MULTIPLE-WAVELENGTH CAPABLE LASER RECEIVER

• US 20110090481A1
• Filed: 10/19/2009
• Published: 04/21/2011
• Est. Priority Date: 10/19/2009
• Status: Active Grant

• Current Assignee: Spectra Precision Inc. (Trimble Inc.)
• Original Assignee: Trimble Navigation Limited (Trimble Inc.)
• Inventors: Snyder, Chris W.
• Granted Patent: US 8,319,950 B2
• Time in Patent Office: Days
• US Class Current: 356/4.01
• CPC Class Codes: G01C 15/006 Detectors therefor
• CPC Class Codes: G01S 7/51 Display arrangements

Abstract

A laser light receiver used to detect pulsed laser light that is produced by a rotating laser light source on a construction jobsite is disclosed. In this manner, the laser receiver acts as an elevation detector and provides an equipment operator, or a construction worker, with the current elevation status with respect to the plane of laser light. The laser receiver is a unitary device that can detect multiple light frequencies/wavelengths, including laser beams that are in the green, red, and infrared spectra. The laser receiver also is capable of discriminating between such laser beams and other interference light sources, particularly fluorescent light sources.

Claims

1. A laser light receiver, comprising:

a processing circuit, at least one photosensor, a variable sensitivity control circuit, an output circuit, and at least one optical filter;

wherein;

(a) said at least one optical filter exhibits an optical characteristic so as to allow only wavelengths of electromagnetic energy at predetermined transmittance characteristics to pass therethrough to impact upon said at least one photosensor, such that said predetermined transmittance characteristics sufficiently pass wavelengths in both the green and red visible light ranges;

(b) said at least one photosensor exhibits a predetermined frequency sensitivity characteristic so as to be sufficiently sensitive to electromagnetic energy in both the green and red visible light ranges; and

said at least one photosensor, after receiving a sufficient amount of electromagnetic energy that impacts thereon, outputs at least one first signal to said variable sensitivity control circuit, which modifies said at least one first signal according to a gain state of said variable sensitivity control circuit to produce at least one second signal, and outputs said at least one second signal to said processing circuit; and

(c) said laser light receiver is configured;

(i) to evaluate said at least one second signal and, based upon a value of said at least one second signal, to determine a relative elevation of said at least one photosensor with respect to said received electromagnetic energy that impacts thereon, and, using said output circuit, to output a third signal to provide an indication of said determined relative elevation; and

(ii) to effectively reject an unwanted interference light signal that may be included in said at least one second signal, by inhibiting an output of said third signal by said output circuit and thereby preventing an indication of said determined relative elevation due to such unwanted interference light signal.

2. The laser light receiver of claim 1, wherein said laser light receiver is further configured to determine said gain state of the variable sensitivity circuit, and to output said third signal for indicating said relative elevation based on that determined gain state.

3. The laser light receiver of claim 2, wherein said laser light receiver is further configured to effectively reject the unwanted interference light signal at a rejection rate that is determined by said gain state.

4. The laser light receiver of claim 2, further comprising at least one user-actuated control input device;

and

wherein;

(a) said laser light receiver is further configured to determine if said at least one user-actuated control input device has been activated, and if so, to perform a function that to configures said laser light receiver into an operating mode that is predetermined by input data that was entered by said at least one user-actuated control input device; and

(b) said gain state of the variable sensitivity circuit is manually controlled by said operating mode that was entered by said at least one user-actuated control input device, as said input data.

5. The laser light receiver of claim 4, wherein a user, who enters said input data on said at least one user-actuated control input device, determines a desired value for said gain state by selecting a first operating range for said laser light receiver that is essentially too sensitive and does not sufficiently reject said unwanted interference light signal, and then selecting a second, different operating range that is somewhat less sensitive such that said laser light receiver does sufficiently reject said unwanted interference light signal.

6. The laser light receiver of claim 2, wherein said variable sensitivity control circuit comprises an automatic gain control circuit, which:

(a) initializes said gain state to a first predetermined gain state value and, outputs said at least one second signal to said processing circuit while operating in said first predetermined gain state value;

(b) then, based on a gain control signal that is output from said processing circuit to said automatic gain control circuit, iteratively modifies said gain state to a second gain state value, and iteratively outputs said at least one second signal to said processing circuit while iteratively operating in said second predetermined gain state value, until said at least first signal produced by said at least one photosensor is not saturated.

