Single charge-coupled-device camera for detection and differentiation of desired objects from undesired objects

• US 5,661,817 A
• Filed: 07/21/1995
• Issued: 08/26/1997
• Est. Priority Date: 07/21/1995
• Status: Expired due to Fees

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Inventors: Hatlestad, John David, Sauter, Gerald Francis
• Primary Examiner(s): Boudreau, Leo
• Assistant Examiner(s): SHALWALA, BIPIN H
• Application Number:
  US08/505,550
• Time in Patent Office: 767 Days
• Field of Search: 382/110, 382/162-165, 348/33, 348/34, 348/144, 348/164, 348/290, 348/291, 348/266, 348/143, 348/148, 348/273
• US Class Current: 382/110
• CPC Class Codes: G06V 10/143 Sensing or illuminating at different wavelengths
• CPC Class Codes: G06V 20/188 Vegetation
• CPC Class Codes: H04N 23/11 for generating image signals from visible and infrared light wavelengths
• CPC Class Codes: H04N 5/33 Transforming infrared radiation cameras or camera modules for generating image signals from infrared radiation H04N23/20; circuitry of SSIS for transforming infrared radiation into image signals H04N25/20

Abstract

A conventional color charge-coupled-device (CCD) camera without a near infrared blocking filter is used to detect desired vegetation from undesired vegetation and other background. This detection technique relies on the fact that near-infrared (NIR) wavelengths are received by CCD cameras in predetermined frequency bands. This provides output signals from the green and blue pixels of the CCD camera which are approximately equal in interests to the intensity of the infrared portion of the signal provided by the red pixels. A filter is placed between a target area and the CCD camera to restrict the light received by the camera to a bandwidth (approximately from wavelengths of 600-1400 nm), which allows the NIR signal component of the green or blue pixels in this bandwidth to be compared by a signal processing device to the NIR plus R output of the red pixels. In this bandwidth the intensity of the output from the red pixels due to red light from the target area is maximized. Therefore, a signal processing device can utilize signals from the red, green and blue pixels to detect plants and crops in an area of undesired vegetation.

Claims

1. A method of detecting objects in a target area which is illuminated by a light source which causes light reflection from the target area comprising:

a) examining red, green and blue pixel group responses of a color CCD camera which is constructed without a filter to block near infrared light from impinging on said pixel groups in order to determine a bandwidth of wavelengths over which the red pixel group provides a red (R) response which peaks in said bandwidth and a near infrared (NIR) response, wherein the CCD is constructed so that at least one of said green and blue pixel groups provides a response in said bandwidth which is approximately equal to said predetermined NIR response of said red pixel group,

b) placing a filter between said target area and said CCD camera which limits the light from said target area that impinges on said pixel groups to approximately said bandwidth,

c) developing signals in said CCD camera such that a first signal which is representative of the response of said red pixel group and a second signal is representative of the response of said at least one of said green or blue pixel groups,

d) subtracting said second signal from said first signal to provide an R signal, and

e) utilizing combinations of said R signal and said second signal to identify objects in said target area.

2. A sensing system for detecting objects in a target area which is illuminated by a light source which causes light reflection from the target area comprising:

a) a CCD camera comprising an image area comprising red, green and blue light-responsive pixel groups which is not constructed to block near infrared light from impinging on said pixel groups and which is capable of transmitting a red output signal representative of said red pixel group and at least a green or blue output signal which if provided are representative of the NIR response of said associated green or blue pixel groups such that said red pixel group provides a red (R) response which peaks in said bandwidth and a near infrared (NIR) response, and said CCD camera is constructed so that at least one of said green and blue pixel groups provides a response which is approximately equal to said NIR response of said red pixel group,

b) a filter positioned between said target area and said CCD camera which limits the light from said target area that impinges on said pixel groups to a bandwidth of wavelengths such that said red pixel group provides a red (R) response which peaks in said bandwidth and a near infrared (NIR) response, and said CCD camera is constructed so that at least one of said green and blue pixel groups provides a response which is approximately equal to said NIR response of said red pixel group, and

c) signal processing means coupled to said CCD camera to provide a first output signal representative of the response of said red pixel group and a second signal representative of the response of said at least one of said green or blue pixel groups, comprising means for subtracting said second signal from said first signal to provide an R signal and to provide combinations of said R signal and said second signal to identify objects in said target area.