Method and system for diffusion attenuated total reflection based concentration sensing

• US 20060087654A1
• Filed: 10/21/2004
• Published: 04/27/2006
• Est. Priority Date: 10/21/2004
• Status: Active Grant

• Current Assignee: Eastman Kodak Company
• Original Assignee: Eastman Kodak Company
• Inventors: Kauffman, Robert E., Wolf, James D.
• Granted Patent: US 7,375,813 B2
• Time in Patent Office: Days
• US Class Current: 356/436
• CPC Class Codes: G01N 21/43 by measuring critical angle
• CPC Class Codes: G01N 21/552 Attenuated total reflection

Abstract

A system for measuring light absorption levels for a liquid for use in a printing system includes a light source adapted to provide a divergent beam of light, a liquid container with a hole that acts as a focusing lens, and a prism disposed over the hole to split the divergent beam of light into a reference beam and a measurement beam. The systems include a measurement detector to measure the intensity of the focused beam to produce a liquid measurement signal. A reference detector measures the intensity of the reference beam for compensating the effects of temperature and light source variations on the system signals. A device calculates signal ratios and stores the ratios so that the signal ratios of subsequent colored liquids can be converted into colorant concentrations from a look-up table or through calculations using a signal ratio/colorant concentration.

Claims

1. 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 comprises a light absorption level;

c. a hole in the container to provide access to the liquid, wherein the hole acts as a focusing lens;

d. a prism disposed over the hole to split the divergent beam of light into a reference beam and a measurement beam, wherein the reference beam comprises a reference beam intensity, wherein a portion of the measurement beam passes through the hole to the liquid, is reflected back from the liquid, and is focused by the hole forming a focused beam comprising 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.

2. The system of claim 1, further comprising a look-up table for comparing the signal ratio to the look-up table to obtain a concentration of colorant in the liquid.

3. The system of claim 2, wherein the look-up table is derived from measurements with the system using a colorless liquid, a liquid with a known colorant concentration, or a toner with a known colorant concentration.

4. The system of claim 1, further comprising a signal ratio/colorant concentration factor to calculate the concentration of the colorant in the liquid.

5. The system of claim 4, wherein the signal ratio/colorant concentration factor is derived from measurements with the system using a colorless liquid, a liquid with a known colorant concentration, or a toner with a known colorant concentration.

6. The system of claim 1, further comprising a seal between the prism and the container.

7. The system of claim 6, wherein the seal is a member of the group consisting of an adhesive, an o-ring, and a gasket.

8. The system of claim 7, wherein the o-ring is an elastomeric o-ring.

9. The system of claim 1, wherein the light source is a visible light emitting diode (LED).

10. The device of claim 9, wherein the LED is a member of the group consisting of red LED, a blue LED, a green LED, an amber LED, and a multiple color LED.

11. The system of claim 1, wherein the light source is a member of the group consisting of a laser diode, a light bulb, and a tungsten filament.

12. The system of claim 1, wherein the container is adapted to flow liquid at a flow rate ranging between 0.1 liters per minute and 10 liters per minute.

13. The system of claim 12, wherein the container is adapted to flow liquid at a flow rate between 0.1 liters per minute and 1 liters per minute.

14. The system of claim 1, wherein the container adapted for batch measurement of a static liquid.

15. The system of claim 1, wherein the container further comprises:

h. a first channel adapted to receive a first liquid;

i. a second channel adapted to receive a second liquid;

j. a first hole adapted to reflect and focus the light for the first liquid; and

k. a second hole adapted to reflect and focus the light for the second liquid.

16. The system of claim 1, further comprising a coating on the container located where the container contacts the prism.

17. The system of claim 1, wherein the prism is a quartz prism or a glass prism.

18. The system of claim 1, wherein the prism is disposed on a side of the container to insure air bubbles rise away from the measurement beam.

19. The system of claim 1, wherein the measurement detector is a light sensor.

20. The system of claim 1, further comprising a pump adapted to flow liquid through the container.

23. The method of claim 19, further comprising the step of comparing the light absorption level of the second liquid to a signal ratio/colorant concentration factor to determine the concentration of the colorant in the second liquid.

24. The method of claim 21 The method of claim 19, wherein the first liquid is a replenisher or colorless liquid and the second liquid is ink or toner.

21. A method for measuring light absorption levels of a liquid to control colorant concentration of the liquid for use in an ink jet printing system, wherein the method comprises the steps of:

l. disposing a first liquid into a container comprising a hole and a prism disposed over the hole;

m. projecting a divergent beam of light from a light source onto the prism;

n. reflecting a first portion of the divergent beam from the prism to a reference detector to measure divergent beam intensity and obtaining a first reference signal;

o. passing a second portion of the divergent beam through the prism and through the hole onto the first liquid, reflecting and focusing the second portion from the first liquid to a measurement detector, and obtaining a first liquid measurement signal;

p. computing a first signal ratio based on the first liquid measurement signal and the first reference signal, wherein the first signal ratio inversely relates to the light absorption level of the first liquid;

q. flowing sequentially a second liquid into the container;

r. projecting the divergent beam of light from the light source onto the prism;

s. reflecting the first portion of the divergent beam from the prism to the reference detector to measure divergent beam intensity and obtain a second liquid reference signal;

t. passing the second portion of the divergent beam through the prism and through the hole onto the second liquid, reflecting and focusing the second portion from the second liquid to the measurement detector to obtain a second liquid measurement signal;

u. computing a second signal ratio based on the second liquid measurement signal and the second reference signal, wherein the second signal ratio inversely relates to the light absorption level of the second liquid; and

v. compare the signal ratio of the first liquid to the signal ratio of the second liquid to determine the light absorption value of the second liquid relative to the first liquid.

22. The method of claim 21, further comprising the step of comparing the light absorption level of the second liquid to a look-up table to determine the concentration of the colorant in the second liquid.

25. The method of claim 21, wherein the method is a batch method for measurement.

26. A method for measuring light absorption levels simultaneously of a first liquid and a second liquid to control colorant concentration of the second liquid for use in an ink jet printing system comprising the steps of:

w. flowing first liquid into a first channel of a container wherein the first channel has a first hole and a prism disposed over the first hole;

x. projecting a divergent beam of light from a light source onto the prism;

y. reflecting a first portion of the divergent beam from the prism to a reference detector to measure intensity of the divergent beam and obtain a reference signal;

z. passing a second portion of the divergent beam through the prism through the first hole onto the first liquid and reflecting and focusing a portion from the first liquid to a first measurement detector to obtain a first liquid measurement signal;

aa. simultaneously with the flowing of the first liquid into the first container, flowing a second liquid into a second channel in the container, wherein the second channel has a second hole and the prism is also disposed over the second hole;

bb. passing a third portion of the divergent beam through the prism and through the second hole onto the second liquid and reflecting and focusing a portion from the second liquid of known colorant concentration to a second measurement detector to obtain a second liquid measurement signal;

cc. computing a first signal ratio, which is inversely related to the light absorption level of the first liquid, using the reference signal and the first light measurement signal;

dd. computing a second signal ratio, which is inversely related to the light absorption level of the second liquid, using the reference signal and the second light measurement signal; and

ee. comparing the first signal ratio and the second signal ratio to determine the colorant concentration of the first liquid based on the colorant concentration of the first liquid.

27. The method of claim 26, further comprising the step of comparing the light absorption value of the second liquid to a look-up table to determine the concentration of the colorant in the second liquid.

28. The method of claim 26, wherein the second liquid is ink or toner.

29. The method of claim 26, wherein the method is a batch method for measurement.