Characterization of the DuPont photopolymer for three-dimensional holographic storage

DuPont's HRF-150 photopolymer film is investigated for use in three-dimensional holographic memories. Measurements of sensitivity, hologram persistence, the lateral spread of the photoinitiated reaction, and the variation of diffraction efficiency with modulation depth, spatial frequency and tilt angle, and intensity are reported. We observed that the diffraction efficiency of the HRF-150 photopolymer for a given exposure decreases with increases in intensity and grating tilt angle. The holograms were nondestructively reconstructed for long periods of time at room temperature. The photoinitiated reaction spread less than 100 µm over a period of 16 h

Cross talk for angle- and wavelength-multiiplexed image plane holograms

The cross talk for image plane holograms is calculated and compared with previously derived results for Fourier plane holograms. Image plane storage is found to have significantly smaller cross talk

Cross talk in phase-coded holographic memories

The cross talk between holograms multiplexed with Walsh-Hadamard phase codes is analyzed. Each hologram is stored with a reference beam that consists of N phase-coded plane waves. The signal-to-noise ratio (SNR) is calculated for a recording schedule for which the center of each stored image coincides with the nulls of the selectivity function for the adjacent plane-wave components of the reference beam. The SNR characteristics for phase coding with Walsh-Hadamard phase codes are then compared with the SNR for angle and wavelength multiplexing

Recording of multiple holograms in photopolymer films

Multiple images were recorded in DuPont HRF-150 photopolymer as transmission holograms by using angle multiplexing. Agreement with Kogelnik's two-wave diffraction theory for phase gratings, the time considerations and its effect on dynamic range, the necessity of a pre-illumination pulse, and good image quality at readout are reported

Method for holographic storage using peristrophic multiplexing

A method of multiplexing holograms by rotating the material or, equivalently, the recording beams is described. Peristropic (Greek for rotation) multiplexing can be combined with other multiplexing methods to increase the storage density of holographic storage systems. Peristrophic multiplexing is experimentally demonstrated with Du Pont's HRF-150 photopolymer film. We multiplexed a total of 295 holograms in a 38-μm-thick photopolymer film by combining peristrophic multiplexing with angle multiplexing

Cross talk in wavelength multiplexed holographic memories

The cross talk between wavelength-multiplexed holograms is analyzed. The signal-to-noise ratio (SNR) is calculated for a recording schedule that places the center of each image at the null (in wavelength space) of the adjacent hologram. An asymptotic closed-form expression for the minimum SNR is derived in a general reflection geometry. The reflection geometry with counterpropagating signal and reference beams is shown to have the best SNR

Overregulation of Health Care: Musings on Disruptive Innovation Theory

Disruptive innovation theory provides one lens through which to describe how regulations may stifle innovation and increase costs. Basing their discussion on this theory, Curtis and Schulman consider some of the effects that regulatory controls may have on innovation in the health sector

Fertility decline, baby boom and economic growth

We present new data documenting the secular decline in fertility in the states of the United States, the dramatic convergence in fertility, child schooling, parental schooling, survival probabilities. In addition we document the disparate nature of the Baby Boom in the United States. There were two different regimes, a large Baby Boom and a Small Baby Boom. The large Baby Boom regions also had the smallest increase in child schooling, whereas the small Baby Boom regions had the largest increase in child schooling. We present suggestive evidence that falling mortality risk is strongly positively correlated with falling fertility, rising education levels of parents is strongly negatively related to fetility, and that population density is negatively related to fertility. Finally we show the robust negative correlation of mortality risk on child schooling attainment, and positve correlation of population density and child schooling attainment.mortality; density; fertility decline; baby boom; economic growth

Software Porting of a 3D Reconstruction Algorithm to Razorcam Embedded System on Chip

A method is presented to calculate depth information for a UAV navigation system from Keypoints in two consecutive image frames using a monocular camera sensor as input and the OpenCV library. This method was first implemented in software and run on a general-purpose Intel CPU, then ported to the RazorCam Embedded Smart-Camera System and run on an ARM CPU onboard the Xilinx Zynq-7000. The results of performance and accuracy testing of the software implementation are then shown and analyzed, demonstrating a successful port of the software to the RazorCam embedded system on chip that could potentially be used onboard a UAV with tight constraints of size, weight, and power. The potential impacts will be seen through the continuation of this research in the Smart ES lab at University of Arkansas