1. Field of the Invention
The present invention relates to an optical coherence tomographic imaging apparatus and an optical coherence tomographic imaging method, and more particularly, to an optical coherence tomographic imaging apparatus and an optical coherence tomographic imaging method which are used for ophthalmologic diagnosis and treatment.
2. Description of the Related Art
An optical tomographic imaging apparatus for optical coherence tomography (OCT) using multi-wavelength optical coherence (hereinafter referred to as OCT apparatus) is capable of acquiring a tomographic image of a retina at a fundus of an eye to be inspected at high resolution, and is widely used for ophthalmologic diagnosis of the retina.
The OCT apparatus is an apparatus for irradiating the fundus of an eye to be inspected with a measuring beam which is a low-coherent beam to obtain interference light between backscattered light from the fundus and a reference beam.
There is disclosed in Japanese Patent Application Laid-Open No. 2006-180926 an operation microscope for imaging the same field of view with two illumination conditions (bright field and dark field) and displaying an image obtained by composing a chroma-key-processed dark field image on a bright field image.
According to such operation microscope, a visible light image is acquired in the bright field condition and a fluorescent image is acquired in the dark field condition. The images acquired in the bright field condition and the dark field condition can be treated as a single image. Therefore, a position of an affected part which generates fluorescence may be accurately determined.
The intensity of the backscattered light for forming the tomographic image depends on the incident angle of the measuring beam on the retina. Therefore, there is a case where it is difficult to measure a target layer or part of the retina with high sensitivity.
This is because, though high-sensitive measurement may be achieved in a case where the measuring beam is substantially perpendicularly incident on the target layer of the retina, high-sensitive measurement is not achieved in a case where the measuring beam is incident on the target layer at an angle which is not substantially perpendicular. In such a case as described above, sensitivity is varied in a tomographic image, with the result that the contrast of the tomographic image becomes lower.
If the intensity of the measuring beam is increased for the case where the contrast of the tomographic image is low, the thermal noise of a light receiving element relatively reduces, and hence the contrast of the tomographic image is improved.
However, in the case where the retina is to be imaged, there is a limit on the intensity of a measuring beam in view of the influence on the retina. Thus, it is not better to increase the intensity of the measuring beam.
In Japanese Patent Application Laid-Open No. 2006-180926, measures against a problem with respect to the contrast of the tomographic image are not taken into account.