M42-Mount Visible Fixed Lens

  • Suitable for Φ43 mm sensor format
  • Standard M42 threaded mount
  • Optimized for the 400–700 nm visible band
M42 Interface Vis Len

The VIS354K is an M42-mount lens introduced by AttosTek for the 400–700 nm visible light band. It features a fixed focal length of 35 mm, a large F2.4 aperture, and is compatible with Φ43 mm large-format sensors (with a 28.6 mm adapter ring included as standard). The lens delivers 4K imaging resolution with uniform image quality across the entire field and excellent distortion control. It has undergone rigorous full-scale reliability testing, including temperature cycling, humidity, vibration, and drop tests, ensuring outstanding optical imaging performance and mechanical stability. It is suitable for high-speed industrial line-scan vision systems in applications such as lithium battery appearance inspection, print defect screening, and panel flaw detection.

  Φ43mm 1/2″ 1/3″
D 58° 13° 10°
H 47.5° 10.4° 8°
V 26.5° 8° 6°
Size
Vis354k Size
Focal Length

Focal length refers to the distance between the optical center (rear principal point) of a lens and its imaging focal point, serving as a key performance parameter of the lens. It determines the angle of view: the shorter the focal length, the wider the field of view and the broader the observable range; the longer the focal length, the narrower the field of view and the more concentrated the observation area.

Focal Length
Aperture

The aperture controls the amount of light entering the lens—a larger aperture results in a brighter image. This parameter directly affects exposure time and, consequently, the camera’s response speed. In daytime shooting, if the light is too strong, the aperture can be narrowed to prevent overexposure; at night or in low‑light conditions, the aperture can be widened to increase light intake, ensuring optimal imaging performance under varying lighting conditions.

Interface

The optical lens interface refers to the standardized mechanical mount connecting a lens to a camera body, determining compatibility and ensuring precise alignment for correct optical focus onto the image sensor. In industrial applications, C-mount and CS-mount are generally employed with cameras featuring smaller sensor sizes, while F-mount is typically used for larger sensors. Additional interfaces commonly found in line-scan cameras include M42, M58, and M72 mounts—essentially threaded connections of specified diameters.

C-mount lenses represent the established standard in machine vision, compatible with cameras housing image sensors up to approximately 20 mm (1.5 inches) in diagonal dimension. This interface supports a wide array of specifications across focal lengths, resolutions, and working distances. All SWIR fixed lenses provided by Attostek are designed with C-mount connectivity.

Resolution and MTF
Lens resolution, also known as resolving power, refers to its ability to distinguish between two closely spaced points. To achieve optimal performance, the lens resolution must be properly matched to the pixel size of the image sensor.
 
Lens resolution is commonly characterized using the Modulation Transfer Function (MTF) curve, which illustrates the relationship between spatial frequency and the transfer function value. The horizontal axis of the MTF curve represents spatial frequency in line pairs per millimeter (lp/mm), indicating how closely two points are spaced. The vertical axis represents the transfer function value, indicating the degree to which two adjacent points can be distinguished.
 
The MTF value at low spatial frequencies reflects the lens contrast performance, while the MTF at high spatial frequencies indicates the lens resolving capability. An ideal imaging lens exhibits an MTF curve that declines gradually from low to high frequencies.
Maximum Sensor Size
The maximum sensor size determines lens and camera compatibility. The lens projects a circular image circle, while the camera sensor is rectangular, meaning the final saved image is also rectangular. The “maximum sensor size” of a lens refers to the largest image sensor size that the lens is designed to fully cover

When used with a larger sensor, the edges of the sensor extend beyond the lens’s image circle, resulting in dark corners or black borders around the photo.
When used with a smaller sensor, only the central portion of the image circle is captured, leading to a reduced field of view and narrower angle of view.
Chief Ray Angle
The Chief Ray Angle (CRA) of a lens refers to the angle between the principal ray of the lens and its optical axis. The CRA of a camera sensor indicates the maximum incident angle at which the sensor’s pixels can effectively receive light. If the incident angle of light exceeds the sensor’s designed CRA limit, the light will not be properly captured by the sensor

To ensure optimal imaging performance, it is generally required that the lens CRA should match the sensor CRA, with the lens CRA not exceeding that of the sensor.
Cra
Depth of Field
Depth of field refers to the axial range in front of and behind the focused plane within which objects can still appear acceptably sharp in an image. This range includes the front depth of field (the clear zone in front of the focal plane) and the rear depth of field (the clear zone behind the focal plane). The sum of these two zones constitutes the total depth of field

Three primary factors influence depth of field: aperture size, working distance, and lens focal length. Increasing the depth of field can be achieved by:
  • Reducing the aperture size (i.e., using a larger f-number)
  • Increasing the working distance
  • Using a lens with a shorter focal length
Depth Of Field
Q1 : What is SWIR?

The word SWIR is an acronym meaning Short Wavelength InfraRed, also frequently referred to as shortwave infrared. SWIR generally refers to the wavelength band of light between 900nm and 2500nm.

Q2 : What exactly is a Short-Wave Infrared (SWIR) lens and how does it work?

A SWIR lens is an optical lens specifically designed to focus light in the short-wave infrared spectrum, typically between 0.9 and 1.7 micrometers (µm). The lens works by collecting SWIR light reflected from objects and converging it onto a specialized sensor, such as an Indium Gallium Arsenide (InGaAs) detector, which then converts the photoelectric signal into a grayscale image.

Q3 : Why can't I just use a standard visible-light lens for SWIR imaging?

While it is physically possible to mount a visible lens on a SWIR camera, the image quality will be severely compromised. Standard optical glasses and anti-reflective coatings are optimized for the visible spectrum (400-700nm). When used for SWIR, these lenses suffer from significant optical aberrations, particularly chromatic aberration, and a sharp decrease in resolution. This happens because the glass elements fail to focus the longer SWIR wavelengths to the same point, resulting in a blurred image. A true SWIR-optimized lens uses special glass types and coatings to ensure all SWIR wavelengths focus correctly, delivering high contrast and resolution.

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Fixed focal length lenses for M42‑mount visible‑light cameras

Model VIS354K
EFL 35mm
F/NO F2.4
Image Format Φ43mm
Mount M42
Distortion ≤-3.6%
Working Distance 0.2~∞m
Dimension Φ58.5*51.66mm
Flange Focal Length 46.5mm
Back Focal Length 26.2mm
Operation Manual Iris
Manual Focus
Design Wavelength 400~700nm
Filter Thread M55*0.75mm
Resolution 4K
IR Correction NO
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VIS354K

35mm Fixed Focal Length, F2.4 Aperture, M42-Mount Visible Lens

2 Weeks
$300.00