The present invention relates to a beam director, directing light for modulation of energy intensity, using multiple reflectors, suited specifically for 2D and 3D scanners as well as printers.
Traditional Scanners (TS) such as galvanometers or polygonal scanners use moving mirrors to direct a laser beam. The scan lines when on the work surface need to be in focus, at a constant speed, with constant Optical Path Length (OPL), This ensures deliver/receive consistent energy to the pixel/voxel under test during the scan to allow for consistent and reliable scanning. TS suffers from a change of energy delivered or received from the scan pixel/voxel. Additionally, the TS system design is based on multiple lenses adding lens-related errors and tradeoffs. To mitigate the non-constant speed, the TS is using f-theta lens. To correct telecentricity the TS may be using a telecentric lens, since the focus of the beam in the TS is on about a sphere a flat field lens is used to flatten the focus plane to a flat plane by using a flat field lens. As a result, multiple lenses are needed to mitigate the symptoms. Since the solution cannot deliver a fix for each problem, tradeoffs are used by the lens manufacturer when delivering the lens.
Using a beam director for surface and subsurface scanning (BDSS) will deliver consistent energy by keeping the beam speed, size, and shape consistent across the scan line.
The introduction of a beam director as described in US Patents US10,473,915, US10,416,444, US9,435,998 opened up new applications in the field of medicine, art, archeology, and document inspection. As it can be used for surface and subsurface scanners (BDSS) The BDSS core function is based on mirrors and the reduction of the number of devices along the optical axis, thus improving and simplifying the scanning process.
In Metal 3D printing one of the main obstacles in the process is controlling the temperature of the part and the printed layer constant during the process of printing. Because of the high heat conductivity of metals, the heated area is much larger than the laser beam diameter and it is quantified by a grid to create hatches. Using hatches gives the user the ability to control the heat by running on a Grid from one hand and losing resolution from the other hand.
Most of the lasers used in 3D printing in the industry are gaussian beam lasers. Where a gaussian beam is more challenging, therefore requires higher metal conductivity; limiting the number of metals that can be used.The industry is dealing with this temperature prediction process by using AI supported by monitoring sensors in an attempt to mitigate the problem.
Energy delivery refs:
The present invention deals with scanning of an area where the scans are composed of a plural number of laser lines or vectors (“scan lines”). When two scan lines or more are close to each other the energy density is calculated based on each scan line properties and the proximity of distance between the scan lines. In this invention, the process of calculating the total energy delivered/received is simplified by calculating the number of pixels/voxels per unit area. As an example, two parallel lines with the same optical properties will be delivering a consistent energy as the number of trapped pixels/voxels per unit are constant.
The present invention recognizes that typical utilization of multiple reflecting surfaces as beam directors changes the characteristics of the final beam; shape, intensity and focus. In selective laser sintering (SLS) and selective laser melting (SLM), printing is controlled by a moving beam produced by a galvanometer (GS) or a polygonal mirror (PM) setup. As the beam moves across the work plane, the energy deposited into each voxel varies because of the changes in the incidence angle and the beam size of the GS / PM beam.
The applicant proposes multiple methods to uniformly deposit energy onto the work surface using specifically the Øgon™ (ZERO-gon) also known as Lens Free Optical Scanner (LFOS) 3D scanner, thereby overcoming the drawbacks encountered with the GS and PM scanning setups. The scan lines for the LFOS composed of arcs with radius R. When an arc scan line is moving by a delta distance the proximity between two adjacent arcs, the distance between the arcs get closer to each other as it is measured further away from the moving line of the delta distance as in
In one embodiment of this invention, the entire Øgon™ printing setup consists of a two main reflective surfaces; the primary and the secondary reflector. The primary reflector rotates around an axis with the rotation velocities adjustable as per application requirements. The incident light on the primary reflector is reflected on to the secondary curved reflector before eventually striking on the work plane, located beneath the entire reflector setup.. The second reflector reflects the beam to the work surface tracing a circular arc.
In another embodiment of this invention, a method for uniformly setting the incident laser power on the work plane is presented. Instead of providing equal power, depending on the position of the pixel on the work plane arc, the laser power is modulated by either adjusting the incident ray amplitudes or by varying the exposure times.
In yet another embodiment of this invention, work plane is divided into layers which are further sub divided into multiple hatches. By using a constant power for the incident laser, the size of the individual hatches is varied to ensure the overall power density through the work plane remains constant. This embodiment applies but is not limited to printed materials with high heat conductivity such as metals.
