Abstract: A finder optical system includes an image taking lens configured to form a photogenic subject image, an erecting image forming member configured to convert the photogenic subject image an erecting image, and an ocular lens configured to enable observation the erecting image of the photogenic subject image therethrough, wherein the ocular lens includes, in an order from the erecting image forming member to the observation side, a first lens group of negative refracting power, a second lens group of positive refracting power and configured to move in an optical axis direction to perform diopter adjustment, and a third lens group having at least one positive lens and at least one negative lens and having a positive or negative overall refracting power, and wherein, when a focal length of the whole system as the ocular lens is at ?1 diopter is denoted by f, a composite focal length of the negative lens or lenses of the third lens group is denoted by f3n, a conditional expression ?0.55<f3n/f<?0.

Abstract: At least one exemplary embodiment is directed to a viewfinder optical system which includes a first mirror having a roof shape configured to reflect light from an object image formed by a photographic lens towards the object image, a second mirror configured to reflect light reflected from the first mirror towards an observation side, and an eyepiece lens configured to receive light reflected from the second mirror. The second mirror includes a rotationally asymmetrical surface. The eyepiece lens includes at least one rotationally asymmetrical surface. The eyepiece lens includes a plurality of lenses, among which a lens closest to the second mirror includes a rotationally asymmetrical surface.

Abstract: A finder optical system includes an image taking lens configured to form a photogenic subject image, an erecting image forming member configured to convert the photogenic subject image an erecting image, and an ocular lens configured to enable observation the erecting image of the photogenic subject image therethrough, wherein the ocular lens includes, in an order from the erecting image forming member to the observation side, a first lens group of negative refracting power, a second lens group of positive refracting power and configured to move in an optical axis direction to perform diopter adjustment, and a third lens group having at least one positive lens and at least one negative lens and having a positive or negative overall refracting power, and wherein, when a focal length of the whole system as the ocular lens is at ?1 diopter is denoted by f, a composite focal length of the negative lens or lenses of the third lens group is denoted by f3n, a conditional expression ?0.55<f3n/f<?0.

Abstract: At least one exemplary embodiment is directed to a viewfinder optical system which includes a first mirror having a roof shape configured to reflect light from an object image formed by a photographic lens towards the object image, a second mirror configured to reflect light reflected from the first mirror towards an observation side, and an eyepiece lens configured to receive light reflected from the second mirror. The second mirror includes a rotationally asymmetrical surface. The eyepiece lens includes at least one rotationally asymmetrical surface. The eyepiece lens includes a plurality of lenses, among which a lens closest to the second mirror includes a rotationally asymmetrical surface.

Abstract: An in-finder display device includes an optical member having prisms and disposed about a position where an objective unit forms an image; an image-inverting unit receiving light from the optical member; an eyepiece unit for guiding the light from the image-inverting unit to an observer; a light source; and an illuminating unit for guiding light from the light source to the prisms. Each of the prisms in the optical member has two prism facets forming a ridgeline nonparallel to a plane orthogonal to an optical axis of the objective unit. Light from the light source is reflected off the prisms, passes through the image-inverting unit, and is guided by the eyepiece unit to the observer.

Abstract: An in-finder display device includes an optical member having prisms and disposed about a position where an objective unit forms an image; an image-inverting unit receiving light from the optical member; an eyepiece unit for guiding the light from the image-inverting unit to an observer; a light source; and an illuminating unit for guiding light from the light source to the prisms. Each of the prisms in the optical member has two prism facets forming a ridgeline nonparallel to a plane orthogonal to an optical axis of the objective unit. Light from the light source is reflected off the prisms, passes through the image-inverting unit, and is guided by the eyepiece unit to the observer.

Abstract: An image pickup apparatus which can perform focusing control with high speed and high precision is disclosed. The image pickup apparatus comprises a focus detection unit that detects a focusing state of the image-taking lens by phase difference detection method using light from the image-taking lens, and an in-focus judgment unit judges whether the image-taking lens is in an in-focus state or not, based on a result of a detection of contrast of an object image that has been taken with an image pickup device. Correction information, for correcting focusing control information of the image-taking lens that has been obtained by using the focus detection unit, is obtained based on information indicating the in-focus state of the lens obtained by using the in-focus judgment unit.

Abstract: In an observation optical system having, in order from an object side, an objective optical system, an erect optical system, and an eyepiece optical system, the objective optical system includes, in order from the object side, a first lens unit of a negative refractive power and a second lens unit of a positive refractive power. The second lens unit is a single lens made of a plastic material. This lens is adapted to be rotatably driven about a point on an optical axis as a rotational center, so that the displacement of an image forming position of the objective optical system is executed.

Abstract: In a lens-interchangeable digital single-lens reflex camera having a focus detection device, an autofocus device corrects a focus detection result by storing, on the camera side, the detection result obtained by a focus detection means and the deviation of the best imaging position of an image formed on an image taking element due to a low-pass filter inserted in front of the image taking element.

Abstract: An image pickup apparatus which can perform focusing control with high speed and high precision is disclosed. The image pickup apparatus comprises a focus detection unit that detects a focusing state of the image-taking lens by phase difference detection method using light from the image-taking lens, and an in-focus judgment unit judges whether the image-taking lens is in an in-focus state or not, based on a result of a detection of contrast of an object image that has been taken with an image pickup device. Correction information, for correcting focusing control information of the image-taking lens that has been obtained by using the focus detection unit, is obtained based on information indicating the in-focus state of the lens obtained by using the in-focus judgment unit.

Abstract: In a lens-interchangeable digital single-lens reflex camera having a focus detection device, an autofocus device corrects a focus detection result by storing, on the camera side, the detection result obtained by a focus detection means and the deviation of the best imaging position of an image formed on an image taking element due to a low-pass filter inserted in front of the image taking element.