G&H | GS Optics

Project Status

G&H | GS Optics understands the necessity of keeping the client fully informed of project status throughout the lifecycle. We adhere to optical device project management methods and strategies in order to reduce cycle times, cut costs, optimize quality, and ultimately to improve success rates for the client. Project management actually begins at the moment the first contact is established.

Fit Assessment

Shortly following initial contact, Sales and Applications staff will perform a fit assessment with the client’s staff. We will develop a firm understanding of the project scope including technical requirements, budgetary requirements, time-to-market expectations, and deliverables. This information is critical to ensure that G&H | GS Optics is a good fit for the project and that we can meet the delivery expectations of the client.

Design for Manufacturability

Once we determine the project is a good fit, we immediately review the design for manufacturability. We works closely with our clients to ensure the intended design is possible through inhouse manufacturing techniques. All design concerns will be worked out with the client before moving forward, while keeping time-to-market a priority. Once a manufacturable design is achieved, G&H | GS Optics will provide a comprehensive proposal covering the client business requirements and the proposed solution to achieve those requirements.

Contract Review

Following a bid award, we performs a contract review with all project stakeholders to ensure the scope and schedule are still in line with the proposal. A project manager is assigned at this time to direct all further optical device project management. This individual will be your point of contact throughout the project life-cycle, up to Production turn-over. The project manager will keep your staff fully informed of all project milestones through regularly scheduled project briefings. These meetings will be facilitated by the project manager, however all stake-holders including Sales, Engineering, Quality and Production will be in attendance as necessary. If the project scope warrants, a project plan will be developed in Microsoft Project and a corresponding Gantt chart will be maintained and updated regularly for quick, visual reference of the project status.

Design for Manufacturability (DFM)

Design for Manufacturability (DFM) of optics is an often-overlooked first step which is crucial to program success. There are many factors that will determine the success or failure of molding a plastic optic. When considering custom optical molding, it’s very important to involve the optical molder during the program concept phase.

During DFM review, G&H | GS Optics engineers address issues such as part shape, material selection, gate location, gate shape and size, as well as tolerances. Further, the process staff will model and optimize the design of your optic for manufacturing. We use sophisticated software packages to maximize product performance while minimizing manufacturing costs and lead times, such as:

• Solid Works
• Solid Works Mold Filling Analysis
• Zemax
• TF Calc
• Diffsys
• MasterCam

Robust modeling and simulation are an absolute necessity to ensure the design is possible through injection molding, and to ensure the proper mold design is selected.

G&H | GS Optics engineers are experts in design for manufacturability of injection molded optical components. They specialize in working with you to converge quickly on high-confidence cost-effective solutions to make your program a success.

Rapid Prototyping Options

Rapid prototyping of optical components is key for optimizing your time to market. Therefore, we embrace the prototyping process and offer two options for development of prototype optics.

Rapid Prototyping of Optical Components by Injection Molding

Producing a prototype as exacting to the production version as possible is imperative to prove concept. Consequently, an injection molded prototype makes sense. To make this a reality we have developed several mold bases that allow our staff to quickly and precisely make inserts that meet the specifications of the customer’s optics.

Depending on the size and complexity of the optic, we can produce small volume, injection molded prototypes in as little as three weeks. As a result, the customer will have a true prototype using the same material, technique and process that will be used in production. This is critical for testing purposes, as it reduces the risk of variables. Once the prototyping effort is complete a production tool would be developed to produce production volumes. At the same time, the prototyping tool may be used for on-going, pre-production efforts.

Rapid Prototyping of Optical Components by Diamond Turning

In some instances, primarily related to size, injection molded prototypes are not feasible. In this case, we rely on single point diamond turning (diamond turning) to meet the customers needs for rapid prototyping of optical components.

Diamond Turning is a manufacturing process used to cut the optical inserts for the mold cavity that will form the optical surface during injection molding. Diamond turning can be used to quickly produce low to moderate volumes of highly accurate plastic optics. These are typically produced to support R&D or prototyping efforts.

