Abstract: This invention discloses a linear/rotary encoder for detecting the state of movement of a grating. The encoder of this invention comprises a system for directing a coherent beam of light onto a predetermined position or positions of a diffraction grating formed on an object to be measured, a converging optical system having a reflection plane at a position on which light is converged, for again making incident on the respective different positions diffracted lights which exit from the position, an interference optical system for forming interference fringes by superposing beam diffracted from the diffraction grating at the predetermined position or positions, and light receiving elements for photoelectrically converting the interference fringes obtained through the interference optical system.

Abstract: In the reference-position detection method and apparatus for detecting a reference position of a scale, first and second patterns are disposed on the scale so that respective detection timings shift inversely to each other in response to a deviation in attitude of the scale. The first and second patterns are detected with timings different from each other by corresponding first and second sensors, and the reference position of the scale is determined according to outputs of respective sensors. Hence, even if the attitude of the scale changes from a predetermined attitude due to an inclination of the scale or a deviation in position of the scale, it is possible to exactly detect the reference position of the scale. Accordingly, it becomes also possible to increase the performance of a displacement measuring apparatus.

Abstract: An encoder of this invention radiates a light beam onto an optical scale, in which a reflection film is formed on a surface of a relief type diffraction grating formed on one surface of a light-transmission substrate, from a surface opposite to the formation surface of the diffraction grating, and detects a change in intensity of interference light caused by diffracted light produced by the diffraction grating, thereby measuring a displacement of the optical scale.

Abstract: A method for detecting a state of rotation of a rotary scale having a diffraction grating therein in which a radiation beam is directed to a first place on the diffraction grating to generate first and second diffracted beams. The first and second diffracted beams are re-diffracted at the first place to form a first re-diffracted beam and a second re-diffracted beam. The first and second re-diffracted beams are directed to a second place on the diffraction grating substantially opposite the first place with respect to the center of rotation of the rotary scale. The first and second re-diffracted beams are diffracted at the second place to interfere with each other so that an interference beam is formed. The interference beam is converted into a signal to detect the state of rotation of the rotary scale.

Abstract: In an optical type encoder for projecting a light beam onto an optical type scale having a diffraction grating formed thereon, forming an interferenced light by the use of a diffracted light from the scale, and photoelectrically converting the interferenced light to thereby measure the displacement of the scale, first and second light beams are caused to enter substantially the same position on the scale from different first and second directions, first and second diffracted light beams emerging from the scale by the first and second light beams being diffracted by the scale are directed to the aforementioned position by a reflecting device, the diffracted light beams emerging in the first and second directions by the first and second diffracted light beams being diffracted by the scale are superposed one upon the other to thereby form an interferenced light, and light components created by the first and second light beams being regularly reflected at the aforementioned position are not included in the interf

Abstract: An encoder having a long length measuring stroke with a simple construction is provided. The encoder comprises a scale formed with a periodic lattice pattern, first and second reading heads arranged along a moving direction of the scale for reading the scale, and an adder for adding output signals from the first and second reading heads. The encoder further has adjusting mechanism for adjusting such that the phase difference between the output signals from the first and second reading head becomes zero. A continuous periodic signal can be always accurately obtained independently of the position of the scale.

Abstract: A displacement measuring apparatus has an illuminating device for illuminating a diffraction grating with a radiation beam, an optical system for directing first and second diffracted beams created by the diffraction grating with to the diffraction grating, the optical system being provided so that the first and second diffracted beams have a common optical path and travel in opposite directions along the optical path. In addition, a device receives an interference beam formed by first and second re-diffracted beams created by the first and second diffracted beams being diffracted by the diffraction grating, and outputs a signal conforming to the displacement of the diffraction grating relative to the radiation beam.

Abstract: A rotary encoder for detecting a rotation status of a rotary scale having a diffraction grating formed along a rotational direction comprises a directing device for directing a radiation beam to a first position on the rotary scale and directing a plurality of diffracted beams generated at the first position to a second position different from the first position. The direction device is constructed such that the plurality of diffracted beams gave a common light path between the first position and the second position. The encoder also includes a forming device for forming an interference beam from a plurality of rediffracted beams generated at the second position, and a convertor for converting the interference beam to a signal to produce the signal representing the rotation status.

Abstract: An encoder for measuring the displacement of a movable diffraction grating has means for applying a radiation beam to the diffraction grating, a reflecting optical system for causing first and second reflected and diffracted beams created on the diffraction grating by the application of the radiation beam to be reflected and diffracted at least twice by the diffraction grating, and means for receiving an interference beam formed by the first and second reflected and diffracted beams reflected and diffracted at least twice and converting it into a signal conforming to the displacement of the diffraction grating.

