Method and apparatus for detecting innovations in a scene

• US 4,931,868 A
• Filed: 05/31/1988
• Issued: 06/05/1990
• Est. Priority Date: 05/31/1988
• Status: Expired due to Fees

• Current Assignee: Grumman Aerospace Corporation (Northrop Grumman Corporation)
• Original Assignee: Grumman Aerospace Corporation (Northrop Grumman Corporation)
• Inventors: Kadar, Ivan
• Primary Examiner(s): Groody, James J.
• Assistant Examiner(s): Kostak, Victor R.
• Application Number:
  US07/200,605
• Time in Patent Office: 735 Days
• Field of Search: 358/125, 358/135, 358/136, 358/126, 358/125, 364/518, 364/521, 364/554
• US Class Current: 348/155
• CPC Class Codes: G06E 3/005 using electro-optical or opto-electronic means
• CPC Class Codes: G08B 13/19602 Image analysis to detect motion of the intruder, e.g. by frame subtraction
• CPC Class Codes: G08B 13/19634 Electrical details of the system, e.g. component blocks for carrying out specific functions

Abstract

A method and apparatus for detecting innovations in a scene in an image of the type having a large array of pixels. The method comprises the step of generating a multitude of parallel signals representing the amount of light incident on a group of adjacent pixels (masks) and these signals may be considered as forming a n by one vector, Z, where n equals the number of pixels in the masks. L such groups of adjacent pixels or elementary masks are used to geometrically cover the entire image in parallel. The method further comprises the step of replicating the generating step a multitude of times to generate a multitude of Z vectors by taking multiple frames of observations of the image (scene). These Z vectors may be represented in the form A_k, where k equals 1,2,3, . . . , m, where m equals the number of replicates. Each of the Z_k vectors are related to a vector β_k of three parameters by a measurement equation in a linear model framework, i.e. Z_k =Dβ_k +e_k, where e_k is an additive noise term. In one embodiment, a solution of the linear model yields the best estimates of the parameters β_k =D^t Z_k, where D^T is a three by four matrix, β_k is a three by one vector, and Z_k is a four by one vector of the measurements. β_k includes three components u_k, A_k and β_k. The values of u_k, A_k, and B_k are monitored over time, and a signal is generated whenever any one of these variables rises above a respective preset level.

Claims

1. A method for detecting innovations in a scene comprising an array of pixels, the method comprising the steps of:

generating at each of a multitude of times, a set of input signals representing the amount of light incident on a group of adjacent pixels, each set of input signals forming an n by one vector, where n equals the number of signals in the set, the sets of input signals being represented by Z_k, where k=1, 2, 3, . . . , m, and m equals the number of said input sets;

conducting the sets of input signals to a processing network;

the processing network transforming each set of input signals to a respective one set of output signals, the sets of output signals being represented by β

_k, wherein Z_k and Z_k satisfy the relation Z_k =Dβ

_k +e_k , where D is an at least four by an at least three matrix, and e_k represents noise in the set of signals Z_k ;

conducting the sets of output signals to a detection means; and

the detection means,

(i) sensing the magnitude of at least one signal of each set of output signals, and

(ii) generating a detection signal to indicate a change in the scene when said one signal rises above a respective one preset level.

2. A method according to claim 1 wherein the group of pixels form a rectangle in the scene.

3. A method according to claim 2, wherein:

the group of adjacent pixels includes four pixels; and

##EQU15##

4. A method according to claim 3, wherein the group of pixels form a square in the scene.

5. A method according to claim 1, wherein the transforming step includes the step of obtaining an approximation of β

_k, given by the symbol β

_k, by means of the equation;

space="preserve" listing-type="equation">β

.sub.k =D.sup.t Z.sub.k

where D^T is the transpose of D.

6. A method according to claim 1, wherein the transforming step includes the step of obtaining an approximation of β

_k, given by the symbol β

_k, by means of the equation;

##EQU16## where A is an at least three by at least three matrix, and D^T is the transpose of D.

7. A method according to claim 6, where ##EQU17##

8. A method according to claim 1, wherein the obtaining step includes the step of obtaining an approximation of β

_k, given by the symbol β

_k, by means of the equation;

##EQU18## where, q_i D^T [Z_k+1 -Dβ

_k ],

W^b is a data dependent noise attentuation factor derived from two groups of data samples, each sample having b data values,

i=1, 2, 3 . . . b,

k¹ =b(k-1)

A is an at least three by an at least three gain matrix.

9. Apparatus according to claim 1, wherein the group of pixels form a rectangle in the scene.

10. Apparatus according to claim 9, wherein:

the group of adjacent pixels includes four pixels; and

##EQU19##

11. Apparatus according to claim 10, wherein the group of pixels form a square in the scene.

12. Apparatus according to claim 1, wherein:

the source means includes voltage generating means to generate voltage potentials representing the amount of light incident on the pixels; and

the processing network is connected to the voltage generating means to receive the voltage potentials therefrom, and to generate from each group of voltage potentials, Z_k, at least one output signal representing the β

_k vector associated with said Z_k vector.

