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Cameras in Machine Vision – Part 1
by Nello Zuech, Contributing Editor - AIA Posted 06/22/2005
Cameras or the ‘‘eyes’‘ of a machine vision system have come a long way. When I first became involved in the early days of machine vision the standard camera was a vidicon. These truly all analog cameras left a lot to be desired – sensitivity varied pretty much indiscriminately +/- 30%, as fields changed with temperature during the day so, too, did position of readout. To assure consistency in performance required a TV technician – hardly a cost-effective substitution for a direct labor inspector.
Fortunately, driven by military requirements, solid-state cameras were developed. As with any new developments, the main barrier to adopting these solid-state cameras in machine vision was their cost. A 128 x 128 pixel version initially sold for $5K. Today we find 2000 x 2000 versions selling for less than this.
Solid-state cameras also opened up opportunities in other markets – security, camcorders, etc. As the volumes associated with these markets increased, the prices of the cameras came down, making them more affordable for machine vision applications. Initially, these cameras were built around analog standards – PAL, NTSC, etc. As the machine vision market expanded, the camera suppliers recognized this niche market as one with potential. Hence, designs emerged offering features more consistent with machine vision applications: progressive scan, exposure control, etc. Today, one finds many camera parameters can be set in a PC.
Also, today one finds all digital cameras. As standards have been developed such as IEEE-1394, CameraLink, USB 2 and now the emerging GigE Ethernet-based standard, more camera suppliers are offering products designed with these connectivity standards. It is now possible to input digital camera data directly into a PC based on these connectivity standards and eliminate the frame grabber/frame store board, essentially creating a configurable machine vision system within the framework of the PC based on appropriate machine vision software.
To catch up with the latest activities in machine vision related cameras, input for this article was canvassed from all known suppliers of cameras in the machine vision market. The following submitted responses to the questions that follow. Because we received as many responses as we did, we have reduced the answers into two articles. This first part looks at the answers to the first four questions asked. This includes a review of products in the market as well as camera parameter considerations.
- Dave Gilblom – President, Alternative Vision
- Christophe Robinet – Marketing Manager, Cameras, Atmel
- Dr. Joachim Linkemann – Product Manager, Basler Vision Components
- Dave Lane – Senior Application Engineer, Cohu Electronics
Jin Kwon – Sales Engineer, Cohu Electronics
- Steve Daicos - President, The COOKE Corporation
Dr. Gerhard Holst – Head of Research Department, PCO AG
- Bill Laraway – Sales and Marketing Manager, Daitron
- David Cochrane – Director of Product Mgmt and Marketing, Vision for Machines, Dalsa Corporation
- Loren Ulrich – Marketing Manager, Imperx
- Gunnar Jonson – Director of Product Marketing, JAI Group
- Dr. Bernhard Mandel – Director of Sales & Marketing, Camera Business, Photonfocus AG
- Marty Furse – President, Prosilica
- Keith Russell – Director of Marketing, Redlake
- Ilias Levis – Product Manager, Sony Visual Imaging Products
- John Merva – President, Tattile, USA
1. Can you provide a brief general description of your camera product line targeted specifically at machine vision applications?
[John Merva – Tattile] Tapix CameraLink and TAG GigE Ethernet cameras in both area and line scan as well as monochrome and color. Tattile’s on-board FPGA provides many image pre-processing functions, freeing the frame grabber from performing these tasks. These include full frame histograms, Sobel edge filtering, user programmable 5 x 5 filter, erosions/dilations, ROI windowing, image statistics, look up table, image normalization and gain, all without slowing the maximum frame rate of the sensor. Also included are camera/strobe triggering with user programmable delay times and in camera image recording of up to 64 MB of memory. Tattile includes a full SDK and example programs with each product. Tattile’s newest product, TAG Plus, features all the above capability plus providing an internal Intel X Scale and an Analog Devices Blackfin DSP while running Linux or Tattile Antares environments for complete in-camera image processing.
