An endoscope includes: a first lens located at a distal-most position, a part of the first lens being exposed outside; a movable lens barrel configured to be able to move, and configured to hold a movable lens disposed on a proximal end side with respect to the first lens; an actuator unit including a coil that drives the movable lens barrel and generates heat by receiving a supply of electric power; and a control section that outputs first electric power to the coil when holding the movable lens barrel at a predetermined position, and outputs second electric power larger than the first electric power to the coil when conducting heat generated from the coil to the first lens at the predetermined position.

The present specification describes a novel system for dynamically modifying the magnification power of optical devices used in high performance and critical applications such as medical procedures. The present specification describes an optical imaging system having a magnification control system connected to a sensor device for enabling movement of sensor device with respect to a lens assembly of the imaging system, wherein distance between the sensor device and the lens assembly is altered to enable different levels of magnification capability.

An endoscope realized as either a borescope or a fiberscope including one or more fluid filled lenses is described. In an embodiment, the optical power of the fluid filled lenses may be adjusted to adjust the focal length associated with the endoscope. Thus, variable working distances are allowable while maintaining focus on an object in front of the endoscope. The endoscope may include a distance sensor, which is used to determine a distance between the endoscope and a sample. A processor may compare the measured distance to the current optical power of the one or more sealed fluid filled lenses. The processor may transmit signals to one or more actuators coupled to one or more sealed fluid filed lenses to change the optical power of the one or more sealed fluid filled lenses based on the comparison.

An observation optical system unit includes a first lens which is positioned closest to an object side, among rear-group lenses, and which is configured by a stepped lens including a proximal portion, an outer circumference of which is held by a rear-group lens frame, and a protruding portion formed to have an outer circumference smaller than the outer circumference of the proximal portion and protruding into a region where a moving lens frame is allowed to advance and retract, where the moving lens frame overlaps with the protruding portion at a retracted position.

To provide an image pickup unit that can prevent axis deviation of a movable lens barrel and obtain high-quality picked-up image, a stopper member is positioned and fixed in a state in which the stopper member is abutted against an outer circumferential surface of a rear group lens barrel, movement of a movable lens barrel to a retraction side along a photographing optical axis is restricted by contact of a stopper section of the stopper member and an operation rod, and a movable lens is held in a position for realizing a second focal length.

An objective lens including a first lens group immovable in changing magnification from a normal observation state to a close-up observation state, a second lens group arranged nearer to the image side than the first lens group and moving along the optical axis in the change of magnification, a third lens group arranged nearer to the image side than the second lens group and immovable in the change of magnification, and an aperture stop arranged between the second lens group and an image plane and immovable in the change of magnification, and the objective lens satisfying the following condition:
1.24<|F.sub.1f/F.sub.n|<1.8
where F.sub.1f denotes the focal length of a lens that is placed nearest to the object side in the first lens group and F.sub.n denotes the focal length of the whole system in the normal observation state.

The wide angle optical system includes in order from a side of an object in front, a first lens group having a negative refractive power, a second lens group having a catadioptric optical element, an aperture stop, and a third lens group having a positive refractive power, and the catadioptric optical element has a first surface, a second surface, and a third surface, and the first surface has a first transmitting surface and a first reflecting surface, the second surface has a second transmitting surface and a second reflecting surface, and the third surface has a third transmitting surface, and the third transmitting surface is a side surface of a circular truncated cone, and the following conditional expressions (1), (2), and (3) are satisfied:

νp<νn  (1),

|φp|<|φn|  (2), and

90°−θk<α/2  (3).

An image pickup apparatus includes an image forming optical system which includes an aperture stop that sets an axial light beam, and a diffracting optical surface disposed at a position different from a position where the aperture stop is disposed, and an imager which is disposed on an image side of the image forming optical system, and has a light-receiving surface which is not flat and is curved to be concave toward the image forming optical system, wherein the diffracting optical surface satisfies the following conditional expression (1).

0.1<|DSD/TL|≦1.0  (1) where, TL denotes an actual distance on an optical axis of the image forming optical system, from a surface of incidence of the image forming optical system up to the light-receiving surface, DSD denotes an actual distance on the optical axis of the image forming optical system, from a position of the aperture stop up to the diffracting optical surface, and when a focal length of the image forming optical system is variable, conditional expression (1) is a conditional expression in a state at a wide angle end.

A stereoscopic vision optical system includes a first lens group having a negative refractive power, disposed nearest to an object, a second lens group having a positive refractive power, and a rear-side lens group having a positive refractive power. The rear-side lens group includes a first rear group and a second rear group. The optical axis of the first lens group, an optical axis of the first rear group, and an optical axis of the second rear group is positioned on the same plane. The optical axis of the first lens group is positioned between the optical axis of the first rear group and the optical axis of the second rear group, and the following conditional expression (1) is satisfied:
0.08≤((−L/2)×(f1/f2))×(1/WD)≤0.25  (1).

This endoscope includes an observation optical system capable of changing a magnified observation and a normal observation with each other, and a plurality of illumination optical systems, wherein a most tip side lens surface of at least one of the illumination optical systems is disposed at a position which is closer to a proximal end side than a most tip side lens surface of the observation optical system, and the following conditional expressions are satisfied.
0.03<D_Back(max)/ft<2  (1)
1.05<ft/fw<5  (2) In the expression, D_Back(max) is a maximum value of a distance between the most tip side lens surface and the most tip side lens surface, ft is a focal length in a close-distance magnified observation state, and fw is a focal length in a normal observation state.