for Web Inspection in Vacuum Processes
Historical Use of CIS Sensors in Vacuum Applications The Industrial CIS Sensor Story started in 2002, when Tichawa Vision first adapted Fax Machine Technology for Machine Vision Applications The first generation of Vacuum CIS devices was introduced in 2007, The new generation Vacuum CIS devices have been significantly advanced using a whole bunch of both optic and electronic improvements, fully benefiting from General Purpose CIS Progress over the past years
CIS Technology Progress
Basic Operation of a CIS Sensor The CIS sensors differs from conventional Line Scan by - GRIN lens Array Optics Optics for compact size - Sensor Size equalling Object Size NO YES!
Operation of a GRIN Lens - Types of Multi Mode Fibers Step Index Fiber Propagation of light via TIR (Total Internal Reflection) significant tunnel effect losses Graded Index (GRIN) Fiber Propagation of light via Index Profile Low loss mass product for telecom industry suitable for imaging
Operation of a GRIN Lens Array
Operation of an CIS Sensor Element
Detailed CIS Cross Section
Specification of Traditional Vacuum CIS Sensors Dual Sensors e. g. for capacitor Film Inspection Densitometer Side Resolution 20 dpi / 1.3 mm Dynamic Range 0-3,3 OD (16 Bit) Scanwidth up to 2 m Line Rates to 20kHz for 26 m/sec (1560 m/min) CIS Side Resolution 600 dpi / 42 µm Dynamic Range 256 Gray Levels (8 Bit) Scanwidth up to 2 m Line Rates to 60kHz, elongated pixels Quasi telecentric operation also useful for kinegram / hologram inspection
Limitations of Traditional Vacuum CIS Sensors Dual Sensors Crosstalk Densitometer <=> CIS (20 mm spacing) No economy single sensor solution Densitometer Side Limited Spatial Resolution 20 dpi / 1.3 mm Limited Dynamic Range 0-3,3 OD (16 Bit) Limited Step Response typ. 8 mm for 3 OD Step CIS Side Limited Spatial Resolution 600 dpi / 42 µm Inline Sensor with Gaps
Typical Examples VARICIS Sensor Cross Section 50 x 75 mm Vacuum CIS Sensor Cross Section 130 x 100 mm
Overcoming the Limits - Crosstalk Using different wavelengths for the two sides eliminates Crosstalk The Densitometer uses RED light at 630-660 nm matching traditional Reference Densitometers The CIS uses either GREEN or BLUE light Color Filters on both sensor elements reduce crosstalk to a minimum
Overcoming the Limits No economy single sensor solution The standard sensor is built from 2 separate sensor lines for Densitometer and CIS to optimize performance There are situations where the smaller size and/or lower cost of a single sensor line device might be preferred The new family provides a new 400 dpi sensor with a 4000:1 dynamic range. Properly processing these raw data provides both 400 dpi (63 µm) CIS with 256 gray levels (8 Bit) 25 dpi (1 mm) Densitometer with approx. 10 000:1 dynamic range
Overcoming the Limits Limited Spatial Densitometer Resolution The new generation is based on a new 400 dpi sensor with a 4000:1 dynamic range. Properly processing this single set of raw data provides 25 dpi (1 mm) Densitometer with approx. 10 000:1 dynamic range OR 50 dpi (0.5 mm) Densitometer with approx. 7000:1 Dynamic Range
Overcoming the Limits Limited Densitometer Range The new generation is based on a new 400 dpi sensor with a 4000:1 dynamic range. Properly processing this single set of raw data provides 25 dpi (1 mm) Densitometer with approx. 10 000:1 Dynamic range Further averaging these data allows for 0-4 OD range
Overcoming the Limits Limited Step Response The GRIN lens itself limits the Densitometer Step response. As known from traditional optics the MTF of any imaging system is specified for typical modulation depths of 30, 50, maybe 90%. Using Contrast Ration of 1000:1 and above reveals a long tail of up to several mm To overcome this limitation we have eliminated the GRIN lens array for the Densitometer side using strictly parallel illumination instead. Our light source allows for 2 m wide parallel light line sources with less then 5 mrad deviation from the perpendicular orientation resulting in a dramatic improved step response
Densitometer Step Response, Transition halfway between Pixels SELFOC vs. Parallel Light, Transititon 3,5 3 Measured Density OD 2,5 Density using SELFOC Lens Density using parallel Light 2 1,5 1 0,5 0 20 25 30 35 40 45 50 55 60 65 70 Position across Web mm
Overcoming the Limits Limited CIS Resolution Part 1 The new family offers Resolution for general application of up to 1200 dpi or 21 µm Pixel Size (vs. 600 dpi or 42 µm Pixel Size) A second, possibly more important improvement lies in the switch from the traditional inline structure to the more refined staggered sensor structure
What about Gaps? INLINE CIS SENSOR CIS devices have gaps between the single sensor dies. The gaps are much smaller than with butted CCD sensors. Desktop Scanner Software Interpolation is used to hide the gaps from the user. TiVi's inline sensor 200-600 dpi Gap on the order of 20 µm, less than 1 pixel. STAGGERED CIS SENSOR TiVi's Zero Gap Sensor 600-2400 dpi Sensor elements are aligned in two lines, effectively overlapping each other. A line delay buffer recombines the two lines into one.
Conventional Inline Sensors CIS devices have small gaps between the single sensor dies, typically about 13 µm INLINE CIS SENSOR Desktop Scanner Software Interpolation is used to hide the gaps from the user.
Effect of Gaps on Image INLINE CIS SENSOR Object Image with Gap
What about Gaps? TiVi's staggered sensor 1200-2400 dpi STAGGERED CIS SENSOR Overlapping Sensor elements are aligned in two lines. A line delay buffer recombines the two lines into one.
Flawless Images with Zero Gap Technology STAGGERED CIS SENSOR Object Gapless Image
Overcoming the Limits Limited CIS Resolution Part 2 For PinHole Inspection a different approach is needed. The sheer amount of data introduces very complex and expensive data processing systems. We have created an entirely new solution saving both complexity and cost as outlined below
Data Reduction in a Vision System
10 µm Pixel for 30 µm Defects, 2 m Width, 1.2 m/min
1 µm Pixel for 3 µm Defects, 2 m Width, 1.2 m/min
New Approach: 10 µm Pixel for 3 µm Defects, 2 m Width, 1.2 m/min
Burgwallstraße 14 86316 Friedberg Phone: +49 (0) 821/455 553-0 Fax: +49 (0) 821/455 553-20 E-Mail: info@tichawa.de www.tichawa-vision.com NO YES!