[Ilias Levis – Sony] Sony Visual Imaging Products, a division of Sony Electronics Inc., is a world-renowned leader in camera technology. Sony offers an extensive line of high-quality color and monochrome CCD cameras that offer a wide variety of features and benefits, performance levels and packaging styles for use in diverse industrial imaging applications. From machine vision, factory automation, microscopy and inspection to security and process control, Sony's emphasis is on image quality, reliability, choice and flexibility regardless of your application.
[Keith Russell – Redlake] Redlake offers a complete line of high-resolution CCD cameras for machine vision applications featuring 1.9 to 11 mega-pixels called MegaPlus II. The MegaPlus II design lends itself well in multiple camera applications because of the head and controller configuration. Up to four heads can be used with a single controller whether the heads are alike or unlike. The controller supports both CameraLink (base or medium or dual base) and FireWire.
[Marty Furse – Prosilica] Prosilica designs and manufactures high-performance digital cameras for machine vision and industrial applications. Features that distinguish Prosilica cameras are high-performance, small size, high-speed, low power consumption, plug and play compatibility, industrial ruggedness, fiber optic output, and many other features.
Our CV-Series cameras are feature rich, high-performance cameras with advanced triggering features, industrial FireWire cabling, and simple plug & play triggering. Our EC-Series cameras are ultra small, high-performance FireWire cameras designed for OEM customers and price conscious volume buyers.
[Dr. Bernhard Mandel – Photonfocus] Photonfocus cameras focus on demanding applications in industrial image processing. The cameras offer an extraordinary wide dynamic range and a high frame rate combined with high-resolution. Due to the global shutter, even high-speed applications with exposure times in the µs-area are possible. Cameras are available: with CameraLink® or USB 2.0 interface.
Our camera product line covers:
- Resolution from VGA to IM
- Speed: up to 150fps
- Monochrome and color
- Interfaces like CameraLink, USB
[Gunnar Jonson – JAI Group] The JAI and PULNiX product lines are almost exclusively targeted towards machine vision (and associated applications, i.e. ITS/Traffic and certain medical applications). The main features that distinguish such products are: asynchronous trigger (reset) capability; rugged connectors; robust housing; various mounting possibilities (not just a tripod mount); high S/N ratio and a wide range of user selectable modes of operation.
[Loren Ulrich – Imperx] Imperx area scan cameras were designed to provide the user with access to all parameters, giving them the flexibility to use the same camera in different applications. If the sensor design allows for it, we've provided access to it through a GUI or by ASCII commands via Hyper Terminal programs. To also assist them in standardizing on the camera line, all cameras have the same housing and the same set of serial commands. This minimizes the change over from one camera to the other.
[Bill Laraway - Daitron] Daitron is introducing two new camera lines to the North American market, CIS and NED. CIS offers progressive scan area scan cameras from VGA up to UXGA 2 megapixel models, specifically offering new CameraLink solutions offering up to 30fps or more at full UXGA resolution, both in color RGB and RAW data as well as monochrome. Analog versions are also available from CIS. NED offers line scan cameras in all formats (LVDS, analog, CameraLink) in monochrome, and color one and three CCD models. Cameras range from 1000 to 7500 pixel resolution. Both manufacturers are well established in Asia but are new to the North American market.
[David Cochrane – Dalsa] DALSA offers the industry’s most complete selection of area and line scan imaging products including sensors, cameras and entire vision modules. Our standard products offer the latest advances in resolution, speed and dynamic range, providing the greatest detail and the highest throughput for machine vision applications.
In addition, DALSA’s Custom Solutions team applies DALSA’s innovative imaging technology to develop unique solutions for customer-specific applications that require additional capability. Our in-house foundry allows us full control of the entire sensor design process, from inception to production. DALSA’s customers benefit from greater flexibility, extensive support and accelerated time-to-market.
