens axis arbitrarily within a solid angle of 1 pi. The collection angle of the emitted electrons with respect to the polarization axis of the light is set by means of a three-axes goniometer, operating under vacuum. An important requirement for this setup was the possibility to perform coincidences between the electron analyzed by the spectrometer and one or several other particles, such as ions, electrons, or photons. The lens system and the hemispheres have been designed to accommodate such experimental demands, regarding parameters such as the resolving power, the acceptance angle, or the width of the kinetic energy window which can be recorded for a given pass energy. We have chosen to detect the impact position of the electron at the focal plane of the hemispherical analyzer with a delay line detector and a time-to-digital converter as acquisition card rather than using a conventional charge-coupled device camera.

Development of surgical confocal scanning microscope for intra-operative imaging of brain tumors using near infrared fluorescence: Technicalnote

We developed a confocal laser scanning microscope for intra-operative imaging of brain tumors using near infrared fluorescence. The quality of near infrared images of Indocyanine Green (ICG) was compared with the surgical confocal scanning (SCS) microscope and a conventional charge-coupled device (CCD) camera; we compared images of a tube filled with ICG, which was located in the mouse brain. Compared to the CCD camera, the SCS microscope could obtain a more precise image of ICG fluorescence through the brain tissue. In addition, the SCS microscope could image ICG fluorescence clearly in a relatively light room because of elimination of stray light, while the CCD camera required high darkness to obtain ICC images. The present SCS microscope can give useful intra-operative imaging of brain tumors, particularly detection of residual tumor tissues that extend into normal brain tissues. [Neurol Res 2000; 22: 533-536]

Particle Image Velocimetry via Wavelet Analysis

Novel analytical and image processing methods derived as part of the development of a digital particle image velocimetry system, based on multiresolution analysis, are presented. The derivation of wavelet-based multiresolution methods for velocity e eld reconstruction is addressed, and the experimental setup used for validation of results is described. New techniques are proposed with improved spatial resolution and reliability over some existing methods. The techniques are based on wavelet-based representations of digital particle image data that are used to calculate spatially localized and frequency localized e ltered correlations of successive images. An essential feature of the method is the development of windowed cross-correlation expressions for wavelet-based expansions that are not orthogonal (or biorthogonal) over the cross-correlation window. The methodology makes use of recently introduced ree nable functions and generalized connection coefe cients derived in wavelet-based e nite element methods. A conventional charge-coupled device camera is used with a frame rate of 30 frames/s and pixel resolution of 512 £ 480 per frame. The images are acquired in pairs at 30 frames/s, with a user-dee ned time delay between image pairs, to capture the e owe eld structure evolution. The e ow illumination was achieved using a 5-W, argon-ion laser. Finally, hardware and algorithm performance is demonstrated via sample water-tunnel experiments.

A device structure and spatial spectrum for checker-pattern CCD color camera

In order to develop practical color cameras with useful resolution, a novel image processing and charge-coupled device (CCD) structure is proposed which results in shrinking chip size and easing photolithography. The resolution of CCD cameras is limited by the aliasing errors associated with spatially discrete sampling on a photosensing area. The photosensing array arranged in a two-dimensional face-centered rectangular lattice scheme, and the spatial offsetting technique among three CCD's avoid undesirable signal carriers accompanied by aliasing errors. A unique signal processing about vertical correlation of an image is put to use, in order to reduce spurious effects of aliasing. These image processing techniques are theoretically treated on a spectrum space. The photosensing array arranged in a face-centered rectangular lattice scheme is successfully implemented with a zigzag-transfer CCD with checker-pattern sensing sites, which relax some of the lithography requirements and improve image qualities. By means of the zigzag-transfer CCD structure and the image processing, the resolution of color camera has been expanded by a factor of 2.5, compared with that of the conventional CCD cameras employing the same number of pixels. According to the theory, the factor may be increased further up to three or four.

A Device Structure and Spatial Spectrum for Checker-Pattern CCD Color Camera

In order to develop practical color cameras with useful resolution, a novel image processing and charge-coupled device (CCD) structure is proposed which results in shrinking chip size and easing photolithography. The resolution of CCD cameras is limited by the aliasilrng errors associated with spatially discrete sampling on a photosensing area. The photosensing array arranged in a two-dimensional face-centered rectangular lattice scheme, and the spatial offsetting technique among three CCD's avoid undesirable signal carriers accompanied by aliasing errors. A unique signal processing about vertical correlation of an image is put to use, in order to reduce spurious effects of aliasing. These image processing techniques are theoretically treated on a spectrum space. The photosensing array arranged in a face-centered rectangular lattice scheme is successfully implemented with a zigzag-transfer CCD with checker-pattern sensing sites, which relax some of the lithography requirements and improve image qualities. By means of the zigzag-transfer CCD structure and the image processing, the resolution of color camera has been expanded by a factor of 2.5, compared with that of the conventional CCD cameras employing the same number of pixels. According to the theory, the factor may be increased further up to three or four.