1. Field of the Invention
The present invention relates to a laser irradiation device used for various medical treatments such as transpiration (cutting out) and coagulation (stopping bleeding) of tissues by irradiating intensive laser light to tissues of living bodies, in particular, human bodies.
2. Prior Art
Before describing the prior art of the laser irradiation device for medical treatment, the basic transpiration and coagulation principles by irradiating laser light are described below referring to FIG. 21.
Transpiration and coagulation by laser light irradiation are performed by converting laser light into thermal energy and by applying the energy to tissues. The transpiration and coagulation capabilities greatly depend on the irradiation conditions of the laser light, such as the irradiation angle and diffusion conditions of the laser light.
More specifically, in the case of sharp transpiration which does not require coagulation on the sides of a transpiration section, the laser light 101 should be irradiated in a concentrated beam within a small angle range from the end of a contact probe 100 as shown in FIG. 21 (a).
In the case of fairly deep transpiration which requires coagulation on the sides of a transpiration section, laser light 101 should be irradiated at a large irradiation angle of .theta..degree. from the end of the contact probe 100 as shown in FIG. 21 (b). By setting the large irradiation angle .theta..degree., the coagulation capability during transpiration, that is, the capability of stopping bleeding on the sides of the transpiration section is enhanced. In particular, by setting the irradiation angle of the laser light 101 at a uniform value in the range of the irradiation angle .theta..degree., the transpiration on the sides is smoothened and the coagulation capability is enhanced. In addition, the transpiration and coagulation capabilities on the sides are also enhanced. By restricting an excessive output in the axial direction of the probe and distributing the output to the sides, the output of the laser light can be reduced. This can reduce the effect of the laser light to the operator, the patient and the peripheral tissues of the transpiration section. The affected area of the patient can thus less damaged. When a greater transpiration depth is required in the case of transpiration and coagulation at tissues with numerous blood vessels, the laser light 101 should be irradiated from the probe's side having a length from the end to the base section of the contact probe 100 as shown in FIG. 21 (c). The above explanations regarding the relationship between the transpiration and coagulation capabilities and the laser light irradiation angle applies to a contact probe including a cylindrical base section and a tapered cone section being symmetrical around the axis of the probe (hereafter referred to as "a cone probe"). In addition, a hemispheric probe with a hemispheric end which offers a converging convex lens effect and can be pressed against affected areas is primarily used for transpiration. A flat probe with a flat end is primarily used for coagulation at affected areas. Moreover, a point chisel-shaped probe with symmetrical chisel surfaces is primarily used to slantly cut off affected areas. There is no doubt that the transpiration and coagulation capabilities are also greatly dependent on the irradiation and diffusion conditions of the laser light from the end sections of these kinds of various probes in the same way as the above-mentioned cone probe.
A means for changing the incidence energy of the laser light to the incidence end surface at the base section of the probe of a conventional laser irradiation device is generally used to change the transpiration and coagulation capabilities. Other means for changing the capabilities, such as a means for changing the overall length (L1) of the probe 100 with taper angle .theta.2 to change the irradiation angle .theta..degree. of the laser light 101 as shown in FIG. 22 and a means for changing the outside diameter (D2) of the base section of the probe 100 with taper angle .theta.2 to change the irradiation angle .theta..degree. of the laser light 101 as shown in FIG. 23 have been known when cone probes are taken as examples. Among the above-mentioned conventional capability changing means, in the case of the means for changing the incidence energy of the laser light to the incidence end surface at the base section of the probe, the transpiration and coagulation capabilities can be changed by proportionally adjusting the irradiation energy of the laser light depending on the adjustment of the incidence energy of the laser light. However, in that case the transpiration and coagulation capabilities depending on the laser light irradiation angle and diffusion conditions cannot be changed. Accordingly, the increase in rate of the transpiration and coagulation capabilities is low even when the output of the laser generation unit is increased significantly. The increase of the output energy causes danger to the operator and the patient, damage to the tissues of the affected area and early worn-out of the probe. As shown in FIGS. 22 and 23, in the case of the means for changing the overall length of the probe or the diameter of the base section of the probe, the increase rate of the transpiration and coagulation capabilities is restricted depending on clinical purposes, the structural limitations of the holding members used to coaxially secure the probe and the optical fiber, and the operation limitations by the operator.