US 5,471,049 AGranted

Light detecting apparatus having low noise automatic gain control circuit

AssigneeApache Technologies, Inc.

InventorGary L. Cain

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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. Multiple discrete steps of elevation indication are provided, which can easily be increased to a larger number of discrete steps, if so desired. The laser light detector is available with several options, including dead band adjustment, normal or offset on-grade displaying, and averaging.

Claims6

Dependent claims

A light detecting circuit, comprising:

(a) a plurality of light-sensitive elements arranged in an array for detecting pulses of light energy striking said light detecting circuit, thereby creating a plurality of first electrical signals, wherein the magnitude of each of said plurality of first electrical signals is proportional to the power of light striking its corresponding light-sensitive element, each of the light-sensitive elements in said array having a known physical location with respect to one another, and each pair of adjacent light-sensitive elements forming an individual gap of known distance between the respective proximal edges of said pair of adjacent light-sensitive elements;
(b) an amplifying and integrating circuit that amplifies and integrates each of said plurality of first electrical signals, thereby creating a plurality of second electrical signals, wherein the gain of said amplifying and integrating circuit is automatically controlled so as to keep said plurality of second electrical signals within the active dynamic range of said light detecting circuit, and wherein the peak magnitude of each of said plurality of second electrical signals is proportional to the power and to the duration time of light striking its corresponding light-sensitive element;
(c) a comparator device that determines which of said plurality of second electrical signals is greater in magnitude, said greater second electrical signal being indicative of the physical location that substantially the center of said light energy is striking said array of light-sensitive elements;
and
(d) a display for indicating said actual physical location, in comparison to the desired physical location, that substantially the center of said light energy is striking said array of light-sensitive elements.

2 more elements

A low noise automatic gain control circuit comprising:

(a) an input stage that receives an electrical signal and communicates said signal to at least two electronic switching circuits wherein each switching circuit has a different impedance from one another, each switching circuit having an output, said input stage configured to have only one of said switching circuits active at any particular time period thereby creating an interface signal at the output of the active one of said at least two electronic switching circuits;
(b) an amplifier/integrator stage that amplifies and integrates said interface signal while operating at a gain that is related to the impedance of the active one of said at least two electronic switching circuits, said amplifier/integrator stage thereby reducing over time the noise component of said interface signal and thereby creating an output signal;
and
(c) a magnitude detector having both high and low threshold limits, said magnitude detector sensing the magnitude of said output signal, wherein if the output signal's magnitude is less than said low threshold limit, then said input stage switches its active switching circuit to the one providing the next higher gain unless the highest possible gain is already the active switching circuit of said automatic gain control circuit, and wherein if the output signal's magnitude is greater than said high threshold limit, then said input stage switches its active switching circuit to the one providing the next lower gain unless the lowest possible gain is already the active switching circuit of said automatic gain control circuit.

1 more element

Dependencies are inferred from the claim text.

Facts

Application: 08/295,592Filed 25 Aug 1994 · continuation
Priority: 22 Jun 1993
Granted: 28 Nov 1995
Term ends: Not estimatedThe source records don’t support an estimate.

Classification4 codes

G01C 15/006
Reference lines, planes or sectors: detectors therefor
H03K 17/795
Using opto-electronic devices, i.e. light-emitting and photoelectric devices electrically- or optically-coupled: controlling bipolar transistors
G01C
Measuring distances, levels or bearings
H03K
Pulse technique