Sensing of material of construction and color of containers

• US 4,919,534 A
• Filed: 09/30/1988
• Issued: 04/24/1990
• Est. Priority Date: 09/30/1988
• Status: Expired due to Fees

• Current Assignee: Environmental & Medical Products, Ltd.
• Original Assignee: Environmental & Medical Products, Ltd.
• Inventors: Reed, Michael A.
• Primary Examiner(s): Evans, F. L.
• Application Number:
  US07/251,559
• Time in Patent Office: 571 Days
• Field of Search: 356/73, 356/364, 356/366, 356/367, 356/402, 356/406, 356/407, 356/416, 356/419, 356/425, 356/428, 250/223 B, 250/225, 250/226, 209/524, 209/580-582, 209/588
• US Class Current: 356/73
• CPC Class Codes: B07C 5/3416 according to radiation transmissivity, e.g. for light, x-rays, particle radiation detecting hidden objects G01V
• CPC Class Codes: G01N 21/21 Polarisation-affecting properties G01N21/19 takes precedence
• CPC Class Codes: G01N 21/25 Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands

Abstract

An apparatus and process permit the material of construction and the color of transparent and partly transparent containers to be determined rapidly and accurately. To determine the material of construction, polarized light is passed through the container, portions of the transmitted beam are analyzed by parallel and cross polarizers, the intensities of the analyzed beams are measured, and the sum and difference of the analyzed beams are determined. Preferably, the determination is made with at least two wavelengths of polarized light, and the sums and differences of the intensities of the different wavelengths are determined. Glass containers do not alter the polarization of the transmitted light, while many types of plastic containers do alter the polarization, and this difference serves as the basis for the differentiation. The color of the container, whether it be glass or plastic, is determined by calculating a color index as the difference in the transmitted intensity for light of different wavelengths, and this difference, particularly when normalized by the sum of the transmitted intensities, serves as a color index for characterizing the color of the container. An automated apparatus for performing this determination is provided.

Claims

1. Apparatus for analyzing the character of a light transmitting container, comprising:

a container support adapted for supporting a container;

a first source of beam of polarized light of a first wavelength disposed to direct the beam of polarized light through the container supported in the container support;

a second source of a beam of polarized light of a second wavelength disposed to direct the beam of polarized light through the container supported in the container support;

a first light analyzer having

a parallel polarizer relative to the polarization of the light from the first source, the parallel polarizer being disposed to intercept a first portion of the beam from the first source of polarized light after the beam has passed through the container,

a cross polarizer relative to the polarization of the light from the first source, the cross polarizer being disposed to intercept a second portion of the beam from the first source of polarized light after the beam has passed through the container,

a first detector that measures the intensity of a light beam, the first detector being disposed to detect the first portion of the beam from the first source, after the beam has passed through the parallel polarizer, and

a second detector that measures the intensity of a light beam, the second detector being disposed to detect the second portion of the beam from the first source, after the beam has passed through the cross polarizer;

a second light analyzer having

a parallel polarizer relative to the polarization of the light from the second source, the parallel polarizer being disposed to intercept a first portion of the beam from the second source of polarized light after the beam has passed through the container,

a cross polarizer relative to the polarization of the light from the second source, the cross polarizer being disposed to intercept a second portion of the beam from the second source of polarized light after the beam has passed through the container,

a first detector that measures the intensity of a light beam, the first detector being disposed to detect the first portion of the beam from the second source, after the beam has passed through the parallel polarizer, and

a second detector that measures the intensity of a light beam, the second detector being disposed to detect the second portion of the beam from the second source, after the beam has passed through the cross polarizer;

means for analyzing the character of the container using the intensities measured by the first light analyzer and the second light analyzer.

2. The apparatus of claim 1, where the means for analyzing includes

means for determining the sum of the intensities measured by the first detector of the first light analyzer and the first detector of the second light analyzer.

3. The apparatus of claim 1, where the means for analyzing includes

means for determining the difference of the intensities measured by the first detector of the first light analyzer and the first detector of the second light analyzer.

4. The apparatus of claim 1, wherein the first light source and the second light source are disposed so that the beams of light produced by the first light source and the second light source are coincident, and further including

a beam controller that controls the operation of the first light source and the second light source to operate in an alternating fashion.

5. The apparatus of claim 4, wherein the first light analyzer and the second light analyzer are included within a single light analyzer, and further including

a light analyzer controller that controls the operation of the light analyzer so that it performs the functions of the first light analyzer when the beam controller operates the first light source, and performs the functions of the second light analyzer when the beam controller operates the second light source.

6. Apparatus for analyzing the character of a light transmitting container, comprising:

a container support adapted for supporting a container;

a first source of a beam of light of a first wavelength disposed to direct the beam of light through the container supported in the container support;

a second source of a beam of light of a second wavelength disposed to direct the beam of light through the container supported in the container support, the first source and the second source being disposed so that the beam of light of the first wavelength and the beam of light of the second wavelength are at least in part parallel and coincident on a beam path;

a first polarizer disposed in the beam path at a location prior to passage of the beams through the container;

a beam controller that controls the operation of the first light source and the second light source to operate in an alternating fashion.

a light analyzer having

a parallel polarizer relative to the polarization of the light from the first polarizer, the parallel polarizer being disposed to intercept a first portion of the beam path at a location after the beams have passed through the container,

a cross polarizer relative to the polarization of the light from the first polarizer, the cross polarizer being disposed to intercept a second portion of the beam path at a location after the beams have passed through the container,

a first detector that measures the intensity of a light beam, the first detector being disposed to detect the light passing through the parallel polarizer, and

a second detector that measures the intensity of a light beam, the second detector being disposed to detect the light passing through the cross polarizer; and

means for analyzing the character of the container using the intensities measured by the light analyzer.

