NIST traceable automated visual inspection system for an inspection of particles in solution

• US 7,310,143 B2
• Filed: 11/05/2004
• Issued: 12/18/2007
• Est. Priority Date: 11/09/2003
• Status: Active Grant

• Current Assignee: Gerald Walter Budd
• Original Assignee: Gerald Walter Budd
• Inventors: Budd, Gerald Walter
• Primary Examiner(s): Toatley, Jr., Gregory J.
• Assistant Examiner(s): Nur, Abdullahi
• Application Number:
  US10/981,801
• Publication Number:
  US 20050099625A1
• Time in Patent Office: 1,138 Days
• Field of Search: 356/335, 356/427, 356/428, 356/237.1, 356/238.1, 356/240.1, 250/223.B, 250/208.1
• US Class Current: 356/335
• CPC Class Codes: G01N 15/0205 by optical means

Abstract

A method for the substantially complete detection and measurement of all particles, within a predetermined size, range, contained in an injectable solution comprising the steps of: a) rotation of the container causes substantially all of the particles in the injectable solution in the container to be set in motion; b) uniformly illuminating the background around the container with light; and c) detecting at least one of light scatter, light reflection and light extinction caused by said particles, with detectors having a depth of focus of detection in a specified volume of the container. Wherein the detectors are positioned, relative to the container whereby the optical path and field of view allows the sensor sufficient focus to view substantially all of the bottom interior surface of the container and substantially all of the solution volume within the container. The method and apparatus produces a geometric representation of the particles in the detection region, whereby the size of detected particles can be is accurately adjusted to an actual size by either calculation or by calculated offset to allow accurate measurement of particle dimensions.

Claims

1. An improved apparatus for the detection of contaminating particles in the fluid of small containers in which the apparatus produces a uniform illumination field for consistent grayscale detection and measurement of moving particles in the solution using a machine vision measuring system comprising:

a) an image processing computer for image acquisition, image storage and image processing capability;

b) the image processing computer comprising memory for storing the images formed by the camera;

c) the image processing computer also comprising digital parallel input/output digital serial, and Ethernet communication capabilities for providing messages to external devices to report one or more measurements or characteristics of the particles moving in the solution;

d) the image processing computer executing control software stored in a computer readable medium, for allowing request and response signals from external devices indicating a small container to be inspected, for causing the image processing computer to perform image analysis for extraction of the summation of grayscale values of the moving particles in the solution found within the small container, as well as for causing the image processing computer to store a reference images of an acceptable quality of small container with no presence of contamination particles in a memory location referenced by a specific identification code that is unique to a small container size and shape with a specific fluid fill level;

e) an image sensor with appropriate lens for providing a spatial resolution and depth of field necessary to form a sharp focus image of substantially all of the bottom interior surface of the small container;

f) wherein the image sensor comprises sufficient pixel resolution to resolve a contaminating particle of at least 40 micrometers diameter resting on the interior bottom center of the small container;

g) wherein the image sensor will acquires images at a rate of 20 to 30 frames per second;

h) the image sensor and optical components are mounted inside a sealed enclosure with an optical window so that the image sensor can view objects outside the enclosure without obstruction;

i) the optical components are aligned so that the optical path is at a downward angle less than perpendicular from the axis of rotation permitting the sensor to view substantially all of the bottom interior surface of the small container;

j) an illumination system comprised of a cube structure with a “

U”

shaped channel cut into a cube of optical grade polycarbonate or acrylic so that the center of radius of the curved portion of the “

U”

shaped channel is aligned with the axis of rotation of the container;

k) an illumination system with the “

U”

shaped channel providing uniform diffuse illuminated surface large enough to allow the diameter of a small container to fit inside without interference with the walls;

l) the illumination system implements multiple light emitting diodes (LED'"'"'s) arranged around three side of the diffusing cube and positioned to uniformly illuminate an cylindrical object place at the center of the “

