Sasaki, Shizuki

写真a

Affiliation

Research Centers and Institutes, Keio University Global Research Institute (Mita)

Position

Project Assistant Professor (Non-tenured)/Project Research Associate (Non-tenured)/Project Instructor (Non-tenured)
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Papers 【 Display / hide 】

  • Randomizing polarization of displays for fundamental improvement of color mura caused by birefringence

    Sasaki S., Koike Y.

    Optics letters 49 ( 22 ) 6501 - 6504 2024.11

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    Most existing displays utilize polarization technologies to produce images and improve image quality. However, polarized light from displays causes color mura because of the birefringence of the polymer films used. Thus, eliminating color degradation remains a challenge despite the incorporation of complex polarization technologies such as retardation films. Our proposed random depolarization film (RDF) addresses this issue by randomizing the polarization of light from displays. Chromaticity measurements demonstrate that the RDF effectively compensates for color mura due to low-cost polymer films. Notably, the RDF compensation mechanism is independent of the RDF position and light source spectrum. Therefore, the RDF could be an innovative solution for color degradation in existing displays.

  • Random depolarization film design based on modulation transfer function measurements of displays with different pixel pitches

    Sasaki S., Masaoka K., Koike Y.

    Applied Optics 63 ( 11 ) 2900 - 2905 2024.04

    ISSN  1559128X

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    Polarized light emitted frommost displays causes blackout and color change problems when viewed through polarized sunglasses. These problems are addressed by random depolarization films (RDFs) doped with birefringent particles. These dopant particles, however, scatter light and degrade the sharpness of the displayed images.To maintain the image sharpness, we designed an RDF based on modulation transfer function measurements of displays with different pixel pitches. RDFs doped with larger particles achieved higher modulations; however, particles larger than a specific size caused undesirable sparkles on the displayed image. A display with a larger pixel pitch achieved higher modulations, suggesting that the RDF is particularly suitable for large-screen displays.

  • Proposal of Novel Random Depolarization Film for Real-Color Displays with Sharp Images

    Sasaki S., Koike Y.

    Digest of Technical Papers - SID International Symposium 55 ( 1 ) 425 - 428 2024

    ISSN  0097966X

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    The random depolarization film (RDF), a polymer film doped with birefringent particles, converts linearly polarized light to randomly polarized light. This paper shows that a novel RDF with controlled birefringence resolves polarization problems of the display such as blackout, color change, and color mura problems. Furthermore, the novel RDF achieved a higher contrast ratio and a sharper image than a conventional RDF doped with calcite particles.

  • Design of Random Depolarization Films Based on Modulation Transfer Function Measurements

    Sasaki S., Masaoka K., Koike Y.

    Digest of Technical Papers - SID International Symposium 54 ( 1 ) 547 - 550 2023

    ISSN  0097966X

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    The random depolarization film (RDF), a polymer film doped with birefringent microparticles, solves polarization problems of displays. To design the RDF that realizes sharper images, the optimal dopant particle size and suitable display’s pixel size were investigated based on modulation transfer function (MTF) measurements. The MTFs indicated that the dopant particle size of the RDF and the pixel size of the display should be larger to prevent the sharpness degradation.

  • Random depolarization film design for real-color displays

    Sasaki S., Udono M., Koike Y.

    Applied Optics 61 ( 3 ) 669 - 675 2022.01

    ISSN  1559128X

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    Liquid crystal displays and organic light-emitting diode displays emit polarized light through polarizers and quarter-wave plates, which cause blackout and color change problems when the displays are viewed through polarizers, such as polarized sunglasses. Random depolarization films (RDFs) are polymer films doped with calcite particles, which randomize the polarization of light emitted from displays to resolve polarization problems. To realize displays without any color change, we investigate the retardation values and fabrication conditions required for RDFs. Analysis of the transmittance spectra and interference colors of different RDFs suggested that retardation values of approximately 600–1200 nm are sufficient to realize real-color displays. In addition, the color change measurements of displays with the RDFs revealed that an optimal dopant particle size exists and that the RDFs doped with 3.6 and 7.3 µm calcite particles achieved chromaticity changes of less than 0.02 for all 24 colors in the Macbeth chart.

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