Imaging optical system for compensating change of temperature
First Claim
1. An imaging optical system for compensating for a change of temperature comprising:
- a lens system, in which a focal point change due to a change of temperature is defined as follows, ##EQU12## where;
i;
lens position from an object sideN;
number of component lenses of the whole lens systemmi ;
lateral magnification from i-th lens to an image sidemi+1 ;
lateral magnification from i+1-th lens to the image sidedfni /dt;
fluctuation in focal length of i-th lens caused by change of refractive indexdfLi /dt;
fluctuation in focal length of i-th lens caused by thermal expansiona light receiving element for receiving an image formed by said lens system, anda correcting member adapted to change a relative distance between said light receiving element and said lens system by means of linear expansion due to change of temperature, in which a thermal expansion (dL/dt) of said correcting member is set within a range as set forth hereunder;
##EQU13##
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Abstract
An imaging optical system for compensating for changes of temperature according to the present invention corrects a focal point for an entire optical system due to temperature change by changing a relative distance between a lens and a light receiving element. To this end, a correcting member, which expands and contracts due to temperature change, is disposed between the lens and the light receiving element. Moreover, the coefficient of thermal expansion is set to such a value so as to be able to substantially correct for the focal point change. According to another aspect of the present invention, the optical system includes a lens system which has at least a positive lens and a negative lens in order to offset the effect of the temperature change.
43 Citations
28 Claims
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1. An imaging optical system for compensating for a change of temperature comprising:
-
a lens system, in which a focal point change due to a change of temperature is defined as follows, ##EQU12## where;
i;
lens position from an object sideN;
number of component lenses of the whole lens systemmi ;
lateral magnification from i-th lens to an image sidemi+1 ;
lateral magnification from i+1-th lens to the image sidedfni /dt;
fluctuation in focal length of i-th lens caused by change of refractive indexdfLi /dt;
fluctuation in focal length of i-th lens caused by thermal expansiona light receiving element for receiving an image formed by said lens system, and a correcting member adapted to change a relative distance between said light receiving element and said lens system by means of linear expansion due to change of temperature, in which a thermal expansion (dL/dt) of said correcting member is set within a range as set forth hereunder;
##EQU13## - View Dependent Claims (2, 3, 4)
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5. An imaging optical system for compensating for a change of temperature comprising:
-
a lens system including at least a lens in which a change rate (dn/dt) of refractive index n with respect to change of temperature is negative, a light receiving element for receiving an image formed by said lens system, a correcting member adapted to change a relative distance between said light receiving element and said lens system by means of thermal expansion due to change of temperature, in which a thermal expansion (dL/dt) is set within a range as set forth hereunder;
##EQU14## i;
lens position from an object side, N;
number of component lenses of whole imaging optical system,fi ;
focal length of i-th lens,mi ;
lateral magnification from i-th lens to an image side,mi+1 ;
lateral magnification from i+1-th lens, to the image side,(dn/dt)i ;
rate of change of refractive index of an i-th lens, and ##EQU15## thermal expansion coefficient due to change of temperature of an i-th lens. - View Dependent Claims (6)
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7. In an imaging optical system for compensating for a change of temperature composed of a lens system which has at least a positive lens and a negative lens, wherein a focal point change dε
- /dt, which is defined as follows, of said system due to change of temperature is set within a 1/10 range of depth of focus;
##EQU17## where;
i;
lens position from an object sideN;
number of component lenses of the whole lens systemmi ;
lateral magnification from i-th lens to an image sidemi+1 ;
lateral magnification from i+1-th lens to the image sidedfni /dt;
fluctuation in focal length of i-th lens caused by change of refractive indexdfLi /dt;
fluctuation in focal length of i-th lens caused by thermal expansion. - View Dependent Claims (8, 9, 10, 11, 12, 13)
- /dt, which is defined as follows, of said system due to change of temperature is set within a 1/10 range of depth of focus;
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14. An imaging optical system for compensating for a change of temperature comprising:
-
a lens system, in which a focal point change dε
/dt due to a change of temperature is defined as follows, ##EQU18## where;
i;
lens position from an object sideN;
number of component lenses of the whole lens systemmi ;
lateral magnification from i-th lens to an image sidemi+1 ;
lateral magnification from i+1-th lens to the image sidedfni /dt;
fluctuation in focal length of i-th lens caused by change of refractive indexdfLi /dt;
fluctuation in focal length of i-th lens caused by thermal expansiona light receiving element for receiving an image formed by said lens system and which satisfies the following expression;
##EQU19## where;
m;
lateral magnification of whole lens system, at a reference temperature,f;
focal length of whole lens system at a reference temperature,Ki ;
dynamic factor originating in the position of the i-th lens in the lens system, andTi ;
