Abstract: A modulated laser light detector that converts laser light energy into electrical signals which exhibit a frequency that is substantially the same as the laser light modulation frequency, in which these signals allow the detector unit to determine a position where the laser light is impacting upon a photodiode array. A superheterodyne receiver circuit is used to provide high gain at an improved signal-to-noise ratio to improve the range at which the modulated laser light signal can be reliably detected. Various types of signal detection circuits are available. Various processing algorithms are disclosed, including one which rejects laser light strikes that are due to reflections, rather than due to a direct strike from the laser transmitter.

Abstract: A modulated laser light detector that converts laser light energy into electrical signals which exhibit a frequency that is substantially the same as the laser light modulation frequency, in which these signals allow the detector unit to determine a position where the laser light is impacting upon a photodiode array. A superheterodyne receiver circuit is used to provide high gain at an improved signal-to-noise ratio to improve the range at which the modulated laser light signal can be reliably detected. Various types of signal detection circuits are available. Various processing algorithms are disclosed, including a Discrete Fourier Transform with a simplified computational algorithm for use with a low-power processor device.

Abstract: A modulated laser light detector that converts laser light energy into electrical signals which exhibit a frequency that is substantially the same as the laser light modulation frequency, in which these signals allow the detector unit to determine a position where the laser light is impacting upon a photodiode array. A synchronous rectifier circuit is provided which, by use of a phase locked loop, converts a full-wave analog signal representative of the modulated laser energy into a half-wave analog signal, which is filtered and demodulated to generate a DC level that is indicative of the strength of the received laser light energy. At least two channels of these signals are used to determine the impacting position of the laser light energy.

Abstract: An improved level indicating system is provided for use with excavating equipment based upon a family of laser light receivers. In a first embodiment, a laser receiver with a single “long” photocell is mounted directly on the dipperstick of an excavator in a position that is designed to intercept pulses of laser light being emitted by a rotating laser light transmitter, and an angle-sensing sensor is also mounted to the dipperstick. In a second embodiment, a laser receiver with two parallel “long” photocells is mounted directly on the dipperstick, in which the pair of photocells are of sufficient precision to determine the angle of the dipperstick. In a third embodiment, a laser receiver with two parallel photocells is mounted directly on the dipperstick on a “servo mast” that can be re-positioned along the length of the dipperstick. The movable photocells thus can be shorter in length than the “long” photocells used in the second embodiment.

Abstract: An improved photocell configuration is provided to create a more accurate laser receiver that not only is very accurate and flexible in its operational capabilities, but also can greatly reduce the effect of rotational offset due to shading of the photocell. In one embodiment, a very long photocell is provided in which multiple split-cells are used to present a geometry that will tend to negate some of the effects of shading. The shading effects are minimized by having a different active photocell area along each vertical edge of the photocell. In another embodiment, a "segmented" photocell is used, in which the split-cell design of a long photocell is also divided into vertical segments. These segments can be re-configured so that alternating segments comprise a mirror image about the longitudinal of the long photocell. Such an arrangement tends to reduce the effect of rotational offset due to shading to an extremely small percentage of error.

Abstract: A laser light detector is provided which can be used to detect pulsed laser light that is produced by a rotating laser light source on a construction job site. The laser light detector provides an easily-read display which is indicative of the present level or elevation of the laser light detector with respect to the plane of rotating laser light. The laser light detector has a very large dynamic range, while maintaining a very good signal-to-noise ratio, and can, therefore, be used at both short and long distances from the rotating laser light source. The laser light detector is not dependent upon the energy level received of laser light, or by the spot size of laser light as it reaches the light detectors. The laser light detector is available with several options, including dead band adjustment and audible indication of the elevation.

Abstract: A laser beam three dimensional position measurement system includes a laser transmitter mounted at a stationary reference position at a work site and a receiver mounted on a mobile machine at the site. The transmitter produces a laser reference plane by sweeping a laser beam about the transmitter. The receiver includes two spaced apart laser beam detectors for measuring the horizontal angle of the incoming beam with respect to the face of the receiver at two spaced apart locations on the face of the receiver. The horizontal angles are used to determine the range of the receiver from the transmitter. The transmitter includes an azimuth device for providing signals to the receiver indicative of the azimuth angle at which the receiver is positioned with respect to a reference axis that extends from the transmitter. The receiver includes a decoder signal receiving device for receiving the angle signals from the transmitter in order to determine its azimuth angle.

Abstract: A device for detecting and displaying the relative position of a generally horizontal reference plane of light, even when partial shading of the device occurs, produces a linear response that is independent of spot size and energy distribution. The device includes a photodetector means having first and second interdigitated photodetector elements positioned adjacent each other on the device. The first and second interdigitated photodetector elements provide first and second detection signals, respectively. A circuit means, responsive to the photodetector means, determines the relative levels of the first and second detection signals such that the position of the reference plane of light with respect to the detector device is determined. A display means, responsive to the circuit means, provides an indication of the position of the reference plane of light with respect to the detector device.

Abstract: A device for detecting and displaying the relative position of a generally horizontal reference plane of light. even when partial shading of the device occures, includes a photodetector means having including first and second interdigitated photodetector elements positioned adjacent each other on the device. The first and second interdigitated photodetector element provide first and second detection signals, respectively. A circuit means, responsive to the photodetector means, for determines the relative levels of the first and second detection signals such that the position of the reference plane of light with respect to the detector device is determined. A display means, responsive to the circuit means, for provides an indication of the position of the referece plane of light with respect to the detector device.

Abstract: A laser beam alignment system includes a transmitter which establishes a laser reference plane by continuously rotating a horizontal laser beam about the transmitter. A remotely located receiver senses the elevation of the laser reference plane and reflects a portion of the laser energy back to the transmitter where the reflected energy is employed to produce a signal indicative of the range of the receiver and its location with respect to a reference axis. The position of the receiver is thus established in three dimensions.