Patent ID: 7375813

Claim:
A system for measuring light absorption levels for a liquid for use in a ink jet printing system, wherein the system comprises: a. a light source adapted to provide a divergent beam of light; b. a container adapted to receive a liquid, wherein the liquid has a light absorption level; c. a hole in the container to provide access to the liquid, wherein the hole is capable of focusing light reflected back from the liquid in the container and through the hole; d. a prism disposed over the hole to split the divergent beam of light into a reference beam and a measurement beam before the light can pass through the hole to the liquid, wherein the reference beam has a reference beam intensity and does not pass through the hole to the liquid, wherein a portion of the measurement beam does pass through the hole to the liquid, is reflected back from the liquid and through the hole into the prism, and is focused by the hole to form a focused beam of light that is reflected via the prism and has a focused beam intensity; e. a measurement detector adapted to measure the focused beam intensity, wherein the measurement detector produces a liquid measurement signal, wherein the liquid measurement signal is inversely related to the light absorption level of the liquid; f. a reference detector adapted to measure the reference beam intensity forming a reference signal; and g. a device adapted to receive the liquid measurement signal and the reference signal, wherein the device computes a ratio of the liquid measurement signal to the reference signal to determine a signal ratio, wherein the signal ratio is inversely related to the light absorption level of the liquid.