[Steve Daicos/Dr. Gerhard Holst – Cooke/PCO] The pixelfly and pco.camera series comprise our machine vision and industrial application camera product lines. The pixelfly camera series feature rugged ultra compact camera heads (39X39X68mm) providing high-resolution (1360X1024) and high dynamic range (12bit). The pco.camera series comes in two flavors: the pco.1200hs provides high-speed (636fps) together with high-resolution (1280X1024) at 10bit dynamic range; while the pco.2000 and pco.4000 cameras offer extremely high-resolution (2048X2048 and 4008X2672 respectively) and excellent 14bit dynamic range.
[Jin Kwon and Dave Lane – Cohu Electronics] Cohu designs and manufactures cameras for use in the machine vision industry ranging from small compact off-the-shelf cameras to specially designed cameras that are integrated into systems for diverse industries from semiconductor handling and inspection to robotic material systems. Cohu Electronics 6100 series, 7200 series, 7700 series, 7800 series, and 7900 series target machine vision applications:
- Megapixel Imager with a 1360 x 1024 active pixel array.
- 12-bit depth.
- Low light imaging.
- IEEE 1394(FireWire) Iidc v1.3 DCAM compliant.
- High-performance VGA FireWire. (1/2’‘ Format CMOS imager)
- Compact size. Lightweight.
- Rugged construction.
- IEEE 1394 interface (power over IEEE 1394A)
- 1004 x 1004 Pixel CCD camera. (CameraLink or FireWire. 30fps via Camlink. 15fps via IEEE1394A)
- High-performance ½’‘ progressive scan megapixel sensor.
- Partial readout for faster frame rate.
- Offset, Gain, Shutter/Integration over CameraLink, or IEEE 1394A.
- 1280 x 1024 pixels at 30 frames/sec.
- Low power consumption for design simplification and heat dissipation.
- Color or monochrome versions for application-specific flexibility.
- 2K x 2K(high-resolution) precision imaging camera.
- Compact size and rugged construction.
- CameraLink output for simplified integration.
- Partial readout for even faster frame rates.
[Dr. Joachim Linkemann – Basler Vision Components] Basler has almost two decades experience in industrial imaging. Basler-VC designs and manufactures advanced vision components for industrial users. Machine Vision is one of our target markets. Products include color and monochrome line scan and area scan digital cameras for high-speed and/or high-resolution applications. Product designs are driven by industry requirements offering easy interfacing, compact size and a good price/performance ratio. At Basler-VC, we pride ourselves on being a quality and a technology leader. Continuous innovation is our strength and through it, we have given direction to the field of image processing technology.
Area scan cameras are offered with resolutions from VGA to 4 Megapixels and can operate at up to 500 frames per second. Most cameras also include an Area of Interest (AOI) feature, which allows them to operate with higher frame rates at lower resolutions. Our area scan cameras feature CameraLink® and IEEE 1394 connectivity.
Line scan cameras are offered with resolutions from 1024 to 8160 pixels, with data rates up to 120 Megapixels per second and with the CameraLink Interface.
[Christophe Robinet – Atmel] With over 25 years experience in imaging, ATMEL (formerly THOMSON TCS) is a key supplier of sensors and cameras serving the machine-vision market. Our AVIIVA™ and AKYLA™ line scan product lines cover resolution sizes ranging from 512 to 8K pixels, dynamic range up to 12 bits, data rate up to 160 MHz, monochrome or color, with LVDS or CameraLink®. These cameras are known for their excellent SNR, accurate positioning and versatile implementation modes.
ATMEL is now also recognized as the challenger in the line scan camera segment. ATMEL area scan offering includes the CAMELIA™ CCD camera with resolutions up to 8M Pixels, and ATMOS™ CMOS camera, featuring 1.3M (just released) and 2M (to come shortly) up to 60 frames per second in Camera Link format.
