F-Theta lenses made for laser material processing
Powerful and robust lenses for the high demands of your laser beam guidance system
Jenoptik F-Theta objective lenses
Low-contaminating mounting technologies, no adhesives and lubricants, clean room assembly
Thanks to high-performance optical design
Quickly and easily integrate components into any existing system
Available as a standardized solution or can be adapted to your individual requirements
FEM analyses of optical assemblies monitor thermal and mechanical stress to save money
Extensive testing ensures interchangeability in the field
F-Theta JENar™ lenses for wavelengths from 355 to 1080 nm
The F-Theta JENarTM lenses are suitable for uses in micromaterial processing, especially for microstructuring or for marking and labeling different materials.
The JENarTM series is used for laser wavelengths in the UV, VIS or IR range, but they are also available for wavelengths from 355 to 1080 nm. The standard lenses are produced with protective glass and are extremely durable.
These lenses can be quickly and easily integrated into any system using the available STEP files. Each lens undergoes a standardized application-specific test, which ensures consistency of the optical properties during series production. This makes it easy to replace lenses, and customer benefit from an increased product lifecycle.
|Lens||Order number||Wave length||Data sheet||Step data||Zemax data||Back reflections|
|JENarTM125-1030...1080-80 + VIS1)||601926||1030...1080 nm||DB 601926||STP 601926||ZIP 601926||PDF 601926|
|JENarTM160-1030...1080-170 + VIS1)||601914||1030...1080 nm||DB 601914||STP 601914||ZIP 601914||PDF 601914|
|JENarTM255-1030...1080-239 + VIS1)||601948||1030...1080 nm||DB 601948||STP 601948||ZIP 601948||PDF 601948|
|JENarTM347-1030...1080-355||609661||1030...1080 nm||DB* 609661||STP* 609661||ZIP* 609661||PDF 609661|
Optimized for micromaterial processing
High-power F-Theta JENar™ APTAline™ objective lenses
F-Theta JENar™ APTAline™ objective lenses for wavelengths from 355 nm to 1080 nm
With the new JENarTM APTAlineTM series, we offer lenses that are optimally tailored to customers' requirements. This means that we respond to the constantly changing requirements of the industry and increase the possible range of applications with the APTAlineTM series.
These quartz glass, high-power lenses offer a cost-optimized alternative for demanding applications where reliability, series stability and durability count. They are available for wavelengths of 1030...1080 nm. The APTAlineTM lenses are based on proven mechanical and optical designs and are subject to the same high-quality standards as our other F-Theta products.
|Lens||Order number||Wave length||Data sheet||Step data||Zemax data||Back reflections|
|JENarTMAPTAlineTM 160-1030...1080-110-AL||689620||1030...1080 nm||DB 689620||STP 689620||ZIP 689620||PDF 689620|
|JENarTMAPTAlineTM 255-1030...1080-160-AL||689622||1030...1080 nm||DB 689622||STP 689622||ZIP 689622||PDF 689622|
|JENarTMAPTAlineTM 161-1030...1080-71-AL||679781||1030...1080 nm||DB 679781||STP 679781||ZIP 679781||PDF 679781|
Always with an eye on the market
High-power F-Theta JENar™ Silverline™ objective lenses
F-Theta JENar™ Silverline™ objective lenses for wavelengths from 355 to 1080 nm
SilverlineTM F-Theta lenses from Jenoptik have been specially developed for applications that require high-power lasers and short-term pulses. These lenses consist of low-absorbing, full quartz glass to offer particularly high laser power. They are available for wavelengths of 266 nm, 355 nm, 1030...1080 nm or 900...1100 nm.
The SilverlineTM F-Theta lenses limit diffraction and produce a high image quality. They are also highly resistant to damage and provide high spot consistency over the entire scanning range. With beam power of up to four kilowatts, the SilverlineTM lenses do not require active cooling and guarantee a minimal focal point shift for high-power lasers.
Specifically, the SilverlineTM F-Theta lens 170-355-140 covers the 355 nm range. It has a low maximum telecentric angle of only 4.9 degrees and a homogeneous spot size distribution over a working field of 100 x 100 mm. This large working field combined with diffraction-limiting imaging quality enables increased output in comparison to conventional lenses ensured by our innovative, patented mounting technology.
