  We study light propagation and gravitational lensing in scalar-tensor
theories of gravity by using a static, axisymmetric exterior solution. The
solution has asymptotic flatness properties and is reduced to Voorhees's one in
the case of a constant scalar field. Our studies are done by using a technique
of the conformal transformation such that their results are independent of
details of scalar-tensor theories. For some specific cases, we analytically
obtain a deflection angle of the light path and find that it can become
negative. The appearance of a negative deflection angle indicates
``reflection'' of a light path, and we investigate under which conditions the
light reflection occurs. As for the optical scalars, the Weyl source-term shows
significantly different properties compared with that in the Schwarzschild
spacetime. We therefore classify a space of the model parameters into four
distinct regions on the basis of the qualitative properties of the Weyl
source-term and find a close relationship between this classification and the
occurrence of the light reflection. We finally solve the null geodesic
equations and the optical scalar equations numerically. We find that a picture
of the thin lens is applicable and give a simple analytic model for the optical
scalars. As for the properties of gravitational lensing, the deflection angle
and the image distortion rate are obtained as functions of the impact
parameter. Again, we find a close relationship between their qualitative
properties and the classification above.
