# L

### Lattice constant

In a crystal, atoms are arrayed uniformly to form a crystal lattice. The lattice constant is a measure that defines the size of the unit lattice, which is the minimum unit of a crystal lattice.

### Linearity

When light strikes a photodiode, a photocurrent is generated in proportion to the light level. This proportional relationship between the photocurrent and light level is called the linearity. If the incident light level becomes higher than a certain level, then the linearity begins to deviate, causing the photocurrent in the photodiode to saturate. The light level causing saturation depends on the photodiode structure and also varies according to the load resistance, reverse voltage, and the size of the incident light spot.

### Luminous gain

The ratio of the phosphor screen's luminous emittance (lm/m2) to the illuminance (lx) incident on the photocathode.