[Dave G. Gilblom – Alternative Vision] Two kinds:
1. Digital color cameras made by HanVision using the Foveon color image sensors. LVDS or CameraLink outputs. Two models with different resolutions and speeds – HVDUO-10M – 2268 x 1512 x 3 @ 4.5 fps and HVDUO-5M – 1420 x 1064 x 3 @ 7 fps.
2. Contact image line scanners up to 3 meters long in color or monochrome with integral LED illumination. Resolution from 200 to 1200 dpi. Scan rates from 5 to 40 KHz. Operating distance from contact to 1.9 cm. CameraLink interface. Made by Tichawa Vision.
2. What are some challenges that you have offering products to the machine vision industry?
[John] Getting the word out that GigE cameras are available NOW.
[Ilias] Long design cycles, customization requests and a diverse list of requirements are major challenges faced in the machine vision market. Also, the lack of one industry-wide digital interface standard complicates the decision making process for new product lines and stretches engineering resources.
[Keith] Price/Performance ratios continue to decline as machine vision users expect high-performance cameras for less. In addition the number of competitors has increased greatly contributing to price erosion on the market.
[Marty] The challenge for Prosilica is to further provide excellent products and customer support at an affordable price, and to do all this better than our competitors.
[Gunnar] We are from time-to-time confronted with the question, why aren't industrial cameras priced the same as digital still cameras, when they use the same or similar image sensors?
[Loren] There are a wide variety of challenges that continue to surface. One of the most important ones are features that require a custom design through changes to hardware and/or firmware. A considerable amount of work and negotiations are required in working through the requirements, costs and time lines on everyone's part. Although a challenge, it is an opportunity for companies such as Imperx, in this time when some of the larger manufacturers are pulling out of the custom market.
[Bill] For these two brands, the biggest hurdle is the lack of name recognition. Also, integration with frame grabber manufacturers can be difficult as some companies are not open to building configuration files without the initial business to support the design work. Even though high-technology industries are generally open to new products, brand recognition still plays a factor in choosing a camera.
[David C.] The challenge for DALSA lies in ensuring that we keep a balance between our commitment to developing new technology with the varied needs of our diverse machine vision customer base. For example, customers inspecting flat panel displays may need the next generation in speed, while those performing web inspection require the next generation in resolution.
DALSA products incorporate the industry's latest imaging technology, advanced technology that customers may not be prepared for. We face a challenge today where our customers do not have technology available to them that can adequately acquire information at the speeds that our cameras are capable of.
[Steve/Gerhard] The most challenging aspect of offering our cameras to the machine vision world is the misconception that our cameras’ performance, resolution and dynamic range are too high, and in turn too expensive. Unfortunately, this is wrong in many cases. Although the cost of the our cameras are more expensive when compared to other component cameras used in machine vision systems, our cameras can substantially reduce the complexity of overall machine vision systems and bring about greater returns and economic efficiency to the application for the user.
Regrettably, most initial users take the path of perceived least expense, and fall into the trap of having to do much more work with the lighting, optics and software manipulation of the image to achieve their goal, if they obtain it at all. In short, the ‘‘plug and play’‘ mentality soon becomes the ‘‘plug and slug’‘ reality.
[Jin/Dave] Machine vision cameras need to be tailored to the conditions that they will be used in. Factors such as vibration and shock resistance become very important along with light sensitivity and spectral responses. As cameras are progressing toward the digital world output formats and system control becomes a critical component. Other challenges include:
Higher resolution, higher fps camera, and bigger pixel dimension at low cost.
The limited interface that must support the customer’s current software.
[Joachim] The main challenges are the price pressure, the expectations to get a reliable and calibrated product, easy of use/easy to integrate camera and last but not least customers requires a brilliant image quality with the condition of low power consumption and a small form factor. Image quality is one of the main issues when selecting a digital camera for industrial purposes. To deliver an image, e.g. with a CMOS sensor is easy, but to provide an excellent image quality, especially with higher frame rates is a real challenge. Besides the reliability within industrial environment like EMI compatibility is a must-be-standard. Industrial requirements are also shown in respect to the form factor of the housing, mounting holes, and connectors that have to be tightly mounted to the camera.
