Vari-focal image pickup optical system for endoscopes
First Claim
1. A vari-focal image pickup optical system for endoscopes which is to be used in a condition attached to an eyepiece of an endoscope comprising, in order from the object side:
- a first focusing lens unit which is capable of adjusting a diopter within a range covering positive and negative values, and has a positive refractive power;
a second variator lens unit which has a vari-focal function and a negative refractive power; and
a third compensator lens unit which corrects a deviation of an image location caused by changing a magnification,wherein magnifications of said second lens unit and said third lens unit are changed around -1×
,wherein a magnification of said optical system is changed from that at a wide position to that at a tele position by moving said second lens unit from the object side toward the image side and moving said third lens unit from the image side toward the object side, andwherein said third lens unit is set at a magnification of -1×
when said second lens unit is set at the magnification of -1×
during a change of the magnification of said optical system.
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Accused Products
Abstract
A vari-focal image pickup optical system for endoscopes comprising, in order from the object side, a first focusing lens unit which is capable of adjusting a diopter within a range covering positive and negative values, and has a positive refractive power, a second variator lens unit which has a vari-focal function and a negative refractive power, and a third compensator lens unit which maintains an image at a constant location by correcting a deviation of an image location caused by changing a magnification, wherein magnifications of the second lens unit and the third lens unit are changed around a magnification level of -1×, wherein a magnification of the optical system is changed from that at a wide position to that at a tele position by moving the second lens unit from the object side toward the image side and moving the third lens unit from the image side toward the object side, and wherein the third lens unit is set at the magnification level of -1× when the second lens unit is set at the magnification level of -1×. The image pickup optical system is compact and light in weight, requires simple procedures for operation and can sufficiently cope with image pickup devices having picture elements arranged at high densities.
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Citations
10 Claims
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1. A vari-focal image pickup optical system for endoscopes which is to be used in a condition attached to an eyepiece of an endoscope comprising, in order from the object side:
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a first focusing lens unit which is capable of adjusting a diopter within a range covering positive and negative values, and has a positive refractive power; a second variator lens unit which has a vari-focal function and a negative refractive power; and a third compensator lens unit which corrects a deviation of an image location caused by changing a magnification, wherein magnifications of said second lens unit and said third lens unit are changed around -1×
,wherein a magnification of said optical system is changed from that at a wide position to that at a tele position by moving said second lens unit from the object side toward the image side and moving said third lens unit from the image side toward the object side, and wherein said third lens unit is set at a magnification of -1×
when said second lens unit is set at the magnification of -1×
during a change of the magnification of said optical system. - View Dependent Claims (8, 9)
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2. A vari-focal image pickup optical system for endoscopes which is to be used in a condition attached to an eyepiece of an endoscope comprising, in order from the object side:
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a first focusing lens unit which is capable of adjusting a diopter within a range covering positive and negative values, and has a positive refractive power; a second variator lens unit which has a vari-focal function and a negative refractive power; and a third compensator lens unit which corrects a deviation of an image location caused by changing a magnification, wherein magnifications of said second lens unit and said third lens unit are changed around -1×
,wherein a magnification of said optical system is changed from that at a wide position to that at a tele position by moving said second lens unit from the object side toward the image side and moving said third lens unit from the image side toward the object side, and wherein said third lens unit is set at a magnification of -1×
when said second lens unit is set at the magnification of -1×
during a change of the magnification of said optical system,said varifocal image pickup optical system satisfying the following conditions;
space="preserve" listing-type="equation">18<
f.sub.1 <
25
space="preserve" listing-type="equation">0.5<
f.sub.w /f.sub.1 <
1wherein the reference symbol f1 represents a focal length of said first lens unit and the reference symbol fw designates a focal length of said vari-focal optical system at the wide position.
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3. A vari-focal image pickup optical system for endoscopes which is to be used in a condition attached to an eyepiece of an endoscope comprising, in order from the object side:
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a first focusing lens unit which is capable of adjusting a diopter within a range covering positive and negative values, and has a positive refractive power; a second variator lens unit which has a vari-focal function and a negative refractive power; and a third compensator lens unit which corrects a deviation of an image location caused by changing a magnification, wherein magnifications of said second lens unit and said third lens unit are changed around -1×
,wherein a magnification of said optical system is changed from that at a wide position to that at a tele position by moving said second lens unit from the object side toward the image side and moving said third lens unit from the image side toward the object side, and wherein said third lens unit is set at a magnification of -1×
when said second lens unit is set at the magnification of -1×
during a change of the magnification of said optical system,said varifocal image pickup optical system satisfying the following conditions;
space="preserve" listing-type="equation">0.5<
f.sub.3 /f.sub.w <
1
space="preserve" listing-type="equation">0.6<
|f.sub.2 /f.sub.3 |<
1wherein the reference symbols f2 and f3 represent focal lengths of said second lens unit and said third lens unit respectively, and the reference symbol fw designates a focal length of said vari-focal image pickup optical system at the wide position. - View Dependent Claims (5, 6, 7, 10)
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4. A vari-focal image pickup optical system for endoscopes which is to be used in a condition attached to an eyepiece of an endoscope comprising, in order from the object side:
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a first focusing lens unit which is capable of adjusting a diopter within a range covering positive and negative values, and has a positive refractive power; a second variator lens unit which has a vari-focal function and a negative refractive power; and a third compensator lens unit which corrects a deviation of an image location caused by changing a magnification, wherein magnifications of said second lens unit and said third lens unit are changed around -1×
,wherein a magnification of said optical system is changed from that at a wide position to that at a tele position by moving said second lens unit from the object side toward the image side and moving said third lens unit from the image side toward the object side, and wherein said third lens unit is set at a magnification of -1×
when said second lens unit is set at the magnification of -1×
during a change of the magnification of said optical system,wherein each of said first lens unit, said second lens unit and said third lens unit comprises a cemented lens component consisting of a positive lens element and a negative lens element.
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Specification