Patent Description:
Issued patents relating to low-level laser therapy (LLLT) apparatus configurations include <CIT>and <CIT>. The system of Patent No. <CIT> employs a single lens, and its shape corresponds to the original dimensions of a laser diode beam and may make partial correction to laser diode astigmatism by using a toroid lens. The system of the Patent No. <CIT> employs two cylindrical lenses, which corrects the laser astigmatism and then uses beam expander to expand the beam and to improve collimation of the beam.

<CIT> discloses a handheld, low-level laser apparatus comprising at least <NUM> lenses in order to collimate near infrared (NIR) laser emission.

<CIT> discloses a handheld laser apparatus comprising just only one lens in order to collimate an output laser beam.

The present system and method improve astigmatism correction and collimation of a laser beam in a low-level laser therapy system, but advantageously without using a complex optical configuration. Laser energy with therapeutic characteristics is generated by a laser diode known in the art. To achieve the object and advantage of the invention, a first divergent lens of a beam expander is configured as a cylindrical lens, and the divergence of this first lens is applied in the direction in which the laser diode's beam has relatively small divergence. Thus, the lens is designed to create divergence in the beam in a first axis that will more closely approximate the divergence in the second, perpendicular axis. This creation of a divergence in the first axis corrects, at least partially, the astigmatism in the optical system of the low-level laser therapy apparatus. The therapy apparatus thus emits a beam with an elliptical cross-section with an axes ratio of less than <NUM>:<NUM> (i.e., of the major axis versus minor axis of the ellipsis of the beam's cross section), despite that the diode may emit an original beam with an axes ratio exceeding <NUM>:<NUM>. A second lens of the beam expander according to the present system is a collimating lens with elliptical shape, preferably an aspheric lens adapted to maximize emitted beam collimation.

This system configuration achieves about the same ultimate performance as that of Patent No. <CIT>, but with the significant advantage of simplicity, by using only two lenses. The two lenses serve to correct astigmatism in addition to expanding the emitted beam.

The second (i.e. front) collimating lens is changeable by the user. Interchangeable lenses with different apertures (having different focal lengths and different positions) improve the versatility and adaptability of the overall system.

The elements of the figures are not necessarily to scale, either between views or within a single view.

The present system and method address the problem that many, if not most, of the laser diodes used in portable hand-held low-level laser therapy devices are diodes that emit an elliptical beam with a high ellipse axes ratio. For example, many such diodes generate a beam with an elliptical cross section in which the major axis of the ellipse is four times longer than the length of the minor axis, i.e., an axes ratio exceeding <NUM>:<NUM>. Such a high axes ratio is undesirable for a beam to be applied to a patient in a low-level laser therapy context. The output of the laser diode diverging in an asymmetrical pattern increases the difficulty of collimating the beam to a shape and size useful in therapy.

The present system and method accordingly provides an optical arrangement for reducing the axes ratio of the beam initially emitted by the generating laser diode. The optical system configuration employs two and no more than two lenses in the optical train. A first lens, which receives the beam as emitted from the laser diode, is a cylindrical diverging lens. The cylindrical lens in effect "circularizes" the beam. An attempt to collimate with spherical optics a beam with a high axes ratio would result in collimation in one direction only, with a diverging or converging beam in the other direction. With a cylindrical lens in the optical train of a low-level laser therapy device, the beam is collimated in one dimension to decrease the elliptical axes ratio of the beam ultimately applied to the patient.

Attention is invited to the drawing figure, <FIG>. A preferred embodiment of an optical system <NUM> according to the present disclosure may be adapted for use in a low-level laser therapy (LLLT) apparatus, such as that of <CIT>, or that of <CIT>. More particularly, the system disclosed herein is useable, for example, in the hand-held laser therapy apparatus seen in Figures 5A-5C of Patent No. <CIT>. The optical system of <FIG> of the present disclosure can be adapted for installation and use within such a device. The system <NUM> includes an optical train having a laser diode <NUM>, a first lens <NUM>, and a second lens <NUM>. The laser diode <NUM> emits an initial beam <NUM> of light with an elliptical cross-section, this first beam's cross-section ellipsis <NUM> having a major axis and a minor axis according to conventional geometric terminologies. For a typical diode <NUM>, the axes ratio (major axis to minor axis) of the axes of the ellipse <NUM> of the first beam cross-section exceeds <NUM>:<NUM>. It is desired to reduce this ratio so to regulate astigmatism and thereby improve the performance of the overall system.

The first lens <NUM> is a cylindrical diverging lens. First lens <NUM> is located and oriented in the system to increase the divergence of the first beam <NUM> (with cross section <NUM>, initially emitted from the diode <NUM>) in the minor axis (that is, where the divergence is lower). The first lens <NUM> features cylindrical optics for diverging the beam in one axis, as known in the art. The length dimension of the minor axis of the first elliptical cross section <NUM> of the original beam <NUM> thus is increased, toward the length dimension of the major axis of ellipsis <NUM>, approximately to match the initial degrees of divergence of the major axis - and thus to correct the astigmatism of the first beam <NUM>. As seen in <FIG>, the lens <NUM> is oriented such that at least one of its cylindrical axis/axes are approximately parallel to the major axis of the of the first beam's cross-section ellipsis <NUM>.

After the beam <NUM> has passed the first cylindrical diverging lens <NUM>, the manipulated beam <NUM> has a second beam cross-section <NUM>. Because of the beam manipulation by the first lens <NUM>, this elliptical second beam cross-section <NUM> has a minor axis dimension closer in length to the length of the major axis of this second ellipsis <NUM>. In a preferred embodiment, the first lens <NUM> adjusts the beam axes ratio to a second axes ratio, in the second beam cross section <NUM>, of about <NUM>:<NUM> or lower.

