Delivering Turnkey Test Systems for Head-up Display Windshield Glass

Full-service tooling company, CP Industries, is based in Granger, Indiana, but has facilities located in both Mexico and the United States. CP Industries is a family-owned (fifth generation) business, and it supplies manufacturers with end-to-end testing and assembly systems for glass, thermoform, trim and injection-molded components.

Custom-built to customer’s specific needs and requirements, CP Industries delivers everything from product design assembly, machining, installation as well as necessary training to minimize the overall time, expense and complications for their customers.

Founded in 1937, CP Industries has established a wealth of expertise in providing solutions to the automotive industry.

Its experience in gaging, tooling and fixturing for automotive glass comes from working extensively with glass manufacturers, major automotive industry OEMs and tiered suppliers to guarantee quality glass components for vehicles.

This wealth of experience has meant that the introduction and increasing use of head-up displays (HUDs) in the automotive market makes CP Industries ideally suited to tackle windshield testing requirements as an essential element of HUD systems.

Delivering an objective measure of HUD visual quality that meets OEM and automotive industry specifications is a challenging task for the sophisticated inspection equipment and software that is traditionally employed to perform this function.

In the initial stages of developing its new HUD test system, CP Industries investigated the optimization of components that would meet the advanced specifications of HUD glass inspection while offering customers innovative solutions from the offset.

Requirements for HUD Glass Testing

HUD systems in vehicles operate by projecting simulated images onto the windshield of the vehicle.

These images are perceived to be at a distance of several meters through the glass, which allows drivers to see data, like navigation and speed, within their line of sight while driving. This reduces the need for drivers to shift their attention from the road.

The windshield performs as an optical component of the HUD system, meaning that the effectiveness of HUDs can be significantly affected by the glass through which data is both projected and viewed.

Differences in windshield glass form, layer thickness, lamination and wedge angle may lead to perceptible flaws that can cause dimensional distortion or ghosting (duplication) of HUD virtual images when seen through the glass.

The specifications for HUD testing are based on industry-standard test guidelines and formulas, as well as OEM requirements that need to be adhered to by suppliers at every stage of the HUD ecosystem - from glassmakers to the manufacturer of the projection systems.

Example of testing visual HUD performance through the windshield, using a camera system for automated visual inspection.

Example of testing visual HUD performance through the windshield, using a camera system for automated visual inspection. Image Credit: Radiant Vision Systems

Our glass customer receives test requirements from the automotive OEM, and those requirements are changing all the time. We have also worked in cases where the customer doesn’t have any specifications upfront, and we have to try to develop something to meet what they’re asking for.

Cruz Palafox, Project Engineer, CP Industries

The complex nature of HUD testing is further complicated by the variety of visual criteria that needs to be evaluated during a complete inspection. HUD glass is analyzed for a number of primary defect categories, including ghosting and distortion.

While test parameters for individual defect categories may differ, they invariably involve a test image, such as a line or dot pattern that is projected through the glass. Formulas that utilize coordinate points within the image calculate geometric measurements of any variations between the projected pattern and the ideal pattern.

Within each defect category, there are a number of qualities that must be assessed, and each quality within the category is calculated by utilizing a particular formula and method, as stipulated in OEM or industry specifications.

A comprehensive distortion evaluation for HUD glass inspection may involve 10-20 calculations to assess every visual quality in order to factor in the range of possible deviations within a projected test image.

A thorough HUD glass inspection will result in a measurement or data point for every quality under evaluation. Limits can be utilized to pass or fail the glass as part of an automated testing process, centered on the type of defects detected or their severity, as revealed by the values obtained.

Source: Radiant Vision Systems

Defect Category Distortion Ghosting
Test Image
(example)
Defect
(example)


Horizontal trapezoid distortion


Single ghost, with separation
Resulting HUD
Image (example)
Qualities
Evaluated*
(example)
  • Size (horiz./vert.)
  • Aspect ratio
  • Rotation
  • Translation (horiz./vert.)
  • Angular displacement (horiz./vert.)
  • Trapezoid (horiz./vert.)
  • Smile (horiz./vert.)
  • Magnification (horiz./vert.; avg., max.)
  • Number of ghosts
  • Distance to primary ghost
  • Average ghost (horiz./vert.)
  • Max. ghost (horiz./vert.)

* Performed for each eyebox position.