7. The laser light receiver of claim 1, wherein said unwanted interference light signal comprises electromagnetic energy produced by at least one of:

(a) a fluorescent light source, and (b) a strobe light source.

8. The laser light receiver of claim 1, wherein:

(a) said predetermined transmittance characteristics of said at least one optical filter sufficiently pass wavelengths in all of;

(i) said green visible light range;

(ii) said red visible light range, and (iii) an infrared light range; and

(b) said predetermined frequency sensitivity characteristic of said at least one photosensor includes a sufficient sensitivity to electromagnetic energy in all of;

(i) said green visible light range;

(ii) said red visible light range, and (iii) said infrared light range;

and therefore, said laser light receiver operates as an elevation detection device for laser transmitters which output laser light in all of the visible green, visible red, and infrared light wavelengths.

9. The laser light receiver of claim 1, wherein said third signal produced by said output circuit is used to drive at least one of:

(a) a display that is visible to a user; and

(b) a machine.

10. A laser light receiver, comprising:

a processing circuit, at least one photosensor, a variable sensitivity control circuit, an output circuit, and at least one optical filter;

wherein;

(a) said at least one optical filter exhibits a high-pass wavelength optical transmittance characteristic so as to effectively pass a range of wavelengths of electromagnetic energy above and including a green visible light spectrum through an infrared light spectrum, such that said passed electromagnetic energy will impact upon said at least one photosensor;

(b) said at least one photosensor exhibits a predetermined frequency sensitivity characteristic so as to be sufficiently sensitive to electromagnetic energy in a range of visible light above and including green visible light through an infrared spectrum; and

said at least one photosensor, after receiving a sufficient amount of electromagnetic energy that impacts thereon, outputs at least one first signal to said variable sensitivity control circuit, which modifies said at least one first signal according to a gain state of said variable sensitivity control circuit to produce at least one second signal, and outputs said at least one second signal to said processing circuit;

(c) said laser light detector is positioned within a space so as to intercept pulses of laser light, which represent a desired source of said electromagnetic energy that impacts said at least one photosensor; and

(d) said laser light receiver is configured to evaluate said at least one second signal and, based upon a value of said at least one second signal, to determine a relative elevation of said at least one photosensor with respect to said received pulses of laser light that impact thereon, and, using said output circuit, to output a third signal to provide an indication of said determined relative elevation, and can effectively operate as an elevation detector while operating in a fluorescent light environment, by its ability to distinguish the received pulses of laser light from an unwanted interference light signal produced by other light sources.

11. The laser light receiver of claim 10, wherein said received pulses of laser light are output by rotating laser transmitter, which creates a plane of laser light that represents a predetermined elevation on a jobsite.

12. The laser light receiver of claim 10, wherein said unwanted interference light signal comprises electromagnetic energy produced by at least one of:

(a) a fluorescent light source, and (b) a strobe light source.

13. The laser light receiver of claim 10, wherein said gain state of said variable sensitivity control circuit is controlled by one of:

(a) an automatic gain control circuit that is included in said variable sensitivity control circuit, and operates in conjunction with said processing circuit; and

(b) a manually controlled command that is entered by a user using at least one user-actuated control input device.

14. The laser light receiver of claim 13, wherein said unwanted interference light signal is inhibited from causing a false elevation reading at a rejection rate that is determined by said gain state.

15. The laser light receiver of claim 13, wherein said third signal drives at least one of:

(a) a display that is visible to a user; and

(b) a machine.

16. A method for using a laser light receiver as a relative elevation detector, said method comprising:

(a) providing a processing circuit, at least one optical filter that receives pulses of laser light energy, at least one photosensor, a variable sensitivity control circuit, and a housing, all combined as a unitary device;

(b) passing a portion of electromagnetic energy, including said received pulses of laser light energy, through said at least one optical filter, in which said passed portion of electromagnetic energy is controlled by predetermined transmittance characteristics of said at least one optical filter, such that said predetermined transmittance characteristics sufficiently pass wavelengths in both the green and red visible light ranges;

(c) allowing said passed portion of electromagnetic energy to impact upon said at least one photosensor, in which said at least one photosensor exhibits a predetermined frequency sensitivity characteristic so as to be sufficiently sensitive to electromagnetic energy in both the green and red visible light ranges;

