3 Importance of Comparator's Minimum Pulse Width Detection Capability

Generally, the laser driver in a ToF system is required to operate under a specific wattage so that if any human comes between the transmitter and target option, the laser will not damage their retina or skin. Below are two images depicting the wave in the transmitter side.

Figure 3-1 Examples of ToF Transmitted Pulses

Although the pulse widths of the two images are different, the area under the curve of both images is the same – depicting that they have the same wattage use. The image on the left with the narrower pulse width is used to detect a target object several meters further than the image on the right. The image with the wider pulse would be used to detect an object at a shorter distance. To detect objects further away from the ToF System while operating under the same power requirements, the receiver needs to have the capability to detect narrower pulse widths.

For ADC’s, this translates to the amount of samples per second the ADC can measure. If the ADC does not have a high enough sampling rate and the reflected pulse is too narrow, the ADC will not be able to accurately digitize the data to bits to calculate the distance to the target object. The same will happen if using a comparator that cannot detect the reflected pulse width. In fact, the comparator may not respond to the signal at all and a distance measurement might not be calculated.

ADC’s with a sample rate equivalent to a comparator’s minimum pulse width detection capabilities will be much more expensive to both purchase and incorporate into a ToF system. However the decision to use one over the other should still mostly depend on if more than just distance is needed to be calculated in a ToF system. If a decision has been made to use a comparator as a receiver in the ToF system, than selecting a comparator with better minimum pulse width capabilities will result in being able to measure a target object at a further distance.