Patent Description:
Light heads for medical device support systems, suspension systems and/or other carry systems, are used in health treatment settings such as hospital examination rooms, clinics, surgery rooms and emergency rooms to illuminate a region interest such as a surgical treatment site or other medical site below the light heads. The light heads typically include a housing, one or more light sources mounted inside the housing, one or more lenses through which light emitted by the light sources is transmitted to the region of interest, and a handle mounted to the housing to enable a healthcare professional to adjust the position of the light head according to the needs of a specific medical procedure.

For light heads in some medical device support systems or carry systems, there remain various shortcomings, drawbacks, and disadvantages relative to certain applications.

For example, although there exist light heads for which a user may adjust an illumination pattern size of an emitted light beam at the region of interest, these light heads either fail to provide or inadequately provide adjustment to the light source(s) based on the illumination pattern size selected by the user. This can result in the illuminance at the region of interest either dimming considerably as the pattern size is increased or being excessively bright as the pattern size is decreased. In other words, as the pattern size is enlarged the same amount of light is spread over a larger or smaller area; since the total visible flux is constant, the illuminance decreases due to the larger area of the pattern size or increases due to the smaller area of the pattern size.

Some light heads provide means for varying power in different light source(s) according to conditions within the surgical field, for example to reduce shadow effects owing to blockage of light source(s). The downside here, however, is that the power variation does not maintain a uniform light distribution but rather only "fills in" shadows or other abnormalities caused by the conditions. The provision of illumination in highly concentrated areas, i.e. dark spots, leads to inconsistent illumination across the region of interest.

There also are light heads that are designed to form a desired beam at a specific distance by means of tilting a first set of light sources to produce a small illumination pattern at a region of interest and tilting a second set of light sources to produce an outer ring illumination pattern at the region of interest, the result being a large illumination pattern at the region of interest. The light head is able to adjust power to the different sets of light sources but, due to the different sets of light sources being directed to different portions of the region of interest, the light beam produced by the light head is inconsistent in size, shape, and uniformity, especially as the distance is varied from the light head to the region of interest. A further disadvantage of such a light head is that the light sources that are not used in producing the small pattern, i.e. the second set of light sources that form the outer ring, are essentially underutilized which is an inefficient use of space of the light head and inefficient use of the expensive components that make up the light sources.

Accordingly, there remains a need for further contributions in this area of technology.

United States Patent Application <CIT> discloses a surgical lamp for illuminating an operating site. The surgical lamp includes a lamp body that includes first and second light sources that respectively generate first and second light fields of different diameter on the operating site. When a change in a distance between the lamp body and the operating site is detected, the first and second light intensities of the first and second light sources, respectively, can be controlled such that the predetermined diameter (dx) at which the preset relative central illuminance (Ecx) of the resultant light field is generated is maintained at a substantially constant value as the distance changes.

According to one aspect of the invention, a light head for a medical device support system includes a first zone of light sources and a second zone of light sources, an optical system, and a control system. The first zone of light sources emits a first beam of light and the second zone of light sources emit a second beam of light, and the first and second beams of light form an illumination pattern having a pattern size at a region of interest. The optical system is arranged in a path of the second beam of light to adjust a beam spread of the second beam of light to change the pattern size of the illumination pattern at the region of interest from a first pattern size to a second pattern size. The control system is configured to vary power to the first and second zones of light sources in response to adjustment of the beam spread of the second beam of light by the optical system to maintain a substantially constant magnitude of illuminance at the region of interest as the pattern size of the illumination pattern at the region of interest is changed from the first pattern size to the second pattern size.

Embodiments of the invention may include one or more of the following additional features separately or in combination.

The control system may be configured to vary power to the first and second zones of light sources in response to adjustment of the beam spread of the second beam of light by the optical system to maintain a substantially constant magnitude of illuminance at a center of the region of interest as the pattern size of the illumination pattern at the region of interest is changed from the first pattern size to the second pattern size.