Optimizing Efficiency with Imaging & Software

Inspecting HUD glass for dimensional flaws involves a spatial knowledge of the HUD projection - an image captured by a camera - and the capacity to detect and evaluate a number of coordinate points across a projected test image. The latter involves image analysis, which is usually carried out by a software application.

We started using machine vision cameras, which is how we built a foundation of working with cameras. Customers wanted us to be able to view different things on glass, from barcode labels to QR codes to components that are mounted on glass.

Connor Cassady, Project Engineering Manager, CP Industries

As CP Industries progressed towards developing HUD test systems, machine vision cameras continued to offer imaging advantages for visualizing a full HUD projection through the windshield.

The images analyzed in machine vision software provided essential data, such as coordinate locations of test image features - lines and dots - to be utilized in the calculations needed for ghosting and distortion inspection.

We were capturing dimensional data from the HUD test patterns, and the captured data was sent back to Excel® into a report.

Andrew Early, Control Engineer, CP Industries

Yet, unlike reading a barcode or detecting a component, processing images and applying analyses for the breadth of criteria in a single HUD glass inspection proved taxing for the machine vision system.

As Early explains, “The biggest issue we experienced with the initial machine vision cameras was limited memory space and the amount of data that could be output at once. This meant our programs had to be limited to a certain number of tools.”

Reducing and readdressing data output from the machine vision system was one possible answer, but this added to the development work needed. “I had to basically break out my data output, which took more time,” says Early.

Managing data turned into an even larger issue where the customer required images of every HUD analysis to be saved and stored for authentication and reporting reasons.

Once data was outputted, one last challenge that needed addressing was the application of unique formulas to the data and the calculation of measurement values for HUD glass evaluation.

As Early recalls, “Originally, we did that work post-process, on the Excel side. We developed the inspection test program ourselves in an Excel format, including all formulas for HUD glass inspection. But that increased our cycle time.”

If an operator unlocked the Excel file after test system delivery, unintended edits or resorting of the formulas or data could lead to errors in the output measurement values of the test report.

When CP Industries’ engineering team commenced working on the company’s seventh-generation HUD glass test system (the HUDSON test system) maximum effectiveness was vital.

Replacing the initial machine vision imaging software and system, the team could streamline data management, reduce development time and complexity. The engineering team could also reduce cycle times, lead times and improve usability for their customer.

The HUDSON test system from CP Industries addresses complete customer requirements for HUD glass inspection and can be incorporated as part of a fully automated production line or used in offline measurement.

The HUDSON test system from CP Industries addresses complete customer requirements for HUD glass inspection and can be incorporated as part of a fully automated production line or used in offline measurement. Image Credit: CP Industries

For its new HUDSON system, CP Industries chose a scientific HUD measurement system from Radiant Vision Systems to take the place of its machine vision cameras and software systems.

As a supplier of measurement and test products for automotive light sources and displays, Radiant has developed a thorough understanding of HUD measurement criteria through the use of colorimetric and photometric imaging systems for HUD testing across suppliers and OEM tiers.

Radiant’s HUD measurement solutions include test criteria specified in the Society of Automotive Engineers guidelines (SAE J1757-2) as well as features built around individual user’s application specifications.

Radiant’s systems test photometric qualities such as chromaticity, luminance and contrast, as well as dimensional tests for warping, distortion and ghosting. The scientific-grade, high-resolution ProMetric® imaging systems utilized in these analyses are capable of handling considerable data processing and output requirements.

They also offer onboard image processing and advanced calculations for image-based measurement.

CP Industries built the Radiant ProMetric® Y Imaging Photometer into the HUDSON test system to carry out the image capture and processing requirements for HUD glass inspection. Data from the ProMetric® system is analyzed utilizing Radiant’s TT-HUD™ software platform.

With analyses and user interfaces developed especially for automated visual inspection of automotive HUDs, the TT-HUD™ software offers all data capture and analysis functions which include built-in calculations that are required to assess the qualities of HUD projections based on standard formulas.

The ProMetric® Y Imaging Photometer captures images of complete HUD projections, and provides on-board image processing and analysis using a suite of HUD measurement tests in TT-HUD™ Software.

The ProMetric® Y Imaging Photometer captures images of complete HUD projections, and provides on-board image processing and analysis using a suite of HUD measurement tests in TT-HUD™ Software. Image Credit: Radiant Vision Systems

“I was having to program all of the tests from scratch that Radiant was providing out of the box. Whenever the customer needed to make a small change, it drastically impacted the programming I had done and required me to restructure every­thing,” recalls Early.

