Minolta Camera Kabushiki Kaisha

Kazumi Sugitani

Toshihiko Karasaki

A focus detecting device which comprises an objective lens for forming an image of an object, a condenser lens, located behind a predetermined focal plane of the objective lens, for converging the light passed through the objective lens, a pair of image re-forming lenses, located behind the condenser lens, for re-forming a pair of secondary images of the image formed by the objective lens on an off-axial region of the objective lens located at a position far from the optical axis thereof, a light direction changing device, located nearby the condenser lens, for changing the direction along which light bundles forming the secondary images passes towards the optical axis, and a light receiving device for receiving the pair of the secondary images formed by the secondary image forming device to produce a light intensity distribution signal representing the light intensity distribution of the secondary images, a focus condition calculating device for calculating a focus condition of the objective lens by means of detecting the positions of the pair of the secondary images in accordance with the light intensity distribution signal.

Focus detecting device

An optical system for detecting focusing condition comprises a pair of image re-forming lenses and an aperture mask. The image re-forming lenses are configured with a pair of plano-convex lenses having equal radius of curvature R and an equal axial thickness T. R is nearly equal to T (R.apprxeq.T). The aperture mask has apertures corresponding to the respective plano-convex lenses and is attached closely to the flat surfaces of the plano-convex lenses. Comatic aberrations for the respective light fluxes passing through the apertures become nearly same, and therefore point images formed by the respective light fluxes also become nearly same. Consequently, high accuracy of focusing condition detection is established.

Optical system for detecting focusing condition

A focus detecting device which comprises an objective lens for forming an image of an object, a condenser lens, located behind a predetermined focal plane of the objective lens, for converging the light passed through the objective lens, a pair of image re-forming lenses, located behind the condenser lens, for re-forming a pair of secondary images of the image formed by the objective lens on an off-axial region of the objective lens located at a position far from the optical axis thereof, a light direction changing device, located nearby the condenser lens, for changing the direction along which light bundles forming the secondary images passes towards the optical axis, and a light receiving device for receiving the pair of the secondary images formed by the secondary image forming means to produce a light intensity distribution signal representing the light intensity distribution of the secondary images, a focus condition calculating device for calculating a focus condition of the objective lens by means of detecting the positions of the pair of the secondary images in accordance with the light intensity distribution signal.

A focus detection apparatus of a camera comprising a plurality of focus condition detecting units, each of which includes at least a pair of re-imaging lens forming a pair of secondary images using a pair of light rays passed through a photo-taking lens and a condenser lens, and a CCD (charge-coupled device) line sensor receiving the images and detecting a focus condition of the photo-taking lens. All of the focus detection areas defined by each of the focus condition detecting units are located parallel one another and overlaps partially at least one other focus detection area in a perpendicular direction to a direction in which all of the focus detection areas extend. Therefore, there is no space, where the focus condition cannot be detected, among the focus detection areas in the parallel direction in which all of the focus detection areas extend.

Focus detection apparatus of camera

A focus detecting optical system is disclosed which includes an objective lens for forming an image of an object, a plurality of focus detecting blocks, and a focus condition calculating device for calculating a focus condition of the objective lens in accordance with the light intensity distribution signals produced by the plurality of the focus detecting blocks. Each of the focus detecting blocks includes a condenser lens located nearby a predetermined focal plane of the objective lens, a pair of image re-forming lenses located behind the condenser lens for reforming a pair of secondary images of the image formed by the objective lens, a mask plate having a pair of apertures through which light fluxes forming the secondary images pass and a light receiving unit for receiving the pair of the secondary images formed by the pair of image re-forming lenses to produce a light intensity distribution signal representative of the light intensity distribution of the secondary images. The apertures in the mask plate of at least one specified focus detecting block has a configuration different from that of the other focus detecting blocks.

Focus detecting optical system

A focus detecting optical system comprises an objective lens for forming an image of an object, at least one condenser lens disposed behind a predetermined image plane of the objective lens for converging light passed through the objective lens, at least one pair of image re-forming lenses located behind the condenser lens for re-forming a pair of secondary images of the image formed by the objective lens, at least one pair of rows of light receiving elements arrayed in a single line behind and in alignment with the paired image re-forming lenses for detecting the paired secondary images, and a light deflecting member disposed between the image re-forming lenses and the element rows and separated from said image re-forming lenses by an air space for deflecting light fluxes forming the secondary images outwards in a direction of array of the element rows with respect to a center of the paired secondary images. By such a construction, a state of focus adjustment of the objective lens can be detected on the basis of a change of the position of the secondary images detected by the element rows.

A focus detecting device has a plurality of focus detection blocks, which blocks reproduce images of an object once produced by an objective lens as a pair of images on first and second CCD line sensors arrayed in a line, by means of a condenser lens, a pair of re-imaging lenses, and an aperture mask having a pair of aperture openings provided in the proximity of the re-imaging lenses, which blocks detect the positions of the paired images formed on the CCD line sensors, and detects the focus condition of the objective lens. In the focus detecting device, a light shield member to prevent the incidence of harmful light on the CCD line sensors is provided between at least the condenser lens and the CCD line sensors.

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Osaka, Japan

Kazumi Sugitani