The machine performing the diamond turning is a precision CNC lathe. The cutting tool is a diamond that has been specially prepared to cut the required surface geometry of the lens. Diamond turning may be used to create optical surfaces ranging from spherical to aspheric plastic lenses. The lathe is capable of cutting freeform polymer optics as well. Because the surface is generated on a CNC lathe, the process is very deterministic and highly repeatable. As a result, surface form errors may be as low as 2 waves per 2.5 cm of diameter, and surface finishes of 3 to 4 nanometers (Ra) are regularly achieved. With surface finishes this fine, the diamond turned optics are very specular, requiring no post-machine polishing. They can be readily coated with a multi-layer thin film coating, for enhanced transmission. Likewise, they can be metalized with Aluminum, Gold or Silver for use as a first surface mirror. We coat all of its lenses and mirrors at its in-house thin film coating facility.

Disadvantages of Diamond Turned Prototypes

The main disadvantage of diamond turned prototypes is the fact that the optic is not being produced in the identical manner intended for production: injection molding. The primary intent of prototyping is risk reduction and proof of concept. Using any means of prototype production other than the means intended for mass production introduces a variable that could lead to production iterations or even failure.

The second disadvantage is the inability to incorporate mounting features (tabs, mounting holes, etcetera) into the prototype. Due to the tool path required for the diamond turning process, features which are incorporated into a mold with relative ease may be nearly impossible to create during diamond turning.

Diamond Turning Materials

Many different polymers may be diamond turned. A partial list includes:

• Acrylic (PMMA)
• COC (Topas)
• COP (Zeonex and Zeonor, APEL)
• Styrene
• Polyester (OKP-4)
• Polyetherimide (Ultem)
• Other select polymers

Some plastics such as polycarbonate are not suitable for diamond turning because they are too soft. For certain, it is important to discuss material choices with your diamond turning supplier at the outset of the project. The team at G&H | GS Optics will assist you in selecting the correct material to rapidly create your light weight plastic lens.

Bespoke CNC Machined Optics

We have a long history of providing custom CNC machined optics or windows from specialized cast polymers. Our team will custom profile edges to meet your specific demands, using our CNC machining.

Working with our partners, we offer a special cell-cast, cross-linked acrylic material that offers unique features such as:

• Excellent transmitted wave front characteristics: typically 2 to 5 λ/2.54cm
• Wide range of thicknesses: from 0.5mm to 6.3mm in steps of 0.1mm
• Close thickness tolerance: ±0.1mm
• High internal transmission: ~92%
• A wide range of colors, including long-pass IR filters
• Low internal stress

For certain types of flat windows and flat mirrors, using a low internal stress cast material and machining it to the appropriate edge geometry is the best solution.

Our team offers you expertise in custom CNC machined optics in addition to diamond turning and molding lenses, mirrors and windows.

Advantages of Polymer Versus Glass

Our engineers work very closely with you to understand the application, evaluate the tolerances, establish what quality metrics need to be in place, and build a mold that will consistently deliver optical elements to print.

Custom injection molded polymer optics offer many advantages over glass optics as noted below:

• Lower cost thermoplastics such as PMMA (acrylic), Cyclic-Olefin Polymer ‘COP’ (such as Zeonex), Polycarbonate, Polyesters (such as OKP-4) and Polystyrene
• The Injection Molding process offers economies of scale
• Cost-effective ability to produce complex shapes (aspheric and freeform optics)
• Mounting features combined directly onto the optical element

While it is not possible to use plastic optics in every application, designers will gain competitive advantages by using well designed plastic optics in applications well suited for their use.

Lower Material Costs

Generally speaking, the thermoplastics used in custom injection molding are less expensive than glass. Thermoplastic material is made in very large volumes, and its pelletized form is what is directly injected into the molding press. Unlike glass optics the thermoplastic is not pre-formed or shaped into a blank before injection molding the finished optic.

