We report a new iodine spectrometer for absolute frequency measurements of various transitions of molecular iodine in the 633 nm region. To obtain good frequency accuracy, the laser beams used in spectroscopy have been optimized for spatial and spectral quality. This is achieved by injection locking a microlensed diode laser with nearly Gaussian output beam to an external-cavity diode laser. The external-cavity laser has been designed for enhanced frequency stability and reproducibility by minimizing the effects of ambient pressure and temperature, and by utilizing transmission-grating geometry for compact and robust structure. The high stability combined with the invariant output beam pointing makes the laser design adaptable also for other purposes of length metrology and atom optics.