How to Choose Lenses for Machine Vision

Machine vision is a broad and varied application requiring compact and powerful optical systems and lenses that provide telecentricity, excellent contrast, and high resolution.

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Compact Zoom and Fixed Lenses from Resolve Optics

Resolve Optics Ltd has several years of experience in manufacturing compact zoom and fixed focus lenses for vision applications such as parts recognition, precise component placement, and the placement, automated alignment, and automated inspection of manufactured parts.

The range of optical systems and machine vision lenses is substantial because of the broad range of sensor formats and the varied resolution versions of cameras.

Challenges Faced

One of the most common errors made when developing a vision system is that the engineer or researcher will generally select a camera and a sensor before choosing a lens. This could lead to a situation where an enhanced lens is unavailable for the application.

It must be noted that all machine vision systems require an image of sufficient quality to be generated to perform the required measurements. The choice of lens or lens combination mainly governs the image quality.

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The selection of lenses can further impact other factors like the achievable speed, reproducibility and reliability of the downstream analysis, and measurement precision of the vision system.

How to Select a Machine Vision Lens

A suggested selection process for a machine vision lens should involve the identification of the optical needs of the application and arriving at a consensus on the key specifications to accomplish this.

Such optical parameters should comprise resolution (or size of the tiniest part or detail to detect or observe), working distance, the field of view, and the depth and range of field (the height of the objects being detected).

Once these four major specifications are decided and fixed, an enhanced camera and lens can be easily selected.

There is a certain relation between the most suitable lens and the sensor used in the camera. When the size of the sensor is known, an enhanced lens can be selected, which will light up the whole area of the sensor without shading and vignetting.

The chosen lens should also be able to resolve the sensor’s pixel size. If the optical resolution of the lens is high, a more comprehensive machine vision analysis can be realized.

Typical resolution lenses (MTF of 70 to 90 lp/mm creating low vignetting and distortion) are the most commonly used lens for machine vision sensors with less than a 1 MP resolution.

High-resolution lenses (MTF > 120 lp/mm and very low distortion) offer enhanced imaging performance when compared to normal lenses. They are particularly suitable for cameras that have a small pixel size.

Conclusion

This article has given an overview of various factors that should be considered while creating an improved inspection solution using machine vision.

Customers can contact Resolve Optics Ltd to review any application and learn more about the advanced manufacturing solutions and optical design provided by the company for use in applications concerning machine vision.

This information has been sourced, reviewed and adapted from materials provided by Resolve Optics Ltd.

For more information on this source, please visit Resolve Optics Ltd.