US 12,189,163 B2
Light modulation element and information recording medium
Tsuyoshi Yamauchi, Tokyo-to (JP); Mitsuru Kitamura, Tokyo-to (JP); and Tomoe Sato, Tokyo-to (JP)
Assigned to DAI NIPPON PRINTING CO., LTD., Tokyo (JP)
Appl. No. 16/645,527
Filed by DAI NIPPON PRINTING CO., LTD., Tokyo-to (JP)
PCT Filed Sep. 7, 2018, PCT No. PCT/JP2018/033211
§ 371(c)(1), (2) Date Mar. 9, 2020,
PCT Pub. No. WO2019/049990, PCT Pub. Date Mar. 14, 2019.
Claims priority of application No. 2017-173263 (JP), filed on Sep. 8, 2017; application No. 2017-173286 (JP), filed on Sep. 8, 2017; and application No. 2017-173292 (JP), filed on Sep. 8, 2017.
Prior Publication US 2021/0405274 A1, Dec. 30, 2021
Int. Cl. G02B 5/18 (2006.01); B42D 25/328 (2014.01); G02B 5/32 (2006.01); G03H 1/02 (2006.01)
CPC G02B 5/32 (2013.01) [B42D 25/328 (2014.10); G03H 1/0272 (2013.01)] 7 Claims
OG exemplary drawing
 
1. An information recording medium comprising:
a light modulation element comprising:
a factor element that modulates a phase of incident reproduction light so as to reproduce a light image, the factor element having an uneven surface with a different height of three or more steps,
the factor element having a first-order maximum diffraction efficiency in a wavelength band from 380 nm to 780 nm of first-order diffracted light with a full width at half maximum of 200 nm or less, and the factor element having a negative first-order maximum diffraction efficiency in a wavelength band from 380 nm to 780 nm of negative first-order diffracted light with a full width at half maximum of 200 nm or less,
the factor element being configured to:
reproduce a first-order diffracted light image with the first-order diffracted light; and
reproduce a negative first-order diffracted light image with the negative first-order diffracted light,
wherein a wavelength showing the first-order maximum diffraction efficiency is different from a wavelength showing the negative first-order maximum diffraction efficiency,
wherein the first-order diffracted light image and the negative first-order diffracted light image represents information based on at least one of a letter, a symbol, and a picture,
the first-order diffracted light image and the negative first-order diffracted light image are point-symmetric about the incident reproduction light to each other, and
the factor element is a Fourier transform hologram, and
wherein a difference between the wavelength showing the first-order maximum diffraction efficiency and the wavelength showing the negative first-order maximum diffraction efficiency is 100 nm or less.