There isn’t one official parameter defining the speed that high-speed cameras should have. Models capable of recording images at speeds up to even a million frames per second are available on the market. This is an astonishing result, both in terms of sensor capabilities and, most importantly, the amount of data the device must record in one second.
High-speed imaging allows for recording and analyzing processes that occur too quickly to be observed with the naked eye. After recording the footage, the videos are “stretched” so that the speed of the final video material is a standard 25-30 fps. This achieves the so-called “slow motion” effect.
Currently, high-speed imaging technology is gaining momentum. It is increasingly encountered in both industry and laboratories. The “slow motion” effect can even be found in high-performance smartphones, where it functions more as a visual effect.
Technology and Sensors
High-speed cameras, just like regular cameras, focus light collected from the surroundings onto a sensor, where it is converted into an electrical charge. The mastery of CMOS technology brought a particular revolution to the high-speed imaging market. Unlike CCD sensors, where each pixel converts light entering through the lens into a voltage sent from the chip through a limited number of output nodes (one to several), CMOS sensors contain amplifiers and analog-to-digital converters (DAC) on the sensor chip. Such a solution, in addition to higher image digitization speed, also allows for energy savings.
Sensors used in high-speed cameras often feature a large size of individual pixels. This design increases the sensor’s sensitivity and, consequently, the amount of light captured. This approach is used due to the very short exposure time with which cameras record images at thousands of fps.
CMOS sensors are the dominant type in high-speed cameras.
An alternative to standard area scan cameras are linear cameras, where the acquisition speed is given not in frames per second, but in the frequency at which several lines of pixels collect images of moving objects. The short exposure time means that these devices often work with very bright illuminators, creating vision systems.
Memory and Performance
An acquisition speed of 1000 fps at a resolution of 1280 x 800 pixels means that 1000 HD-resolution images must be transmitted and saved in one second. Due to interface limitations, these cameras do not transmit images to the computer in real-time but use their own built-in memory. This memory must also be high quality – built-in SSDs do not yet offer the speed required for real-time digitization. For this purpose, SDRAMmemory is used. In high-end high-speed cameras, it can have a larger capacity than in many computers. From there, the recorded image is then transferred to an SSD or a computer. It’s worth noting, however, that SDRAM memory with a capacity of, for example, 128 GB, may only allow recording a few seconds of footage at a time if recording in high resolution and at high speed.
In summary, every component of a device designed for high-speed imaging must be of the highest quality available in its respective field. This shows how challenging the issue itself is and how complicated a “high-speed” camera can be.
Limitations and Challenges
The field of high-speed imaging also has to contend with other difficulties. Acquisition speed is inversely proportional to exposure time. This necessitates adequate illumination of the scene. Otherwise, the image may be very noisy or simply very dark, in the worst case, to the point where proper interpretation is not possible. Models with built-in light sources to prevent unwanted blurring can be found on the market. This solution makes the system more compact, which is particularly desirable when frequently changing the device’s working location.
The enormous amount of data processed also creates other problems. Cameras designed for high-speed imaging can record images at their highest speed only at a limited resolution. There is a correlation: the higher the resolution, the lower the maximum available frame rate. And vice versa.
Types of Cameras
Two main solutions dominate the market: cameras that work with computers and cameras that can operate as standalone devices.
“PC-Connected” cameras have internal SDRAM memory for fast image recording. They transmit a live preview at several tens of frames per second to a PC, while the high-frame-rate image is recorded in the internal SDRAM for later download. These cameras may be slightly cheaper than their “Handheld” counterparts, but they are less mobile and require a connection to a computer, e.g., via a Gigabit Ethernet interface. For these reasons, they are more recommended for stationary applications.
Handheld cameras are mobile and do not require a connection to a PC. They have internal SDRAM memory for fast recording, built-in SSDs for image storage, and live preview capability. Furthermore, they are often equipped with a screen for real-time image viewing and a powerful light source to prevent image blurring during short exposure times. Their additional advantage is the ability to connect the camera to a PC in the same way as PC-Connected cameras. Handheld cameras are excellent for situations where they need to be used to record various processes in different locations.
Applications
High-speed imaging is used to record processes and phenomena that are too dynamic for the human eye. This makes them applicable in many fields, both in industry and science. Very often, “high-speed” cameras are used to analyze fast processes occurring on production lines. They also provide invaluable help, for example, in conducting car crash tests or in ballistics. High-speed imaging is also present in the observation of biological and chemical processes and in laboratories. It also proves fruitful in measuring high-frequency, low-amplitude vibrations.
It’s worth noting that in addition to information about the process, “slow motion”footage also offers an interesting visual effect. It is precisely from this perspective that high-speed cameras are increasingly being used in the entertainment field. They are used in television, music video recording, and sports.
Avicon’s Offer
Our offer includes special integration services for high-speed process imaging, where the primary system parameter is the number of frames per second. We provide stationary and portable (handheld) solutions with acquisition frequencies ranging from 100 up to 100,000 frames/second.
Our solutions are utilized by many corporations, including:
- 3M
- Colgate-Palmolive
- Phillip Morris
- Ball Packaging
- Gdańsk University of Technology
- ETC PZL Aerospace
- International Paper Kwidzyn
