Method and system for imaging an object or pattern

• US 6,603,874 B1
• Filed: 03/03/2000
• Issued: 08/05/2003
• Est. Priority Date: 11/12/1996
• Status: Expired due to Fees

• Current Assignee: Rudolph Technologies Incorporated (Onto Innovation Inc.)
• Original Assignee: Robotic Vision Systems, Inc. (Acuity Brands, Inc.)
• Inventors: Stern, Howard, Maali, Fereydoun
• Primary Examiner(s): Ahmed, Samir
• Assistant Examiner(s): Bali, Vikkram
• Application Number:
  US09/518,559
• Time in Patent Office: 1,250 Days
• Field of Search: 382/141, 382/144-151, 348/86, 348/87, 348/125, 348/126, 356/376, 356/237
• US Class Current: 382/144
• CPC Class Codes: G01N 2021/8825 Separate detection of dark field and bright field
• CPC Class Codes: G01N 2021/95646 Soldering
• CPC Class Codes: G01N 21/8806 Specially adapted optical and illumination features
• CPC Class Codes: G01N 21/9501 Semiconductor wafers manufacturing processes per se of semiconductor devices implementing a measuring step H01L22/10
• CPC Class Codes: G01N 21/95607 using a comparative method
• CPC Class Codes: G02B 21/367 providing an output produced by processing a plurality of individual source images, e.g. image tiling, montage, composite images, depth sectioning, image comparison
• CPC Class Codes: G06T 1/00 General purpose image data processing
• CPC Class Codes: G06T 1/0007 Image acquisition
• CPC Class Codes: G06T 2200/32 involving image mosaicing
• CPC Class Codes: G06T 2207/30148 Semiconductor; IC; Wafer
• CPC Class Codes: G06T 2207/30152 Solder
• CPC Class Codes: G06T 5/50 using two or more images, e.g. averaging or subtraction
• CPC Class Codes: G06T 7/0002 Inspection of images, e.g. flaw detection
• CPC Class Codes: G06T 7/0004 Industrial image inspection

Abstract

A system and method for simultaneously obtaining a plurality of images of an object or pattern from a plurality of different viewpoints is provided. In an exemplary embodiment, proper image contrast is obtained by replacing the light sources of earlier systems with equivalent light sensitive devices and replacing the cameras of earlier systems with equivalent light sources. With such a system, bright-field images and dark-field images may be simultaneously obtained. In one aspect of the invention, a light source is positioned to illuminate at least a portion of an object. A plurality of light guides having input ends are positioned to simultaneously receive light reflected from the object and transmit the received light to a plurality of photodetectors. The light guides are arranged such that their respective input ends are spaced substantially equally along at least a portion of a surface of an imaginary hemisphere surrounding the object. The signals generated by the photodetectors (as a result of light detection) are processed and a plurality of images of the object are formed. Another aspect of the invention provides a method for generating composite images from simultaneously obtained images. Equivalent regions of each image (corresponding to geographically identical subpictures) are compared. The subpicture having the highest entropy is selected and stored. This process continues until all subpictures have been considered. A new composite picture is generated by pasting together the selected subpictures. In another aspect of the invention, the vector of relative light values gathered for each pixel or region of an object illuminated or scanned (i.e., one value for each photodetector) is used to determine reflectance properties of points or regions illuminated on the object or pattern. The reflectance properties may be stored in a matrix and the matrix used to read, for example, a Bar Code of a data matrix symbol.

Claims

1. A system for imaging an object comprising:

a light source positioned to transmit light along a first path for illuminating at least a portion of the object;

a first photo sensitive device positioned to detect light reflected from the object at a first preselected position and generating a first signal representing information concerning the light detected;

a photodetector array having a plurality of photodetectors positioned to detect light reflected from the object at a second preselected wherein said photodetector array generates a plurality of second signals representing information concerning the light detected;

a summing amplifier, in communication with the photodetector array, that receives the plurality of second signals and generates a third signal as a function of the plurality of second signals; and

a processor in communication with the first photo sensitive device and the summing amplifier that receives the first signal and generates a first image of the at least a portion of the object as a function of the first signal, and that receives the third signal and generates a second image of the at least a portion of the object as a function of the third signal.

2. The system of claim 1 further comprising:

a lenslet array having a plurality of lenses positioned to focus light reflected from the object onto the photodetector array wherein each lens of the plurality of lenses focusses light onto one of the photodetectors of the plurality of photodetectors.

3. A system for imaging an object comprising:

a light source positioned to transmit light along a first path for illuminating at least a portion of the object;

a first photo sensitive device positioned to detect light reflected from the object at a first preselected position and generating a first signal representing information concerning the light detected;

a photodetector array having a plurality of photodetectors positioned to detect light reflected from the object at a second preselected wherein said photodetector array generates a plurality of second signals representing information concerning the light detected;

a photodetector, in communication with the photodetector array, that receives the plurality of second signals and generates a third signal as a function of the plurality of second signals; and

a processor in communication with the first photo sensitive device and the summing amplifier that receives the first signal and generates a first image of the at least a portion of the object as a function of the first signal, and that receives the third signal and generates a second image of the at least a portion of the object as a function of the third signal.

4. The system of claim 3 further comprising:

a plurality of light guides positioned to transmit the plurality of second signals to the photodetector.

5. A system for imaging a semiconductor package comprising:

a light source positioned to transmit light along a first path for illuminating at least a portion of the semiconductor package;

a first photo sensitive device positioned to detect light reflected from the semiconductor package at a first preselected position and generating a first signal representing information concerning the light detected;

a photodetector array having a plurality of photodetectors positioned to detect light reflected from the semiconductor package at a second preselected wherein said photodetector array generates a plurality of second signals representing information concerning the light detected;

a photodetector, in communication with the photodetector array, that receives the plurality of second signals and generates a third signal as a function of the plurality of second signals; and

a processor in communication with the first photo sensitive device and the summing amplifier that receives the first signal and generates a first image of the at least a portion of the semiconductor package as a function of the first signal, and that receives the third signal and generates a second image of the at least a portion of the semiconductor package as a function of the third signal.

6. The system of claim 5 further comprising:

a plurality of light guides positioned to transmit the plurality of second signals to the photodetector.