Understanding core optical and camera terminology is critical when designing reliable, high-performance machine vision systems. This guide outlines the key lens and camera concepts used in industrial imaging, automation, and inspection applications. Each term is presented with practical context to support real-world system design and implementation.

  • Aperture

    The aperture is the opening inside a lens that controls how much light reaches the camera sensor. A larger aperture lets in more light, which is helpful in low-light environments. A smaller aperture lets in less light but increases depth of field. In machine vision, aperture also affects image sharpness and contrast. It is usually expressed as an f-number (e.g. F2.8).

  • Back focus

    Back focus describes the distance from the vertex of the rearmost glass element of the lens to the point where the image is in focus. This distance must match the camera and mount type to achieve sharp images. If back focus is incorrect, the image cannot be focused properly. Some lenses allow back focus adjustment. It is especially important when using different sensors or adapters.

  • Broadband coating

    Broadband coating is a multi-layer optical coating applied to lens surfaces to reduce reflections over a wide range of wavelengths. The benefits: it improves light transmission and image contrast. Broadband coatings are especially useful when a system operates across multiple spectral ranges, such as visible and near-infrared (NIR) illumination. It also helps reduce ghosting and flare.

  • Control

    In machine vision, control refers to how camera or lens functions are managed. This can include exposure, gain, focus, or iris control. Control can be manual or automatic, depending on the system. Many industrial cameras allow control via software. Reliable control is essential for stable and repeatable imaging.

  • Field of view

    Field of view describes the physical area of the object that is visible to the camera. It is determined by the sensor size, lens focal length, and working distance. A wider field of view captures more area but with less detail. A narrower field of view shows more detail but less area. Choosing the right field of view is critical for accurate inspection.

  • Focus shift

    Focus shift is a change in focus when lighting conditions or wavelengths change. It commonly occurs when switching between visible and infrared illumination. If a lens is not optically corrected for multiple wavelengths, the image may become blurry. Focus shift can reduce measurement accuracy. IR-corrected lenses help minimize this effect.

  • IR correction

    IR correction means the lens is designed to focus visible and infrared light at the same point. Without IR correction, infrared images may appear out of focus. This is important in applications using IR illumination. IR-corrected lenses ensure consistent image sharpness. They are commonly used in machine vision and surveillance.

  • Flange back

    Flange back is the fixed distance between the lens mount and the camera sensor. Each mount type (C-mount, CS-mount, etc.) has a defined flange back distance. The lens and camera must match this distance to focus correctly. An incorrect flange back leads to focus problems. It is a key mechanical specification.

  • Frames per second (fps)

    Frames per second describes how many images a camera captures each second. Higher FPS allows faster motion to be captured clearly. Lower FPS may cause motion blur or missed events. FPS depends on sensor speed, interface, and resolution. It is crucial for high-speed inspection and automation.

  • Working distance

    Working distance is the distance between the lens and the object being imaged. It affects magnification and field of view. Short working distances allow high detail but limit space. Longer working distances are useful for large objects or harsh environments. Lenses are often specified for a certain working distance range.

  • Focal length

    Focal length determines how strongly a lens magnifies an image. Short focal lengths provide a wide field of view. Long focal lengths provide higher magnification and a narrower field of view. Focal length is measured in millimeters. It is one of the most important lens selection criteria.

  • Focus range

    Focus range defines the distances over which a lens can focus. Some lenses focus only at close range, others from near to infinity. A wider focus range offers more flexibility. In fixed setups, the focus range must match the working distance. Industrial lenses are often optimized for specific ranges.

  • Mount

    The mount is the mechanical interface between the lens and the camera. Common mounts include C-mount, CS-mount, F-mount, and M42. The mount determines compatibility and flange back distance. A secure mount is essential for stable imaging. Industrial mounts are designed for vibration resistance.

  • IP-rating (67, 69)

    IP rating describes how well a device is protected against dust and water. IP67 means dust-tight and protected against temporary water immersion. IP69 means protection against high-pressure, high-temperature water jets. Higher IP ratings are important in harsh environments. Cameras and lenses with high IP ratings are used in industrial and outdoor applications.

