Origins
Time Delay Integration (TDI) is a specialized imaging technique that has played an important role in advancing remote sensing, astronomy, medical imaging, and machine vision. Its origins can be traced back to the mid-20th century, when researchers sought ways to overcome the limitations of conventional photographic and electronic imaging in scenarios where targets moved relative to the sensor.
The earliest roots of TDI can be found in aerial reconnaissance during the 1950s and 1960s. Traditional film-based cameras suffered from image blur when capturing fast-moving objects or when mounted on high-altitude aircraft. Engineers began experimenting with methods of synchronizing film movement with the motion of the ground below to reduce smearing. These early mechanical attempts set the stage for electronic solutions.
The CCD Era
With the rise of charge-coupled devices (CCDs) in the 1970s, the concept of electronically “shifting” charge across a detector array in synchrony with target motion became practical. This breakthrough is generally considered the birth of true TDI. Instead of capturing a single exposure, the CCD would accumulate charge line by line, transferring it across the sensor in step with the movement of the image. This allowed much longer effective integration times without introducing motion blur, significantly boosting signal-to-noise ratio.
By the 1980s and 1990s, TDI imaging had been adopted widely in satellite-based Earth observation systems, where spacecraft motion across the planet’s surface could be matched with the electronic shifting of charges on the detector. This enabled sharper, higher-resolution imagery than would have been possible with conventional frame-based sensors. Similar principles were applied in astronomy, particularly for tracking faint celestial objects moving against the night sky.
The Move to CMOS Technology
For decades, CCDs dominated TDI imaging because of their low noise, high sensitivity, and ability to shift charge with high precision. However, in recent years the industry has been steadily transitioning to CMOS-based TDI sensors. This move has been driven by several factors:
- Higher speeds: CMOS architectures allow faster readout rates and more flexible multi-channel designs, making them better suited for the extremely high data rates demanded by modern TDI applications.
- Integration: CMOS processes enable on-chip functionality such as timing control, digitization, and advanced readout modes, reducing system complexity.
- Lower power and cost: CMOS manufacturing benefits from economies of scale in the broader semiconductor industry, lowering power consumption and long-term costs.
- Design flexibility: CMOS enables hybrid designs that combine TDI with other imaging functions, opening up new application possibilities.
Today, CMOS-based TDI sensors are rapidly becoming the standard in cutting-edge systems. While CCDs remain in use for certain niche applications, the future of TDI clearly lies in CMOS, where performance, scalability, and integration can continue to advance at the pace required by industries like semiconductor inspection and life sciences.
Applications
TDI technology is used across a wide range of fields where both speed and sensitivity are critical. Common applications include:
- Industrial vision inspection: inspection of high-speed manufacturing lines, printed materials, and electronics.
- Satellite imaging: Earth observation systems that capture high-resolution data from orbit without motion blur.
- Semiconductor imaging: wafer and mask inspection at the nanometer scale, where the highest speeds and sensitivity are required to keep pace with production. Tucsen’s Gemini 8K is a prime example of a camera designed to meet these stringent demands, offering high-resolution and high-speed imaging to enable precise defect detection and process control.
- Life sciences: next-generation sequencing (NGS) platforms and, more recently, flow cytometry, where samples in extremely fast flows are imaged with high resolution. Here, Tucsen’s Dhyana 9KTDI has been widely adopted, demonstrating the advantages of TDI in generating sensitive, high-quality data in biological research and diagnostics.
While TDI is valuable in all of these areas, the technology is being pushed hardest in semiconductor inspection and life sciences. These fields can fully utilize higher line rates, larger numbers of TDI stages, and enhanced sensor architectures to break through performance barriers that traditional imaging cannot meet.
Recent Advances
In recent years, TDI technology has reached remarkable speeds. Cameras now operate at line rates of 500 kHz and even up to 1 MHz, enabling the inspection of materials moving at extremely high velocities. This leap in performance has created new challenges in data handling: interface cards must be faster and more robust to manage the massive data throughput required for capturing and processing imagery in real time.
Another major advancement has been the adoption of back-illuminated sensors. By moving circuitry behind the photosensitive layer, these designs significantly increase the quantum efficiency (QE) of TDI cameras. The result is higher sensitivity and improved image quality, even when operating at the demanding speeds of modern applications.
In parallel, improvements in thermal management have been critical. As higher speeds generate more heat, customized solutions such as liquid cooling and forced-air cooling systems are being implemented alongside traditional fin and fan designs. These advanced methods help maintain stability, reduce noise, and preserve image integrity under extreme operating conditions.
Tucsen’s History with TDI
Tucsen entered the TDI market at a pivotal moment—when the technology was expanding from traditional industrial vision into the life sciences. The company was an early adopter of the Gpixel GLT5009BSI sensor, which powered its Dhyana 9KTDI product. For more than five years, Tucsen has manufactured cameras based on this sensor and has become the dominant global supplier in this segment.
Building on this foundation, Tucsen developed its Gemini series of TDI cameras using the GLT5008BSI and GLT50016BSI sensors, along with other non-commercial variants. The Gemini 8K, for example, has become a flagship product that demonstrates Tucsen’s ability to combine high resolution, sensitivity, and speed in a robust design tailored to the demanding requirements of semiconductor inspection and advanced life science imaging.
These developments reflect Tucsen’s leadership in adapting the latest sensor technologies to meet evolving customer requirements in both life sciences and semiconductor inspection.
Tucsen Photonics’ Value
Tucsen Photonics has become a global leader in TDI imaging, delivering thousands of cameras for applications in both life sciences and semiconductor inspection. As the predominant choice for major customers who fund custom development through NRE, Tucsen is consistently at the forefront of new innovations. By collaborating closely with these customers, the company drives advancements such as higher-speed interfaces and improved sensor designs, ensuring performance keeps pace with future market needs.
Tucsen also understands the scientific importance of high-quality data for precise measurement. With this in mind, the company has customized its cameras beyond standard cooling methods, introducing liquid cooling and forced-air cooling systems that provide stable performance, reduced noise, and superior image quality for the most demanding high-speed applications.
In addition to its standard product lines like Dhyana and Gemini, Tucsen develops fully custom cameras under NRE agreements. The company currently has six dedicated engineering teams working on custom TDI projects for major clients worldwide. These efforts range from tailoring existing platforms to building completely new designs—including advanced systems that incorporate multiple sensors into a single camera for greater capability and flexibility.
The company’s scale of manufacturing—both within China and internationally—has positioned it as a truly global player. This capacity allows Tucsen not only to serve large industrial clients but also to extend TDI technology into broader markets once exclusivity periods have ended. By combining technical expertise, customer-driven innovation, and manufacturing strength, Tucsen continues to define the cutting edge of TDI imaging.
Conclusion
What began as a workaround for motion blur in reconnaissance photography has matured into a sophisticated, versatile imaging method. Today, TDI remains a cornerstone technology for high-performance imaging, continuing to evolve as sensor speeds increase, CMOS architectures replace CCDs, advanced cooling enables stability, customer-driven development pushes innovation, and global leaders like Tucsen Photonics accelerate progress through scale and collaboration.