Device for compensating a derived signal

Claim 2

Apparatus for linearizing a second derived signal over a range of values relative to a final function for undesired deviation in said second derived signal caused by an undesired signal component of substantially constant amplitude in a first measured signal from which said second signal is derived according to a first logarithmic relationship, comprising: means for establishing an onset value of said first measured signal, at which compensation of said second derived signal is desired for values of said first measured signal departing in one direction of magnitude from said onset value, said undesired constant amplitude component causing a specific percentage error at said onset value; means for forming a correction signal varying as a second mathematical function of said first measured signal for values thereof different from said onset value in said one direction, said correction signal being zero for values of said first measured signal both at and departing from said onset value in the other direction of magnitude, and said correction signal when algebraically added to said undesired signal component in said first measured signal causing the resultant to be proportional to said first signal free of said constant undesired signal component; and means for algebraically combining said correction signal and said first measured signal, whereby said second derived signal is linearized relative to said final function over a range of values corresponding to said first measured signal departing from said onset value in said one direction, without affecting said second derived signal for other values corresponding to said first measured signal at and departing from said onset value in said other direction of magnitude, thereby avoiding any need to eliminate any over-compensation of such other values of said second derived signal.

Claim 3

Apparatus for compensating a second derived signal over a range of values for undesired deviation in said second derived signal caused by an undesired signal component in a first measured signal from which said second signal is derived according to a first mathematical relationship said undesired signal component being of substantially constant amplitude, so that the relative percentage error caused thereby in said first measured signal is inversely proportional to the value of said first measured signal, comprising: means for establishing an onset value of said first measured signal, at which compensation of said second derived signal is desired for values of said first measured signal, departing in one direction of magnitude from said onset value, said onset value being a particular value of said first measured signal, so that said constant amplitude component causes a specific percentage error at said onset value; means for forming a correction signal varying as a second mathematical function of said first measured signal for values thereof different from said onset value in said one direction, said correction signal being zero for values of said first measured signal both at and departing from said onset value in the other direction of magnitude; said forming means comprising means for generating, for values of said first measured signal less than said onset value, a correction signal equal to the amount said first measured signal falls below said onset value multiplied by a proportionality factor; said forming means further comprising mEans for setting said proportionality factor to such value that the difference between the absolute value of said correction signal and the absolute value of said constant undesired signal component is proportional to said first signal free of said constant undesired signal component; and means for algebraically combining said correction signal and said first measured signal; said algebraic combining means effectively subtracting said absolute values of said correction signal from the absolute value of said constant amplitude undesired signal component in said first measured signal, whereby the resulting compensated first signal is made at least proportional to the first signal free of said constant undesired signal component, so that said second derived signal is compensated over a range of values corresponding to said first measured signal departing from said onset value in said one direction, without affecting said second derived signal for other values corresponding to said first measured signal at and departing from said onset value in said other direction magnitude, thereby avoiding any need to eliminate any over-compensation of such other values of said second derived signal.

Claim 4

Apparatus for compensating a second derived signal over a range of values for undesired deviation in said second derived signal caused by an undesired signal component in a first measured signal from which said second signal is derived according to a first mathematical relationship said undesired signal component being of substantially constant amplitude, so that the relative percentage error caused thereby in said first measured signal is inversely proportional to the value of said first measured signal, comprising: means for establishing an onset value of said first measured signal, at which compensation of said second derived signal is desired for values of said first measured signal, departing in one direction of magnitude from said onset value, said onset value being a particular value of said first measured signal, so that said constant amplitude component causes a specific percentage error at said onset value; means for forming a correction signal varying as a second mathematical function of said first measured signal for values thereof different from said onset value in said one direction, said correction signal being zero for values of said first measured signal both at and departing from said onset value in the other direction of magnitude; said forming means comprising means for generating, for values of said first measured signal less than said onset value, a correction signal equal to the amount said first measured signal falls below said onset value multiplied by a proportionality factor; said forming means further comprising mEans for setting said proportionality factor to such value that the difference between the absolute value of said correction signal and the absolute value of said constant undesired signal component is proportional to said first signal free of said constant undesired signal component; and means for algebraically combining said correction signal and said first measured signal; said algebraic combining means effectively subtracting said absolute values of said correction signal from the absolute value of said constant amplitude undesired signal component in said first measured signal, whereby the resulting compensated first signal is made at least proportional to the first signal free of said constant undesired signal component, so that said second derived signal is compensated over a range of values corresponding to said first measured signal departing from said onset value in said one direction, without affecting said second derived signal for other values corresponding to said first measured signal at and departing from said onset value in said other direction magnitude, thereby avoiding any need to eliminate any over-compensation of such other values of said second derived signal.

Claim 5

Apparatus according to claim 2, in which: said forming means comprises a unidirectional amplifier means for generating a departure signal proportional to the extent said first measured signal departs in said one direction of magnitude from said onset value.

Claim 6

Apparatus according to claim 3, in which: said forming means further comprises a variable amplifier means for multiplying said departure signal by said proportionality factor.

Claim 7

Apparatus according to claim 2, in which: said first mathematical relationship is such that said second derived signal would be a straight line if said first measured signal were completely free of said constant amplitude undesired signal component, said second signal derived from said compensated first signal thereby being also a straight line.

Claim 8

Apparatus according to claim 2, in which: said constant amplitude undesired signal component is positive so as to increase said first measured signal; said correction signal is negative; and said algebraic combining means algebraically adds said correction signal to said first measured signal.

Claim 9

Apparatus according to claim 2, in which: said first mathematical relationship is a logarithmic relation and said second derived signal would be a straight line if said first measured signal were completely free of said constant amplitude undesired signal component, said signal derived from said compensated first signal thereby being also a straight line.

Claim 10

Apparatus according to claim 7, in which: said second derived signal is apparent absorbance Am, and the first measured signal is apparent transmission Im of radiant energy by a material; the first mathematical relationship is Am log Io-log Im, where Io is the intensity of the radiant energy incident on the material; said first apparent transmission signal Im is equal to the actual transmission, I, plus the undesired stray radiation signal component, S; and said correction signal compensates the original apparent transmission signal, Im I+S, to a compensated transmission signal I''m which is proportional to the actual transmission, I, of said material.