Nec Corporation

Nippon Electric Co., Ltd.

Yuzo Ono

Yasuo Kimura

Akitomo Oba

Hiroyuki Miyazaki

Yutaka Yamanaka

Ichiro Fujieda

Akitomo Ohba

Seiji Kawata

Kazuhisa Shirakabe

Seijin Sugama

An optical head device uses a birefringent diffraction grating polarizer configured in a reflection type. The device includes a polarizing hologram element which reflects the light from a light source to a converging lens system and diffracts the polarized light returning from a recording medium. A total reflection film is formed on a surface of a diffraction grating which is provided periodically by an ion exchange region and a dielectric film on a surface of a crystal plate having optically anisotropic characteristics. A polarizing beam splitter film formed on a surface of the polarizing hologram element has reflectivity and transmissivity having dependency on the polarization of the incident light. In another form, a polarizing hologram element includes a polarizing hologram which has diffractive efficiency having dependency on polarization of incident light and a polarizing beam splitter film which has reflectivity and transmissivity having dependency on the polarization of the incident light. The diffracted light is received by multi-split photodetectors. The arrangements enable to make the optical head device compact, light in weight and low cost.

Optical head device and birefringent diffraction grating polarizer and

In an image forming apparatus, a mechanism for scanning the inner periphery of a hollow cylindrical drum has stationary optics including two semiconductor lasers fixed in place. The two lasers have their p-n junction planes positioned perpendicular to each other, i.e., one of them is horizontal while the other is vertical. Lights from the lasers are combined on the same axis by a polarizing beam splitter. A quarter-wave plate has its optical axis inclined .+-.45 degrees relative to the direction of polarization. The combined wave from the beam splitter is transformed by the quarter-wave plate to light having a clockwise and a counterclockwise polarization overlapping each other on the same axis. In the rotary optics, another quarter-wave plate converts the incident light to a composite wave of linear polarizations perpendicular to each other. This composite wave is incident to a splitting element as a P wave and an S wave or as ordinary rays and extraordinary rays. As a result, the P wave and S wave or the ordinary rays and extraordinary rays are spatially separated into two beams for scanning a film in parallel.

Mechanism for scanning the inner periphery of a drum included in an

A light radiated from a light source is focused on an optical disc by a focusing lens. A light reflected from the optical disc is introduced to a signal detection system. In the signal detection system, the introduced light is diffracted by a birefringent diffraction grating element utilizing an optical crystal. The diffracted light is received by a photodetector. Consequently, focus and track errors are detected, and information stored in the optical disc is re-produced.

Optical head using birefringent diffraction grating

A two-dimensional image sensor 12 having openings 28 through which light can pass is formed on a transparent substrate 21 and combined with a planar light source 11 and an optical element 13 which defines optical paths. The optical element 13 is formed by combining one of a diffraction grating, a microlens and a specular surface of V-shaped grooves with a collected fiber member formed from bundled optical fibers having light shielding side faces so as to allow the transfer of an image. The profiles of these components are determined so that light may be focused upon a finger contacting area on the center line between the openings 28 and photo-sensitive elements 24 of the sensor 12.

Fingerprint image input device having an image sensor with openings

In order to generate a Bessel beam at a location remote from an optical arrangement, the optical arrangement includes, a first beam converging element which is illuminated by a collimated beam, a second beam converging element which is illuminated by a beam which has passed through the first beam converging element. The first and second beam converging elements ere arranged in a manner to radiate a ring beam which is parallel with an optical axis. A third beam converging element is further provided which is illuminated by the ring beam. The third beam converging element is arranged to generate a non-diffractive beam at a location which is remote therefrom. Further, an improvement of a bar code reader is disclosed, which includes a laser source for producing a laser beam. A laser beam deflecting member is provided to deflect the laser beam so as to form a scan pattern comprised of two scan lines. The two scan lines are oriented at a predetermined angle with respect to one another. A combination of photo sensor and electric circuitry is provided to detect the beginning of the scan pattern and to discriminate between the two scan lines.

Method and arrangement of generating a non-diffractive beam at a

An optical head comprises a grating lens for diffracting light beam separated from the light beam path. The grating lens is composed of a plurality of regions having different focal length and diffraction direction so that the light beam is divided into a predetermined number of light beams. Therefore, a conventional beam splitter or polarizing beam splitter is replaced by a grating lens so that the optical head can be smaller and lighter, and the precision of detecting a track and focus errors is improved.

Optical head with diffraction grating producing five diffracted

First to third lenses are arranged in order to have a common optical axis. The first and second lenses provide a combined lens structure for shifting an object point along the common optical axis by moving one of the first and second lenses along the common optical axis, while an image point is formed in accordance with the shifted object point by the third lens. A spot diameter is kept constant at the image point by shifting the object point.

