1. An apparatus for optical coherence tomography, the apparatus comprising: a light source configured to generate beams having different central wavelengths; a light coupler configured to split the beams into measurement beams and reference beams; transmit the measurement beams to a target object via a probe; and receive response beams from the probe; a detector configured to detect interference signals based on interference between the response beams and the reference beams; and an image processor configured to: generate a first image of the target object based on any one of the interference signals; generate a second image of the target object having at least one of an axial resolution, a lateral resolution, and transmittance different from those of the first image based on another one of the interference signals; and generate an output image by synthesizing a high-frequency region of the first image and a high-frequency region of the second image, wherein the high-frequency region of the first image is different from the high-frequency region of the second image.