Dynamic shading compensation for IR tracking system

DETAILED DESCRIPTION OF THE INVENTION A conventional IR tracking system is commonly known as a FLIR system.
This type of system is typically fabricated with a common module which incorporates a number of IR electronic components.
Such a module is generally indicated by reference numeral 10 in FIG.
1.
The module includes a scanner mirror 12 which is driven between two angular positions indicated by reference numerals 14 and 16.
A reflected scene impinges upon an IR sensor array 18 which converts the infrared sensed scene to an electronic signal which is amplified by preamps 20.
An electrical light feedback circuit is created when the signal from preamps 20 is fed to postamps 22 which further amplify the electrical signal for driving an array of LEDs 24.
The array then simulates the IR detected scene and projects an LED image, represented by rays 26 and 28, to a back surface 30 of scanner mirror 12.
The LED image is reflected from mirror 12 to a vidicon 36, as represented by reflection rays 32 and 34.
Thus far described, the IR detected scene has been translated to an LED image and then converted to a vidicon electrical output.
This output undergoes processing by a video processor 38 having a first indicated output containing composite video which is displayed on a CRT.
The second output of the video processor 38 is fed to an automatic gain circuit 40 which has its output connected to a gain control input of the postamps 22.
In order to achieve the dynamic shading compensation of the present invention, a compensation circuit 44, to be discussed in greater detail hereinafter, generates an output connected to a level control input terminal 42 of the postamps 22.
FIG.
2 illustrates the inventive compensation circuit in block diagram form.
A triangular function signal is derived from the drive (not shown) of the prior art scanner mirror 12 (FIG.
1).
This signal represents the scan position signal and serves as an input to amp network 46.
The output 48 of this network develops an amplified triangular signal which serves as a first primary compensating signal transferred along line 50 to components which will be discussed hereinafter