  In conventional approach to the chameleon mechanism, by assuming a static and
spherically symmetric solutions in which matter density and chameleon field are
given by $\rho=\rho(r)$ and $\phi=\phi(r)$, it has been shown that mass of
chameleon field is matter density-dependent. In regions of high matter density
such as earth, chameleon field is massive, in solar system it is low and in
cosmological scales it is very low. In this article we revisit the mechanism in
cosmological scales by assuming a redshift dependence of the matter density and
chameleon field, i.e. $\rho=\rho(z)$, $\phi=\phi(z)$. To support our analysis,
we best fit the model parameters with the observational data. The result shows
that in cosmological scales, the mass of chameleon field increases with the
redshift, i.e. more massive in higher redshifts. We also find that in both
cases of power-law and exponential potential function, the current universe
acceleration can be explained by the low mass chameleon field. In comparison
with the high redshift observational data, we also find that the model with
power-law potential function is in better agreement with the observational
data.