7. The apparatus of claim 6, wherein the means for analyzing includes

means for determining the sum of the intensities measured by the first detector when the first light source operates and the first detector when the second light source operates.

8. The apparatus of claim 6, wherein the means for analyzing includes

means for determining the difference of the intensities measured by the first detector when the first light source operates and the second detector when the first light source operates.

9. The apparatus of claim 6, wherein the means for analyzing includes

means for determining the sum of the intensities measured by the first detector when the first light source operates and the first detector when the second light source operates;

and

means for determining the difference of the intensities measured by the first detector when the first light source operates and the second detector when the first light source operates.

10. The apparatus of claim 6, wherein the light produced by the first source is red.

11. The apparatus of claim 6, wherein the light produced by the second source is green.

12. Apparatus for determining whether a container is formed of glass or an optically active plastic, comprising:

a container support adapted for supporting a container of an unknown, but optically transmissive material;

a source of a beam of light disposed to direct the beam of light through the container supported in the container support;

a first polarizer disposed in the beam path at a location prior to passage of the beam through the container;

a light analyzer having

a parallel polarizer relative to the polarization of the light from the first polarizer, the parallel polizer being disposed to intercept a first portion of the beam at a location after the beam has passed through the container,

a cross polarizer relative to the polarization of the light from the first polarizer, the cross polarizer being disposed to intercept a second portion of the beam at a location after the beam has passed through the container,

a first detector that measures the intensity of a light beam, the first detector being disposed to detect the light passing through the parallel polarizer, and

a second detector that measures the intensity of a light beam, the second detector being disposed to detect the light passing through the cross polarizer; and

means for determining the difference of the intensity measured by the first detector and the intensity measured by the second detector.

13. Apparatus for determining the color of a container that is transmissive to light, comprising:

a container support adapted for supporting a container;

a first source of a beam of light of a first wavelength disposed to direct the beam of light through the container supported in the container support;

a second source of a beam of light of a second wavelength disposed to direct the beam of light through the container supported in the container support;

a first light analyzer having

a first detector that measures the intensity of a light beam, the first detector being disposed to detect the intensity of the beam from the first source, after the beam has passed through the container, and

a second detector that measures the intensity of a light beam, the second detector being disposed to detect the intensity of the beam from the second source, after the beam has passed through the container; and

means for determining the difference of the intensities measured by the first detector and the second detector.

14. Apparatus for determining the color of a container that is transmissive to light, comprising:

a container support adapted for supporting a container;

a first source of a beam of light of a first wavelength disposed to direct the beam of light through the container supported in the container support;

a second source of a beam of light of a second wavelength disposed to direct the beam of light through the container supported in the container support, the first source and the second source being disposed so that the beam of light of the first wavelength and the beam of light of the second wavelength are at least in part parallel and coincident on a beam path;

a beam controller that controls the operation of the first light source and the second light source to operate in an alternating fashion;

a light analyzer having a detector that measures the intensity of a light beam, the detector being disposed to detect the intensity of the coincident beam; and

means for determining the difference of the intensity measured by the detector when the first source is operating and the intensity measured by the detector when the second source is operating.

15. A process for determining whether a container is formed of glass or an optically active plastic, comprising the steps of:

finding a polarization difference index for the container, utilizing the steps of

passing a beam of polarized light through a container,

passing a portion of the beam through a parallel polarizer, after it has passed through the container,

passing another portion of the beam through a cross polarizer, after it has passed through the container, and

determining the polarization difference index as the difference in intensity of the portion of the beam passed through the parallel polarizer and the intensity of the portion of the beam passed through the cross polarizer;

repeating the step of finding with no container present; and

comparing the polarization difference index determined with a container present and with no container present.

16. A process for determining the color components of a container that is at least partly transparent to light, comprising the steps of:

transmitting a beam of light through the container, the beam having at least two different wavelengths therein;

measuring the intensity of the transmitted beam at the two different wavelengths; and

calculating a normalized color index of the container as the difference between the intensities of the beam at the two different wavelengths divided by the sum of the intensities of the beam at the two different wavelengths.

17. A process for characterizing the nature of a container that is at least partially transparent to light, comprising the steps of:

transmitting the beam of light through the container, the beam having at least two different wavelengths therein;

measuring the intensity of the transmitted beam at the two different wavelengths;

calculating a color index of the container as the difference between the intensities of the beam at the two different wavelengths.

finding a polarization difference index for the container, utilizing the steps of

passing a beam of polarized light through a container,

passing a portion of the beam through a parallel polarizer, after it has passed through the container,

passing another portion of the beam through a cross polarizer, after it has passed through the container, and

determining the polarization difference index as the difference in intensity of the portion of the beam passed through the parallel polarizer and the intensity of the portion of the beam passed through the cross polarizer;

repeating the step of finding with no container present; and

comparing the polarization difference index determined with a container present and with no container present.