Sensor Readout Technology

◈ CMOS image sensor 

    ◇ Introduction


- As analog image capturing devices using a film have been replaced by digital devices such as charge-coupled devices(CCDs)
and complementary metal-oxide semiconductor(CMOS) image sensors, imagers was miniaturized and capable of performing
the real-time image processing. Nowadays, digital imagers are widely used in many applications such as mobile devices,
industrial robots, and medical electronics. Especially, CMOS image sensors are increasingly adopted because they have
advantages of low-power consumption, high-resolution pixel and circuit integration capabilities.

- Image sensor group in IELAB has been researching low power, wide dynamic range, low noise, high speed, and high
bit-depth technologies in CMOS image sensors for from consumer to medical applications.

    ◇ Research area
      · Low-power and high-speed CMOS image sensor
          - Low-power, small-area, and high-speed column-parallel ADC
          - Wide dynamic range readout technique

      · Smart CMOS image sensor
          - Compressed sensing CMOS image sensor

CMOS image sensor

Wafer-scale CMOS X-ray detector

    ◇ Research results
      · 1.92 Mpixel CMOS image sensor with integrating type SA ADC and switched-power technique
          - Process: 0.13-μm 1P4M CIS
          - Chip size: 5 mm × 7 mm
          - Pixel size: 2.25 μm × 2.25 μm
          - Resolution: 1600(V) × 1200(H)

          - ADC resolution: 10-bit
          - Max. frame rate: 150 frames/s

Full frame image captured at 60 frames/s

Chip Microphotograph

    ◇ Research results
      · 0.3 Mpixel CMOS image sensor with 12b two-step ADC
          - Process: 90-nm 1P4M CIS
          - Chip size: 5 mm × 5 mm
          - Pixel size: 3.5 
μm × 3.5 μm
          - Resolution: 640(V) × 480(H)
          - ADC resolution: 12-bit
          - Max. frame rate: 300 frames/s

Captured Image

Block diagram of image sensor

◈ Touch Screen System

    ◇ Introduction


- Capacitive touch screens are widely used in mobile devices such as tablets, note-books, and smart phones. As people
require capacitive touch screen system with high-sensitivity, touch screen systems demand high-accuracy read-out circuits.
We have researched noise reduction methods and analog-to-digital converters for high-accuracy read-out circuits.

    ◇ Research area

      · Read-out circuits for capacitive touch screen system

    ◇ Research results

      · 3.5-inch add-on type capacitive touch screen system
          - Spatial resolution of TSP: 7×9
          - Pattern pitch: 8mm
          - Measuring type: mutual capacitance
          - Compensation of capacitance variation

(a) before compensation

(b) after compensation

Touch screen system

3-D image of touched point

    ◇ Research results

      · 13.3-inch on-cell type capacitive touch screen system
          - Spatial resolution of TSP: 53×29
          - Pattern pitch:5.5mm
          - Measuring type: mutual capacitance
          - Differential sensing method for noise reduction

Display system with an on-cell
capacitive TSP

2-D image of touched point

3-D image of touched point