Machine Vision Basics 03 - Optics Fundamentals

Summary

This video script delves into the intricacies of machine vision applications, emphasizing the importance of using a 'perfect object' for testing to ensure reliable results. It explores different lens types, such as conventional and telecentric lenses, detailing their features, benefits, and ideal applications. The script also explains key concepts like focal length and aperture, and how they impact image quality and depth of field. Additionally, it touches on useful lens accessories that can enhance magnification and inspection precision in various working environments.

Takeaways

• 🔍 The importance of using a 'perfect object' as a benchmark for testing in machine vision applications, ensuring it passes every test and embodies all desired features.
• 📐 The significance of good contrast and measurable, repeatable, and robust features in creating an ideal inspection image for machine vision.
• 🌀 The components of a conventional lens including the mount base, aperture adjustment, lock down screws, filter threads, and focus adjustment.
• 🔬 The benefits of a conventional lens such as lower cost, smaller size, and the ability to change magnification with a change in working distance.
• 🤖 The typical applications of conventional lenses in detecting larger objects, feature detection, presence or absence checks, code reading, and guiding robots.
• 📏 The design of telecentric lenses to minimize perspective and distortion, with features like lockdown screws, aperture adjustment, and focus adjustment.
• 💡 The necessity of lockdown screws in high vibration environments to prevent lens loosening and image blurring.
• 💰 The higher cost and larger size of telecentric lenses due to their precision in minimizing perspective error and providing constant magnification.
• 🔎 The utility of telecentric lenses for inspecting smaller objects and in scenarios where the product moves in the working distance from the lens.
• 📈 The comparison between conventional and telecentric lenses in terms of light and image path, showing the straight-on path of telecentric lenses for better resolution.
• 🔢 The definition of focal length as the distance from the optical center of the lens to the focal point on the imager when in focus, usually measured in millimeters.
• 🌀 The explanation of aperture as the ratio of the lens's focal length to its effective diameter, affecting the f-stop value and depth of field.
• 🛠️ The role of lens accessories like extenders and tubes in enhancing magnification, adjusting the field of view, working distance, and light reaching the camera.

Q & A

What is the importance of having a 'perfect object' in machine vision testing?

A 'perfect object' is crucial for machine vision testing as it serves as the benchmark for all good and bad reads, ensuring that the object has all the features to be emphasized and none to be minimized, providing good contrast, and being measurable, repeatable, and robust.

What are the benefits of using a conventional lens in machine vision applications?

Conventional lenses offer benefits such as lower cost, smaller size, and the ability to change magnification with a change in working distance. They are useful for detecting larger objects, feature detection, presence or absence, code reading, and form check but are not typically recommended for gauging.

Why are telecentric lenses designed to minimize perspective and distortion?

Telecentric lenses are designed to minimize perspective and distortion to provide a more accurate and consistent image, which is essential for high-precision applications in machine vision.

What is the purpose of lockdown screws on telecentric lenses?

Lockdown screws on telecentric lenses are used to keep the lenses in place and prevent them from coming loose, especially in high vibration environments. If not secured, the lens can become loose, leading to blurry images and inaccurate readings.

How does the conventional lens differ from the telecentric lens in terms of light and image path?

In a conventional lens, the light and image path tend to angle out, whereas in a telecentric lens, the light and image path are more direct, entering straight into the lens. This difference contributes to the better resolution and detail in telecentric lenses.

What is the definition of focal length in the context of lenses?

Focal length is defined as the distance from the optical center of the converging lens to the focal point located on the imager when the subject is in focus. It is typically measured in millimeters.

How does the aperture of a lens affect the depth of field?

A larger aperture opening results in a smaller f-stop value, which means a shallower depth of field. Conversely, a smaller aperture (higher f-stop value) provides a greater depth of field, allowing for a clearer image of objects at various distances.

What are lens accessories and how can they be beneficial in machine vision?

Lens accessories are additional components that can be used with lenses to enhance their performance. They can improve magnification, alter the field of view, and adjust the working distance. Depending on the application and environment, these accessories can be very useful for inspecting objects in machine vision.

What is the function of extension rings and extension tubes in machine vision lenses?

Extension rings and tubes are used to increase the focal length of a lens, which enhances magnification and decreases the field of view. They help in focusing more closely on the object of interest while reducing the amount of light reaching the camera.

What is the range of extension rings and tubes typically used in machine vision applications?

Extension rings can range from 0.25 millimeters to 2 millimeters, while extension tubes can range from 5 millimeters to 40 millimeters, offering a wide variety of options to adjust the lens configuration according to specific vision inspection needs.

How does the working distance change when using extension rings or tubes?

Using extension rings or tubes decreases the working distance, allowing the camera to be positioned closer to the object being inspected, which can be advantageous for high-magnification inspections.