Digital Driving Method for Low Frame Frequency and 256 Gray Scales in Liquid Crystal on Silicon Panels

Kang, Jahyo; Kwon, Oh‐Kyong

doi:10.1109/jdt.2012.2220335

Cited by 17 publications

(7 citation statements)

References 14 publications

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“…[71][72][73] These pulses are binary in nature and are applied to the LC. In this case, different average voltage levels are implemented using pulse width modulation on the basis that LCs respond to the RMS value of the applied voltage waveform.…”

Section: Sram-based Pixel Circuitrymentioning

confidence: 99%

Fundamentals of phase-only liquid crystal on silicon (LCOS) devices

2014

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This paper describes the fundamentals of phase-only liquid crystal on silicon (LCOS) technology, which have not been previously discussed in detail. This technology is widely utilized in high efficiency applications for real-time holography and diffractive optics. The paper begins with a brief introduction on the developmental trajectory of phase-only LCOS technology, followed by the correct selection of liquid crystal (LC) materials and corresponding electro-optic effects in such devices. Attention is focused on the essential requirements of the physical aspects of the LC layer as well as the indispensable parameters for the response time of the device. Furthermore, the basic functionalities embedded in the complementary metal oxide semiconductor (CMOS) silicon backplane for phase-only LCOS devices are illustrated, including two typical addressing schemes. Finally, the application of phase-only LCOS devices in real-time holography will be introduced in association with the use of cutting-edge computer-generated holograms. The architecture of LCOS devices is similar to conventional LC devices except that a silicon backplane constitutes one of the substrates (Figure 1). The silicon CMOS backplane consists of the electronic circuitry that is buried underneath pixel arrays to provide a high 'fill factor'. The pixels are aluminum mirrors deposited on the surface of the silicon backplane. The incident light is transmitted through the LC layer with almost zero absorption. The integration of high-performance driving circuitry allows the applied voltage to be changed on each pixel, thereby controlling the phase retardation of the incident wavefront across the device. Currently, there are two types of light modulation using LCOS devices, amplitude modulation and phase modulation. In the former case, the amplitude of the light signal is modulated 6,7 by varying the linear polarzation direction of the incident light passing through a linear polarizer, the same principle used in a standard LC television. In the latter case, the phase delay is accomplished by electrically adjusting the optical refractive index along the light path, which is possible because of the non-zero birefringence of the LC materials in use but should be carefully characterized. [8][9][10][11][12][13] In a phase-only LCOS SLM modulator, no light absorption by polarizers or other light-absorbing components will occur, such that the maximum light efficiency can be expected.Currently, most of the conventional LC devices are not able to efficiently modulate the phase of an incident wavefront. For instance, the LC device structure using thin film transistors is not suitable for phase modulation because an appropriate electro-optic effect has not been used (see the section on 'Twisted nematic (TN) configuration' and the section on 'VAN configuration' for details). Moreover, the pixels of this type of device are too large to provide acceptably large diffraction angles. In addition, the pixel circuitry and connection tracks are in the light path such that the ...

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Section: Sram-based Pixel Circuitrymentioning

confidence: 99%

Fundamentals of phase-only liquid crystal on silicon (LCOS) devices

2014

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“…Many proposed digital method to generate gray level by timemultiplex FLC pixels as high speed shutters [1] [2], but this approach poses heavy burden in driver circuit and the large loading capacitance inhering from thin cell gap also demands FLC pixel to be charged with high current, these limited the choices of source driver applicable and made it suitable only for LCOS display with driving circuit integrated to silicon panel. Our objective is to overcome this problem by designing a TFT FLC pixel that is capable to generate gray level while preserving the capability for high speed display application such as field sequential display.…”

Section: Objective and Backgroundmentioning

confidence: 99%

P‐43: A Novel TFT Pixel Design for Active Matrix FLC with Grayscale Generation

Srivastava

Zhou

et al. 2014

Symp Digest of Tech Papers

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Most active-matrix FLC (AMFLC) devices were mainly realized in the form of LCOS display rather than in the TFT platform. This is because FLC devices normally require higher power and current to drive due to the larger pixel capacitance inhering from the small cell gap. Difficulty in generating grayscale also poses great challenge in commercializing AMFLC. We proposed a new TFT pixel design incorporating ESH FLC mode and BGTFT that successfully demonstrated AMFLC display with grayscale while preserving FLC's fast switching property.

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“…The drawbacks of digital modulation such as Dynamic False Contouring (DFC) [3] and stability in phase modulator are mainly from the digitized LC reaction by the digital voltage pulse. The DFC is easier to be solved by replacing long pulse with several short pulse since human vision is not critical[3] [4]. Compare to DFC, phase stability is much more critical since the modulated wavefront is not an "average" result as gray scale.…”

Section: Introductionmentioning

confidence: 99%