Smart imagers of the future

Benefits of three-dimensional circuit stacking for image sensors

“…On-macropixel compression, possible due to 3D integration [7], will resolve this problem and even lead to a gain on interconnection power consumption. As the ADC is not working with the same speed in both architectures, another increase in the gain, and even resolution, can be obtained by using a more specific architecture for the 3D solution [4]. In this paper, a power consumption comparison between a 2D and a 3D HDR image sensor was presented.…”

“…However important criteria in an imager are the image quality and the power consumption. And for this latter, the AD conversion is usually the most important power consumer of the architecture [4]. Image quality itself depends on various parameters and we choose to focus on the sensor dynamic as while natural scenes feature lightning dynamic of about 120dB, standard 3T or 4T pixel CMOS image sensors have a dynamic at most of about 70dB.…”

A Fast and Low Cost Embedded Test Solution for CMOS Image Sensors

“…Equations in (1) are defined in a generic manner to allow their use irrespective of the CIS under test, considering that the threshold values may change from one CIS to another with the modification of the pixel architecture, the gain of the ADC, the number of pixels in the array, etc. This generic formulation also allows the computation of thresholds values irrespective of the detection environment (light or dark).…”

“…In order to save test time of a CIS, a solution consists in using an embedded test solution (BIST) to screen out local defects (singlets, couplets, clusters) and to use ATE-based tests to target global defects, such as pixel values uniformity along the array or noises like Fixed Pattern Noise (FPN) [1], which represents the variation of pixel values in the array. BIST allows to test each pixel on-the-fly without the need to store a full image before testing as is the case with ATE-based testing.…”

“…Although the Charge Coupled Device (CDD) technology was initially dominant due to superior sensitivity and picture quality, various improvements in CISs have led them to surpass CCD sensors in shipment volume since about 15 years. In particular, they can benefit from their low fabrication cost, low power consumption, as well as the possibility of combining analog and digital functions [1,2].…”