The control system may be configured to increase power to the second zone of light sources and decrease power to the first zone of light sources in response to the second pattern size being adjusted to be relatively larger than the first pattern size.

The light head may further include a handle mounted for rotational movement relative to a housing of the light head and coupled to the optical system, wherein rotation of the handle adjusts the optical system to adjust the beam spread of the second beam.

The optical system may include first and second wave lenses and rotation of the handle may move the first and second wave lenses relative to one another to adjust the beam spread of the second beam.

The control system may be configured to detect rotation of the handle and vary the power to the first and second zones of light sources based on the detected rotation.

The illumination pattern may include a first illuminance at the first pattern size and a second illuminance at the second pattern size, where the second illuminance is no more or no less than <NUM> percent different (+ / - <NUM> percent) from the first illuminance.

The illumination pattern may include a first illuminance at the first pattern size and a second illuminance at the second pattern size, where the second illuminance is no more or no less than five percent different (+ / - <NUM> percent) from the first illuminance
The control system may be configured to vary power to the first and second zones of light sources in response to adjustment of the beam spread of the second beam of light by the optical system to maintain a substantially uniform illuminance across the illumination pattern as the pattern size at the region of interest is changed from the first pattern size to the second pattern size.

The illumination pattern may have a diameter and a center, a d50/d10 ratio may be defined as a ratio of the diameter at which the illuminance reaches <NUM> percent (<NUM>%) of the illuminance value at the center of the illumination pattern, referred to as d50, over the diameter at which the illuminance reaches <NUM> percent (<NUM>%) of the illuminance value at the center of the illumination pattern, referred to as d10, and the substantially uniform illuminance across the illumination pattern may include the d50/d10 ratio being greater than <NUM>.

The substantially uniform illuminance across the illumination pattern may include the d50/d10 ratio being greater than <NUM>.

According to another aspect of the invention, a light head for a medical device support system includes a first zone of light sources and a second zone of light source, an optical system, and a control system. The first zone of light sources emit a first beam of light and the second zone of light sources emits a second beam of light. The first and second beams of light form an illumination pattern having a pattern size at a region of interest. The optical system is arranged in a path of the second beam of light to adjust a beam spread of the second beam of light to change the pattern size of the illumination pattern at the region of interest from a first pattern size to a second pattern size. The control system is configured to vary power to the first and second zones of light sources in response to adjustment of the beam spread of the second beam of light by the optical system to maintain a substantially uniform illuminance across the illumination pattern as the pattern size at the region of interest is changed from the first pattern size to the second pattern size.

According to another aspect of the invention, a method of operating a light head of a medical device support system includes emitting first and second beams of light by respective first and second zones of light sources, wherein the first and second beams of light form an illumination pattern having a pattern size at a region of interest; adjusting a beam spread of the second beam of light by an optical system in the path of the second beam of light to change the pattern size of the illumination pattern at the region of interest from a first pattern size to a second pattern size; and, varying power to the first and second zones of light sources in response to adjustment of the beam spread of the second beam of light by the optical system to maintain a substantially constant magnitude of illuminance at the region of interest as the pattern size of the illumination pattern at the region of interest is changed from the first pattern size to the second pattern size.

Varying power may include varying power to the first and second zones of light sources in response to adjustment of the beam spread of the second beam of light by the optical system to maintain a substantially constant magnitude of illuminance at a center of the region of interest as the pattern size of the illumination pattern at the region of interest is changed from the first pattern size to the second pattern size.

The method may further include varying power to the first and second zones of light sources in response to adjustment of the beam spread of the second beam of light by the optical system to maintain a substantially uniform illuminance across the illumination pattern as the pattern size at the region of interest is changed from the first pattern size to the second pattern size.

According to another aspect of the invention, a method of operating a light head of a medical device support system includes emitting first and second beams of light by respective first and second zones of light sources, wherein the first and second beams of light form an illumination pattern having a pattern size at a region of interest; adjusting a beam spread of the second beam of light by an optical system in the path of the second beam of light to change the pattern size of the illumination pattern at the region of interest from a first pattern size to a second pattern size; and, varying power to the first and second zones of light sources in response to adjustment of the beam spread of the second beam of light by the optical system to maintain a substantially uniform illuminance across the illumination pattern as the pattern size at the region of interest is changed from the first pattern size to the second pattern size.