The pricing of digital industrial cameras, like Basler offers, are often compared with consumer cameras. Main focus of consumer still cameras is to increase the number of pixels, although the optical resolution is not achieved. On the other hand, cameras for machine vision applications have to offer standard resolution with high frame rates and global shutter. Therefore, costs of an industrial camera cannot be compared with consumer cameras.
[Christophe] There are many. As for us in ATMEL, I choose to mention:
1. Small volumes of pieces: typically, the biggest OEMs consume thousands cameras/year; but, in most cases, the standard machine vision clients consume one or a few hundreds of units/year.
2. Various requirements: we cover a wide variety of applications, going in pair with various implementation modes. Our choice in the design of AviivA families has been to propose a very versatile product, able to be operated at various data rates, timing mode, dynamic...and still, we deliver custom versions of these products to meet specific (sometimes exotic!) requirements.
3. Reluctance to changes: although the industry is moving fast, new solutions always appearing, we still face many clients whose main concern is to be delivered a stable product for 3 or even 5 years!
4. Reactivity: our clients work mainly by projects; they are often unable to provide forecasts but expect short lead times. This is a constant challenge at the level of the supply chain.
5. Price pressure: although a camera is one component of (often big) a system, the pressure on price is permanent, and getting stronger this time, especially for companies based out of the Dollar area.
[Dave G.] Unfamiliarity with how to apply color imaging. Unfamiliarity with how to apply line scan imaging. Most vision integrators stick with VGA monochrome area cameras.
3. What are some challenging machine vision applications your cameras have addressed?
[John] CameraLink - color line scan applications GigE - High-resolution or medium frame rate applications that require the camera be located some distance from the processor. The fact that a frame grabber is not needed here is also important to customers.
[Ilias] Sony’s industrial cameras are ideal for high-speed PCB inspection applications, small particle inspection and applications that subject cameras to extreme environmental conditions are at the top of our list.
[Keith] The most challenging have been: Flat Panel Inspection, contact lens inspection, print inspection, wafer inspection, and document scanning.
[Marty] Prosilica’s products are used in a wide range of machine vision applications. A significant area is manufacturing quality assurance where speed and flexible triggering are a requirement. The ability of our CV-Series cameras to daisy chain the trigger I/O with simple cables has made it a favorite for multi-camera applications.
Another application area that has been uniquely addressed by Prosilica cameras is automotive crash testing. The very long cable length (up to 500 meters) offered by the fiber-optic output of our CV1280F and CV640F cameras have enabled bird’s-eye views of crash test sites while providing full camera controls.
Wood processing also presents some challenges. We have customers who are imaging logs and lumber where the near-IR sensitivity of our CV640 cameras has enabled them to easily differentiate blue-stain defects in lumber and logs for grading and milling purposes.
Our new EC-series cameras have found application in semiconductor imaging where their ultra-compact size and light weight are of high value.
[Gunnar] High-performance metrology applications are extremely challenging. In these cases, sub-pixel interpolation providing accuracy below 1/10 of a pixel requires cameras with very low noise and high MTF. At the same time, the cameras must be moderately priced, as the systems are now also being used in production lines, and not only in the research labs.
[Loren] Imperx is a young company in the camera industry and many of the applications that we have addressed are still in the design stage so I am limited in what we can discuss. One that I can discuss involved the scanning of old negatives. The image needed to be inverted in real time and then a nonlinear correction applied. The application required that this be done in real time on the camera. The process of applying the image corrections, prompted the engineers to implement a more open architecture on the LYNX cameras. Custom LUT's can be created and uploaded to the camera by the user.