The second lens <NUM> is a conventional collimating lens having an elliptical shape substantially proportional to the shape of the beam <NUM> transmitted from the first lens <NUM>. The cross-sectional dimensions (in a plane perpendicular to the optical axis of the second beam <NUM> of the second lens <NUM>) is at least equal to the cross-sectional dimensions of the incident second beam, and preferably substantially matches or corresponds in size and shape to the cross-section of the incident beam. Lens <NUM> collimates the incident beam <NUM> received from the first lens <NUM>, so that the beam emergent from the second lens <NUM> is well-collimated for beneficial use in the LLLT apparatus. The second lens <NUM> preferably is an aspheric lens to eliminate spherical aberration, and preferably providing diffraction-limited spot sizes for the beam.

An advantage of the invention is that the second lens may be interchangeable with another second lens <NUM>. A user accordingly may remove the second lens <NUM> and replace it with another lens <NUM> selected to adapt the system <NUM> to the particular intended use, or functional context, of the system. In a preferred embodiment of the system <NUM>, both the lenses <NUM> and <NUM> (or <NUM>) preferably are made by plastic injection and coated with anti-reflection coating for the bend of the laser diode wavelength.

<FIG> depicts a hand-held low-level laser therapy appliance <NUM> within the housing of which the optical assembly <NUM> of the present disclosure may be installed. <FIG> shows the collimating lens <NUM> in an assembly removably attached to the LLLT apparatus <NUM>. <FIG> illustrates that some other second collimating lens <NUM> may be provided (e.g., corresponding to lens <NUM> in <FIG>). The second lens <NUM> assembly may be removed from the appliance <NUM> and replaced with another assembly with a second lens <NUM> having optical characteristics selected for the particular use to which the appliance <NUM> is to be put.

There is provided, therefore, a system <NUM> for generating an astigmatism-corrected beam having an elliptical cross-section shape emitted from a low-level laser therapy device <NUM>. The system comprises a laser diode <NUM> for generating a first beam <NUM> with an elliptical cross section <NUM> having a low-divergence minor axis and a high-divergence major axis; a first-divergence cylindrical lens <NUM> which increases a divergence of the low-divergence minor axis toward the divergence of the high-divergence major axis, the cylindrical lens <NUM> thereby transmitting a second beam <NUM> with a second elliptical cross section <NUM>; and a first collimating lens <NUM> for receiving and collimating the second beam <NUM>. By these means the collimating lens <NUM> emits an emitted beam having an emitted beam elliptical cross section with a minor axis length and a major axis length, and wherein the ratio of the major axis length to the minor axis length is less than <NUM>:<NUM>.

As evident from the foregoing, there also is provided a method for generating an astigmatism-corrected beam having an elliptical cross-section shape emitted from a low-level laser therapy appliance <NUM>, the method including the steps of: generating with a laser diode <NUM> a first beam <NUM> with an elliptical cross section <NUM> having a low-divergence minor axis and a high-divergence major axis; increasing with a first-divergence cylindrical lens <NUM> a divergence of the low-divergence minor axis toward the divergence of the high-divergence major axis, thereby transmitting with the cylindrical lens <NUM> a second beam <NUM> with a second elliptical cross section <NUM>; receiving and collimating the second beam <NUM> with a first collimating lens <NUM>; and emitting with the collimating lens <NUM> (and from the appliance <NUM>) an emitted beam having an emitted beam elliptical cross section with a minor axis length and a major axis length, and wherein the ratio of the major axis length to the minor axis length is less than <NUM>:<NUM>. In this method, the step of generating the first beam <NUM> includes generating the first beam with an initial beam elliptical cross section <NUM> with a minor axis length and a major axis length, in which the ratio of the initial beam elliptical cross section major axis length to the initial beam elliptical cross section minor axis length to be at least <NUM>:<NUM>. The method may include the step of interchanging the first collimating lens <NUM> with a second, selected different, collimating lens <NUM>.

As mentioned, an advantage of the present system and method is that astigmatism in a LLLT apparatus can be suitably corrected in a simple optical train consisting, in one preferred embodiment, of only two lenses, a first cylindrical lens and a second collimating lens. The need for two diverging lenses is eliminated. This advantage promotes use of the system in a physically compact hand-held LLLT apparatus, with relatively reduced manufacturing cost.

Although the invention has been described in detail with particular reference to these preferred embodiments, other embodiments may achieve the same results. In the previous description, specific details are set forth, such as specific materials, structures, chemicals, processes, etc., in order to provide a thorough understanding of the present invention. However, as one having ordinary skill in the art would recognize, the present invention can be practiced without resorting to the details specifically set forth. In other instances, well known principles of mechanics and physics have not been described in detail, in order not to unnecessarily obscure the present invention.

Claim 1:
A system (<NUM>) for generating an astigmatism-corrected beam having an elliptical cross-section shape emitted from a low-level laser therapy device (<NUM>), the system (<NUM>) having a laser diode (<NUM>) for generating a first beam (<NUM>) with an elliptical cross section (<NUM>) having a low-divergence minor axis and a high-divergence major axis,
characterized by
an optical train of only two operative lenses being,
a divergence cylindrical lens (<NUM>) which increases a divergence of the low-divergence minor axis toward the divergence of the high-divergence major axis, the cylindrical lens (<NUM>) thereby transmitting a second beam (<NUM>) with a second elliptical cross section (<NUM>); and
a first collimating lens (<NUM>) for receiving and collimating the second beam (<NUM>); wherein the collimating lens (<NUM>) has an elliptical shape and emits an emitted beam
having an emitted beam elliptical cross section with a minor axis length and a major axis length, and wherein the ratio of the major axis length to the minor axis length is less than <NUM>:<NUM>.