Abstract: An encoder includes a light illuminating device, an optical scale and a photosensor, and detects information of relative displacement between the scale and the illuminating light. A birefringent element, such as a Savart plate or the like, is disposed in the optical path between the light illuminating device and the photosensor to generate a plurality of images of the scale having different phases. A plurality of output signals having a phase difference are obtained using the images of the scale.

Abstract: Disclosed is a displacement detecting device for measuring displacement or velocity of an object. The device is provided with a casing having an optical window, a light-emitting element and a light-receiving element incorporated in the casing, a transparent plate member provided in the vicinity of the window, a first optical function element provided on the transparent plate member for splitting the light generated by the light-emitting element into plural light beams emitted therefrom, and a second optical function element provided on the transparent plate member for guiding the lights to the light-receiving element, the lights being modulated when the emitted light beams are irradiated onto a relatively displacing object.

Abstract: A rotary encoder and a scanning system using the same for detecting rotation of a galvano scanner which comprises a rotary scale coupled to a rotating driver, a scale with slits formed at a non-uniform pitch circumferentially on the rotary scale within a limited rotation angle and detection means for detecting a rotation status by reading the slits.

Abstract: A light beam is incident on a first position on a scale at such an angle that diffracted lights substantially coincide with an incident optical path, and two diffracted lights are directed along a substantially common optical path and are incident on a second position symmetrical with the first position. An interference light formed by rediffracted lights reflected from the second position is detected to thereby detect the displaced state of the scale.

Abstract: A method of and apparatus for optically detecting the position or amount of movement of a movable object, in which a plurality of position data element arrays are provided on a scale attached to the object such that the arrays are arranged in the direction of movement of the object. A string of light beam such as a laser beam, which extends in the same direction as the position data element array, is made to illuminate one of the arrays, and the light reflected by or transmitted through the position data element array is received by a sensor array such as CCD sensor which produces a signal representing the pattern of arrangement of the data elements in the illuminated position data element array and indicating absolute position of the object, whereby the instant absolute position of the object is detected.

Abstract: An encoder includes a first polarizing beam splitter for splitting a beam into first and second beams, and a first .lambda./4 plate arranged in respective first and second optical paths. A first optical device causes the beams to be incident on a diffraction grating so that positive first and negative second mode diffracted beams travel along the first and second optical paths, respectively, and superposes the diffracted beams on each other. A second polarizing beam splitter splits the diffracted beams from each other, and a second .lambda./4 plate is arranged in third and fourth optical paths for the diffracted beams, respectively. A second optical device causes the diffracted beams to be incident on the diffraction grating so that positive and negative first mode rediffracted beams travel along the third and fourth optical paths, respectively, and superposes the rediffracted beams on each other.

Abstract: A rotary encoder wherein coherent beams are caused to be incident at different positions of a diffraction grating mounted on a rotary object, different beams diffracted from the diffraction grating are caused to overlap and form interference fringes, the fringes are detected by a light receiving detector to detect a rotational state of the rotary object, and the parallelism a of the rotary object satisfies the following inequality:a.ltoreq.tan.sup.-1 [{.pi.(m-n).lambda./360n.sub.0 P}.theta.k].

Abstract: A displacement measuring apparatus comprises a scale relatively displaced to an irradiating beam, a reading head to read the scale by the irradiating beam, and control device to control the apparatus for avoiding substantially the leakage of the irradiating beam out of the apparatus in response to the positional error of the scale and the irradiating beam.

Abstract: A device comprises output device for receiving signals having predetermined phases and outputting first and second signals having different phase angles and amplitudes, conversion device for converting the first signal into a first binary signal and the second signal into a second binary signal, the conversion device being arranged so that widths of the first and second binary signals are substantially equal to each other regardless of a difference in amplitude of the first and second signals, and generating device for generating first and second pulses according to phase angles on the basis of the first and second binary signals.

Abstract: A reference position detecting device comprises an optical device for directing a light beam to a pattern indicating the reference position and plural photoreceptor elements for receiving the light beam obtained through the pattern. A reference position signal is obtained from signals from the photoreceptor elements.

Abstract: An encoder for measuring movement of an optical scale by photoelectrically converting light from the optical scale obtained by applying light from a light source to the optical scale, by means of light receiving element, includes detector for detecting a variation in intensity of the light received by the light receiving element and a comparator for comparing a signal from the detector with a predetermined reference signal. Consequently, a predetermined alarm signal is generated on the basis of the result of comparison obtained from the comparator.

Abstract: A scale, for measuring the displacement of an object to be examined, has a division and a mark for alignment of the division, and a displacement measuring apparatus, for measuring the displacement of a scale, has a device for reading the division of the scale and a detector for detecting the positional error of the division relative to the direction of the displacement.

Abstract: An encoder in which a light beam emitted from a semiconductor laser or the like is applied to a diffraction grating from a predetermined direction which is not contained in a reference plane defined by direction of relative movement of the diffraction grating and a direction normal to the diffraction grating. A diffracted light created from the diffraction grating by the application of the light beam by the light applying means is reflected by re-entering means and the reflected light is caused to re-enter the diffraction grating at substantially the same position as the position at which the diffracted light is created.

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.