What is a lens optical format? Can I use any machine vision camera with any format? NOT!

Common lens questions we are often asked are, “What is a lens’s optical format (or size; we will use the two interchangeably) and how does it relate to specific image sensor sizes in industrial cameras? Along with, “Can any size machine vision camera be used on any lens format or do they need to be matched exactly?”

First lets review the sizes of the machine vision camera image sensors themselves (as seen below).

Lens Optical format — Image sensor sizes given in ” vs. true diagonal size in mm

The image sensor size is typically put in terms of “inches”, but really has nothing to do with this and dates back to the “image tube” days. Without a big history lesson, a sensor that fit into an image tube with a 1” (inch) yoke was deemed a 1” image format . Today, we still use these terms and see commons sizes stated as 1/3”, ½”, 2/3” as seen in the image above. Note: The image size in ” does NOT calculate to mm and vice versa! It is nomenclature only.

However, what is important is to look at the diagonal across the given image sensor which is the “image circle”. (i.e The 1/3” format above has a diagonal of 6 mm. )

The size of the lens MUST be equal or greater than the size of the sensor ( circle size that covers the sensor) or you simply will not get the whole image!

Lens optical format vs sensor size — Lens optical format (circle) vs sensor size (rectangle)

The diagram above shows a 1/3″ format image sensor (6mm diagonal). In order to adequately cover the image sensor, you need a 1/3″ lens format or larger. On the left, we show a lens with a 1/4″ format, and it does not cover the sensor.

The end results from the improper mating of a smaller lens format than the image sensor format will be vignetting (dark corners where the lens does not cover the sensor) of the image.

What can I do when there is no specific lens format matching the image sensor format?

Lens manufacturers are continuing to design lenses to address the changing sensor market. However you will not always find a specific size format to match the lens. In these cases, you just need to ensure the lens format (image circle diameter) is larger than the sensor as mentioned in the above example.

An example is the newer 1/1.2” sensor sizes (IMX174, IMX249 ) which have a diagonal of 13.4mm. Although there are some lens manufacturers that designed a lens with the specific 1/1.2” format, there are not many. Referring to lens format diagram, the 1/1.2” format is between a 2/3” and 1” format. The 2/3” format has a image circle of 11 mm which will not fully cover the 1/1.2” format (13.4mm diagonal), and you will get vignetting of the image. The solution is to use the next size up which is a 1” format. This format is commonly found in many lens manufacturers, in turn providing many lens manufacturers to choose from.

Click here now for all lens sizes and manufacturers

In conclusion, you can use an image format on a lens on smaller image sensor size, but not the other way!.. You’ll have vignetting and lose part of your image!

What else do we need to consider in lens selection?

This blog post simply covers sensor formats vs sensor sizes. There is much more to consider in a lens selection such as resolution of the lens to resolve the pixels themselves, what focal length is needed etc.

Here are some further resources to help in the selection process. Additionally, 1^st Vision has over 100 years of combined experience in industrial imaging in which you can contact us to aid in the section.

How to choose a lens –

Calculating resolution for a machine vision application – https://www.1stvision.com/machine-vision-solutions/2015/07/imaging-basics-calculating-resolution.html

Video Tutorial – Using the On-line lens focal length calculator https://www.youtube.com/watch?feature=player_embedded&v=baF4lwl0LwM

1^st Vision newly added our high quality 1” format lenses which provide an excellent price vs performance ratio – Read more here.

Images courtesy of Wikipedia

August 30, 2017August 11, 2022

Learn about 1stVision’s new OEM 1” machine vision lenses which provide excellent price vs performance ratios

For many years 1stVision has offered several lines of OEM machine vision lenses. These lenses are ‘unbranded’ but they are made with the glass of one of the big three Japanese optical manufacturers.

1^st Vision lenses have excellent optical performance for a great price currently offering a product line designed for a 2/3” image formats with 2MP and 3MP resolutions.

Click here to see the full line of OEM lenses here and request a quote

Advantages
The OEM machine vision lenses offer some distinct advantages:

They are less expensive than similarly performing ‘branded’ lenses
When designed into instruments for resale, all issues come back to the original manufacturer. The end user cannot bypass the manufacturer, ensuring you, when your users have problems, you know about them!
With a good price point, the 1″ format can be used for all smaller sensor sizes using the “sweet spot” of the lens!

What’s new? OEM 1” Optical format machine vision lens.

Recently, 1stVision have begun offering a new OEM line of 1” format, high performing 2 and 3 MP lenses, which offers all the above advantages, but you can now use it with the new Sony Pregius and On Semi Python sensors that require lens optical formats greater than 2/3” (For example the Sony Pregius 2MP ( IMX 174, IMX249 ), 8.9MP ( IMX267, IMX255 ) and ON-SEMI 5MP Python 5000 sensors ) Search on the image sensors here

Click here now to view the new product line and request a quote

1^st Vision maybe a distributor, but we are really your value-added vision consultants! With combined experience of over 100 years, we can help discuss the optical performance, how it relates to your image sensor and help you in the design process. Please contact us to start a conversation

August 28, 2017September 11, 2019

Learn how liquid lenses keep continuous focus on machine vision cameras when the working distance changes.

Optotune lenses solve a machine vision industry problem!

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Machine Vision applications requiring the inspection of objects at various heights can become a challenge as normal lens have limited depth of field. Objects outside of the depth of field become out of focus, limiting the vision application. Historically, a lens with motorized focus adjustment would be implemented adding complexity, cost and long cycle times. In reality, this challenge is applicable to any imaging application requiring refocusing due to various lens working distances.