Abstract: A rotating condition detection apparatus includes a light source for illuminating a radial lattice having a plurality of lattice patterns marked on a periphery of a rotating body at an equi-angle; an optical unit for superimposing two refraction lights having a predetermined number of order reflected in two predetermined directions by the radial lattice; a photosensing device for sensing the superimposed light; and a detector for detecting a rotating condition of the rotating body in accordance with the output of the photosensing means.

Abstract: An encoder for detecting the state of movement of a scale having a plurality of tracks consisting of arranged predetermined codes comprises first detecting device for reading the codes of the plurality of tracks and detecting data comprising a row of the codes, and second detecting device for detecting the state of movement of the codes of a particular track plurality of tracks to obtain more detailed data. The state of movement of the scale is detected on the basis of the signals from the first and second detecting devices.

Abstract: An optical type encoder for projecting a light beam onto an optical type scale having a diffraction grating formed thereon, forming interference fringes by the use of the diffracted light from the scale, and photoelectrically converting such interference fringes to thereby detect the displacement of the scale. The first and second light beams are caused to obliquely enter substantially the same position on the scale from different first and second directions, first and second diffracted light beams emerging perpendicularly from the scale by the light beams being diffracted by the scale are received by a common reflecting element, the first and second diffracted light beams are directed to said position by the reflecting element, and interference fringes formed by diffracted light beams emerging from the scale in the first and second directions by the first and second diffracted light beams being diffracted by the scale are photoelectrically converted.

Abstract: An optical type encoder comprises a light source for supplying a light beam for illuminating a diffraction grating formed on a movable scale, photoelectric converting means for photoelectrically converting interference fringes formed by causing a plurality of diffracted lights created by the diffraction grating to interfere with one another to measure the displacement of the movable scale and outputting a predetermined signal, detecting means for receiving a predetermined diffracted light created by the diffraction grating and detecting any fluctuation of the intensity thereof, and control means for modulating the intensity of the light beam illuminating the diffraction grating, on the basis of a signal from the detecting means, so that the amplitude of the output signal from the photoelectric converting means may become substantially constant.

Abstract: A rotating state detection apparatus comprising, an optical device for detecting coherent beams toward a plurality of positions on a diffraction grating present along a rotational direction of a rotating object, an interfering device for superposing diffraction beams of a specific order with each other, the diffraction beams being diffracted at the plurality of different positions on the diffraction grating, and light-receiving device for receiving the superposed beams obtained by the interfering device, and for photoelectrically converting interference fringes formed by the superposed beams.

Abstract: There is disclosed a moving state detection apparatus comprising optical unit for superposing a light beam of a specific order diffracted by a diffraction grating with a nondiffracted reference light beam; and light-receiving unit for receiving the superposed light beam from the optical means, the light-receiving unit being adapted to detect a change in contrast of interference fringes upon movement of said diffraction grating, and detect a moving state of the diffraction grating.

Abstract: A photographic optical apparatus including a beam splitter for splitting the optical path of an objective lens, a video pickup device arranged in one of the split optical paths, an optical low pass filter and a color separation filter arranged between the beam splitter and the video pickup device, a prism for changing the direction of the optical path arranged on the other split optical path, an eyepiece arranged on the optical path of the light coming through the prism, a pre-assumed image plane lying between the beam splitter and the prism and an image correcting plate of equal optical thickness to the sum of the lengths of the optical paths of the optical low pass filter and the color separation filter. The plate is arranged between the pre-assumed image plane and the beam splitter. The image correcting plate also serves to split off part of the light and then to guide it to a sensor for light metering.

Abstract: An image pickup apparatus including an electrical image sensor, means for detecting the reflection of a light beam incident on the image sensor, and control means for controlling the operation of the image sensor in accordance with the output of the detecting means so that the output signal of the image sensor has always a proper level.

Abstract: The disclosed finder system is constructed with three prisms. The first prism has a first entrance face, a first reflection face and a first exit face. The second prism has a second entrance face in contact with the first exit face, a second reflection face, and a second exit face. The third prism has a third entrance face in contact with the second exit face, a pair of roof-type reflection faces, a third reflection face in a common plane with the third entrance face, and a third exit face. Light entering through a photographic objective lens reflects from a quick return mirror to a focusing screen on which an image of an object forms. Light from the image reflects from the first reflection face to a direction parallel with an optical axis of the lens. The second reflection face then reflects the light progressively farther away from the optical axis to the pair of roof faces.

Abstract: A view finder optical system comprises an optical path split mirror which divides a second optical axis from a first optical axis of an objective optical system; a predetermined image forming plane arranged on the second optical axis to have an image coming from the objective optical system formed thereon; a first prism arranged along the second optical axis to bring about reflection twice on the second optical axis and to have the incidence plane thereof and a second reflection plane on the same plane; a second prism which is disposed behind the first prism and is provided with a roof type reflection plane for a first reflection and a reflection plane for further reflecting the second optical axis after the second optical axis is reflected by the roof type reflection plane; and an eye-piece on the second optical axis after it comes out from the second prism.