The following description and the annexed drawings set forth certain illustrative embodiments of the invention. These embodiments are indicative, however, of but a few of the various ways in which the principles of the invention may be employed. Other objects, advantages and novel features according to aspects of the invention will become apparent from the following detailed description when considered in conjunction with the drawings.

While the present invention can take many different forms, for the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. Any alterations and further modifications of the described embodiments, and any further applications of the principles of the invention as described herein, are contemplated as would normally occur to one skilled in the art to which the invention relates.

<FIG> show a medical device support system <NUM> including two light heads <NUM> in accordance with an embodiment of the invention. Each light head <NUM> includes a first zone <NUM> of light sources <NUM> that emits a first beam of light <NUM> and a second zone <NUM> of light sources <NUM> that emits a second beam of light <NUM>. The first beam of light <NUM> and the second beam of light <NUM> form an illumination pattern <NUM> having a pattern size at a region of interest <NUM>. The region of interest <NUM> may be a surgical site or other medical site below the light heads <NUM>. The light head <NUM> includes an optical system <NUM> that is provided in the paths of the first and second beams of light <NUM>, <NUM>. The optical system <NUM> is configured to adjust a beam spread of the second beam of light <NUM> to change the pattern size of the illumination pattern <NUM> at the region of interest <NUM> from a first pattern size <NUM> shown for example in <FIG> to a second pattern size <NUM> shown for example in <FIG>. As will be described in greater detail below, a control system <NUM> is configured to vary power to the first zone <NUM> of light sources <NUM> and the second zone <NUM> of light sources <NUM> in response to adjustment of the beam spread of the second beam of light <NUM> by the optical system <NUM> to maintain a substantially constant magnitude of illuminance at the region of interest <NUM> as the pattern size of the illumination pattern <NUM> at the region of interest <NUM> is changed from the first pattern size <NUM> to the second pattern size <NUM>.

Turning initially then to <FIG>, the medical device support system <NUM> includes a central shaft or support column <NUM> that is suspended from the ceiling, and two generally horizontal extension arms <NUM> mounted to the shaft <NUM> for rotational movement about the shaft <NUM>. The central shaft <NUM> could be mounted to a wall or stand rather than the ceiling. Two load balancing arms <NUM> are pivotably mounted to the distal ends of the respective extension arms <NUM>. The distal ends of the load balancing arms <NUM> are configured with yoke assemblies <NUM> which, in turn, support the respective light heads <NUM> for multi-axis movement relative to the load balancing arms <NUM>. Each light head <NUM> includes a bushing or other coupling member <NUM> that rotatably connects the light head <NUM> to the distal end of an arm <NUM> of a respective yoke assembly <NUM>, as shown. The load balancing arms <NUM> and yoke assemblies <NUM> enable positioning of the light heads <NUM> to a proper orientation relative to for example the region of interest <NUM> and healthcare professionals in the operating room.

Referring to <FIG>, each light head <NUM> of the system <NUM> includes a housing base <NUM>, the first and second zones <NUM>, <NUM> of light sources <NUM>, <NUM>, the optical system <NUM>, a housing cover <NUM>, and a motion transfer member <NUM> which may include a lever, gear arrangement, or articulating assembly. The housing base <NUM> and the housing cover <NUM> together define an overall form and structure of the light head <NUM>. The optical system <NUM> includes an annular shape lens <NUM> and a housing lens <NUM> made up of an annular shape outer housing lens <NUM> and an inner round housing lens <NUM>. The annular shape lens <NUM> and the annular shape outer housing lens <NUM> are in a light emitting path LP2 of the second zone <NUM> of light sources <NUM> that emit the second beam of light <NUM> shown in <FIG> and <FIG>. The inner round housing lens <NUM> is in a light emitting path LP1 of the first zone <NUM> of light sources <NUM> that emit the first beam of light <NUM> shown in <FIG> and <FIG>. With reference to <FIG>, the motion transfer member <NUM> is configured to movably interact with a boss <NUM> of the annular shape lens <NUM> to rotate the annular shape lens <NUM> about a rotation axis A-A and within a cavity of the housing cover <NUM>. The motion transfer member <NUM> may be movably coupled to a driving source <NUM>, such as a handle, of the light head <NUM> such that motion from the driving source <NUM> translates into rotation of the annular shape lens <NUM> about the rotation axis A-A.