|Lens||Order number||Wave length||Data sheet||Step data||Zemax data||Back reflections|
|JENarTMSilverlineTM 160-1030...1080-110||017700-025-26||1030...1080 nm||DB*-025-26||STP*-025-26||ZIP*-025-26||PDF*-025-26|
|JENarTMSilverlineTM 161-1030...1080-71 - NEW||660149||1030...1080 nm||DB 660149||STP 660149||ZIP 660149||PDF 660149|
|JENarTMSilverlineTM 255-1030...1080-160||017700-026-26||1030...1080 nm||DB*-026-26||STP*-026-26||ZIP*-026-26||PDF*-026-26|
|JENarTMSilverlineTM 423-1030...1080-360||609120||1030...1080 nm||DB 609120||STP 609120||ZIP 609120||PDF 609120|
|JENarTMSilverlineTM 160-900...1100-1101)||601787||900...1100 nm||DB 601787||STP 601787||ZIP 601787||PDF 601787|
|JENarTMSilverlineTM 255-900...1100-1601)||601804||900...1100 nm||DB 601804||STP 601804||ZIP 601804||PDF 601804|
|JENarTMSilverlineTM 423-900...1100-3601)||628951||900...1100 nm||DB 628951||STP 628951||ZIP 628951||PDF 628951|
|JENarTMSilverlineTM 115-515...540-71||624103||515...540 nm||DB 624103||STP 624103||ZIP 624103||PDF 624103|
|JENarTMSilverlineTM 163-515...540-92 - NEW||659612||515...540 nm||DB 659612||STP 659612||ZIP 659612||PDF 659612|
|JENarTMSilverlineTM 55-355-21||605678||355 nm||DB 605678||STP 605678||ZIP 605678||PDF 605678|
|JENarTMSilverlineTM 103-355-71||017700-402-26||355 nm||DB*-402-26||STP*-402-26||ZIP*-402-26||PDF*-402-26|
|JENarTMSilverlineTM 125-355-75||628956||355 nm||DB 628956||STP 628956||ZIP 628956||PDF 628956|
|JENarTMSilverlineTM 510-355-431||017700-405-26||355 nm||DB*-405-26||STP*-405-26||ZIP*-405-26||PDF*-405-26|
|JENarTMSilverlineTM 255-355-240||017700-406-26||355 nm||DB*-406-26||STP*-406-26||ZIP*-406-26||PDF*-406-26|
|JENarTMSilverlineTM 170-355-140||586840||355 nm||DB 586840||STP 586840||ZIP 586840||PDF 586840|
|JENarTMSilverlineTM 103-266-71||017700-601-26||266 nm||DB*-601-26||STP*-601-26||ZIP*-601-26||PDF*-601-26|
Additional information about F-Theta lenses
Basic knowledge about F-Theta lenses
F-Theta objective lenses
Jenoptik‘s F-Theta objectives are optimized for the requirements of laser material processing. They realize even focal planes over the scan area independent from scan angle. On the one hand, they are designed to yield excellent optical performance, manifesting itself in small field curvature, small distortion and diffraction limited focus sizes. On the other hand, F-Theta lenses realize a linear dependence between the angle Θ of the incoming laser beam and the image height h of the focussed spot on the workpiece. The proportionality factor is the focal length f. This relation is mathematically expressed as h = f Θ, which gives those special lenses their name "F-Theta."
Whereas the merits of good optical performance are easy to see, the advantages of the F-Theta relation are more subtle and best understood considering polygon scanners. Those scanners rotate with a constant angular velocity at very high scan speeds for dynamic processing. If, for example, the image height would be proportional to the tangens of Θ, then the speed of the spot on the workpiece would increase for higher angles, and therefore, the energy deposited in the material would decrease, possibly resulting in inhomogeneous application performance. Since the F-Theta objective translates the constant angular velocity of the polygon to a constant velocity of the spot on the workpiece, this problem disappears. F-Theta lenses can be used for high speed processing with very reliable quality. This allows for most efficient laser material processing.
In theoretical nomenclature, the focal length is the distance from the second cardinal plane to the paraxial focus point of the objective. That means, if one would represent the objective as having vanishing length, then the distance from this ideal lens to the focus would be the focal length.
From the F-Theta relation h = f * theta, the image height is proportional to the focal length, i.e. if one wants to increase the area of application then one can use lenses with bigger focal length. However, if one wants to retain the same spot size, then, according to the focus size definition, one would also have to increase the laser input beam size. Another property is the distance between lens and workpiece. If this has to be increased, usually an increase in focal length is required (see also back working distance).
In theoretical nomenclature, the focal length is the distance from the second cardinal The max full diagonal scan angle corresponds to the scan field diagonal, i.e. using the objective with angles above this maximum angle will lead to clipping of the beam.
From the F-Theta relation one sees that an increase of the field size can also be achieved by using bigger scan angles. This would have the advantage that the beam size would stay the same. However, big scan angles pose a considerable complication for the design of cost effective F-Theta lenses.
Input beam diameter
To control stray light, and also reduce the required size of optical elements in laser material processing applications, the incoming Gaussian laser beam will usually be clipped at the diameter where the intensity has fallen to 1/e² of the maximum value. The lenses are designed such that those beams will pass through the objective without being clipped anywhere.