In one final embodiment of this invention, the rotational speed of the primary reflector is varied as the beam scans towards the edge of the work plane. Varying the rotational velocity of the primary reflector changes the incident power of the laser on the work surface, thus enabling uniform power delivery.
These and other embodiments and advantages of the invention herein and summary will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.
The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.
A more precise appreciation of the disclosure and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:
[24]
Subject matter will now be described fully hereinafter with reference to the accompanying drawings, which form a part hereof, and which show, by way of illustration, specific exemplary embodiments and performance metrics. Subject matter may, however, be embodied in a variety of different forms and, therefore, covered or claimed subject matter is intended to be construed as not being limited to any exemplary embodiments set forth herein; exemplary embodiments are provided merely to be illustrative. Likewise, a reasonable broad scope for claimed or covered subject matter is intended. Among other things, for example, the subject matter may be embodied as methods, devices, components, or systems. The following detailed description is, therefore, not intended to be taken in a limiting sense.
The word “exemplary” is used herein to mean “serving as an example, instance, or illustration”. Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments. Likewise, the term “embodiments of the present invention” does not require that all embodiments of the invention include the discussed feature, advantage or mode of operation.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of embodiments of the invention. As used herein, the singular forms “a”, “an”, and “the” are intended to include the plural forms as well, unless the context indicates otherwise. It will be further understood that the terms “comprises”, “comprising”, “includes” and/or “including”, when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
The following detailed description includes the best currently contemplated mode or modes of carrying out exemplary embodiments of the invention. The description is not to be taken in a limiting sense but is made merely for the purpose of illustrating the general principles of the invention since the scope of the invention will be best defined by the allowed claims of any resulting patent.
The Øgon™ 3D scanner, as installed in the final form, is shown in
The print head of the Øgon™ comprises the primary reflector (M1) 21 and a curved secondary reflector (M2) 22 installed on a motor 23 as shown in
The Øgon™ uses a modified raster scanning method in which the x-axis (as depicted in
For additive manufacturing applications, information is compiled by slicing the design into layers and then rendering each layer with arcs. Each layer data is saved in an array; layer rendering information is contained in a two-dimensional array Arc[i][j] where i is the arc number and j represents a pixel within the arc. The modulation for this case is performed by turning the laser beam on or off with a set time interval between the voxels. For precise control of energy deposition, the ØgonTM laser energy output can be modulated by pulse width and/or analog intensity for each voxel.
Referring to
where β is the beam location, and f is the rotational frequency of M1 21.
The scanning of the Øgon™ is done by using a linear conveyor mechanism to scan between arcs. The beam position on the work plane in Cartesian coordinates can be expressed as:
Alternatively, the beam location on the work plane 32 can be expressed as a function of the arc number i and the pixel location j on any given arc i (as shown in
Considering the pixel geometry shown in
The energy density of the i th pixel on any given arc can be mathematically expressed as:
The laser power for the i th pixel can be calculated as:
The first method of uniform power delivery provided by this invention involves adjusting the individual pixel power as per Eq. 11. By either amplitude modulating the Pl signal, or, by prolonging the exposure time of the laser for any particular pixel, the power can be adjusted to remain constant for all the pixels on any given arc.
The second method of power delivery relies on slicing each individual layer into arcs, resulting in a simpler mathematical analysis. Considering the four neighboring pixels 53 on two adjacent arcs 52 as shown in
The slicing strategy of Eq. 13 relies on subdividing each layer into parallelograms with different areas while keeping the laser power constant. Such an approach would utilize a slicing algorithm to actively slice and define the areas on the work plane and operate the laser accordingly.
The third method to ensure uniform energy density involves slicing chords parallel to the x-axis as shown in
The fourth and final method to deliver uniform energy required modifying the rotational speed of M1 21 to accommodate for the increase in energy density. Mathematically the rotational speed can be expressed as:
By varying the rotational speed of M1 21, in accordance with Eq. 9 and Eq. 10, the energy density can be made constant by keeping the other factors intact.
While the foregoing written description of the invention enables one of ordinary skill to make and use what is considered presently to be the best mode thereof, those of ordinary skill will understand and appreciate the existence of variations, combinations, and equivalents of the specific embodiment, method, and examples herein. The invention should therefore not be limited by the above-described embodiments, methods, and examples, but by all embodiments within the scope and spirit of the invention as claimed.
This application incorporates by reference and claims priority to and the benefit of US Provisional Pat. Application serial. No. US63/251,460 with filing or 371(c) date of Oct. 01, 2021.
Number | Date | Country | |
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63251460 | Oct 2021 | US |