 “The Radiant system does all image and data processing internally, rather than having to manage the calculations of the data in post-processing. The flexibility and the adaptability of Radiant to different testing requirements was another plus.”

The imaging processing and calculation functions are carried out by the Radiant system and the data delivered to the customer’s test report is the final output data, with every formula already applied.

This reduces the possibility of errors occurring if the Excel report is adjusted. There are no extra procedures required to manage data, leading to an overall reduction in both cycle times per test and development time for the system.

“One of our main goals was cycle time. Since add­ing the Radiant system, we definitely see an im­provement in speed,” says Palafox. “This gives us a better lead time on our end to provide a machine to a customer—from around 24 weeks for a system to around 14.”

Radiant’s expertise and range of test functions can be applied to expand and develop test systems to address new range of criteria in HUD glass testing. This allows CP Industries to address a wider range of needs and carry out further projects for its glass and automotive customers.

Palafox explains, “We have the ability to do certain measurements that we haven’t done before, but with Radiant, we can easily do. Before, we could perform basic tests for ghosting and image rota­tion - but not dynamic geometric measurement. The Radiant camera seems like it’s capable of doing a lot more if we get to the point of having to measure even more specifications. We can handle that now, whereas we were much more limited with the other camera options.”

Optimizing Repeatability with Robotics and Optics

A HUD projection’s visual performance may be considerably affected by the angle and position from which the projection is viewed. Eyebox is a key issue in HUD glass testing, accounting for the area of space where the driver’s eyes could be located to visualize the HUD projection.

The position and rotation of the imaging system may be stipulated in HUD test conditions to factor in eyebox positions and simulate the possible position or height of a driver.

Such variations could affect the appear­ance of defects like ghosting and distortion produced when light from the HUD projection is refracted and reflected through the different windshield layers and influenced by the wedge angle.

The wedge angle is the angle between the inner and outer layers of the windshield glass. To meet test requirements for position and angle, CP Industries’ team knew they would need to factor motion into their HUD glass test system.

Illustration of the HUD eyebox — within this area, the HUD virtual image is completely visible through the windshield.

Illustration of the HUD eyebox—within this area, the HUD virtual image is completely visible through the windshield. Image Credit: Radiant Vision Systems

“We started with three stationary-positioned ma­chine vision cameras and a HUD projector, which moved during testing,” states Palafox. Moving the projector, however, turned out to be problematic for re­peat inspections.

“A HUD projector that’s integrated in the car is intended to be adjusted for maybe 10 seconds every month,” explains Early. “Whereas in a pro­duction setting, it would be moving up and down every 10 seconds, with its motor running 24 hours a day.”

This degree of movement would quickly wear out the HUD projection system. When designing the HUDSON test system, the engineering team at CP Industries solved this by removing the HUD projector completely.

They added an LED to imitate projection when cast through a custom metal grating and robotics to manage the location of the inspection camera.

“We created a plate with a test pattern (that the customer usually specifies), and behind that are LEDs that shine through the plate to project the pattern through the glass,” explains Palafox.

“The LEDs that we put on our HUDSON machine have a lifespan of up to 10 years. And now the cam­era is moving instead of the projector. That’s a big benefit for the glass companies compared to having to buy a new projector every one-to-two months.”

The Radiant ProMetric® Imaging Photometer allowed the team to reduce the amount of equipment in the HUDSON system by removing components previously required to guarantee test system perfor­mance.

As Cassady explains, “We used to have a luminance meter in the test system to make sure the LEDs were emitting enough light for the test projection. But now we don’t need that.”

As a photometric camera, the ProMetric® Y captures absolute luminance values, or cd/m2, as well as dimensional HUD inspection data.

The rotation and movement of numerous parts meant that the HUDSON test system needed to be designed to factor in variables that could im­pact misalignment of the optics, camera system and robotics in relation to the HUD glass and projection.

The team at CP Industries included an auto­mated calibration routine in the HUDSON system utilizing a target plate above the camera. This was illuminated by an LED to create a golden sample of the ideal HUD projection test image.

During HUD glass inspection, LED light is cast through the HUDSON’s projector plate (left) and through the windshield under test, emulating a HUD projector. The target plate (right) is used similarly to produce an ideal HUD projection for system calibration.

