US 12,271,005 B2
Scope optical system, imaging apparatus, and endoscope system
Naomichi Kikuchi, Kanagawa (JP); and Satoshi Nagae, Tokyo (JP)
Assigned to Sony Group Corporation, Tokyo (JP)
Filed by Sony Group Corporation, Tokyo (JP)
Filed on May 3, 2023, as Appl. No. 18/311,295.
Application 18/311,295 is a continuation of application No. 16/981,698, granted, now 11,675,204, previously published as PCT/JP2019/007059, filed on Feb. 25, 2019.
Claims priority of application No. 2018-061788 (JP), filed on Mar. 28, 2018.
Prior Publication US 2023/0350218 A1, Nov. 2, 2023
Int. Cl. A61B 1/00 (2006.01); A61B 1/04 (2006.01); G02B 27/14 (2006.01)
CPC G02B 27/141 (2013.01) [A61B 1/00163 (2013.01); A61B 1/043 (2013.01); A61B 1/00009 (2013.01)] 21 Claims
OG exemplary drawing
 
1. A scope optical system comprising:
an image-formation optical system configured to form an image in each of wavelength bands to in a predetermined imaging sensor, the wavelength bands including a fluorescence wavelength band belonging to a near-infrared light wavelength band and a visible light wavelength band; and
a color-separation-prism optical system having a dichroic film constructed to separate an optical path of light to be imaged by the image-formation optical system into an optical path of the visible light wavelength band and an optical path of the fluorescence wavelength band, wherein
the image-formation optical system is configured to form the respective images in a fluorescence imaging sensor and a visible light imaging sensor, the fluorescence imaging sensor and the visible light imaging sensor being disposed to cause an amount of misalignment between a fluorescence image formation position and a visible light image formation position caused by the image-formation optical system to correspond to a difference between an optical path length of fluorescence and an optical path length of visible light, the fluorescence and the visible light forming the respective images via the color-separation-prism optical system, and,
where a focal length of the image-formation optical system is represented by f [mm], and an air-equivalent optical path length from the image-formation optical system to an imaging sensor is represented by Fb [mm], the image-formation optical system has the focal length and the air-equivalent optical path length that satisfy a condition represented by the following expression (1),
Fb/f>0.72  expression (1),
the image-formation optical system includes, in order from object side to image side,
at least a diaphragm, a third lens group having a positive refractive power, and a second lens group having a positive refractive power,
the second lens group being a focus group configured to focus depending on an object distance,
the second lens group satisfies a relationship represented by the following expression (2), where a curvature radius at an object-side surface of a lens located on most object side in the third lens group is represented by R3 [mm],
0.85<R3/f  expression (2).