1. Field of the Invention
The present invention relates to an optical tomographic imaging apparatus and, more particularly, to an optical tomographic imaging apparatus for use in opthalmological treatment or the like.
2. Description of the Related Art
Various kinds of optical equipment are currently used as ophthalmological equipment. Among them, there are various kinds of equipment used for observing an eye. For example, such equipment used includes an anterior ocular segment photographing device, a fundus camera, and a scanning laser ophthalmoscope (abbreviated as “an SLO”). Otherwise, also used is a low coherent optical tomographic imaging apparatus (optical tomographic imaging apparatus) and the like with an optical coherence tomography (abbreviated as “OCT”) device (hereinafter referred to as “an OCT device”). Among them, the OCT device can obtain a tomographic image of a fundus in a high resolution, and therefore, it has become indispensable for out patient department specializing in a retinas.
The OCT device is adapted to irradiate a sample typified by a retina with a low coherent beam, so as to measure a beam reflected on the sample in a high sensitivity by using an interferometer. In addition, the OCT device can obtain a tomographic image by scanning the sample with the low coherent beam. In particular, a tomographic image of a retina is widely utilized for an ophthalmological diagnosis. Since the OCT device forms an image by scanning, there arises a problem that an involuntary motion of an eye ball called involuntary eye movement of a human eye ball or a back and forth motion of an eye ball including the whole head may deform an acquired image.
Conventionally, various attempts have been made to prevent the deformation of the image caused by the above-described motion of the human eye ball. For example, an OCT device for detecting the back and forth position of a cornea by using a low coherent interferometer is disclosed in the following literature: Christoph K. Hitzenberger, “Simultaneous SLO/OCT imaging of the human retina with axial eye motion correction,” Optics Express, Vol. 15, No. 25 (2007). This device attempts to obtain the back and forth moving amount of an eye ball based on the resultant back and forth position detection value, and then, correct the reference beam path length of a low coherent optical tomographic imaging apparatus by the moving amount of the eye ball, so as to reduce deformation of the acquired image in the depth direction of the eye ball.
The above-described literature discloses the attempt of the reduction of the deformation in the depth direction of the eye ball. In contrast, the bandwidth of a light source has been widened in recent years, thereby further enhancing a resolution in the depth direction. Therefore, highly accurate correction beyond the prior art has been demanded.
The present invention has been accomplished in view of the above problem, and an object thereof is to provide an optical tomographic imaging apparatus capable of further reducing deformation of an acquired image in a depth direction of an eye ball caused by a back and forth motion of the eye ball during measurement.