focal length fluctuation of i-th lens due to a change of refractive index and thermal expansion per unit temperature change, anda correcting member adapted to change a relative distance between said light receiving element and said lens system by means of linear expansion due to change of temperature, in which a thermal expansion (dL/dt) of said correcting member is set within a range as set forth hereunder;
##EQU20##
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15. An imaging optical system for compensating for a change of temperature comprising:
-
a lens system, in which a focal point change dε
/dt due to a change of temperature satisfies the following expression;
##EQU21## where;
m;
lateral magnification of the lens system, at a reference temperature,f;
focal length of the whole lens system at reference temperature;Ki ;
dynamic factor originating in the position of the i-th lens in the lens system, andTi ;
focal length fluctuation of i-th lens due to a change of refractive index and thermal expansion per unit temperature change, anda lighting receiving element for receiving an image formed by said lens system; and a correcting member adapted to change a relative distance between said light receiving element and said lens system by means of linear expansion due to change of temperature, in which a thermal expansion (dL/dt) of said correcting member is set within a range as set forth hereunder;
##EQU22##
-
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16. In an imaging optical system for compensating for a change of temperature composed of a lens system comprising at least three lenses which has at least a positive lens and a negative lens, wherein a focal point change dε
- /dt, which is defined as follows, of said lens system due to change of temperature is set within a 1/10 range of depth of focus;
##EQU23## where;
i;
lens position from an object sideN;
number of component lenses of the whole lens systemmi ;
lateral magnification from i-th lens to an image sidemi+1 ;
lateral magnification from i+1-th lens to the image sidedfni /dt;
fluctuation in focal length of i-th lens caused by change of refractive indexdfLi /dt;
fluctuation in focal length of i-th lens caused by thermal expansion. - View Dependent Claims (17)
- /dt, which is defined as follows, of said lens system due to change of temperature is set within a 1/10 range of depth of focus;
-
18. In an imaging optical system for compensating for a change of temperature composed of a lens system which has at least a positive lens and a negative lens and comprises an asymmetric lens structure, wherein a focal point change dε
- /dt, which is defined as follows, of said lens system due to change of temperature is set within a 1/10 range of depth of focus;
##EQU24## where;
i;
lens position from an object sideN;
number of component lenses of the whole lens systemmi ;
lateral magnification from i-th lens to an image sidemi+1 ;
lateral magnification from i+1-th lens to the image sideΔ
fni ;
fluctuation in focal length of i-th lens caused by change of refractive indexΔ
Li ;
fluctuation in focal length of i-th lens caused by thermal expansion.
- /dt, which is defined as follows, of said lens system due to change of temperature is set within a 1/10 range of depth of focus;
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19. An imaging optical system for compensating for a change of temperature, said optical system comprises three lens groups consisting of a first positive plastic lens, a second double concave negative plastic lens, and a third double convex positive lens arranged in that order from an object side, said system satisfies the following expressions:
-
space="preserve" listing-type="equation">0.30<
|f.sub.2 |/f<
0.40
space="preserve" listing-type="equation">0.40<
f.sub.3 /f<
0.50
space="preserve" listing-type="equation">0.28<
|r.sub.3 |/f<
0.40
space="preserve" listing-type="equation">n.sub.5 >
1.75where; f;
focal length of whole system,fi ;
focal length of i-th lens,r3 ;
radius of curvature of third surface, andn5 ;
refractive index of third lens.
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20. An imaging optical system for compensating for a change of temperature including a positive plastic lens, having a focal length fi, and a refractive index ni placed in an i-th position from an object side, and a negative plastic lens, having a focal length fj and a refractive index nj, placed in a j-th position from the object side, and satisfying the expression set forth hereunder wherein the lateral magnification from the i-th lens to an image surface is mi, the lateral magnification from the i+1-th lens to the image surface is mi+1, the lateral magnification from the j-th lens to the image surface is mj, the lateral magnification from the j+1-th lens to the image surface is mj+1, the F number of the whole system is F, the lateral magnification of the whole system is m, and the picture element size of a light receiving element is p;
- ##EQU25## (dn/dt)i ;
rate of change of refractive index of an i-th lens, ##EQU26## coefficient thermal expansion of an i-th lens. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27)
- ##EQU25## (dn/dt)i ;
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28. An imaging optical system for compensating for change of temperature comprising a lens system which has at least a positive lens and a negative lens, wherein a focal point change dε
- /dt of said lens system due to a change of temperature satisfies the following expression;
##EQU28## F;
F number of the whole system, m;
lateral magnification of the whole system,p;
the picture element size of a light receiving element,i;
lens position from an object sideN;
number of component lenses of the whole lens systemmi ;
lateral magnification from i-th lens to an image sidedfni /dt;
fluctuation in focal length of i-th caused by change of refractive indexdfLi /dt;
fluctuation in focal length of i-th caused by thermal expansion.
- /dt of said lens system due to a change of temperature satisfies the following expression;
Specification