High performance microshutter device with space-division modulation

Abstract

This paper presents a microshutter device with space-division modulation for high brightness and improved grayscale level. High brightness is achieved with a large aperture that originates from out-of-plane movement with a large deflection, and space-division modulation improves the grayscale level by overcoming the operating speed limitation of digital modulation. The proposed microshutter device has multiple microshutters consisting of a single pixel, and the grayscale level is modulated by the number of actuated microshutters. We adopted a novel electrostatic actuation method in which the number of actuated microshutters is proportional to the applied analog voltage level. The actuation method was verified theoretically by means of an equivalent electrical circuit model. Furthermore, to test the proposed actuation method, we fabricated quarter-circle curl-shaped microshutters and demonstrated the proposed microshutter device with a control signal of 20 V to 33 V. The switching time is 20 μs from the open state to the closed state, and the lifetime is estimated to be 500 billion cycles.

Review of microshutters for switchable glass

“…This release step is delicate and can lead to fabrication issues such as improper curling up. 29 Some groups [28][29][30][31] have included special and extra patterning steps (such as corrugation) to promote the proper release or curling behavior.…”

“…KAIST developed cascaded microshutters for variable transmission in next-generation displays. 30,31 Their microshutters are composed of ITO/SiO 2 /photoresist (sacrificial)/Ti-Au and require four patterning steps, including one to make corrugations [ Fig. 4(c)].…”

“…As for the reliability, many researchers have proven experimentally that the microshutters (at least on small areas) are very reliable, cycling them millions of time. 24,30,32 Table 2 presents the various microshutters based on their actuation voltages, speeds, demonstrated sizes, visible transmissions, and applications. The required performances depend on the application; however, there are obvious general advantages in low operating voltage, high contrast, temperature stability (no CTE gradient in top electrode, highmelting-point materials), UV durability (inorganic), and low manufacturing cost (thin layers and simple patterning).…”

“…Microblinds were also compared with other switchable glass technologies in review papers 14,15 and market reports. [19][20][21] Several groups have worked on various versions of microshutters, namely NRC, 17 New Visual Media Group (NVMG), 22,23 University of Kassel, 24,25 Institut National d'Optique (INO), 26 University of Tokyo, 27 Samsung, 28 U.S. Air Force (USAF), 29 Korea Advanced Institute of Science and Technology (KAIST), 30,31 Microelectronic Center of North Carolina (MCNC), 32 Fiat, 33,34 and University of Stuttgart. 35 These groups used various versions of curling electrodes actuated by electrostatic forces for switchable glass applications (window, display, imaging, eyewear, etc.).…”

Correction of optical phase aberrations using binary-amplitude modulation

“…Low-cost, transmissive, liquid-crystal phase modulation, on the other hand, is limited to use at visible and near-infrared wavelengths. Binary phase modulation using ferroelectric liquid crystals has been considered as an alternative to continuous modulation [4]; however, binary-amplitude modulation offers lower complexity and cost, and it can be accomplished efficiently from ultraviolet to far-infrared wavelengths with a wide variety of fixed or agile spatial-light amplitude-modulation techniques [5][6][7][8]. We show that a binary-amplitude mask located at the aperture stop can be optimized to mitigate phase aberrations and allow sufficient information to be recorded for the recovery of a sharp image using standard digital-image restoration.…”