A firearm sighting optic that can have the lenses easily and quickly replaced by the user is disclosed. This sighting optics allows the lens to be inserted from the bottom of a red dot sighting unit and then be secured by set screws. The firearm sighting optic includes a base and a hood. The lens is removably retained with the firearm sighting optic by user removable fasteners securing the hood to the base. The lens is housed in a hood that makes sliding the replacement lens into the unit much easier. The hood and base include an interconnecting protrusion and recess for reliable alignment of the lens within the hood and the base.

A firearm sighting optic that can have the lenses easily and quickly replaced by the user is disclosed. This sighting optics allows the lens to be inserted from the bottom of a red dot sighting unit and then be secured by set screws. The firearm sighting optic includes a base and a hood. The lens is removably retained with the firearm sighting optic by user removable fasteners securing the hood to the base. The lens is housed in a hood that makes sliding the replacement lens into the unit much easier. The hood and base include an interconnecting protrusion and recess for reliable alignment of the lens within the hood and the base.

A lens apparatus includes an holding barrel configured to hold a lens, movable relative to a fixed barrel in an optical axis direction, and configured to form a retracted state having an overall length of the lens apparatus smaller than when the lens apparatus is in an imaging state, an operating member configured to switch between a lock state that locks the holding barrel and an unlock state that unlocks the holding barrel, a state detector configured to detect a state of the holding barrel relative to the fixed barrel in the optical axis direction, a lock detector configured to detect whether the operating member is in the lock state or the unlock state, and an output unit configured to output detection results by the state detector and the lock detector, or information on whether imaging is available according to the detection results.

A lens apparatus includes an holding barrel configured to hold a lens, movable relative to a fixed barrel in an optical axis direction, and configured to form a retracted state having an overall length of the lens apparatus smaller than when the lens apparatus is in an imaging state, an operating member configured to switch between a lock state that locks the holding barrel and an unlock state that unlocks the holding barrel, a state detector configured to detect a state of the holding barrel relative to the fixed barrel in the optical axis direction, a lock detector configured to detect whether the operating member is in the lock state or the unlock state, and an output unit configured to output detection results by the state detector and the lock detector, or information on whether imaging is available according to the detection results.

A projection apparatus projects an image by an optical system having at least one optical characteristic being variable, and the projection apparatus includes a processor configured to perform a control of regulating a movement of a projection region to which the image is projected, based on the at least one optical characteristic in the optical system.

A projection apparatus projects an image by an optical system having at least one optical characteristic being variable, and the projection apparatus includes a processor configured to perform a control of regulating a movement of a projection region to which the image is projected, based on the at least one optical characteristic in the optical system.

An interchangeable lens is removably attached to a camera body including a body-side mount, an image sensor, body-side terminals and a first to fourth body-side claws. The interchangeable lens includes the lens-side mount, lens-side terminals which are in contact with body-side terminals, a first to fourth lens-side claws engaged with the first to fourth body-side claws once the interchangeable lens is attached to the camera body. The first and third lens-side claws are disposed on a third lens-side line intersecting with the first lens-side line at an optical axis with approximately 45 degrees. The first lens-side line passes through a center between opposite ends of the first lens-side claw to the optical axis. The second and fourth lens-side claws are disposed on a fourth lens-side line orthogonal to the third lens-side line at the optical axis.

An interchangeable lens is removably attached to a camera body including a body-side mount, an image sensor, body-side terminals and a first to fourth body-side claws. The interchangeable lens includes the lens-side mount, lens-side terminals which are in contact with body-side terminals, a first to fourth lens-side claws engaged with the first to fourth body-side claws once the interchangeable lens is attached to the camera body. The first and third lens-side claws are disposed on a third lens-side line intersecting with the first lens-side line at an optical axis with approximately 45 degrees. The first lens-side line passes through a center between opposite ends of the first lens-side claw to the optical axis. The second and fourth lens-side claws are disposed on a fourth lens-side line orthogonal to the third lens-side line at the optical axis.

A fixed focal length imaging optical system includes a first lens group having positive power, a second lens group having positive power, and a third lens group having negative power in order from an object side toward an image side. Upon focusing, the second lens group moves along an optical axis, and the first lens group and the third lens group do not move. The present disclosure provides the fixed focal length imaging optical system capable of favorably correcting various aberrations such as spherical aberration, astigmatism, and distortion, and an imaging device and a camera system each of which includes the fixed focal length imaging optical system.

A fixed focal length imaging optical system includes a first lens group having positive power, a second lens group having positive power, and a third lens group having negative power in order from an object side toward an image side. Upon focusing, the second lens group moves along an optical axis, and the first lens group and the third lens group do not move. The present disclosure provides the fixed focal length imaging optical system capable of favorably correcting various aberrations such as spherical aberration, astigmatism, and distortion, and an imaging device and a camera system each of which includes the fixed focal length imaging optical system.