No abstract

In most cases, the distribution of an object can be calculated by measuring its Fourier transform distribution. When a general laser wave plane is used, the measurement of Fourier transform distribution has a large error because of the digitizing of Fourier amplitude. In this study, we suggest a method to generate a laser light distribution with pseudo random phase that can reduce the error of Fourier amplitude.

Science of dealing with the prevention and treatment of disease is important for the maintenance of health in human social life. Laser technology plays an important part in various fields of medical science. In general, a spot laser light is used in laser therapy because of the limitation of laser output. Therefore, the operator has to move the spot position by hand when the treatment area is larger then the laser light spot. We propose a method to convert a laser light to match the target treatment surface using time-divided computer-generated hologram (CGH). In order to get a high laser light efficiency, we consider the phase-only type CGH. We use discrete reconstruction CGH to overcome the speckle problem in the generation CGH. A spatial continuous laser light distribution can be obtained by superimposing the discrete reconstruction from several time-divided CGHs.

As an algorithm that generates a kinoform which is a kind of phase-type computer-generated hologram, there is an iterative dummy area method. However, this algorithm produces the error in dummy area, because it reduces the error in the original image space using the degree of freedom in the dummy area. It is undesirable for an error to occur in the dummy area in use efficiency of the light. In this study, we aim to reduce the error in the dummy area. In the computer generated hologram, the reconstructed image is modulated by a sinc function in both the horizontal direction, vertical direction. Therefore, the peripheral part of reconstructed image darkens in comparison with center. Considering the optical reconstruction, we can ignore the error that exists in the peripheral part of reconstructed image. From this, we use only a peripheral part at the start as a dummy area and widen a range to gradually use as a dummy area. We call the area that newly added flexible dummy area. By this method, we can collect errors in the peripheral part.

As an algorithm that generates a kinoform is a phase-type computer-generated hologram,