Circuit for machine-vision system

Abstract

Manufacturing lines include inspection systems for monitoring the quality of parts produced. Manufacturing lines for making semiconductor devices generally inspect each fabricated part. The information obtained is used to fix manufacturing problems in the semiconductor fab plant. A machine-vision system for inspecting devices includes a light source for propagating light to the device and an image detector that receives light from the device. Also included is a light sensor assembly for receiving a portion of the light from the light source. The light sensor assembly produces an output signal responsive to the intensity of the light received at the light sensor assembly. A controller controls the amount of light received by the image detector to a desired intensity range in response to the output from the light sensor. The image detector may include an array of imaging pixels. The imaging system may also include a memory device which stores correction values for at least one of the pixels in the array of imaging pixels. To minimize or control thermal drift of signals output from an array of imaging pixels, the machine-vision system may also include a cooling element attached to the imaging device. The light source for propagating light to the device may be strobed. The image detector that receives light from the device remains in a fixed position with respect to the strobed light source. A translation element moves the strobed light source and image detector with respect to the device. The strobed light may be alternated between a first and second level.

1 . A machine-vision system for inspecting a device, said machine-vision system comprising: 
 a light source for propagating light to the device;    an image detector that receives light from the device;    a light sensor assembly receiving a portion of the light from the light source, said light sensor assembly producing an output responsive to the intensity of the light received at the light sensor assembly; and    a controller for controlling the amount of light received by the image detector, said controller controlling the amount of light within a desired range in response to the output from the light sensor.    
     
     
         2 . The system of  claim 1  wherein the light sensor assembly further comprises: 
 a beam splitter positioned between the light source and the device; and  
 a light sensor positioned to receive light from the beam splitter.  
 
     
     
         3 . The system of  claim 2  wherein the beam splitter filters infrared light from the light source.  
     
     
         4 . The system of  claim 1  further comprising a power supply which supplies power to the light source, said controller controlling the amount of light received by the image detector by controlling the amount of power output from the power supply.  
     
     
         5 . The system of  claim 1  wherein said controller controls the amount of light received by the image detector by controlling the amount time the image detector receives light to acquire an image.  
     
     
         6 . The system of  claim 1  wherein the image detector further comprises an array of imaging pixels, wherein said controller controls the amount of light received by the image detector by controlling the amount time the array of imaging pixels receives light to acquire an image.  
     
     
         7 . The system of  claim 6  further comprising a memory device which stores correction values for at least one of the pixels in said array of imaging pixels, wherein the value associated with said at least one of the pixels is corrected with a correction value stored in said memory.  
     
     
         8 . The system of  claim 6  further comprising a memory device which stores correction values for at least one of the pixels in said array of imaging pixels, wherein the controller can control a correction value stored in said memory.  
     
     
         9 . The system of  claim 1  wherein said light sensor assembly further comprises a photo diode.  
     
     
         10 . A machine-vision system for inspecting a device, said machine-vision system comprising: 
 a light source for propagating light to the device;    an image detector that receives light from the device; and    a cooling element attached to said imaging device, said cooling element removing heat produced by the image detector to keep the image detector within a selected temperature range.    
     
     
         11 . The system of  claim 10 , wherein the cooling element is a thermoelectric semiconductor unit.  
     
     
         12 . The system of  claim 10 , wherein the image detector is an array of imaging pixels.  
     
     
         13 . The system of  claim 10  wherein the image detector is an array of semiconductor imaging pixels, said thermoelectric semiconductor unit further comprising: 
 a temperature sensor for sensing the temperature of the array of semiconductor imaging pixels;  
 a cool portion attached to the array of semiconductor imaging pixels to form a thermally conductive path between the array of semiconductor imaging pixels and the thermoelectric semiconductor unit;  
 a heat rejection portion; and  
 a controller for controlling the amount of power input to the thermoelectric semiconductor to keep the image detector within a selected temperature range.  
 
     
     
         14 . A machine-vision system for inspecting a device, said machine-vision system comprising: 
 a strobed light source for propagating light to the device;    an image detector that receives light from the device, said image detector remaining in a fixed position with respect to the strobed light source; and    translation element that moves the strobed light source and image detector with respect to the device.    
     
     
         15 . The machine-vision system for inspecting a device of  claim 14  comprising a ring light source.  
     
     
         16 . The machine-vision system for inspecting a device of  claim 14  further comprising a strobed light controller which controls the strobed light source to produce light having a first level and to produce light having a second level, said first level different from the first level.  
     
     
         17 . The machine-vision system for inspecting a device of  claim 16  wherein the image detector further comprises: 
 an array of imaging pixels; and  
 an imaging pixel controller which controls the amount of light received by the image detector by controlling the amount time the array of imaging pixels receives light to acquire an image.  
 
     
     
         18 . The system of  claim 17  further comprising a memory device which stores correction values for at least one of the pixels in said array of imaging pixels, wherein the value associated with said at least one of the pixels is corrected with a correction value stored in said memory.  
     
     
         19 . The system of  claim 17  further comprising a memory device which stores 
 a first correction value associated with the first level of light from the strobed light source, and  
 a second correction value associated with the second level of light from the strobed light source for at least one of the pixels in said array of imaging pixels, wherein the values associated with said at least one of the pixels is corrected with the first and second correction values stored in said memory.  
 