13. Apparatus according to claim 12, wherein:

the processing network includes first, second, third and fourth input means;

first, second and third voltage inverters; and

first, second and third summing devices;

the voltage generating means generates first, second, third and fourth voltage signals representing the amount of light incident on first, second, third and fourth of the pixels respectively;

the first, second, third and fourth input means of the processing network are connected to the voltage generating means, respectively, to receive the first, second, third and fourth electric voltage potentials from the voltage generating means;

the first inverter is connected to the second input means to generate a first internal voltage signal having a polarity opposite to the polarity of the second input means;

the second inverter is connected to the third input means to generate a second internal voltage signal having a polarity opposite to the polarity of the third input means;

the third inverter is connected to the fourth input means to generate a third internal voltage signal having a polarity opposite to the polarity of the fourth input means;

the first summing means is connected to the first, second, third and fourth input means and generates an output signal having a voltage equal to the sum of the voltages of

the first, second, third and fourth input means;

the second summing means is connected to the first and second input means and to the second and third inverters to generate an output signal having a voltage equal to the sum of the voltages of the first and second input means and the second and third inverters; and

the third summing means is connected to the first and third input means and the first and third inverters to generate an output signal having a voltage equal to the sum of the voltages of the first and third input means and the first and third inverters.

14. A method according to claim 1, wherein the input signals representing the amount of light on the pixels are electric voltage signals.

15. A method according to claim 14, wherein:

the step of generating the signals representing the amount of light incident on the group of pixels includes the step of, for each set of input signals, generating at least first, second, third and fourth electric voltage signals respectively representing the amount of light incident on at least first, second, third and fourth of the group of pixels;

the transforming step includes the steps of, for each set of input signals conducted to the processing network,

(i) summing the first, second, third and fourth voltage signals, and generating a first output signal proportional to the sum of said first, second, third and fourth voltage signals,

(ii) summing the first and second voltage signals and the negatives of the third and fourth voltage signals, and generating a second output signal proportional to the sum of said first and second voltage signals and the negatives of the third and fourth voltage signals, and

(iii) summing the first and third voltage signals and the negatives of the second and fourth voltage signals, and generating a third output signal proportional to the sum of the first and third voltage signals and the negatives of the second and fourth voltage signals; and

the sensing step includes the step of sensing the magnitude of one of the first, second and third output signals of each set of output signals.

16. A method according to claim 15, wherein the network includes first, second, third and fourth input means;

first, second and third voltage inverters, and first, second and third summing devices, and wherein;

the conducting step includes the steps of applying the first, second, third and fourth voltage signals respectively to the first, second, third and fourth input means of the network;

the transforming step further includes the steps of

(i) applying the voltage of the second input means to the first inverter to generate a first internal voltage signal having a polarity opposite to the polarity of the second input means,

(ii) applying the voltage of the third input means to the second inverter to generate a second internal voltage signal having a polarity opposite to the polarity of the third input means, and

(iii) applying the voltage of the fourth input means to the third inverter to generate a third internal voltage signal having a polarity opposite to the polarity of the fourth input means;

the step of summing the first, second, third and fourth voltage signals includes the step of applying to the first summing device, the voltages of the first, second, third and fourth input means;

the step of summing the first and second voltage signals and the negatives of the third and fourth voltage signals includes the step of applying to the second summing device, the voltages of the first and second input means and the voltages of the second and third internal voltage signals; and

the step of summing the first and third voltage signals and the negatives of the second and fourth voltage signals includes the step of applying to the third summing device the voltages of the first and third input means and the voltages of the second and third internal voltage signals.

17. A method according to claim 1, wherein:

each set of output signals includes first, second and third output signals;

the first output signals of the sets of output signals rise above a given value when an object moves across the scene in a given direction;

the sensing step includes the step of sensing the first output signal of each set of output signals; and

the step of generating the detection signal includes the step of generating the detection signal when the first output signal rises above the given value to indicate motion of the object across the scene in the given direction.

18. A method according to claim 1, wherein:

each set of output signals include first, second and third output signals;

the first, second and third output signals each rise above a respective given value when an object moves across the scene in a given direction;

the sensing step includes the step of sensing the first, second and third output signals of each set of output signals; and

the step of generating the detection signal includes the step of generating the detection signal when all of the first, second and third output signals rise above the respective given values to indicate motion of the object across the scene in the given direction.

19. Apparatus for detecting innovations in a scene including an array of pixels, the apparatus comprising:

source means to generate at each of a multitude of times, a set of input signals representing the amount of light incident on a set of adjacent pixels, each set of input signals forming an n by one vector, where n equals the number of signals in the set, the sets of input signals being represented by Z_k, where k=1, 2, 3, . . . , m, and m equals the number of said input sets;

a processing network coupled to said source means to receive said sets of input signals therefrom, and to transform each set of input signals to a respective one set of output signals, the sets of output signals being represented by β

_k, wherein Z_k and β

_k satisfy the relation Z_k =Dβ

_k +e_k, where D is an at least four by an at least three matrix, and e_k represents noise in the set of signals Z_k ; and

detection means coupled to said processing network to receive said sets of output signals therefrom, to sense the magnitude of at least one signal of each set of output signals, and to generate a detection signal to indicate a change in the scene when said one signal rises above a respective one present level.