US 11,874,448 B2
Lens system and image observation apparatus
Manabu Ishioka, Tokyo (JP); Yasutoshi Katsuda, Kanagawa (JP); and Shotaro Tada, Tokyo (JP)
Assigned to Sony Interactive Entertainment Inc., Tokyo (JP)
Appl. No. 17/269,435
Filed by Sony Interactive Entertainment Inc., Tokyo (JP)
PCT Filed Aug. 28, 2019, PCT No. PCT/JP2019/033760
§ 371(c)(1), (2) Date Feb. 18, 2021,
PCT Pub. No. WO2020/045518, PCT Pub. Date Mar. 5, 2020.
Claims priority of application No. 2018-159721 (JP), filed on Aug. 28, 2018; and application No. 2018-196914 (JP), filed on Oct. 18, 2018.
Prior Publication US 2021/0333523 A1, Oct. 28, 2021
Int. Cl. G02B 13/18 (2006.01); G02B 3/04 (2006.01); G02B 3/08 (2006.01); G02B 5/04 (2006.01); G02B 25/00 (2006.01); G02B 27/01 (2006.01); G02B 27/02 (2006.01)
CPC G02B 13/18 (2013.01) [G02B 3/04 (2013.01); G02B 3/08 (2013.01); G02B 5/04 (2013.01); G02B 25/00 (2013.01); G02B 27/0172 (2013.01); G02B 27/02 (2013.01)] 8 Claims
OG exemplary drawing
 
1. A lens system, comprising:
a Fresnel lens having a lens surface including a plurality of grooves that are concentrically formed, wherein:
both a pitch that is a distance between two adjacent grooves and a depth of each of the plurality of grooves vary with a distance from an optical axis that passes through a center of the lens system,
a distance from a center of the Fresnel lens and the pitch are defined as X (mm) and P (mm), respectively,
when 0 mm≤X≤10 mm, X and P satisfy following conditions:
P≤(0.00021(X−10) 4+0.6)×1.5
P≥(0.00021(X−10) 4+0.6)×0.5, and
when 10 mm≤X, P satisfies a following condition:
0.3≤P≤0.9.