Abstract: Apparatus for reading optically detectable indicia on a record carrier, such as video information which is recorded in the form of pits on a record medium, for example, a video disc. A source of coherent light transmits a beam to the record carrier. A hologram is interposed between the coherent light source and the carrier, the hologram serving to focus the beam on the record carrier. The intensity of the focussed beam is modulated by the recorded indicia, and at least one photodetector is disposed in an optical path traversed by the modulated beam so as to detect the intensity thereof. In a preferred embodiment, the hologram focusses the beam onto the surface of the record medium whereat it is modulated and reflected therefrom to the photodetector.

Abstract: A rotatable record carrier upon which reproducible information is recorded in the form of spaced apart pits in substantially concentric circular tracks on a surface of the carrier. The pits may represent frequency-modulated information signals, and the lengths of the pits are independent of the frequency of the information signals. A method and apparatus for reproducing information from this record carrier is disclosed, wherein a light beam is used to scan the tracks of the record medium, and the size of the scanning light beam is changed as a function of the radius of the track which then is being scanned so as to increase the size of the beam when a track of larger radius is scanned. This control over the size of the scanning beam establishes a constant relationship between the size of the beam and the length of the pits despite changes in the pit length due to the different radii of the tracks.

Abstract: In a record disk having a spiral groove in a surface thereof with the depth of the groove varying along the latter for representing recorded information, such as video signals; the groove has an inverted bell-shaped cross-section which is symmetrical about the median of the groove with each of the opposite side surfaces of the groove, at any location therealong, being defined approximately by the equationd.sub.x =d.sub.o .multidot.exp [-(x/w).sup.2 ]in which d.sub.o is the depth of the groove at the median thereof, w is the distance from the median of the groove to the point at the side surface of the groove where the depth is d.sub.o /e (e being the base of the natural logarithm), and d.sub.x is the depth of the groove at the respective side surface at a distance x from the median.

Abstract: In optically producing a reproducible recording of video or other signals, the intensity of at least one laser light beam is modulated by the signals to be recorded while such light beam scans a substantially flat surface on a photo-sensitive recording medium which is photo-reacted to a degree varying substantially linearly in correspondence with the intensity of the light impinging thereon over a predetermined range of light intensities, and the intensity of the light beam and the degree of modulation thereof by the signals are selected to maintain the maximum and minimum intensities of the modulated light beam within such predetermined range so as to form simultaneously on the record medium a tracking path portion and a recorded signal portion which is unified with the latter.

Abstract: A rotatable record carrier upon which reproducible information is recorded in the form of spaced apart pits in substantially concentric circular tracks on a surface of the carrier. A method of producing this record carrier is disclosed wherein, although the linear velocity of each track is dependent upon the radius of the track, the length of the pits in the respective tracks does not vary as a function of the change in the radius from one track to the next. A light beam is modulated with a rectangular pulse information signal, the duration of each pulse being controlled as a function of the radius of the track which is being scanned by the modulated light beam. For tracks having a smaller radius, the pulse duration is made larger than for tracks having a larger radius.

Abstract: A method of and apparatus for recovering information from a record medium of the type wherein the information is modulated onto a carrier and recorded in one portion of the record medium and the carrier is recorded in another portion of the record medium. The modulated information is reproduced from the record medium while the medium is rotated, and simultaneously, the carrier also is reproduced from the medium. The reproduced modulated information then is demodulated with the reproduced carrier to recover the original signal information. In one embodiment, the recorded information is a composite color television signal and the carrier constitutes the chrominance subcarrier for the color television signal.Also disclosed is a method and apparatus for recording signal information on a rotatable record medium. A reference signal is provided and is recorded in a circular track on the record medium.

Abstract: Such a ground excavating apparatus that conducts excavation of a soft stratum by means of a bucket and employs an impact crusher for the excavation of such a hard stratum as a rock bed or the like is disclosed.Introduced in the present application is a ground excavator of such a category that comprises a housing, a bucket boom properly set in place in the said housing in a manner of being capable of traveling forward and rearward, a bucket properly fitted in place on the front end section of the said bucket boom in a manner of being capable of inclining, and an impact crushing mechanism well capable of traveling forward and rearward by virtue of a hydraulic jack housed in the said bucket boom, and employs the said bucket and the said impact crushing mechanism in an alternate manner to best suit the nature of the ground to be excavated.

Abstract: Such a ground excavating apparatus that conducts excavation of a soft stratum by means of a bucket and employs an impact crusher for the excavation of such a hard stratum as a rock bed or the like is disclosed.Introduced in the present application is a ground excavator of such a category that comprises a housing, a bucket boom properly set in place in the said housing in a manner of being capable of traveling forward and rearward, a bucket properly fitted in place on the front end section of the said bucket boom in a manner of being capable of inclining, and an impact crushing mechanism well capable of traveling forward and rearward by virtue of a hydraulic jack housed in the said bucket boom, and employs the said bucket and the said impact crushing mechanism in an alternate manner to best suit the nature of the ground to be excavated.

Abstract: Tunnel excavator for forming an upper half annular hollow space in the solid earth. The excavator has an arch shaped shield provided with a plurality of chambers in which excavating machines are located. Each of the excavating machines is swingably supported in the respective chamber and gripper means for securely abutting against the outer and inner surfaces of the solid earth formed by the upper half annular hollow space is located in each of the chambers. Thrust generating means is connected between the respective excavating machines and the respective gripper means so that the excavating machines can be advanced by the action of the thrust generating means when the gripper means is actuated to abut against the earth.