The input beam diameter immediately affects the spot size via the spot size relation antiproportionally and consequently intensity distribution in processing area. Bigger beam diameters result in smaller spot sizes and vice versa. Using beams with diameters above the maximum allowed beam size will lead to clipping of the beam at the edges of the field. This effects non ideal intensity distribution and leads to lower processing quality (see beam-clipping).
When focusing light, the spot size σ can not surpass the limit of diffraction, i.e. the spot size does not depend on the aberrations of the lens anymore but only on the physical properties wavelength λ, the input beam diameter Ø, and the focal length f. As for the laser input beam diameter, it is common to define the focus size as the diameter at which the intensity is dropped to 1/e² of the maximum intensity at the spot center. For input beams defined as in "input beam diameter," the focus size is given as σ = 1.83 λ f / Ø.
Decreasing the focus size immediately decreases e.g. the structure sizes of the patterns written. It also increases the maximum intensity in the center of the spot, therefore lifting it above the application threshold of a particular material. If, however, the intensity is way above the application threshold, the energy not needed for the application processed is deposited in the material leading to varying non-controllable side effects, possibly reducing the application performance. Therefore, the user has to find the optimal focus size for the application under question.
If the beam diameter of the incoming laser beam is too big or the scan angle is above the maximum allowed angle, parts of the laser beam might hit mechanical parts when passing through the objective. This is referred to as clipping of the laser beam.
A laser beam being clipped inside the objective will generate unwanted stray light and might also heat up the objective leading to thermal focus shift and even destruction of the lens. All JENar™ Standard and Silverline™ lenses are designed to show no beam clipping when used with the scanner setup described on the datasheets.
Back working distance
Whereas the focal length is a rather theoretical construct, the back working distance describes the real distance between the end of the objective (the edge closest to the workpiece) and the workpiece.
The back working distance describes how much free space there is between workpiece and lens. Since focal length and back working distance are closely related, the need for a bigger free space between workpiece and objective usually results in the requirement of using lenses with bigger focal lengths.
When using a galvanometric 2D-scanner, changing the mirror angles moves the laser spot over the workpiece. The Jenoptik‘s F-Theta lenses are then optimized for a quadratic scan field where the diagonal of this square is denoted as the scan field diagonal.
If the galvanometer mirrors are tilted more than the angles corresponding to the quadratic scan field area two major effects appear. Firstly, the optical performance will degrade above diffraction limit, and secondly the laser beam might be clipped inside the objective (see beam-clipping).
Telecentricity describes the angle of the centroid of the laser beam at the edge of the scan field, for example how much the entire beam is tilted with respect to the optical axis.
Telecentric lenses usually show a more homogeneous focus size distribution over the full field. Furthermore, telecentric lenses are more "scale preserving“ when the workpiece is defocussed. For example, if the workpiece is moved away from the lens, but the tilt of the laser beam is vanishing, the spot position will not change. This is important for example in drilling applications. An immediate consequence of a small telecentricity angle is that the lenses have approximately the same diameter as the field diagonal. Therefore, telecentric lenses are usually more expensive than non-telecentric ones.
Telecentricity describes the angle of the centroid of the laser beam at the edge of the scan field, for example how much the entire beam is tilted with respect to the optical axis.The geometry of a 2D galvanometric scanner is very important for the design of an efficient lens. Since the two scan mirrors must have a certain distance to prevent collision, the application performance will not be rotationally symmetric, instead they will exhibit a twofold mirror-symmetry in X and Y. The distance between the mirrors is given by the parameter a1. The distance from the second mirror to the flange of the objective is described by parameter a2. The separation of mirrors makes the physical concept of a pupil inadmissable. One therefore defines an effective pupil as being positioned in the middle between the two mirrors. The non-existence of a real pupil also has the consequence that a 2D-galvanometric scan system can not be perfectly telecentric.
Different optical properties of an existing F-Theta lens can be modified by modifying the scanner geometry. But care must be taken not to create clipping of the laser beam somewhere in the objective. For example, increasing the distance between objective and effective pupil changes the telecentricity angle (usually it decreases it). But to prevent clipping the maximum scan angle, and therefore the maximum field size, must be reduced as well.
Damage threshold LIDT
The laser induced damage threshold (LIDT) describes the laser intensity (or fluence) above which damage of the lenses occurs. This threshold depends on several parameters like wavelength and pulse duration and involves different physical phenomena. For CW and long pulses (> 10 ns) the main problem is the accumulation of energy inside the material and subsequent melting and evaporation. For ultrashort pulses (< 10 ps), on the other hand, non-thermal processes like avalanche ionization and coulomb explosion are dominant reasons for damage. This variety of different processes makes an analytical description very difficult and for industrial purposes it seems to be advisable to test coatings and materials and derive phenomenological descriptions.
