Systems and methods for optical measurement of container wall thickness

Abstract

Systems and methods are provided for determining a thickness of a material or an article of manufacture thereof such as a wall thickness of a plastic container or plastic bottle during manufacturing. In some embodiments, for example, a measurement system can include a light source disposed adjacent to a production line for plastic bottles. The light source can be configured to transmit light of a known frequency through the plastic bottles. A camera can be disposed opposite the light source. The camera can be configured to receive the light transmitted through the plastic bottles. An optional trigger, when present, can be configured to coordinate timing of the camera and the light source. A computer can be configured to determine wall thicknesses for the plastic bottles by an experimentally determined correlation between the light received by the camera and a known absorbance spectrum of the material forming the plastic bottles.

What is claimed is: 
     
         1 . A measurement system for determining container wall thicknesses of containers manufactured on a production line, comprising:
 one or more light sources configured to emit light of one or more known frequencies and oriented to direct the light through the containers;   one or more cameras oppositely oriented to the one or more light sources, the one or more cameras configured to receive light transmitted through the containers; and   a dedicated computer system configured for determining the wall thicknesses of the containers by correlating the light transmitted through the containers and received by the one or more cameras with a known absorbance spectrum of a material of the containers.   
     
     
         2 . The measurement system of  claim 1 ,
 wherein the one or more lights wholly or partially includes at least one calibration light oppositely oriented to at least one camera of the one or more cameras configured to emit light without directing the light through the containers,   wherein the computer system is further configured for calibrating measurements by the measurement system with the at least one calibration light.   
     
     
         3 . The measurement system of  claim 1 ,
 wherein the one or more light sources include one or more lamps, lasers, light emitting diodes (LEDs), infrared sources, or a combination thereof configured to emit the light of one or more known frequencies.   
     
     
         4 . The measurement system of  claim 3 ,
 wherein the one or more light sources include one or more LEDs.   
     
     
         5 . The measurement system of  claim 3 ,
 wherein the one or more light sources include one or more lasers.   
     
     
         6 . The measurement system of  claim 1 , further comprising:
 one or more optical reflectors or diffusers coupled with the one or more light sources configured to spread out the light emitted by the one or more light sources to provide optimal coverage of the containers.   
     
     
         7 . The measurement system of  claim 1 , further comprising:
 a trigger configured to coordinate a timing of at least one camera of the one or more cameras and at least one light source of the one or more light sources,
 wherein the trigger includes suitable hardware components coupled to the computer system, and 
 wherein the computer system includes instructions stored in a memory of the computer system and one or more processors configured to execute the instructions to activate the trigger. 
   
     
     
         8 . The measurement system of  claim 1 ,
 wherein the trigger is further configured to coordinate the timing of the at least one camera and at least two light sources of the one or more light sources configured to emit light at two different known frequencies, and   wherein the at least one camera is configured to image the containers under the at least two different known frequencies for different, superimposable images, from which the computer system is further configured to superimpose the images and determine the wall thicknesses of the containers by differences by the superimposed images.   
     
     
         9 . The measurement system of  claim 1 ,
 wherein the measurement system is configured for determining the container wall thicknesses of plastic containers,   wherein the plastic is selected from polyethylene, polyethylene terephthalate (PET), polyvinyl chloride (PVC), and polypropylene.   
     
     
         10 . The measurement system of  claim 1 ,
 wherein the computer system is further configured for determining the wall thicknesses of the containers by correlating the light transmitted through the containers and received by the one or more cameras with a known absorbance spectrum of a material of the containers over a range of wavelengths the material is known to absorb light based upon the absorbance spectrum of the material.   
     
     
         11 . The measurement system of  claim 10 ,
 wherein the computer system is further configured for returning the wall thicknesses of the containers and providing wall-thickness trend analyses for the containers.   
     
     
         12 . The measurement system of  claim 1 ,
 wherein the one or more cameras include at least a first thermal camera and a second thermal camera,   wherein each thermal camera of at least the first thermal camera and the second thermal camera is configured to thermally image the containers at different locations along the production line, the different locations optionally differing in temperature due to a difference in ambient temperature, a temperature resulting from heating or cooling, or a combination thereof.   
     
     
         13 . The measurement system of  claim 12 ,
 wherein the computer system is further configured for determining the wall thicknesses of the containers by differences in thermal images provided by the first and second thermal cameras in accordance with a known relationship between heat dissipation and the wall thickness of the containers.   
     
     
         14 . The measurement system of  claim 12 , further comprising:
 a heat source configured for applying heat to the containers at a wavelength absorbed by a material of the containers,
 wherein the first thermal camera is positioned to thermally image the containers subsequent to the heat source applying heat to the containers, and 
 wherein the second thermal camera is positioned to thermally image the containers subsequent to the first thermal camera and cooling of the containers. 
   
     
     
         15 . The measurement system of  claim 13 ,
 wherein the computer system is further configured for determining the wall thicknesses of the containers by differences in thermal images provided by the first and second thermal cameras in accordance with a known relationship between heat dissipation and the wall thickness of the containers.   
     
     
         16 . A system, comprising:
 a light source configured to emit light in a band of wavelengths known to be absorbed by polyethylene terephthalate (PET),
 wherein the light source is a light-emitting diode; 
   a detector oppositely oriented to the light source configured to detect light transmitted through PET containers on a production line; and   a dedicated computer system including instructions stored in a memory of the computer system and one or more processors configured to execute the instructions to
 determine wall thicknesses of the PET containers from light transmitted through the PET containers and received by the detector in accordance with a known relationship of absorbance to thickness for the PET containers and 
 return wall-thickness data and wall-thickness trend analyses for the PET containers. 
   
     
     
         17 . A method for determining container wall thicknesses of containers manufactured on a production line, comprising:
 directing light of at least one selected frequency from one or more light sources to the containers,
 wherein a first portion of the light is absorbed by a material of the containers, and 
 wherein a second portion of the light is transmitted through the containers; 
   receiving the second portion of the light with a camera configured to receive the at least one selected frequency;   identifying a correlation between the second portion of the light and container wall thickness;   monitoring the container wall thicknesses of the containers by way of the correlation to obtain real-time feedback; and   using the real-time feedback to control a quantity of the material in the containers.   
     
     
         18 . The method of  claim 17 , further comprising:
 mounting one or more light sources about the production line; and   orienting the one or more light sources for directing the light to the containers as each of the containers is conveyed on the production line.   
     
     
         19 . The method of  claim 18 ,
 wherein directing the light further includes orienting at least one light source of the one or more light sources to emit light directly toward the camera without interference by the containers, and   wherein the at least one light source of the one or more light sources is a calibration light configured for calibration measurements.   
     
     
         20 . The method of  claim 17 , further comprising:
 coordinating a timing of any of the one or more light sources and the camera with the containers as each of the containers is conveyed on the production line.   
     
     
         21 . The method of  claim 17 , further comprising:
 selecting the at least one selected frequency of the one or more light sources to overlap at least one known absorbing frequency from an absorbance spectrum of the material where a relatively large portion of the light is absorbed by the material, thereby enabling a relatively more accurate measurement of the wall thicknesses of the containers.   
     
     
         22 . The method of  claim 17 ,
 wherein identifying the correlation includes comparing an absorption of multiple optical frequencies to provide a relatively stronger correlation between the wall thicknesses of the containers and an absorption of the light by the material of the containers.