(d) producing at least one first signal by said at least one photosensor, after receiving a sufficient amount of electromagnetic energy that impacts thereon, and directing said at least one first signal to said variable sensitivity control circuit;

(e) modifying, by said variable sensitivity control circuit, said at least one first signal according to a gain state of said variable sensitivity control circuit, and producing at least one second signal, and directing said at least one second signal to said processing circuit;

(f) evaluating said at least one second signal and, based upon a value of said at least one second signal, determining a relative elevation of said at least one photosensor with respect to said received pulses of laser light energy that impact thereon;

(g) indicating said determined relative elevation; and

(h) effectively rejecting an unwanted interference light signal that may be included in said at least one second signal, by preventing said unwanted interference light signal from causing a false indication of said determined relative elevation.

17. The method of claim 16, wherein said received pulses of laser light are output by rotating laser transmitter, which creates a plane of laser light that represents a predetermined elevation on a jobsite.

18. The method of claim 16, wherein said unwanted interference light signal comprises electromagnetic energy produced by at least one of:

(a) a fluorescent light source, and (b) a strobe light source.

19. The method of claim 16, further comprising the step of controlling said gain state of said variable sensitivity control circuit by one of:

(a) an automatic gain control circuit that is included in said variable sensitivity control circuit, and operates in conjunction with said processing circuit; and

(b) a manually controlled command that is entered by a user using at least one user-actuated control input device.

20. The method of claim 19, wherein said step of effectively rejecting an unwanted interference light signal comprises inhibiting a false elevation reading at a rejection rate that is determined by said gain state.

21. The method of claim 16, wherein said gain state of said variable sensitivity control circuit is controlled by a manual command entered by a user using at least one user-actuated control input device, and further comprising the steps of:

(a) setting said gain state to a maximum operating range, and determining if said laser light receiver is now in a gain state that is too sensitive to fluorescent light sources at a particular physical location on a jobsite;

(b) if said gain state is too sensitive at step (a), then iteratively setting said gain state to a lower operating range until said laser light receiver is no longer too sensitive to fluorescent light sources; and

(c) continuing to operate said laser light receiver at said gain state of the lowered operating range.

22. A laser light receiver, comprising:

a processing circuit, at least one photosensor, a variable sensitivity control circuit, and at least one optical filter;

wherein;

(a) said at least one optical filter exhibits an optical characteristic so as to allow only wavelengths of electromagnetic energy at predetermined transmittance characteristics to pass therethrough to impact upon said at least one photosensor;

(b) said at least one photosensor exhibits a frequency sensitivity characteristic so as to be sufficiently sensitive to electromagnetic energy at predetermined frequency response characteristics; and

said at least one photosensor, after receiving a sufficient amount of electromagnetic energy that impacts thereon, outputs at least one first signal to said variable sensitivity control circuit, which modifies said at least one first signal to produce at least one second signal, and outputs said at least one second signal to said processing circuit;

(c) a combination of;

(i) said predetermined transmittance characteristics of said at least one optical filter;

(ii) said predetermined frequency response characteristics of said at least one photosensor; and

(iii) amplification characteristics of said variable sensitivity control circuit, produces an overall operating sensitivity characteristic at various wavelengths of received electromagnetic energy, such that said laser light receiver exhibits an overall operating sensitivity characteristic at green visible light wavelengths that is substantially reduced compared to an overall operating sensitivity characteristic at infrared light wavelengths, while still effectively detecting electromagnetic energy in all three wavelength ranges of;

green visible light, red visible light, and infrared light; and

(d) said laser light receiver is configured;

(i) to evaluate said at least one second signal and, based upon a value of said at least one second signal, to determine a relative elevation of said at least one photosensor with respect to said received electromagnetic energy that impacts thereon for all three wavelength ranges of;

green visible light, red visible light, and infrared light of said received electromagnetic energy, and (ii) to output a third signal to provide an indication of said determined relative elevation.

23. The laser light receiver of claim 22, wherein said overall operating sensitivity characteristic at green visible light wavelengths is in the range of about 10-50% of said overall operating sensitivity characteristic at infrared light wavelengths.

24. The laser light receiver of claim 23, wherein:

(a) said overall operating sensitivity characteristic at green visible light wavelengths is about 20% of said overall operating sensitivity characteristic at infrared light wavelengths; and

(b) said overall operating sensitivity characteristic at red visible light wavelengths is at least about 50% of said overall operating sensitivity characteristic at infrared light wavelengths.