Jenoptik tested its standard coatings and materials for the most common application parameters and expressed the pulse-duration dependent damage threshold fluence Φ in terms of a power law of the pulse duration τ. Φ = c * τ ^ p The parameters c and p of this law are wavelength-dependent. Furthermore, the real damage threshold of the system critically depends on several exterior influences, like adequate storage, handling, and cleaning. Inappropriate care of the optical systems reduces the damage threshold and renders the guarantee obsolete. Due to varying intensities inside of the optical system, the system damage threshold might vary from the single element coating damage threshold.
The ability to pass more energy per time through an optical system allows a faster scanning and therefore a higher throughput.
In spite of anti-reflective coatings at highest quality on our optical components low residual reflection can occur and cause beam paths that can get focussed on other optical components. By this and depending on the laser power the affected component can change its characteristics or – in case of extreme illumination – can be damaged.
Hence, Jenoptik particularly considers these effects during the design phase of F-Theta-lenses and beam expanders. The optical design is optimized to place focal planes of reflected beam paths outside optical components and scanners.
In case of different optical setups, e.g.
- Including additional cover glasses
- Differing cover glass mounting
- Divergent or convergent beam paths
- Use of lenses with other scanning systems
- Differing distances between scanning system and lenses
- Reflexes by work pieces (e.g. glasses without anti-reflective coating) back reflection positions can change and can cause damage on optical components or scanning mirrors.
To prevent these effects and ensure reliable operating conditions we would like to ask you to contact us to tune your system.
Thermal focus shift
When the temperature of an optical material changes, the corresponding shape and index of refraction change. These two effects alter the optical properties of the system, mainly the focus position. This change in position is called the thermal focus shift. An objective can be optimized to withstand a global homogeneous temperature change (due to variations of room temperature and sufficient time of relaxation), for example by employing temperature dependent spacers. However, when used with a high power laser, the temperature distribution over the lens elements becomes non-homogeneous and also scan-pattern dependent. The only way to make objectives insensitive towards these effects is to reduce the change in temperature, for example reduce absorption in lens and coating material.
The induced thermal focus shifts for top-hat (Δz_T) and Gaussian (Δz_G) intensity distributions can be calculated analytically. P_0 is the input power of the laser. f is the focal length of the lens. The sum is then over all optical elements in the system, indicated by the index i. n_i and dn/dT_i describe the index of refraction and its thermal derivative. alpha_i is the thermal expansion coefficient, lambda_i is the heat conduction coefficient, A_i and B_i describe the absorption coefficients of coating and material respectively. d_i is the thickness of the element, and phi_i is the diameter of the laser beam on element i.
For high power applications, the range of usable materials is small (fused silica or CaF2) which fixes most of the material coefficients (dn/dT, n, alpha, lambda). Furthermore, the application requirements determine the parameters input power (P_0) and focal length (f) and the beam sizes (phi) on and thickness (d) of the elements in an F-Theta lens usually constitute no powerful optimization parameters. In essence, optical designs which fulfill the optical specification usually do not differ very much in their respective lens shapes. Therefore, the most promising strategy to reduce the thermal focus shift of a system is to reduce the amount of energy being absorbed. This can be achieved by choosing low absorbing materials and coatings.
A thermal focus shift, when uncompensated, changes the application performance over time. A workpiece being in perfect focus at the beginning of the process might be considerably out of focus after some process-time and the application result will look very different.
Fused silica exhibits extremely small material absorption and is therefore very well suited for being used for high power applications. For their NIR (1064 nm) Silverline™ F-Theta lenses, Jenoptik chooses low-absorbing fused silica material and an optimized lowest-absorbing high performance coating. The maximum absorption of 5 ppm of the coating is guaranteed by a standardized absorption measurement procedure for every coating batch.
The Silverline™ series have got outstanding characteristics of minimum focus shift up to high laser powers of several kW. F-Theta Silverline lenses are optimized for smallest spot sizes and excellent spot homogenity across the entire scanning area by this satisfying highest demands on optical performance. We guarantee highest process quality for a wide range of applications in laser material processing.
See thermal focus shift.
Pulse stretching GDD
When light passes through an optical material of non-vanishing dispersion it accumulates a wavelength dependent optical phase. For laser pulses, which are effectively a linear superposition of harmonic oscillations of different wavelengths, this influences the pulse shape. In a second order approximation for gaussian pulses, the temporal stretching of the laser pulse is determined only by the second derivative of the phase change with respect to the light frequency, also called the group delay dispersion (GDD).
A temporal stretching of the laser pulse reduces its maximal intensity. This might have severe impact on the application performance. To remedy the problem of too long pulses at the workpiece due to pulse stretching one could use lasers with even shorter output pulses. This might increase the intensity above the damage threshold of the involved optical system. Another way would be a precompensation of the induced GDD by gratings, prisms, and microoptical elements.