  • Chief ray angle

    Chief ray angle describes the angle at which light hits the sensor. Large angles can cause shading or color shifts, especially on small pixels. Sensors have limits on acceptable chief ray angles. Lenses designed for modern sensors control this angle carefully. This is important for image uniformity and accuracy.

  • Minimum illumination

    Minimum illumination is the lowest light level at which a camera can produce a usable image. It is measured in lux. Lower values mean better low-light performance. This depends on sensor sensitivity, lens aperture, and noise. It is important for night or low-light applications.

  • Iris Control

    Iris control adjusts the aperture opening automatically or manually. Automatic iris control responds to changing light conditions. This helps maintain consistent image brightness. Manual iris control is common in stable lighting environments. Iris control improves image quality and stability.

  • Shutter type

    Shutter type defines how the sensor captures light. Global shutter captures the entire image at once. Rolling shutter captures the image line by line. Rolling shutter can cause distortion with moving objects. Global shutter is preferred for fast machine vision tasks.

  • Spectral response

    Spectral response describes which wavelengths a sensor can detect. Some sensors are optimized for visible light, others for infrared or SWIR. The lens and sensor must match spectrally. This affects sensitivity and image quality. Critical in multi-spectral applications.

  • Pixel size (µm)

    Measured in micrometers (µm), thep ixel size is the physical size of one pixel on the sensor. Larger pixels collect more light and perform better in low light. Smaller pixels allow higher resolution. Pixel size affects lens requirements and chief ray angle tolerance.

  • Image circle (mm)

    Image circle is the diameter of the image projected by the lens. It must fully cover the camera sensor. If the image circle is too small, dark corners appear. Larger sensors require larger image circles. This specification ensures sensor compatibility.

  • Sensor size

    Sensor size describes the physical dimensions of the camera sensor. It is often given in inches (e.g. 1/2", 1"). Larger sensors capture more light and detail. Sensor size affects field of view and lens choice. The lens must support the sensor size.

  • Resolution

    Resolution describes how much detail an image contains. It is usually measured in pixels (e.g. 1920 × 1080). Higher resolution allows finer detail detection. Resolution depends on both sensor and lens quality. A high-resolution sensor requires a matching high-performance lens.

  • TV distortion

    TV distortion describes geometric distortion in an image. Straight lines may appear curved at the edges. Low distortion is important for measurement tasks. Distortion is usually expressed as a percentage. Industrial lenses are designed to minimize distortion.

  • Vignetting

    Vignetting is the darkening of image corners compared to the center. It occurs when light is blocked or falls off toward the edges. Vignetting can affect measurement accuracy. Proper lens and sensor matching reduces vignetting. Some correction can be done in software.

  • Wavelength range

    Wavelength range defines the light spectrum a lens is designed to transmit. This can include visible, near-infrared, or SWIR. Outside the designed range, image quality drops. Matching wavelength range is essential for special lighting. It ensures sharp focus and high contrast.

  • SWIR

    SWIR stands for Short-Wave Infrared. It typically covers wavelengths from about 900 to 1700 nm. SWIR can see through smoke, haze, and some materials. It reveals details invisible in visible light. SWIR is used in inspection, security, and fire detection.

  • Ruggedized

    Ruggedized equipment is designed for harsh environments. This includes resistance to vibration and shock. Operational shock describes sudden mechanical impacts a device can survive. It is usually measured in G-forces. Ruggedized cameras and lenses ensure reliable operation.

  • Telecentric

    A telecentric lens produces images with constant magnification. Object size does not change with distance. This is important for precise measurement. Telecentric lenses eliminate perspective errors. They are widely used in metrology and inspection.

  • Radiation resistance

    Radiation resistance describes how well a lens or camera withstands radiation exposure. Radiation can darken glass and degrade image quality. Resistance is measured in units such as Gray (Gy). Testing is done by exposing products to controlled radiation levels. Radiation-resistant optics are used in nuclear and space-related environments.

  • Camera interfaces

    Camera interfaces define how image data is transferred to a computer. GigE uses Ethernet and allows long cable lengths. CoaXPress supports very high data rates for high-speed cameras. The interface affects speed, cable length, and system cost. Choosing the right interface is key for performance.