Laser speckle photography, as a technique making use of the displaceme
nt of optical speckle by refraction as an information carrier, has rec
ently been used to measure fluid density, temperature, and heat transf
er. The concept of laser speckle photography and the principles of mea
suring the temperature gradient field are briefly described, including
the formation of laser speckle and its displacement, six kinds of rec
ording systems, and two methods for reconstructing a specklegram. The
major advantages of the laser speckle photography method for heat tran
sfer study in comparison with interferometric methods are listed and d
iscussed. Finally, many applications of laser speckle photography in t
he study of heat transfer are given, including cases of natural convec
tion along a vertical plate, measurements of the axisymmetric temperat
ure field of a flame, heat transfer in channel natural convection and
verification of thermal drag phenomena, and heat transfer of small-sca
le objects.