Depth perception is the fundamental technology for achieving advanced cognitive functions such as 3D mapping, object recognition, and spatial perception. For fields that require precise real-time processing of the shape, position, and motion of the environment and objects, this technology is indispensable. Through deep perception technology, the position information of the target object can be accurately obtained, which helps to achieve adaptive and intelligent operations.

Ansenmei's iToF solution: HyperluxTM ID

Although conventional indirect time-of-flight (iToF) technology has enormous potential, it still faces challenges in practical applications. To address this challenge, Anson has developed the Hyperlux ID high-performance iToF sensor series. This series utilizes advanced pixel and stacking technologies and various features to expand the application range of iToF methods. The following introduces the principle of iToF and the main features of the Hyperlux ID aware series.

The principle of iToF

As mentioned earlier, the indirect time of flight (iToF) method determines depth by receiving the reflected wave of illumination light modulated at a specific frequency and calculating the phase shift. To determine the phase shift, four modulation signals were used for measurement, with phase offsets of 0 °, 90 °, 180 °, and 270 °, respectively. Therefore, at least four exposures are required to obtain single depth frame information.

IToF calculates distance based on phase shift. The phase period is determined by the modulation frequency, and the phase has periodicity. When the distance from the target exceeds one cycle, phase ambiguity occurs, which means it is impossible to determine which cycle the measured phase belongs to. For example, if the modulation frequency is 60MHz, one cycle is 2.5 meters. In this case, measuring a distance of 3 meters will be interpreted as 0.5 meters. Therefore, the maximum measurable depth is generally within one cycle of the modulation frequency (0 to 2 π).

The main features of Hyperlux ID

Improve resolution and distance accuracy

Anson has developed an iToF sensor series called Hyperlux ID. This series includes two products, AF0130 and AF0131, with a high resolution of 1.2 million pixels. This resolution is equivalent to four times the resolution (VGA) of most iToF sensors currently on the market, allowing for more accurate measurements.

In addition, these products also support pixel merging. If the VGA resolution is sufficient, merging 1.2 million pixels can improve the sensitivity of the VGA sensor. The distance resolution depends on the modulation frequency. Compared to conventional solutions on the market, our product can use a relatively high modulation frequency of 200MHz. Therefore, our product performance is scalable, supporting both short distance and high-precision sensing as well as long-distance and high-resolution sensing.

Integrated deep computing capabilities (reducing system size and lowering costs)

Conventional iToF sensors do not have the ability to calculate depth distance based on the exposure results of four phases. The process of determining the depth distance must be performed by an external FPGA or processor. These FPGAs or processors store the exposure results of each phase output by iToF sensors in frame memory and perform depth calculations after collecting data from all four phases. Therefore, customers need to ensure that the system has sufficient processing power and memory to support iToF computing.

Our new product AF0130 integrates deep computing capabilities. Customers do not need to prepare a large amount of processing resources, and the system can be simplified. If specialized computing devices such as FPGA were previously used, they can now be removed to help reduce the size of the camera. If high-performance processors were used in the past, computing resources can now be allocated to other applications or replaced with more cost-effective processors. When the resolution is high, our new solution will be more effective.

IToF requires data from at least four phases, so compared to conventional image sensors, it produces more than four times the data output. Due to the calculation being performed on the iToF sensor end, the data rate can be significantly reduced. It can also enhance the flexibility of circuit board design. In addition, if the customer wishes to use their own computing algorithm, we also provide AF0131 without integrated computing functionality.

Reduce motion artifacts

Conventional iToF sensors read data to an external processor after each phase exposure. It takes a certain amount of time to complete the exposure from the first exposure with a diameter of 0 to the completion of the exposure with a diameter of 270. If the target object moves during this period, motion artifacts will appear in the perception results. Hyperlux ID has built-in memory that can retain necessary phase data. The technological breakthrough here is that all four phase information is directly stored in pixels. The exposure result is stored intact in the pixel memory. Therefore, the next phase exposure can start in a very short time, reducing the total exposure time of the four phases and significantly reducing motion artifacts.

Long depth distance and high ambient light suppression

·Dual frequency mode: The typical sensing range of a conventional iToF sensor is around 5 to 10 meters, and due to its susceptibility to ambient light interference, it is typically limited to indoor use. As mentioned earlier, the depth range that iToF can measure is generally one cycle of modulation frequency. To expand the measurement range, a method of fusing two modulation frequencies can be used. Due to the use of two modulation frequencies, the maximum distance that can be distinguished is the least common multiple of these two frequencies. This method has a long history, but conventional iToF sensors require a modulation frequency change every frame when processing four phases, which is then merged by the system. As a result, the final frame rate will be halved, and the exposure time for creating a single depth frame will be extended. Hyperlux ID has the ability to handle two modulation frequencies within a single frame, so there is no need for external processing and the frame rate will not decrease. In addition, by using pixel memory, the time required for eight phase exposures of two modulation frequencies can be shortened. Therefore, not only is the perception range expanded, but motion artifacts are also effectively reduced. However, the maximum resolution of this product when using dual band is VGA. ）

·Improve sensitivity: Assuming that the laser used for emission is a laser in the 940nm wavelength band. In this frequency band, the typical QE (quantum efficiency) of conventional iToF products is 20% to 30%, but Hyperlux ID has reached over 40% thanks to Anson's advanced pixel technology. As the measurement distance increases, the energy of the reflected wave decreases, so the improvement of sensitivity is very helpful in improving the depth measurement distance and accuracy. In addition, under dual frequency, due to pixel merging, the maximum resolution becomes VGA, but this also improves sensor sensitivity, helping to increase depth measurement distance and accuracy, just like QE.

·Enhanced ambient light suppression: Generally speaking, iToF is susceptible to interference from ambient light such as sunlight. Light sources other than lasers can also affect measurements, leading to inaccurate results. Therefore, iToF is usually limited to indoor use only. Our product has enhanced its ability to suppress ambient light. Even under sunlight, it can obtain accurate depth results.

Mixed mode: Conventional iToF sensors use modulated continuous light waves, requiring the shutter to remain open during measurement, which leads to the accumulation of ambient light components in the pixels. In addition, to measure farther targets, it is necessary to increase the laser power. In this case, the laser energy is very strong and will shine on nearby targets, producing strong reflected light that may cause pixel saturation. Therefore, conducting large-scale measurements is very difficult. Hyperlux ID adopts Anson's global shutter technology and patented hybrid technology. It uses specialized modulation based on measurement distance and only opens the global shutter when necessary, effectively reducing the accumulation of ambient light components. This can maximize the use of pixel sensitivity and achieve wide range measurements from close to long distances. At present, measurement results exceeding 30 meters can be obtained both indoors and outdoors.

Application of Hyperlux ID Indirect Time of Flight (iToF) Technology

Hyperlux ID improves the resolution and accuracy of distance perception, enabling more accurate measurements at both close and long distances (up to 30 meters). By applying it to various depth perception scenarios in industrial, commercial, and consumer fields, it helps to enhance depth perception performance.

In summary, Anson's high-performance iToF product line, as part of the new Hyperlux ID series, overturns traditional concepts about iToF methods. This series of products expands the application scope of 3D perception and helps to improve the automation level in many fields such as industrial automation, robotics, and security.

This is reported by Top Components, a leading supplier of electronic components in the semiconductor industry

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