US 5,117,119 A · Auto-ranging film densitometer

Abstract

A film densitometer for generating digital density values as a function of analog transmittance signals received at an input. A comparator coupled to the input compares the transmittance signals to one or more range references characterizing a plurality of ranges of transmittance signal magnitudes, and provides digital transmittance range signals as a function of the comparison. An amplifier amplifies the transmittance signals to provide amplified transmittance base signals. A gain control circuit coupled to the amplifier and the comparator controls the gain factor of the amplifier as a function of the magnitudes of the transmittance signals. The amplified transmittance base signals are converted to digital transmittance base values by an analog-to-digital converter. A lookup table of data characterizing the logarithmic relationship between transmittance base values and density base values is stored in base memory. A lookup table of data characterizing the relationship between the transmittance range signals and range gain values is stored in range memory. A digital processor accesses the memory as a function of the transmittance base values and transmittance range signals, and generates the digital density values as a function of a sum of the density base values and range gain values.

Claims13

Dependent claims

A film densitometer, including:

an input for receiving analog transmittance signals;
an analog amplifier coupled to the input for amplifying the transmittance signals and providing amplified transmittance base signals;
a range detector circuit coupled to the input for providing digital transmittance range signals characterizing the magnitudes of the analog transmittance signals as being within one of a plurality of ranges;
a gain control circuit coupled to the amplifier and range detector circuit for controlling the gain of the amplifier as a function of the magnitudes of the transmittance signals;
an analog-to-digital converter coupled to the amplifier for converting the amplified transmittance base signals to digital transmittance base values;
and
digital processing circuitry coupled to the converter and the range detector circuit for generating digital density value signals as a logarithmic function of the transmittance base values and the transmittance range signals.

4 more elements

A film densitometer including:

an input for receiving analog transmittance signals;
a comparator coupled to the input for comparing the transmittance signals to one or more range references characterizing a plurality of ranges of transmittance signal magnitudes, and for providing digital transmittance range values as a function of the comparison;
an analog amplifier coupled to the input for amplifying the transmittance signals and providing amplified transmittance base signals;
an amplifier gain control circuit coupled to the amplifier and comparator, for controlling the gain factor of the amplifier as a function of the magnitudes of the transmittance signals;
an analog-to-digital converter coupled to the amplifier for converting the amplified transmittance base signals to digital transmittance base values;
base memory for storing data characterizing a logarithmic relationship between transmittance base values and density base values;
range memory for storing data characterizing a relationship between transmittance range values and density range gain values;
and
a processor coupled to the comparator, amplifier, base memory and range memory, for accessing the base memory and range memory as a function of the transmittance base values and transmittance range values, and for generating digital density values as a function of a sum of the density base values and the density range gain values.

6 more elements

Dependencies are inferred from the claim text.

Auto-ranging film densitometer

Life of this patent

Auto-ranging film densitometer

Life of this patent

Abstract

Claims13