F-Theta Lens

What is an F-Theta lens?

F-Theta lenses, also known as scan lenses or galvanometer lenses,are optical lenses designed to focus a laser beam scanned by agalvanometerscanner orpolygon scannerat a position determined by the product of the focal length (F) and the mirror swing angle (θ).

They are designed so that the relationship between the scanning angle and the focal position is linear, and are used for high-speed drilling of printed circuit boards, marking on electronic and plastic components, and microfabrication applications.

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Key Considerations for Selecting F-Theta Lenses and Product Options

When selecting an F-Theta lens, it is necessary to comprehensively evaluate optical characteristics such as focal length, scan area, and focused spot size based on the laser type and required processing accuracy. Options include "standard products" and "custom-made products," which should be used appropriately depending on the equipment specifications and processing requirements.
Standard products offer the advantages of versatility and stable supply, allowing for smooth implementation if specifications match. On the other hand, in recent years, due to the diversification of processing targets and the advancement of laser performance, there has been an increase in cases where standard specifications cannot be met. Consequently, there is a growing need for custom solutions through individual design.

Key Information Required for Selecting an F-Theta Lens

When selecting an F-Theta lens, organizing the following points in advance will help ensure a smooth selection process.

• Type and wavelength of the laser to be used (e.g., CO₂/fiber, etc.)
• Required processing area and precision (focal length, scan area, spot size, etc.)
• Mounting specifications, working distance,and external dimensions

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Structure and Materials of F-Theta Lenses

F-Theta lenses consist of multiple lenses, such as spherical and aspherical elements, and achieve uniform beam irradiation while maintaining a constant working distance across the entire scan area.

There are two types of structures available depending on the application.

• Telecentric type: This structure irradiates the beam perpendicular to the processing surface. It has minimal angular deviation due to positionand often offers good focusing characteristics,making it suitable for precision processing thatrequires high accuracy.
• Non-telecentric type: Used in applications prioritizing a wide scanning area.Sincethe irradiation angleis tilted, simple lenses are generally used in fields where machining precision is not a critical requirement.

Materials usedincludeZnSe (zinc selenide), which is suitable for CO₂ lasers, andsynthetic quartz or optical glass (such as BK7), which aresuitable for fiber lasers. The choice depends on the application and wavelength.Furthermore, advanced processing and coating technologies compatible with these materials determine the performance of F-Theta lenses.

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Why Sumitomo Electric’s F-Theta Lenses Are Chosen

Fully Customized Design to Meet Your Needs

Sumitomo Electric’s F-Theta lenses can be custom-designed to be individually optimized according to customer equipment specifications and processing applications. We analyze various optical characteristics—such as focal length, scan area, spot size, and telecentricity error (beam incidence angle deviation)—using optical simulation to propose the optimal specifications.

We also provide design consultation even before specifications are finalized and can propose comprehensive optical solutions, including DOEs (diffractive optical elements) and beam-shaping optical systems.We accommodate custom manufacturing starting from a single prototypeand can support customers with advanced optical analysis technology during the prototyping and verification phases of equipment development upon request.

High-Precision Machining and Stable Supply Achieved Through Integrated Domestic Manufacturing

Sumitomo Electric manufactures everything in-house in Japan, from the synthesis of ZnSe crystals to aspheric machining, AR coating, assembly, and inspection. As the only manufacturer in Japan capable of synthesizing ZnSe crystals in-house, we are able to provide high-quality F-Theta lenses.

For precision optical processing, we employ SPDT (Single Point Diamond Turning) aspheric processing technology to achieve nano-level processing accuracy and high-precision measurement. We support a variety of materials,including ZnSe and quartz, and can processshapesaccordingtodesign specificationswith high precisionwithin controlled tolerances. Furthermore, we provide comprehensive proposals ranging from material selection tailored to specific applications through to processing.

Furthermore, through advanced process control and in-house manufacturing, we minimize variations in the manufacturing process and can quickly identify causes and verify reproducibility even when issues arise. We support the supply of high-precision, stable lenses from the prototype and development stages of equipment through to mass production.

Achieves uniform focusing performance across the entire scan area

Domestic Reliability and Extensive Industry Track Record

Sumitomo Electric’s F-Theta lenses ensure high quality and long-term stable supply through domestic manufacturing, quality control, and support systems in Japan. Since we handle everything from design to manufacturing, inspection, shipping, and after-sales support entirely within Japan, we can provide rapid technical support in the event of any issues.

To date, we have a proven track record of successful implementation in fields requiring high-precision processing, such as semiconductors, electronic components, medical devices, and aerospace. We also have extensive experience in micro-processing applications, including laser drilling, and have long supported high-precision processing in equipment. As optical components that achieve both long-term stable operation and processing accuracy in demanding industrial applications, they are highly regarded by equipment manufacturers and processing sites.