Objective optical system for endoscopes
First Claim
1. An objective optical system for endoscopes comprising, in order from the object side, a front lens unit having a negative refractive power, an aperture stop and a rear lens unit having a positive refractive power, and satisfying the following conditions (1) through (7):
- ##EQU27## wherein the reference symbol ω
represents a half field angle of the objective optical system, the reference symbols S1 (θ
1) and S2 (θ
1) represent offense against the sine condition of the front lens unit and rear lens unit, respectively, normalized by f sin θ
, and determined by tracing a principal ray having an angle of θ
, relative to the optical axis on the object side of the objective optical system from an image toward an object, the reference symbol β
E represents a paraxial pupil magnification of the objective optical system as a whole, the reference symbol f designates focal length of the objective optical system as a whole, the reference symbol f1 denotes focal length of the front lens unit, the reference symbol f2 represents focal lengths of the rear lens unit, the reference symbol ##EQU28## and k0.8ω
is selected so as to satisfy the following formula;
##EQU29##
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Abstract
An objective optical system for endoscopes consisting, in the order from the object side, of a front lens unit having negative refractive power, an aperture stop and a rear lens unit having positive refractive power and comprising at least one aspherical surface in each of the lens units. This objective optical system for endoscopes has distortion of a small absolute value, a distortion curve of natural shape, favorably corrected aberrations, and is composed of lens elements easily manufacturable.
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Citations
10 Claims
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1. An objective optical system for endoscopes comprising, in order from the object side, a front lens unit having a negative refractive power, an aperture stop and a rear lens unit having a positive refractive power, and satisfying the following conditions (1) through (7):
- ##EQU27## wherein the reference symbol ω
represents a half field angle of the objective optical system, the reference symbols S1 (θ
1) and S2 (θ
1) represent offense against the sine condition of the front lens unit and rear lens unit, respectively, normalized by f sin θ
, and determined by tracing a principal ray having an angle of θ
, relative to the optical axis on the object side of the objective optical system from an image toward an object, the reference symbol β
E represents a paraxial pupil magnification of the objective optical system as a whole, the reference symbol f designates focal length of the objective optical system as a whole, the reference symbol f1 denotes focal length of the front lens unit, the reference symbol f2 represents focal lengths of the rear lens unit, the reference symbol ##EQU28## and k0.8ω
is selected so as to satisfy the following formula;
##EQU29##
- ##EQU27## wherein the reference symbol ω
-
2. An objective optical system for endoscopes comprising, in the order from the object side, a front lens unit having a negative refractive power, an aperture stop and a rear lens unit having a positive refractive power, using at least one aspherical surface in each of said front lens unit and said rear lines unit, satisfying a relation of H(θ
-
1)=k tan (θ
1 /k) when image height is represented by H (θ
1), an angle of incidence of the principal ray on the entrance pupil is designated by θ
1 and a constant having a value within the range defined below, is denoted by k, and satisfying the following conditions (5) through (7);
space="preserve" listing-type="equation">1.15≦
k≦
3
space="preserve" listing-type="equation">|β
.sub.E |>
2.5 (5)
space="preserve" listing-type="equation">|f.sub.1 /f|<
3.5 (6)
space="preserve" listing-type="equation">|f.sub.2 /f|<
2.5 (7)wherein the reference symbol β
E represents a paraxial pupil magnification of the objective optical system as a whole, the reference symbol f designates focal length of the objective optical system as a whole, the reference symbol f1 denotes focal length of the front lens unit and the reference symbol f2 represents focal length of the rear lens unit. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9)
-
1)=k tan (θ
-
10. An objective optical system comprising, in order from the object side, a front lens unit having a negative refractive power, an aperture stop and a rear lens unit having a positive refractive power, each of said front lens unit and said rear lens unit including a cemented doublet, and being designed so as to satisfy the following conditions (1), (13) and (14):
- ##EQU31## wherein the reference symbol ω
represents a half field angle of the objective optical system, the reference symbol S(θ
1) designates offence of sine condition of said objective optical system as a whole normalized by f sin θ and
determined by tracing a principal ray having an angle of θ
relative to an optical axis on the object side of the objective optical system from an image toward the object, the reference symbol represents focal length of said objective optical system as a whole, the reference symbols ν
p1 and ν
n1 represent the Abbe'"'"'s numbers of a positive lens element and a negative lens element, respectively, disposed in said front lens unit, and the reference symbols ν
p2 and ν
n2 designate the Abbe'"'"'s numbers of a positive lens element and a negative lens element, respectively, disposed in said rear lens unit.
- ##EQU31## wherein the reference symbol ω
Specification