| 摘要 |
A laser display apparatus is provided to suppress speckle on a screen without additional components, by controlling the effective reflectance and the cavity distance of a semiconductor laser so as to optimize a coherence length. A semiconductor laser(10) has a first mirror(12) and a second mirror(14) distanced from each other, wherein the first and second mirrors constitute a resonator. A spatial modulator(20) modulates the light, which is transmitted through the first mirror of the semiconductor laser, to supply an image on a screen. When a coherence length, lc, and an effective reflectance, R, of the semiconductor laser are defined by the following mathematic equations, the coherence length satisfies the following conditional equation. The mathematic equations are expressed by lc=2d(piR^1/2)/(1-R) and R=(square root over(R1xR2)), wherein d is cavity distance of the semiconductor laser, R1 is reflectance of the first mirror, and R2 is reflectance of the second mirror. The conditional equation is expressed by 0<lc<0.85 (cm).
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