An endoscope magnification optical system includes, in order starting from an object side, a first lens group having positive power, a second lens group having positive power, and a third lens group including at least a meniscus lens with a concave surface facing the object side and a positive lens, and the endoscope magnification optical system is configured to magnify an optical image by moving at least the second lens group in an optical axis direction with respect to the first lens group, which is a fixed lens group, while a distance from a lens surface located the closest to the object of the first lens group to an image plane is kept constant.

An optical system for a stereo video endoscope, a stereo video endoscope and a method for operating an optical system. The optical system includes a distal optical assembly and a proximal optical assembly with a left lens system channel and a right lens system channel. The distal optical assembly couples light incident from an object space into the left lens system channel and into the right lens system channel of the proximal optical assembly. The distal optical assembly is an optical assembly with an adjustable focal length, wherein a change in the focal length causes a displacement of an axis intersection point in the object space.

An endoscope apparatus has an endoscope and a video processor. The endoscope has a magnet and a coil, the magnet has a voice coil motor configured to be movable with respect to the coil and a Hall device disposed in the vicinity of the coil and configured to detect a magnetic field of the magnet in order to detect a position of the magnet. The video processor includes a position detection circuit configured to detect the position of the magnet from an outputted signal of the Hall device, an arithmetic operation section configured to correct a sensor output signal indicating the position of the magnet detected by the position detection circuit using correction information and output the sensor output signal, and a drive control circuit configured to control a current or a voltage to the coil based on an arithmetic operation result of the arithmetic operation section.

An optical unit includes a fixed barrel configured to accommodate a moving barrel configured to hold an optical element configured to form an object image and formed of a nonmagnetic body to be able to advance and retract between a first position and a second position in a direction along an optical axis, a first magnet provided at the fixed barrel and configured to attract the moving barrel in a first direction along the optical axis to hold the moving barrel at the first position, a coil configured to attract the moving barrel in a second direction opposite to the first direction along the optical axis to hold the moving barrel at the second position by a magnetic field generated by being energized, and a second magnet provided at the moving barrel and configured to be attracted by the first magnet and the magnetic field of the coil.

An optical unit includes a movable section that holds a movable lens group and includes a rotation restricting section, a fixed section that holds a fixed lens group and has specific permeability larger than 1.0, n thinned-down sections being provided in the fixed section, and a voice coil motor including an n magnet sections disposed at every (360/n)° around a center axis of the movable section and a coil section disposed in the fixed section. The n magnet sections are respectively housed in n thinned-down sections in a noncontact manner. The n thinned-down sections are formed in asymmetrical positions different from every (360/n)° around the center axis.

An endoscope system includes an endoscope in which an actuator moves a movable lens and a position sensor outputs a position detection signal, and a processor including a driver circuit configured to drive the actuator and a driving control circuit configured to subject a deviation of the position detection signal to first correction based on individual processor correction data stored in a processor memory and controls the driver circuit based on a target position and the position detection signal subjected to the first correction.

A balloon is attachably and detachably mounted on an insertion part of an endoscope. A distal end part provided at a distal end of the insertion part includes an image pickup optical system, an illumination optical system, and a beam light-emitting unit. A subject is irradiated with measurement light by the beam light-emitting unit. It is possible to recognize the position of a spot from a subject image, and to measure an observation distance to an object to be observed, the size of the object to be observed, and the like.

An endoscope system includes an endoscope having a position/angle sensor and an amplifying circuit, a memory configured to store output error sensitivity data and a first wiring resistance value, and a processor including a signal processing circuit configured to process an output signal from the amplifying circuit. The signal processing circuit corrects an error of the output signal based on a value obtained by multiplying a difference between the first wiring resistance value and a processor wiring resistance value by the output error sensitivity data.

A zoom image pickup apparatus includes a mount portion, a zoom lens which forms an image of light incident from the mount portion, and an image pickup element which is disposed at an image forming position, wherein the zoom lens includes in order from an object side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, a fourth lens unit having a negative refractive power, and a fifth lens unit having a positive refractive power, and the fourth lens unit is a focusing lens unit, and at the time of zooming from a wide angle end to a telephoto end, only the second lens unit and the fourth lens unit move, and the following conditional expression (1) is satisfied:

φ.sub.L1<φ.sub.3GL1  (1).

A large incident angle of an off-axis principal ray is ensured while a stroke of a moving lens group is kept long, and a size is reduced while a focusing operation in magnification is easy.

A magnifying endoscope optical system provided with a negative single lens cemented to an image pickup device and a moving lens group, capable of switching at least between a normal observation state and a proximity magnifying state can be made by moving the moving lens groups; and the following conditional expression (1) is satisfied:

−65<fr/fw<−2  (1) where reference character fr denotes a focal distance of the negative lens cemented to the image pickup device, and reference character fw denotes a focal distance of the entire system in the normal observation state (wide angle end).