[Bill] For CIS, offering a CameraLink solution in a small package (29mm squared) and UXGA formats in color or monochrome at 30fps or higher. We are finding electronics and PCB inspection equipment manufacturers interested in the UXGA units as the camera footprints are the smallest available in the market. For NED, we are working on some different lumber applications in which monochrome systems are being upgraded to color to increase the robustness of the application.
[David C.] Medical imaging requires the clearest images for a finite level of detail that affects critical decisions made by medical personnel. Our foundry’s low noise sensor process currently leads the world in noise performance. This low noise process is leveraged in our sensors producing cameras with the lowest noise for the most detail. An example is DALSA’s Pantera TF 11M4, which easily meets the demands of the bio-medical field with 11 megapixel resolution and 14 bit output for maximum detail detection at four frames per second.
Flat panel display inspection and printed circuit board inspection require the latest generation in speed and resolution. These systems are inspecting for defects under 10-microns in size at incredible speeds. The lighting that is required to keep up with the high speeds that these companies are running their systems becomes a huge challenge and a huge cost. To overcome this challenge, DALSA offers large resolution TDI (time delay and integration) technology in cameras such as the Piranha HS 8K, which potentially achieves up to 640MHz throughput in low light conditions. Designed to function optimally in low light conditions, our TDI technology allows customers to maintain the speeds of their systems without incurring the huge costs of extra lighting.
[Steve/Gerhard] The most challenging machine vision applications involve quality control demonstrating a high dynamic range or put in simpler terms, a wide variation of light levels. A typical example is found in a bottle inspection machine. In this case, it’s not known in advance if the glass bottle material is transparent or dyed, or if the bottles are very clean. Additionally, such an operation will involve a large variety of bottle shapes. All these factors produce a very wide range of light levels during the machine vision application.
To maintain high throughput on the production line, it’s usually not favorable to first measure the glass bottles and subsequently adjust the illumination, as is typically done in most machine vision applications. It’s much better to incorporate a higher dynamic performance on the image capture and use an average illumination. This approach provides much more information within the image because of the higher dynamic range of the camera, over the common approach. Instead of a complex and time consuming light measuring and illumination control set-up, it's simply a 12-bit camera and a constant illumination, which enables a sufficient throughput.
[Jin/Dave] We have built cameras for a wide variety of situations. Probably the most difficult was to build a single camera with multiple vision sensors that are then integrated into a single output. Other challenging applications included:
Fiducial reading with very little working distance in an existing machine.
Reading low contrast, large area LCD Displays.
Solving reflection & working distance issues.
[Joachim] One example is document scanning, which is usually done with line scan cameras. The general trend is to extend to color images. Basler has introduced a tri-linear camera to the market that does not use the prism 3CCD technology. If some alignment conditions are fulfilled, a tri linear line scan camera provides excellent image quality with compact form factor and good price performance ratio.
Another challenging application is the field material testing that requires high frame rate and a good resolution. To achieve these high data rates of more than 600 MB/s (equals one CD per second), special electronics inside the camera, cables, and frame grabbers have to be implemented. The Basler A500 series has been developed for this kind of high-speed applications.
[Christophe] I would say:
Web inspection and the challenge of aligning many cameras side by side, answered by ATMEL via the excellent positioning tolerance of the sensor inside a very compact camera housing.
Packaging inspection (especially glass) where the main challenge is the antiblooming and the behavior for black/white transitions; the camera sees both the light source (very bright) and the bottle (very dark)
Flat panel display inspection and PCB inspection, with the challenges of speed (addressed today with products featuring 160 MHz, higher in the future) and dynamic range to detect very tiny grey level variations differences (achieved thanks to the excellent signal to noise ratio performance of Atmel sensors)... going in pair with the sensitivity of the sensor.
[Dave G.] Color uniformity measurement. Wide-web textile inspection where there is no room for line scan cameras.
<High-performance video with CMOS.
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