Roller coaster ride for high speed imaging
For many of the millions of people who ride most thrilling roller coasters and similar rides in entertainment parks around the world, the experience wouldn’t be complete without a souvenir picture taken at a critical part of the ride. As rides get faster and more complex, so do the technical challenges in capturing those pin-sharp images. Vision technology specialist, STEMMER IMAGING has worked closely with Picsolve, the leading image capture partner for the leisure and entertainment industry, to develop a new high speed imaging system that can meet those challenges.
The imaging challenge
Roller coaster ride photography has traditionally used Digital Single-Lens Reflex (DLSR) camera technology which features mechanical shutters. Although this works well, the mechanism has a limited lifetime (typically around 100,000 exposures) before the lens assembly needs to be replaced, and the cameras have inadequate frame rate for the fastest rides.
Industrial vision cameras, which have electronic shutters, offer an attractive alternative. Short exposure times are needed when imaging a fast moving scene to avoid motion blur and typically the exposure time should be short enough so that the object moves by less than 1 pixel on the camera sensor during the exposure. In order to ensure that the exposure of the camera happens exactly when the object is in the correct position, the camera sensor must be precisely triggered.
For precise triggering great care must be taken to assess and reduce all of the factors that can influence delays from initiating a signal to the resultant action in the sensor in order to ensure the required imaged is acquired. In the case of the rides, a number of factors affect the triggering required. These include whether the ride (car) is accelerating or decelerating, how many rows of seats there are in each car that need to be imaged, how many cars will be passing the imaging point and the spacing between the cars.
The imaging solution
STEMMER IMAGING was asked to design and supply the complete camera and timing solution, engineered to offer the flexibility to be adapted to individual rides, while Picsolve took responsibility for the lighting and software. The system consists of a camera head mounted at the appropriate position on the ride, and a base unit containing power, trigger timer controller, opto-isolated trigger input, network switch.
The base unit also provides the trigger out to the strobe lighting unit. The camera head features a high resolution colour camera, lens and lens controller mounted in an IP67 enclosure with integrated heater and screen wiper enabling operation in all weather conditions. The camera provides 5MP resolution and can operate at 29 fps in burst mode. Remote focus and aperture control is essential since the camera heads are mounted in difficult locations and need to accommodate changing light conditions.
Colour imaging is a complex process which is a function of the illumination method being used and the camera technology. Additional image processing is sometimes required to allow the output image to match the colour quality of DLSR cameras. While the camera used gives excellent colour rendition under the part daylight, part flashlight illumination used on the ride an on-board colour correction capability using a colour recognition and colour calibration tool can deliver corrected colours in all lighting situations.
The base unit features an ethernet-enabled trigger timing controller which provides very flexible triggering capabilities that can be reconfigured on the fly if required and offers the possibility to programme over 25 timing variations on a single ride. Picsolve software takes control of the trigger timing unit and is programmed for the specific ride to provide the appropriate triggers back to the camera.
Fast response and future-proof design
STEMMER IMAGING has already shipped the first camera and base units to Picsolve for deployment at theme parks across Europe. The project took just two months from initial discussions to prototype units being delivered, with production units following soon after. Since the cameras are generally mounted in locations where access is difficult, the entire camera head is designed for easy interchange and it can be swapped in and out for service and routine maintenance.
In addition, the design provides the flexibility to accommodate potential future requirements. The camera’s on-board colour correction capability has already been mentioned, but it also has a number of other features that could be invoked in the future, if required. Firstly it contains on-board memory so if the system is used on rides which require a higher than normal image capture rate, then images can be buffered in the camera before transmission. In addition, jpeg compression is available if needed, depending on data rate constraints on the network back to the paystation.
STEMMER IMAGING has been one of the leaders in the machine vision market since 1987. It is one of Europe's largest technology providers in this field. In 1997 STEMMER IMAGING presented Common Vision Blox (CVB), a powerful programming library for fast and reliable development and implementation of vision solutions, which has been deployed successfully throughout the world in more than 80,000 imaging applications in various industries.