Economies of Scale

Not only is the resin less expensive than glass, the cycle time required to injection mold a polymer optic is much shorter than the cycle time required to produce an optic using grinding and polishing techniques.

Further, it is often possible to build multi-cavity molds to produce more than one lens during each molding cycle. Programs that require larger volumes of parts and have commercial tolerances are good candidates for multi-cavity molds.

Complex Shapes

An aspheric surface can be added to an optical system to correct for certain geometric aberrations such as spherical aberration. Also, depending on its distance from the system aperture stop or pupils, an aspheric surface can affect coma, spherical aberration, astigmatism and distortion. Complex shapes may be created at the optical mold insert and replicated many times during the injection molding process with excellent accuracy.

Additionally, the use of freeform optics is becoming increasingly popular, particularly in AR/VR and HUD applications. The cost of producing a freeform optic can be greatly reduced if the design can be optimized to allow the use of injection molded plastics.

When it comes to custom injection molding the optic, scientific mold processing techniques are used to develop a robust and repeatable molding cycle regardless of surface type. The difference comes when it’s time to measure the part, since spherical surfaces are easily measured with an interferometer but aspheric surfaces require the added expense of holographic null correctors. Aspheres and freeform optics are more commonly measured using a contact profilometer or coordinate measuring machine (CMM). Due to these specialized instruments it is critical to select an optical molder with the proper equipment and metrology expertise.

Combining Optical and Mechanical Features

Polymer optics can easily combine an optical surface with a mechanical mounting datum. In doing this, the optical designer is taking advantage of the manufacturing method of custom injection molding. By adding a mounting feature such as a flange, tab or other structure, the designer may be able to reduce the number of components in the final assembly and simplify the assembly process, and reduce the number of parts on the BOM.

Disadvantages of Polymer Versus Glass

• Spectral transmission: most polymers are suitable for visible or NIR ranges only
• Constant service temperature level: less than glass, in general less than 120°C
• High index of refraction temperature reliance (dn/dt): regarding 20x greater than glass
• High coefficient of thermal expansion (dl/dt): almost 10x more than glass
• Narrow range of indexes of refraction as well as Abbe numbers for available materials

Thin Film Coating

G&H | GS Optics is a long-established optical manufacturer providing thin film coating for optics. Our Rochester, NY plant has a state-of-the-art coating facility that is positioned in the forefront for coating technology specific to polymer substrates.

Polymer optics can be coated using physical vapor deposition techniques, similar to glass, although some limitations exist due to the coating temperature maximum values the polymers can withstand. We can apply dielectric coatings such as broadband AR, V-coatings, and special band pass coatings as well as a wide array of reflective coatings to polymer substrates.

Many of the optics that we mold require reflective coatings, including gold, silver or aluminum, or anti-reflective coatings. Our team specializes in coating plastic substrates and can provide reflective (HR) coatings such as:

• Protected and enhanced Gold
• Aluminum and enhanced Aluminum
• Protected Silver

We also provide single and multi-layer anti-reflection (AR) coatings suitable for V-coats and broadband AR performance.

By offering thin film coating for optics on site, we are able to improve our operational efficiency and offer our customers greater flexibility and responsiveness to their production demands. We provide state-of-the-art vacuum deposited coatings on polymer substrates such as:

• PMMA
• Styrene
• Polycarbonate
• Cyclo olefin polymers (COP) materials (Zeonex, Zeonor, and Topas)

Our coater is a fully automated, CITATION I™ precision optical box coater, built by VPT. The coating chamber includes E-Beam and resistive evaporation with Plasma Ion Assist to form low stress, dense and durable coatings that will satisfy the most demanding thin film deposition coating requirements of polymer optics. In addition, our coating chamber configuration includes a unique, flexible rotation system to accommodate the many complex shapes that are increasingly prevalent in plastic optics design.

To complete our thin film coating capabilities, G&H | GS Optics has complete in-house thin film design capabilities to tailor thin film performance to meet your specific custom optics requirements.

