Long working range light field microscope with fast scanning multifocal liquid crystal microlens array

Abstract

Abstract:The light field microscope has the potential of recording the 3D information of biological specimens in real time with a conventional light source. To further extend the depth of field to broaden its applications, in this paper, we proposed a multifocal high-resistance liquid crystal microlens array instead of the fixed microlens array. The developed multifocal liquid crystal microlens array can provide high quality point spread function in multiple focal lengths. By adjusting the focal length of the liquid crystal microlens array sequentially, the total working range of the light field microscope can be much extended. Furthermore, in our proposed system, the intermediate image was placed in the virtual image space of the microlens array, where the condition of the lenslets numerical aperture was considerably smaller. Consequently, a thin-cell-gap liquid crystal microlens array with fast response time can be implemented for time-multiplexed scanning.

33.3: High Performance Liquid Crystal Micro‐Lens Array Applied to Light Field Display

“…In other words, a flat area will be produced at the center of each micro-lens if the driving voltage of the central part is from Vth to 0 smoothly as shown in Figure 2 Consequently, the LC molecules of the central area is easy to be affected by the interaction force of other LC molecules tilted by the driving voltage. On the other hand, the pre-tilt angle induces the asymmetric distribution of the tilting force for LC molecules although the driving electric field is symmetric [4]. As Figure 2-7 shown, the tilting torque of LC molecules at the left side is a little bit large than that at the right side due to the extra horizontal component of the electric field.…”

“…Hi-R LCMLA is realized by sputtering a high-resistance layer on the patterned electrode [3] [4]. As Figure 2-2 shows, it consists of two planar electrode-glass substrates which are separated by a homogeneous LC layer.…”

Image formation modeling and analysis of near‐eye light field displays

“…From a signal processing point of view, the minimum sampling interval in the system is the pixel size of the microdisplay, and the interpolation function used for the signal reconstruction on the retina is a combination of a pixel's retinal image and optical point spread function (PSF). Different from regular displays whose interpolation functions are usually within the resolution limit of human eyes, the large ratio of the pixel size to the short focal length of the MLA makes a pixel's retinal image usually larger than the resolution limit; that is, the pixel size plays an important role in NE‐LFDs. To quickly estimate the resolution of an NE‐LFD, currently, several widely used models simplify each factor above into a single value . Usually, in such models, the diffraction‐related resolution β 1 is determined by the Fraunhofer approximation, as a function of the lens aperture p and the wavelength λ : β 1 = p /(1.22 λ ).…”

“…For example, the CDP of 1 D (yellow dots) can achieve a DOF of approximately 1 m to infinity, whereas suffering from low resolutions from 0.25 to 1 m. If the CDP of 4 D is used (blue dots), high resolutions can be achieved for very near images, but far images are unusable despite that the resolution decrease plateaus. If a full‐range DOF is needed, multiplexed CDPs are useful, which may be achieved through an electrically controlled LC MLA …”

“…To quickly estimate the resolution of an NE-LFD, currently, several widely used models simplify each factor above into a single value. 20,26,[32][33][34][35] Usually, in such models, the diffraction-related resolution β 1 is determined by the Fraunhofer approximation, as a function of the lens aperture p and the wavelength λ: β 1 = p/(1.22λ).…”