# F

### Fano factor

Average number (J) of electron-hole pairs generated in a crystal by incident radiation is expressed by the following equation: $$J = \frac{E}{ε}$$  E: energy of radiation
ε: average energy required to generate an electron-hole pair

In this case, the standard deviation (σ: Fano noise) which represents statistical fluctuations in the number of electron-hole pairs is expressed by the following equation: $$\sigma = \sqrt{FJ\ }$$ F in this equation is a coefficient for correcting deviations from the Poisson distribution and is called the Fano factor.

### FDA (floating diffusion amplifier)

A low-noise readout method most commonly used for a CCD output section. HAMAMATSU CCDs use this FDA.

### Fill factor

This is the ratio of the “photodiode area excluding the wiring section, etc.” to the area of the pixel.

### Flip-chip bonding

A technique for bonding a chip with bumps (metal protrusions such as solders) attached to the electrodes on the upper surface of the chip, by placing the chip upside down onto a package or another chip to make electrical connections. Chip-on-chip mounting allows much smaller assembly.

### Frequency response - Image intensifier

This indicates the input illuminance required to produce a luminous emittance from the phosphor screen, equal to that obtained when the input illuminance on the photocathode is zero. This indicates the inherent background level or lower limit of detectable illuminance of an image intensifier.

### FTTH (fiber to the home)

This is an ongoing plan to build a high-speed, broadband data communication environment by using optical fibers as telephone subscriber lines extending from telephone stations to each home. FTTH is considered the final goal to replace all subscriber lines with optical fibers. Steps to reach that goal are called as follows depending on the stage of progress: FTTZ (fiber to the zone), FTTC/FTTP (fiber to the curb/fiber to the pedestal), and FTTA/FTTB/FTTO (fiber to the apartment/fiber to the building/fiber to the office).

### Full well capacity

The saturation charge for a CCD is equivalent to the number of signal electrons that can be transferred to an adjacent potential well, therefore it is also called the full well capacity (FW). The saturation charge or full well capacity is expressed in terms of the number of electrons (e- ), in particular, CCDs intended for scientific application.

The full well capacity for CCDs is determined by the following four factors.

• 1. Vertical shift register saturation (vertical full well capacity)
• 2. Horizontal shift register saturation (horizontal full well capacity)
• 3. Summing well saturation (summing full well capacity)
• 4. Output section saturation

In CCD area image sensor applications, the signal charge of each pixel is output individually, so the saturation is determined by the vertical full well capacity. On the other hand, the horizontal full well capacity is designed to saturate at a higher level than to the vertical full well capacity so as to enable line binning (addition of vertical pixel signals). The summing well capacity formed by the summing gate, which is the last clock gate, is designed to be even greater than the horizontal full well capacity in order to add the signals from the horizontal shift register (pixel binning).

Accordingly, the saturation voltage Vsat of an output signal which is derived as a voltage is generally given by: $$Vsat = FW \cdot Sv.$$ $$Sv(conversion\ coefficient) = \frac{uV}{e^-}$$

### FWHM (full width at half maximum)

This is used to describe the width of a normal distribution (Gaussian distribution). FWHM is the full width at half (1/2) maximum of a normal distribution.