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Introduction to the Sony IMX459 Stacked SPAD Depth Sensor 2021-11-15

SONY announced the upcoming release of a 1/2.9” stacked SPAD Time-of-Flight (ToF) depth sensor with 100,000 effective pixels. The IMX459 sensor is the first in the industry to make use of the direct Time-of-Flight (dToF) technique and is suitable for automotive LiDAR applications. The product packs the tiny 10μm2 SPAD (square single-photon avalanche diode) pixels and distance measuring processing circuit onto a compact 1/2.9” form-factor chip to deliver high-precision and high-speed distance measurement. As Advanced drive assistance systems (ADAS) and autonomous driving become more common, the improved automotive LiDAR detection and recognition performance offered by the new sensor will contribute to the realization of safe and reliable future mobility.

In addition to sensing devices such as automotive cameras and millimeter wave radar, LiDAR is becoming ever more important as a method of high-precision detection and recognition of road conditions, and the location and shape of objects such as cars and pedestrians. A variety of methods are used for LiDAR distance measurement. In a dToF sensor, SPAD pixels are used as a type of detector. Distance to an object is determined by measuring how long (time difference) light emitted from a light source takes to reflect off the target and return to the detector. Using the back-illuminated pixel structure, stacked configuration, and Cu-Cu connection technologies developed for CMOS sensors, SONY came up with a unique structure that integrates the SPAD pixel and distance measurement processing circuit into one chip. The tiny 10μm2 square pixel size made possible by this design meant that a compact and high-resolution 1/2.9” form-factor with 100,000 effective pixels could be realized. Enhanced photon detection efficiency and responsiveness allow for high-speed, high-precision distance measurements with a resolution of 15cm from long to short ranges. The product satisfies the functional safety standards for automotive applications and improves the reliability of LiDAR. The single-chip structure means even more compact and low-cost LiDAR can now be developed.
 
Key Features:
Stacked structure with 10μm2 SPAD pixel and distance measurement processing circuit to deliver high-speed and high-precision distance measuring performance
This product employs a stacked configuration. A Cu-Cu connection is used to achieve conduction for each pixel between the back-illuminated SPAD pixel chip (top) and the logic chip equipped with a distance measuring processing circuit. The circuit can then be placed on the bottom of the pixel chip to maintain a high aperture ratio and a small 10 μm2 pixel size. A light incidence plane with surface irregularities is also used in this product to boost the absorption rate. These attributes result in a photon detection efficiency of 24% in the 905 nm wavelength commonly used in automotive LiDAR laser light sources. The high recognition and distance resolution rate allow for the detection of distant objects with low reflectivity. The unique stacked configuration enables high-speed and high-precision distance measurements with a resolution of 15cm from the long to the short range, improving the detection and recognition performance of automotive LiDAR.
 


Complying with functional safety standards for automotive standards enhances the LiDAR reliability
The product has been certified to meet the requirements of the AEC-Q100 Grade 2 automotive electronic component reliability tests. SONY also followed the ISO 26262 standard during development to ensure that design quality complied with the automotive functional safety standard requirements and supported ASIL-B(D) functions such as failure detection, notification and control. These all help improve LiDAR reliability.


Key Features:

Product specification

Model name

IMX459

Number of effective pixels

597 x 168 pixels (H x V),
approx. 100,000 pixels

Image size

Diagonal 6.25 mm (1/2.9-type)

Recommended light source wavelength

905 nm

Unit cell size

10.08 μm x 10.08 μm (H x V)

Element size (ToF pixel unit)    

3 x 3 (H x V)

Photon detection efficiency

24%

Response speed 

Approx. 6 ns

Power supply       

SPAD breakdown voltage              

-20.5V

SPAD excess voltage

3.3V

Analog

3.3V

Digital

1.1V

Interface

1.8V

Interface

MIPI CSI-2 serial output (4 lane / 2 lane)                                         

Package

152-pin plastic BGA

Package size

15.65 mm x 15.35 mm (H x V)

Max. detection distance

300 m

Distance precision at 300 m  

3 x 3 pixels (H x V) additive mode: 30 cm
6 x 6 pixels (H x V) additive mode: 15 cm

 

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