Lens system for optical reader

An optical head includes a reflection type grating lens for dividing specified polarized lights into a reflected light and a diffracted light, a device for detecting a RF signal from the reflected light of the grating lens, and a device for detecting focusing and tracking error signals from the diffracted light of the grating lens. The grating lens consists of a plurality of domains having different optical properties respectively, so that the reflected and diffracted lights are obtained. The optical head further includes a total reflection prism to compensate a phase difference between polarized lights orthogonal to a grating groove of the grating lens and parallel thereto, and a polarizing prism for dividing the reflected light into two polarized lights orthogonal to each other in polarization thereof. Thus, a simple, miniaturized, and inexpensive optical head is obtained.

Optical head using a reflection grating

For use in combination with an optical source for generating a coherent beam along a main optical axis, an optical head device comprises a diffraction grating having a plurality of grating regions which are responsive to the coherent beam for directing a zeroth-order diffracted beam to a focussing lens and are responsive to an optical beaem reflected from an optical recording medium for directing sidewards diffracted beams to an optical detector assembly. An effective area of a diameter of about 5 mm is sufficient for the diffraction grating. Each sidewards diffracted beam may form an angle of 20.degree. with the main optical axis. The optical detector assembly is used in detecting focussing and tracking errors for the recording medium and can be used in reproducing optical information from the recording medium. A six-partitioned optical detector assembly is preferred when the grating regions are four in number. Either a four-partitioned or a three-partitioned optical detector assembly is preferred when the grating regions are two in number. Depending on the grating regions, the optical detector assembly preferably has two optical detector elements which are placed on different levels relative to the diffraction grating.

Optical head comprising a diffraction grating for directing two or more

An optical storage medium comprises a thermoplastic resin substrate having a concave and convex surface grating on one surface thereof, and a metal layer covering the concave and convex surface grating. The period of the concave and convex surface grating is less than a wavelength of light so that light reflected from the concave and convex surface grating is changed from linear polarization to elliptical polarization, while there is no change in the polarization of light reflected from a recording pit in which the concave and convex surface grating has collapsed. Therefore, information can be read out of the optical storage medium in accordance with the change of light polarization.

Optical storage medium

A laser beam scanner that includes a laser source emitting light at a frequency (X.sub.2) and a rotatable hologram produced by interfering lasers at a frequency (X.sub.1) and located a distance (a) from the laser source and a scanned surface at a distance (b) from the hologram. The hologram satisfies the image forming relationship 1/F.sub.1 =1/f.sub.0 +1/f.sub.R where F.sub.1 is the focal distance of the hologram and f.sub.0 and f.sub.R are the respective distances of the hologram from the divergent and convergent points where the interfering lasers are located. The laser source is located in a position away from the optical axis of the hologram so as to enlarge the diffraction angle. However, in order to compensate for resulting astigmatism, the hologram is produced by selecting the positions of the two interfering lasers in order to satisfy the image formation relationship in a region distant from the hologram optical axis and not to satisfy the image formation relationship on the optical axis.

Holographic laser beam scanner

A focus error detector for an optical head utilizes a transmission type diffraction grating and an optical system for converging a beam issuing from a light source onto an object and converting light reflected from the object to a collimated beam to cause the collimated beam to become incident to the diffraction grating at a proper angle of incidence. A photodetector having a plurality of light-sensitive sections, is positioned relative to the grating such that it receives rays diffracted substantially from the grating in the direction of reflection of the diffraction grating. Photodetector data are used to calculate focus correction signals which are supplied to servo-mechanisms providing physical adjustments to the optical system.

Focus error detector and optical head using the same

A hologram is manufactured by making a plurality of coherent spherical-wave beams, N (.gtoreq.3) in number, interfere with one after another to provide a multiplicity of interference fringe configurations. A phase subtract aspheric-wave is produced by an auxiliary hologram manufactured by the use of two of the spherical-waves. The aspheric-wave is made to interfere with a third spherical-wave or a similar aspheric-wave. Phase distribution .phi..sub.N on the interference fringes is defined by: ##EQU1## where r represents a distance on the hologram between a predetermined point and an optional point, f.sub.k is the distance between the principal surface and the point of convergence or divergence of the particular wave and ##EQU2## is the focal power of the hologram for a coherent beam of the common wavelength. In a laser beam scanner, a coherent beam of a longer wavelength is preferably used in illuminating a hologram, which may or may not be a hologram manufactured as above.

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Tokyo, Japan

Yuzo Ono