     
     
         20 . The machine-vision system for inspecting a device of  claim 16  wherein said strobed light controller controls the strobed light source to produce light having a first level and alternated with light having a second level.  
     
     
         21 . The machine-vision system for inspecting a device of  claim 16  comprising a strobed ring light source, said strobed light controller controlling the strobed light source and the strobed ring light source.  
     
     
         22 . The machine-vision system for inspecting a device of  claim 21  wherein the strobed light controller controls the strobed ring light source to strobe alternatively with the strobed light at the first level and at the second level.  
     
     
         23 . The machine-vision system for inspecting a device of  claim 16  wherein the image detector is comprised of a first line of pixels and a second line of pixels, said machine vision system further comprising a strobed ring light source, wherein said strobed light controller controls the strobed ring light source to produce light for the first line of pixels and the second line of pixels.  
     
     
         24 . A method for acquiring physical information associated with of a device using a machine-vision station having a light source and having an image detector, said method comprising the steps of: 
 projecting light from the light source to the device;    receiving light reflected from the device into an image detector; and    controlling the amount of light received at the image detector to a value within a desired range.    
     
     
         25 . The method of  claim 24  wherein the step of controlling the amount of light received at the image detector further comprises the steps of: 
 sensing the projected from the light source; and  
 controlling the amount of power input to the light source in response to the value produced by said sensing step.  
 
     
     
         26 . The method of  claim 24  wherein the image detector further comprises an array of pixels which produce a signal dependent on the length of time the pixel is exposed to the reflected light, wherein the step of controlling the amount of light received at the image detector further comprises the steps of: 
 sensing the projected from the light source; and  
 controlling the length of time the image detector is exposed to reflected light in response to the value produced by said sensing step.  
 
     
     
         27 . The method of  claim 24  wherein the step of controlling the amount of light received at the image detector further comprises the steps of: 
 sensing the reflected from the device; and  
 controlling the amount of power input to the light source in response to the value produced by said sensing step.  
 
     
     
         28 . The method of  claim 24  wherein the image detector further comprises an array of pixels which produce a signal dependent on the length of time the pixel is exposed to the reflected light, wherein the step of controlling the amount of light received at the image detector further comprises the steps of: 
 sensing the reflected from the device; and  
 controlling the length of time the image detector is exposed to reflected light in response to the value produced by said sensing step.  
 
     
     
         29 . A method for acquiring physical information associated with of a device using a machine-vision station having a light source and having an image detector, said method comprising the steps of: 
 projecting light from the light source to the device;    receiving light reflected from the device into an image detector; and    removing heat produced by the image detector to keep the image detector within a selected temperature range.    
     
     
         30 . The method of  claim 29 , wherein the step of removing heat produced by the image detector further comprises attaching a thermoelectric semiconductor unit to the image detector.  
     
     
         31 . A method for acquiring physical information associated with of a device using a machine-vision station having a light source and having an image detector, said method comprising the steps of: 
 fixing the relationship between the light source and the image detector;    moving the light source and the image detector with respect to the device;    projecting strobed light from the light source to the device; and    receiving light reflected from the device into an image detector.    
     
     
         32 . The method of  claim 31  wherein the wherein the step of projecting strobed light from the light source to the device further comprises the steps of: 
 producing a first level of strobed light from the light source; and  
 producing a second level of strobed light from the light source.  
 
     
     
         33 . The method of  claim 32  further comprising the step of producing a strobed light from a ring light.  
     
     
         34 . The method of  claim 31  wherein the wherein the step of projecting strobed light from the light source to the device further comprises the steps of: 
 producing a first level of strobed light from the light source;  
 producing a second level of strobed light from the light source; and  
 alternating the strobed light of the first level with the strobed light of the second level.  
 
     
     
         35 . A manufacturing system, comprising: 
 a semiconductor part fabrication unit that fabricates a part for a semiconductor device; and    an inspection station, the inspection station further comprising: 
 (a) a light source projecting light onto the device;  
 (b) an image detector which receives light reflected from the device, the image detector including a plurality of lines of semiconductor imaging pixels;  
 (c) a light sensor assembly receiving a portion of the light from the light source, said light sensor assembly producing an output responsive to the intensity of the light received at the light sensor assembly; and  
 (d) a controller for controlling the amount of light received by the image detector, said controller controlling the amount of light within a desired range in response to the output from the light sensor.  
   
     
     
         36 . The manufacturing system of  claim 35  wherein the inspection station further comprises memory for storing correction values associated with at least one of the pixels in the image detector.  
     
     
         37 . The manufacturing system of  claim 35  wherein the inspection station further comprises a light source controller for producing strobed light of a first level and strobed light of a second level.  
     
     
         38 . The manufacturing system of  claim 37  wherein the inspection station further comprises a ring light.  
     
     
         39 . The manufacturing system of  claim 35  wherein the inspection station further comprises: 
 a ring light; and  
 a ring light controller for strobin the ring light, said ring light controller strobing the ring light for each of said plurality of lines of pixels in said image detector.