Assembly

We provides complete opto-mechanical assembly services within our Class 10,000 (ISO Class 7) clean room. Our manufacturing engineers understand the delicate nature of optical assembly and we have the ability, experience and equipment to ensure assembly meets specification. Our staff will include assembly considerations during the DFM process to ensure all components are designed to optimize assembly time. This will aid in first article qualification and, ultimately, reduce time to market and BOM cost.

Packaging and Handling

An often-overlooked but extremely important final step is handling and packaging of the finished product. Optics, in general, are delicate and plastic optics present even more concerns due to their susceptibility to abrasion. Handling of the optic must be considered from the time the press opens through inspection and packaging. If the optic will be incorporated into an assembly prior to shipment, handling during the assembly process must be addressed as well. We have extensive experience handling and packaging plastic optics and optical assemblies. This experience is the baseline for ensuring the handling and packaging process that will see the customer’s components and assemblies are delivered safely every time.

Optical Metrology

The optics that we create are key enabling components for our clients’ optical systems. Therefore, we test the molded optics to verify compliance with the required surface form-error and dimensional specifications.

Optical metrology is an absolute requirement when manufacturing optics. Without it, there is no reasonable way to assess the precision of your optical components. Our metrology lab’s high level of service protects you against project downtime by assuring that all parts perform as needed once integrated into your system.

G&H | GS Optics places heavy emphasis on quality and has developed a highly trained quality team that works with each client to understand the key performance metrics for the optic being produced. Once the critical to function attributes are recognized, a quality plan is developed that specifies which features are measured, how often, on how many samples, and by what equipment. These features are then scrutinized during the development phase to guarantee that the manufacturing process is capable of consistently meeting the requirements in the future. Once a part reaches production, the metrology team provides continuous feedback to our production specialists, in turn protecting our clients against project downtime.

To support the above process, our metrology lab has a full suite of inspection equipment to ensure all parts are fully characterized:

• Bruker® Contour GT-K1 3D Optical Microscope: This instrument employs phase shifting and vertical scanning white light interferometry technology. It allows us to measure surface roughness (Ra/Rq), step heights (diffractives) and other micro-features on optical surfaces.
• Zygo Verifire™ XPZ Interferometer: The Zygo system is used to measure spherical and flat surfaces featuring a high-resolution camera and digital electronics that can resolve more fringes than ever before. The reporting using Zygo Mx™ software enhances the reliability and serviceability of our lab.
• Zeiss Micura CMM equipped with VAST XT Gold Sensor: Our latest addition to the line-up offers active, high-speed scanning with accuracy of less than one micrometer. This supports scan speeds up to 200 points per second while allowing two measuring volumes, 500 x 500 x 500 millimeters and 500 x 700 x 500 millimeters.
• Zeiss Surfcom 3000A: Our contact profilometer is a workhorse used to measure aspheres and equation driven freeforms on molded and diamond turned plastic optics.
• Mitutoyo Bright 504 CMM: For more exotic freeform surfaces, off-axis aspheres, or to assess an optic’s 3D location error we use our touch probe CMM and measure directly against a 3D CAD model.
• OGP Flash 302: With a camera and touch probe, this multi-sensor CMM is a daily staple for measuring the size and location of mechanical features, including non-contact measurement of step heights.
• Wells Research OS210B Optical Test Bench: Focal length (EFL/BFL) and/or image quality (MTF) are often what counts most in an optical system, and the autofocus feature both reduces variation and allows a quick assessment of any astigmatism. As a camera based system, optics can be tested in the near IR, which is not possible with manual systems.

In addition to ongoing inspection results, we can provide further analytical support to clients through:

• Capability studies (to calculate Cpk)
• Failure Mode and Effects Analysis (FMEA)
• Production Part Approval Process (PPAP)
• Gauge R&R
• SPC techniques

Our dedicated team of engineers and technologists, working with the most up-to-date equipment, look forward to creating polymer optics that will help to increase your market share and competitiveness.