US 12,085,739 B2
Diffractive optical element and illumination optical system
Ryota Murakami, Fukushima (JP); Kensuke Ono, Tokyo (JP); and Motoshi Nakayama, Fukushima (JP)
Assigned to AGC Inc., Tokyo (JP)
Filed by AGC Inc., Tokyo (JP)
Filed on Apr. 12, 2021, as Appl. No. 17/227,520.
Application 17/227,520 is a continuation of application No. PCT/JP2019/039555, filed on Oct. 7, 2019.
Claims priority of application No. 2018-194341 (JP), filed on Oct. 15, 2018.
Prior Publication US 2021/0255374 A1, Aug. 19, 2021
Int. Cl. G02B 5/18 (2006.01); G01S 7/481 (2006.01); G01S 17/931 (2020.01); G02B 27/44 (2006.01)
CPC G02B 5/1814 (2013.01) [G01S 7/481 (2013.01); G01S 17/931 (2020.01); G02B 27/44 (2013.01)] 10 Claims
OG exemplary drawing
 
1. A diffractive optical element, comprising:
a diffraction unit configured to split light by using a diffraction effect; and
a lens unit configured to convert incident light into parallel light, the lens unit being disposed on a light incident side of the diffraction unit,
wherein the lens unit includes:
a substrate; and
a protrusion and recess portion disposed on a side opposite to a light incident side of the substrate,
wherein the protrusion and recess portion includes:
a kinoform as a periodic structure of a relief-protrusion portion that is disposed in a central part and is a protrusion part of a relief shape having a curved cross-section, or a grating that is disposed in a central part, has three or more steps assuming the substrate as a first step and simulates the relief-protrusion portion; and
a grating having two steps disposed in a peripheral part, and
wherein the peripheral part is defined as a region in which a pitch of the protrusion and recess portion is not more than a predetermined pitch at which a 0th-order efficiency in a wavelength band of the incident light by a 2-level grating becomes lower than a 0th-order efficiency in the wavelength band of the incident light by the kinoform as the relief-protrusion portion or the grating having three or more steps.