An endoscope includes in order from an object side, an objective optical system, an optical-path splitter, an image sensor, and an image processor. A λ/4 wavelength plate is disposed between the objective optical system and the splitter. The splitter includes first and second prisms, and has a beam splitting surface at which the first prism and the second prism are brought into close contact. The splitter splits light at the beam splitting surface, into a first optical path through which P-polarized light is transmitted and a second optical path through which S-polarized light is reflected. The first and second prisms are slid relative to one another along the beam splitting surface to adjust optical path lengths of the first and second optical paths, and are disposed at positions to cancel an amount of shift in focusing positions of extraordinary and ordinary light, and satisfy specific conditional expressions.

An endoscope includes in order from an object side, an objective optical system, an optical-path splitter, an image sensor, and an image processor. A λ/4 wavelength plate is disposed between the objective optical system and the splitter. The splitter includes first and second prisms, and has a beam splitting surface at which the first prism and the second prism are brought into close contact. The splitter splits light at the beam splitting surface, into a first optical path through which P-polarized light is transmitted and a second optical path through which S-polarized light is reflected. The first and second prisms are slid relative to one another along the beam splitting surface to adjust optical path lengths of the first and second optical paths, and are disposed at positions to cancel an amount of shift in focusing positions of extraordinary and ordinary light, and satisfy specific conditional expressions.

A stereoscopic-vision endoscope optical system includes a pair of objective optical systems, a pair of relay optical systems, and a pair of image forming optical systems. The image forming optical system includes a first lens unit, a first optical-path bending element, and a second optical-path bending element. The objective optical system and the relay optical system are disposed in a first optical path. A second optical path is formed between the first optical-path bending element and the second optical-path bending element. A third optical path is formed between the second optical-path bending element and a final image. The second optical path is positioned farther from the central axis, than the first optical path. The third optical path is positioned closer to the central axis, than the second optical path.

A control apparatus controls an operation of a self-propelled mechanism of an endoscope. The control apparatus includes a drive circuit that outputs a motor current, a motor current detection circuit that acquires a value relating to magnitude of the motor current as a detection value, a storage circuit that stores a limit value relating to the detection value, and a control circuit that performs an operation as a first controller that controls the drive circuit so as to stop the motor when it is determined that the detection value exceeds a value relating to the limit value, and performs an operation as a second controller that controls the drive circuit so as to stop the motor when it is determined that the detection value exceeds the value relating to the limit value.

An optical module for endoscope includes a light emitting element, an optical fiber, a ferrule to which the light emitting element is bonded, a wiring board to which the ferrule is bonded, and a resin disposed between the ferrule and the wiring board, wherein the ferrule has a first principal surface made of a transparent material, a second principal surface, and a side surface, the second principal surface has an opening of an insertion hole, the second principal surface has an opening of a groove communicating with the insertion hole, the side surface has an opening of the groove, and a first distance between the opening of the groove on the side surface and the first principal surface is greater than a second distance between the bottom surface of the insertion hole and the first principal surface.

An optical module for endoscope includes a light emitting element, an optical fiber, a ferrule to which the light emitting element is bonded, a wiring board to which the ferrule is bonded, and a resin disposed between the ferrule and the wiring board, wherein the ferrule has a first principal surface made of a transparent material, a second principal surface, and a side surface, the second principal surface has an opening of an insertion hole, the second principal surface has an opening of a groove communicating with the insertion hole, the side surface has an opening of the groove, and a first distance between the opening of the groove on the side surface and the first principal surface is greater than a second distance between the bottom surface of the insertion hole and the first principal surface.

An endoscope processor includes a processor that can be connected to an endoscope including a moving mechanism of a focusing lens included in an objective optical system and an image pickup apparatus. The processor is configured to determine whether or not a transition has been made from a screening state to a proximity state based on positional information of the focusing lens and an image in a proximity determination mode when a variation in an image height in an effective image range with control of the moving mechanism is 1% or less, and when it is determined that a transition has been made to the proximity state, the processor is configured to end the proximity determination mode and control the moving mechanism in an autofocus mode.

An endoscope system includes: a processor that generates first and second feature amount distribution images of a living tissue from an imaged image of the living tissue and generates a second feature amount distribution processed image from these distribution images; and a display that displays the second feature amount distribution processed image. The processor generates a mask image of the second feature amount distribution image by, in the first feature amount distribution image, setting a pixel whose pixel value representing the first feature amount is less than a lower limit value as a non-transmissive pixel having a transmittance of zero and setting a pixel between an upper limit value and the lower limit value as a transmissive pixel while giving the pixel a transmittance determined continuously or stepwise in accordance with the pixel value in the first feature amount distribution image.

A relay optical system 20 for a rigid endoscope includes a lens fixing frame 21 and a plurality of lenses 22. The lens fixing frame 21 has a plurality of tubular bodies 26. The plurality of tubular bodies 26 are joined coaxially to each other. The plurality of lenses 22 are located at positions other than a joint position jp of the tubular bodies 26 in an axis direction of the lens fixing frame 21. The plurality of lenses 22 are located in the lens fixing frame 21 so as to have a coincident optical axis. The plurality of lenses 22 do not include a cemented lens.

A plenoptic endoscope includes a fiber bundle with a distal end configured to receive light from a target imaging region, a sensor end disposed opposite the distal end, and a plurality of fiber optic strands each extending from the distal end to the sensor end. The plenoptic endoscope also includes an image sensor coupled to the sensor end of the fiber bundle, and a plurality of microlenses disposed between the image sensor and the sensor end of the fiber bundle, the plurality of microlens elements forming an array that receives light from one or more of the plurality of fiber optic strands of the fiber bundle and directs the light onto the image sensor. The plurality of microlens elements and the image sensor together form a plenoptic camera configured to capture information about a light field emanating from the target imaging region.