Optotune Focus tuneable lenses solves this problem eliminating motorized zoom lenses or manual intervention.

Click here NOW for full detail specifications on tunable lenses

Adding an Optotune tunable liquid lens to the optical system on a standard C-mount lens and camera, allows refocusing of the imaging system on the fly. When used in conjunction with distance sensors, its possible to inspect objects of various heights, refocusing within 15 milli-seconds.

For example, vision systems using 8mm to 50mm focal length lenses can be equipped with a tuneable lens in the front, typically mounted on the filter thread. In this configuration it is possible to focus from infinity down to about 100mm or less if spacers are added.

This solution can be applied to industrial machine vision applications, ophthalmology, laser, microscopy, postal, packaging and laser applications to name a few.

Contact 1stVision for a quote on Optotunes Tunable lenses

Technology 411

Optotune’s focus tunable lenses are shape-changing lenses based on a combination of optical fluids and a polymer membrane. The core element consists of a container, which is filled with an optical liquid and sealed off with a thin, elastic polymer membrane. A circular ring that pushes onto the center of the membrane shapes the tunable lens. The deflection of the membrane and with that the radius of the lens can be changed by pushing the ring towards the membrane or by exerting a pressure to the outer part of the membrane or by pumping liquid into or out of the container.

Watch this video to see the Optotune liquid lens in action

Advantages

A change in lens radius of several micrometers can have the same optical effect as moving the entire lens several centimeters. In turn there are several advantages

Optical systems can be designed more compact, oftentimes with less lenses and usually with less or no translational movement.
Large working distance ranges can be achieved
Eliminate expensive mechanical actuators resulting in a more robust design, which can be completely closed so that no dust can enter. Essentially no moving parts for long life cycles (> 1B cycles)
Weight and volume is reduced in the system.
Low power consumption.
Fast response time of systems, down to the order of milliseconds.
Easy installation and remote focus control
Advanced controls for very accurate and repeatable control of the lens using Gardasofts TR-CL180 controllers

Want to know more? Download Optotunes comprehensive white paper here

This white paper will review the overall principles of tunable lenses, response times, wavefront quality, drive methods, and applications.

Contact 1stVision for a quote on Optotunes lenses and discuss an overall solution with cameras, lenses and lighting if required.

UPDATE: Video showing some great demo’s from the Stuttgart Vision show in 2018

July 18, 2017March 21, 2023

Considerations in selecting a lens for a large format camera sensor

For most cameras in the automated imaging marketplace, the sensor sizes are 1” and less. (1″ sensors have 16mm image circle/diameters)

Note the size in inches and the image circle size in millimeters do NOT match! 1” does not convert to 16mm!. But that is a topic for another blog post!)

Industrial cameras with C/CS mount sensors normally range from ¼” to 4/3” ( up to 22mm image circle, which is the largest a C mount is by definition).

However, there are many cameras that have sensors larger than this, with many being a full 35mm sensor. These sensors typically require larger F or EF mounts as seen in the picture above.

Click here for F-mount lenses from Kowa

Click here for F-mount lenses from Schneider

The question becomes, how do you find a suitable lens for these cameras?

First, let address the Issues with F mount lenses

The mount most commonly used by camera vendors for sensors larger than C mount are F mounts. F mounts are most popular mount for SLR cameras, designed by Nikon about 1960. https://en.wikipedia.org/wiki/Nikon_F-mount

F mount lenses for commercial and consumer/prosumer cameras are excellent optically and priced well but there are several issues you need to consider with these lenses for automated imaging applications.

First, F mount lenses are bayonet, not screw mount. That means they are not as secure as C mount, and therefore, much more prone to vibration, or even coming lose.
F mount lenses for the consumer/prosumer market are designed to take fantastic color pictures. To do this, the lens coatings are optimized for color. This can affect mono images.
Consumers want their cameras to be light, so the F mount lenses are made with as much plastic as possible. This is not great for industrial applications
These lenses are designed for automatic focus and exposure and have controls for that in the lens itself.
Finally, the last issue is that many of these lenses are designed for the automated controls with prosumer cameras, autofocus and autoexposure.

If you can find an all metal manual F mount lens from 20 to 30 years ago, it would be great for an industrial application! If not, we suggest you turn to one of the companies that make F mount lenses specifically for this market. The major vendors are Schneider, Edmund Optics, and Kowa. All have a series of F mount lenses that are much more rugged than a prosumer F mount lens, and also don’t have the extra controls for automatic focus/iris. They have lock screws as well to hold their settings. The major limitation to these lenses are that they cost more than prosumer lenses, and are in just a small range of focal lengths.

Contact us for further specifications and pricing

EF Lenses

Since many of the new large format lenses can be controlled electronically via the camera, the automated imaging industry has created several products to use these lenses. The solutions from Birger Engineering, www.birger.com are straightforward to use. They make a mount that attaches to the camera and allows for the use of EF mount lenses. Attached to their mount are connections to drive the lenses, via serial commands with their SW. Several camera manufacturers have built cameras with EF mounts as part of the camera. This is an especially nice solution since there are no wires hanging out for control, and the lens is controlled directly from the camera’s SDK.

This provides a high level overview of the considerations in selecting a lens and size for large format camera sensors. 1st Vision has extensive knowledge with lenses and cameras and will help you in the selection process.

Please contact us and discuss your application with our sales engineer!

Related Blog posts:

Canon EF mount integrated into Allied Visions GT1930L

Imaging Basics – Calculating lens focal lengths

Not all lenses are created equal!