U”

shape channel;

m) the illumination system utilizing one or more power supplies with control circuitry to turn on or off sections the LED'"'"'s as required by the image processing system to enhance the contrast of the particles in the solution of small containers;

n) a precision drive motor is connected directly to the recessed bottom holder is used to impart rotational motion to the base of the small container with a motion processing computer and motor drive unit comprising memory for storing one or more defined motion programs;

o) the rotational motion is limited to insure that angular acceleration and velocity do not deform the meniscus to cause cavitation of the fluid or creep up the walls to the neck region of the container;

p) the rotational motion of the container imparts a motion to all particles within the fluid contents of the container;

q) the image sensor will begin to acquire images at a predefined acquisition rate after the rotational motion of the container has stopped, as images are acquired they are stored the image processing memory for analysis after the acquisition of all required images are completed, a minimum of four images are required for analysis but typically are 20 or more are used;

r) whereby the image sensor is positioned relative to the axis of rotation of the small container, whereby the focal point of detection coincides with the axis of rotation of the small container so to view the content of the solution in the small container and specifically the interior bottom of the small container with the illumination system provide a contrasting geometric shape of substantially all of the contaminating particles in the solution being identified and reporting grayscale information of each particle being displayed on a human machine interface.

2. The apparatus as claimed in claim 1, wherein the illumination cube has a clam shell design with an upper and lower shell that may be disassembled to allow access to the interior components for easy assembly and repair.

3. The apparatus as claimed in claim 1, wherein the illumination source of the illumination cube is comprised of flat panel LED'"'"'s constructed with the LED'"'"'s in close proximity to each to provide an extremely uniform illumination field.

4. The apparatus as claimed in claim 1, wherein the LED'"'"'s utilized in the illumination cube may be energized in whole or in sections to illuminate the contents of the container being tested from various directions to provide backlighting, side lighting or a combination or both.

5. The apparatus as claimed in claim 1, wherein the diffusing element of the illumination cube is constructed of single block of optical grade polycarbonate or acrylic that is machined with an elongated “

U”

shaped cutout parallel to the upper and lower surfaces so that the major axis of the container is aligned with the radius of curvature of the “

U”

shaped cutout and thus providing illumination on all sides of the container with the exception of the viewing direction.

6. The apparatus as claimed in claim 1, wherein the sensor module is constructed with a folder optical path design through the use of mirror to extend the distance between the sensor and the container under observation to improve the depth of field while minimizing the physical separation between the sensor and the rotational axis of the container.

7. The apparatus as claimed in claim 1, wherein the sensor module may utilize one or more optical filters in the optical path between the sensor and container positioned for inspection to enhance the contrast of the contaminating particles in the solution.

8. The apparatus as claimed in claim 1, wherein the optical path of the sensor module is oriented at a downward angle relative to the axis of rotation of the container to allow substantially all of the bottom interior surface of the container to viewed by the sensor permitting the image capture of heavy contaminating particles that may be lying on the bottom surface on the container.

9. The apparatus as claimed in claim 1, wherein the optical path between the sensor and the container to be inspected and the viewing angle allow a large percentage of the fluid contents on the container to be viewed with each image acquisition and substantially the entire contents to viewed in four images.

10. The apparatus as claimed in claim 1, wherein the viewing angle of the sensor is oriented at a downward with respect to the axis of rotation with sufficient field of view allow the fluid contents of the container to be inspected from the bottom of the meniscus to the bottom interior surface.

11. The apparatus as claimed in claim 1, wherein the high density spacing of the LED'"'"'s used in the illumination cube provide uniform energy of illumination so a contaminating particle produces approximately equivalent grayscale summation at all locations in the fluid volume with exception of the extreme edges of the container.

12. The apparatus as claimed in claim 1, wherein the precise control of the rotational motion of the container by the drive system is gentle and imparts motion to contaminating particles in the solution without causing violent distortion of the meniscus of cavitation within the fluid the container.

13. The apparatus as claimed in claim 1, wherein the precise rotational motion control and the ability to acquire images allows the user to study the shape of the meniscus and precisely define the parameters for a controlled particle agitation for a specific container size, shape and fluid fill level to insure reliable detection of contaminating particles.

14. The apparatus as claimed in 1, wherein the combination of illumination, sensor and precise motion control for excitation of the particle movement within the fluid of the container under inspection allows the generation of consistent grayscale images that may be compared as part of a sequence of images to identify differences between images as contaminating particles. The summation of the subtle grayscale differences can be recorded and compared with standard samples prepared with known NIST traceable particles of various sizes. A plot of grayscale summation difference versus NIST particle size will yield a calibration curve that can be used to estimate the size of an unknown particle. A separate calibration curve can be constructed for containers different shapes, sizes and fluid fill levels.

15. The apparatus as claimed in claim 14, wherein a calibration curve can be used for the rejection of unacceptable product based on size of the contaminating particle rather than the simple detection of a contaminating particle.