Patent Application
20210231911
Traditional laser beam delivery systems rely on delivering laser energy into a single focal spot, and positioning this spot on the target material. This delivery process is performed either by fiber optic high power laser or by a combination of reflective mirrors installed in special developed hollow joints. Advances in light manipulation as disclosed in this novel art show a beam delivery system based on optical periscopes or elongated retroreflectors which will deliver a beam from point to point for most existing wavelengths with high accuracies overcoming most restrictions found in traditional art.
Laser based Electro-Optic systems are often required to deliver a beam from one point to another. Furthermore, seldom a combination of a number of separate laser beams into a single beam is required. The need to provide a multi-spectral content along with extremely high-power levels is a common practice for industrial lasers, particularly for material processing or fast welding and brazing applications. Those needs have led to a development of flexible fiber lasers which are attached to a robotic arm to deliver the beam from point to point. However, fiber optic delivery systems, while very popular, lack the capability to deliver a significant number of laser wavelengths and perform very poorly when a number of lasers are coupled as a single fiber. Moreover, the fiber technology requires installation of a complicated and heavy end piece at the guiding robotic arm used to deliver the fiber optics energy to working area. This complicated and sometimes very heavy end piece will dictate a large robot capable to carry this extra weight. Said end piece usually includes a fiber laser collimator, a focuser, a camera and gas cooling fittings.
In disclosed art, we show that said beam delivery systems based on periscope or on elongated retroreflector have the advantages of delivery of increased number of lasers over a wide spectral range without the restriction common to fiber optics systems and with inherent accuracies superior to reflective mirror technologies. Delivery of a multi-spectral laser beam having high-power levels, in order to meet various special material processing needs, usually cannot be performed using optical fibers or simple refractive elements and require reflective mirror elements. Mirror based solutions require complicated rotating mirror knuckles with mechanical members in between and are adequate solution for delivering multi wavelength lasers or high peak power pulsed laser. One of most significant drawbacks of a mirror-based solution is its complication, which is derived from requirements of high precision delivery of high-power lasers over large distances in an industrial environment. The disclosed art introduces novel approaches to multi spectral beam delivery problem, which solves the inherent drawbacks of existing art.
The purpose of the present invention is to provide a multi wavelengths superior beam delivery system and beam combining device. Said device will be able to efficiently deliver a laser beam from a stationary laser device with high accuracy by using elongated optical members such as periscopes or retroreflector. By using said elongated members based on reflective periscopes the system is capable to deliver laser beams over a wide spectral range.
Said system is based on a manipulator with a number of axes and elongated members wherein said members are rotated in respect to each other, by a plurality of electric motors controlling the movement of the end point of said manipulators. The laser beam travels through said elongated members and joints to be delivered to the point of interest.
Trajectory is controlled by a programmable electronic control unit, placing a focused laser beam at any position in a relevant working space. Said manipulator has at least one movable lens across the laser beam path for focus adjustment. The possibility of delivering the laser beam to the point of interest with high accuracy without complicated and expensive mechanical devices considerable simplifies the beam delivery system while increasing its performance by allowing multiple wavelength to be applied together when necessary.
The basic configuration of disclosed system is comprised of a robotic device with a number of elongated periscopes connected together through a motorized rotating axis to control the rotational movement of said elongated periscopes. The laser beam is coupled to the system by an input port and it ends by an output port equipped with a focusing element. Said motorized rotating joints connect the periscopes to be concentric in respect to each other's input/output ends. The connecting motors are coupled to a computer processing with an algorithm configured to control driving motors to complete a trajectory in space and activate the said focusing element. Moreover, the hollow robotic arm will have a positive flow of clean gas to actively cool the system and ensure its cleanliness. The said motors could be based on a mechanism of hollow axis gear motors. The said focusing element will be mounted on the external envelope of robotic arm, engulfing said periscopes. In addition, the focusing element could be based on a mirror as a part of the elongated periscope. Said elongated periscopes could be replaced in a yet another configuration by elongated retroreflectors.
The present invention offers a method and device which is free from disadvantages limiting performance of current art.
Further advantages of the invention will emerge from the following descriptions and drawings, which are provided as non-limiting example and in which:
Laser material processing is performed by concentrating laser energy into a focused beam in order to achieve high levels of fluence on material surface, this is usually performed by focusing a collimated beam by an optical element usually denoted as focuser.
The main problematic issues with this technology are positioning errors and the laser type especially when dealing with pulsed laser or its wavelength. The focused laser beam is approximately Gaussian, with a relatively short focal range and a beam size down to several micrometers.
Consequently, positioning error of delivered beam or variation on material surface can lead to inconsistency and poor machining quality. In described art we present a solution based on beam delivery members that accurately deliver the beam regardless the mechanical positioning errors of said members adopting members such as elongated periscopes and elongated retroreflectors, to deliver an almost collimated beam to the required position and then at this far end using a light focuser for creating the necessary beam size. Using this strategy will create a multi wavelength high power beam delivery system with superior accuracies.
A periscope is a device built by two laterally offsets parallel mirrors. The mirror surfaces, if perfectly parallel, will reflect an incoming beam with an offset creating an outcoming beam which is laterally displaced but parallel to incoming beam. If the mirror surfaces are perfectly parallel, the input output parallelism will be preserved regardless of mechanical movement of housing holding the said mirrors together. This enables to preserve parallelism without precisely maintaining the mechanical datum plane of housing. An elongated retroreflector is built out of three perpendicular mirrors section held together by a stretched housing and an incoming beam will be laterally displaced wherein the resulting outgoing beam will be exactly 180 decrees to incoming beam. Combining by a rotary joint several elongated periscopes or a combination of periscopes with elongated retroreflector a beam can be positioned within a circular area having a radius traced by the length of the stretched members. This outcoming beam will always be parallel to incoming beam by definition.
In
The encircled detailed view shows an original beam 503 in a perfect position focusing at the point denoted as 504. The deviated beam 502 being parallel to the original beam will focus at the exact position with no offset. The lens focuses according to the law Δx=F×Δθ. Since Δθ represents the angular deviation between the two beams striking the focusing lens, and it equals to zero by definition, Δx at the focal point will be then zero as well.
