The F-Theta lenses are used for laser scanning systems which use two-axis galvanometers in order to scan an area, but can’t tolerate the angle on the image plane. By introducing a specified amount of barrel distortion in a scanning lens, the F-Theta scanning lens becomes an ideal choice for applications that require a flat field on the image plane such as laser scanning, marking, engraving and cutting systems. By adding a specific amount of barrel distortion to a scanning lenses, it becomes an excellent choice. These diffraction-limited lens systems can be customized to meet the needs of an application. They can take into account wavelength, focal length and spot size. The distortion will not exceed 0.25% across the entire field of view.
SUPERIOR® Optics manufactures high-quality f-theta lenses systems for laser scanning and engraving systems. These lens systems have been designed to produce a barrel distortion with a linear displacement based on the angle of incidence (theta) of the input beam. Each f-theta scanner lens is an array of 3 to 4 air spaced components mounted in a sturdy plastic housing. These lens systems allow for compact scanning systems to be designed without the need for complicated, bulky electronic correction.
F-Theta Lens Overview
F-Theta lenses are used for laser scanning systems which require a flat plane of images and high resolution. The image height of an F-Theta is proportional to scanning angle by introducing a certain amount of barrel distortion into the lens. These diffraction-limited lens systems can be designed to achieve the desired spot size with a distortion less than 0.25 percent of the field of view.
Optical Characteristics
When selecting an f-theta telephoto lens, you should consider the following parameters: operating wavelength, spot size and scan field dimension (SFD).
The scan length is also called the scan field diameter and can be abbreviated as SFD. The diagonal length is the area square in the image plane, where the laser is focused by f-theta lenses. The SFD will determine deflection and focal distance.
OSA is the abbreviation for the angle between the output beam normal and the image plane. The angle does not remain constant throughout the image field. However, the OSA change is so small that it won’t affect scanning applications. The output scan angle for telecentric lenses is always zero. The maximum OSA to avoid vignetting is the optical scan angle.
Calculating the spot size of a laser system is as simple as multiplying the wavelength and effective focal length by the entrance beam’s diameter, then dividing by the constant C. Laser scanning relies on the ability to place the spot in any location within the flat image plane. A good f-theta is the lens that makes this possible. On request, a spot diameter chart that shows the variation in spot diameter based on the field position can be provided.
The distance between the paraxial focal point and the f-theta lenses housing is called the back working distance of an f-theta. The back focal distance, or BFL is the distance between the paraxial focus to the apex (the outer glass element) of the lens.
Our f-theta lenses designs are designed at SUPERIOR® Optics to minimize field distortion, curvature and provide a flat plane of image. Our factory standard lenses are designed to have maximum distortions of less than 0.25% and transmittances of more than 90%. Our lenses are made of high-quality silica, which has a high resistance to damage. The f-theta lenses in stock have focal lengths ranging from 63mm to 645mm and custom optical coatings suitable for UV, visible and infrared use. We offer f-theta optics optimized for wavelengths of 355nm (532nm) and 1064nm (1064nm).
Industrial Standards
- F-theta Lens design: compact design with 3 to 4 elements
- Transmittance: >90%
- Distortion (Max.): <0.25%
- Consider the size of the workpiece and choose the appropriate working area;
The larger working area, the larger focal length of F-theta lenses, the larger focusing spot, and the wider marking line
- Focal length: available from 63mm to 635mm (The shorter focal length, the smaller focal depth, the deeper marking depth, and the higher requirements for flatness of workpiece;
With the larger focal length, the larger focal depth, and the shallower marking depth, you need to choose a high-power machine.)
- Custom optical coating: working wavelength range from UV to visible to infrared (10.6μm——CO2; 1064nm——fiber; 355nm——UV)
- The entrance beam diameter of common machines is 12mm. Under the same focal length, a smaller entrance beam will have a better engraving effect
- Choose the suitable thread for machine installation, the common mounting thread is M85, M55, and M35
- F-theta Lens performance: customized to fit specific application needs
Applications of F-Theta Lenses
F-theta lenses are used in industrial materials processing, mainly in drilling, welding and cutting synthetic materials. They are used in biotechnics and specifically in confocal microscopes and ophthalmology.