During HUD glass inspection, LED light is cast through the HUDSON’s projector plate (left) and through the windshield under test, emulating a HUD projector. The target plate (right) is used similarly to produce an ideal HUD projection for system calibration. Image Credit: CP Industries

“Calibration ensures the robot isn’t worn, the cam­era isn’t damaged, the machine hasn’t shifted or changed,” Early explains. “The target plate above is used to calibrate at the beginning of each test run.

If there’s any doubt that the machine isn’t providing accurate data, the customer can go back to that calibration plate and run a calibration verification.”

The positional changes during both testing and calibration meant that the imaging system would need to react rapidly to new optical parameters, especially camera focus. Theis is because HUD virtual images are projected to a point several meters out from the driver’s position to appear in line with the environment outside the vehicle.

Factoring in further eyebox testing specifications, the focus settings of the imag­ing system would need to adjust for different HUD projection depths as the robotics move the camera to various locations.

Irrespective of these adjustments, the imaging system must make certain that the test images are cap­tured clearly and precisely for reliable measure­ment performance at all eyebox locations.

The integration of the Radiant ProMetric® Y Imaging Photometer into the HUDSON system allowed CP Industries to tap into the potential of the camera’s electronic lens to achieve precise and repeatable focus-setting.

The ProMetric® Imaging Photometer’s aperture and focus settings can be altered remotely utilizing the software and changed dynamically to varied test positions, enabling fully automated measurement. The electronic lens also allows for fast, hands-free calibration of the test system via the HUDSON’s calibration target plate.

“With the electronic lens, there’s less concern when you’re moving the camera around,” states Early. “There are vibrations from the robot, maintenance technicians might clean the system, etc. But you don’t have to worry about someone moving that lens and shifting your focal point, which drastically affects your measurements.”

Electronic lenses enable quick, remote adjustment of the camera’s focus and aperture via software to match exact HUD projection distances. ProMetric Imaging Systems are factory calibrated for each lens across a range of working distances and aperture settings.

Electronic lenses enable quick, remote adjustment of the camera’s focus and aperture via software to match exact HUD projection distances. ProMetric Imaging Systems are factory calibrated for each lens across a range of working distances and aperture settings. Image Credit: Radiant Vision Systems

“Using the machine vision cameras, we had a bunch of trouble with focus and finding the cor­rect distance to the projection. Then, we had to go in and adjust lenses manually,” adds Palafox.

“If you moved the lens even a little bit, you could lose focus, and that would be a big hassle. Radiant’s electronic lens saves us time during the setup of the test system as well — it’s a big advantage in bring­ing down lead time.”

The combination of electronic lenses and completely automated test sequencing in TT-HUD™, Radiant ProMetric® imaging systems offer an ideal in-line HUD measurement solution for pass/fail analysis across numerous visual inspection parameters.

TT-HUD™, along with its built-in API and SDK, allows for integration with robotics and automation equipment or manufactur­ing systems, offering ultimate flexibility in test systems development to meet varied customer requirements in the future.

Summary

CP Industries’ dedication to innovation allows it to tailor its HUD glass test systems to offer the most complete solutions to its customers, including:

  • Meeting complete HUD test specifications
  • Developing custom test routines
  • Designing automation to fit each unique production line

CP Industries’ solutions allow the customer to focus on the production of the best glass products for HUD applications. Alongside the help of Radiant Vision Systems’ HUD measurement technology, CP Industries’ bespoke solutions incorporate powerful functions that ad­dress the full range of HUD inspection tasks, such as HUD software tools, electronic optics, robotics, multi-functional photometric imaging and more.

By utilizing Radiant’s ProMetric® Imaging Photometer and TT-HUD™ Soft­ware in its latest HUDSON system rather than traditional machine vision systems, CP Industries has modernized its development, decreased equip­ment and increased functionality.

These improvements have allowed the company to im­prove lead time, capability, cost-efficiency, and testing speed for its customer base, demonstrating why CP Industries is widely chosen for tooling systems in automotive and other manufacturing sectors.

“If I had to summarize the benefits of switching to Radiant, it would be faster implementation, broader measurements and calculation options, and faster cycle times.” - Andrew Early, Control Engineer, CP Industries

“Radiant and CP Industries build on each other’s knowledge to develop HUD testing. As opposed to working with the previous machine vision systems—which relied on us for all the fundamental HUD test knowledge—Radiant has that background to help us understand what else we can do in HUD testing. It’s not all on us.” - Cruz Palafox, Project Engineer, CP Industries.

This information has been sourced, reviewed and adapted from materials provided by Radiant Vision Systems.

For more information on this source, please visit Radiant Vision Systems.

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