System for identifying flat orthogonal objects using reflected energy signals

• US 5,424,823 A
• Filed: 08/17/1993
• Issued: 06/13/1995
• Est. Priority Date: 08/17/1993
• Status: Expired due to Term

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: Loral Vought Systems Corporation (Martin Marietta Corporation)
• Inventors: Bornowski, Arthur S., Nettles, James L.
• Primary Examiner(s): Buczinski, Stephen C.
• Application Number:
  US08/107,957
• Time in Patent Office: 665 Days
• Field of Search: 356/371, 356/5, 382/27, 382/1, 348/128
• US Class Current: 356/5.01
• CPC Class Codes: G01S 17/89 for mapping or imaging
• CPC Class Codes: G01S 7/4802 using analysis of echo signal for target characterisation; Target signature; Target cross-section

Abstract

An improved system for using reflected energy signals sensed by light detecting optics to identify flat surfaces that are orthogonal to the detecting optics. A light source generates a laser light beam, the beam is scanned across a target scene, and a reflected signal is sensed by light detecting optics to produce an electrical representation of the reflected signal. The representation is stored in an array in the form of a plurality of data elements. The data elements are sequentially analyzed by comparing the range of each data element with the ranges of a selected number of neighboring elements, and giving the data element under analysis a corresponding "index." Data elements whose ranges closely match neighboring data elements are assigned higher indices. Neighboring data elements with high indices therefore signify proximate points on a flat surface, which is orthogonal to the detecting optics. The data elements may be further analyzed by distinguishing elements with higher indices from those with lower indices, to highlight the flatter, more orthogonal surfaces.

Claims

1. A method of identifying flat orthogonal surfaces, comprising steps of:

(a) transmitting energy signals toward a target scene;

(b) detecting energy signals reflected from the target scene using light detecting optics;

(c) using the detected energy signals to determine ranges between the light detecting optics and a plurality of points in the target scene;

(d) storing the ranges in a plurality of data elements of a first memory array; and

(e) sequentially processing the data elements by, for each data element under analysis, performing steps comprising;

(1) comparing the range of a data element under analysis to the ranges of a selected number of neighboring data elements; and

(2) for each neighboring data element having a range within a predetermined threshold of the data element under analysis, incrementing an index corresponding to the data element under analysis.

2. The method of claim 1, wherein step (e)(1) comprises steps of comparing the range of a data element under analysis to the ranges of a group of neighboring data elements representing a region in the target scene have a selected size.

3. The method of claim 1, further comprising steps of creating a second memory array that includes a plurality of data elements corresponding to the indices, where each data element of the second array contains a first value if its corresponding index is greater than a selected number, and each data element of the second array contains a second value if its corresponding index is less or equal to the selected number.

4. The method of claim 3, wherein the first value is 1.

5. The method of claim 3, wherein the first value is zero.

6. The method of claim 3, further comprising a step of performing a Connected Components algorithm on the data elements of the second array.

7. The method of claim 1, further comprising steps of storing the indices in a second memory array.

8. The method of claim 1, wherein the range of a data element comprises the distance between the light detecting optics and a point in the target scene represented by the data element.

9. The method of claim 1, wherein the range of a data element comprises the minimum distance between the light detecting optics and a plane passing through a point in the target scene represented by the data element, wherein said plane is normal to a line between the detecting optics and a focus point in the target scene.

10. A method of identifying orthogonal flat surfaces, comprising steps of:

(a) transmitting energy signals toward a target scene;

(b) detecting energy signals reflected from the target scene using light detecting optics;

(c) using the detected energy signals to determine direct-ranges of a plurality of points in the target scene, wherein the direct-range of each point corresponds to the distance between that point and the light detecting optics;

(d) utilizing the direct-ranges to the points to calculate each point'"'"'s normal-range, where the normal-range of each point corresponds to the minimum distance between the light detecting optics and a plane that passes through the point, wherein the plane is orthogonal to a line between the light detecting optics and a focus point in the target scene;

(e) storing the normal-ranges in a plurality of data elements of a memory array; and

(f) sequentially processing the data elements by, for each data element under analysis, performing steps comprising;

(1) comparing the normal-range of a data element under analysis to the normal-ranges of a selected number of neighboring data elements; and

(2) for each neighboring data element having a normal-range within a predetermined threshold of the data element under analysis, incrementing an index corresponding to the data element under analysis.

11. A method of identifying orthogonal flat surfaces, comprising steps of:

(a) transmitting energy signals toward a target scene;

(b) detecting energy signals reflected from the target scene using light detecting optics;

(c) using the detected energy signals to determine normal-ranges of a plurality of points in the target scene, where the normal-range of each point corresponds to the minimum distance between the light detecting optics and a plane that passes through the point, wherein the plane is orthogonal to a line between the light detecting optics and a focus point in the target scene;

(d) storing the normal-ranges in a plurality of data elements of a memory array;

(e) sequentially processing the data elements by, for each data element under analysis, performing steps comprising;

;

(1) comparing the normal-range of a data element under analysis to the normal-ranges of a selected number of neighboring data elements; and

(2) for each neighboring data element having a normal-range within a predetermined threshold of the data element under analysis, incrementing an index corresponding to the data element under analysis.

12. A method of detecting generally flat and orthogonal surfaces in a target scene, comprising steps of:

(a) ranging a target scene with a laser and a detection system to generate a first array of reflected signals, said first array being indicative of ranges and locations of reflection points of the reflected signals in the target scene; and

(b) comparing the ranges of individual reflection points with their neighboring reflection points and assigning an index value to each said individual reflection point, which value is a function of the number of reflection points neighboring the said individual reflection point that have ranges within a preselected threshold value of the range of said individual reflection point.

13. The method of claim 12, further comprising steps of storing the indices in a second array.

14. The method of claim 12, further comprising a step of generating a second array indicative of the locations in the target scene of those individual reflection points having index values of at least a preselected index value.