As shown in <FIG> and <FIG>, each light head <NUM> includes an annular shape outer portion <NUM>, an inner round portion <NUM>, and a radially protruding arm <NUM> that connects the annular shape outer portion <NUM> to the inner round portion <NUM>. In the illustrative embodiment, the radially protruding arm <NUM> arranges the annular shape outer portion <NUM> and the inner round portion <NUM> in concentric relation to one another, and in concentric relation to the rotation axis A-A of the annular shape lens <NUM>. The radially protruding arm <NUM> also houses the motion transfer member <NUM> and one or more components of the driving source <NUM> for driving the motion transfer member <NUM>. As will be described in greater detail below, the control system <NUM> is configured to control the light sources <NUM>, <NUM> of the annular shape outer portion <NUM> and the inner round portion <NUM> to emit light to the region of interest <NUM> below the light heads <NUM>. Also, in this regard, the first zone <NUM> of light sources <NUM> may be referred to as an inner zone <NUM> of light sources <NUM>, and second zone <NUM> of light sources <NUM> may be referred to as an outer zone <NUM> of light sources <NUM>. It will be appreciated that the annular shape outer portion <NUM> and the inner round portion <NUM>, and/or the inner and outer zones <NUM>, <NUM>, need not be in concentric relation to one another and instead can be arranged by the protruding arm in eccentric relation to one another.

An inside surface <NUM> of the housing base <NUM> supports the first and second zones <NUM>, <NUM> of light sources <NUM>, <NUM>, which may be for example light emitting diodes (LEDs). In the illustrative embodiment, the optical system <NUM> may also include a plurality of collimators <NUM> mounted to the inside surface <NUM> of the housing base <NUM> and in the light emitting paths LP1, LP2 of the respective first and second zones <NUM>, <NUM> of light sources <NUM>, <NUM>. The collimators <NUM> collect and direct, and/or collimate, the light into narrow beams. In one form, the collimators <NUM> may comprise total internal reflection (TIR) lenses. Referring to <FIG>, the annular shape outer portion of the housing base <NUM> includes the second zone <NUM> of light sources <NUM> and the inner round portion of the housing base <NUM> includes the first zone <NUM> of light sources <NUM>. In the illustrative embodiment annular shape outer portion of the housing base <NUM> has <NUM> light sources <NUM> and collimators <NUM> evenly spaced <NUM> degrees apart, while the inner round portion of the housing base <NUM> has <NUM> light sources <NUM> and collimators <NUM> distributed in an outer ring of nine and a triangle of three within the outer ring.

<FIG> shows an axial arrangement of the light sources <NUM>, <NUM>, the collimators <NUM>, the annular shape lens <NUM>, and the housing lens <NUM>, where axial refers to the direction of emission of light from the light heads <NUM>, or downward in <FIG>. The annular shape outer housing lens <NUM> and the inner round housing lens <NUM> are in the light emitting paths LP1, LP2 of the first and second zones <NUM>, <NUM> of light sources <NUM>, <NUM>. The annular shape lens <NUM> is in the light emitting paths LP2 of the second zone <NUM> of light sources <NUM>, positioned between the light sources <NUM> and the annular shape outer housing lens <NUM>. The collimators <NUM> are also arranged in the light emitting paths LP1, LP2 of the first and second zones <NUM>, <NUM> of light sources <NUM>, <NUM>, both in the annular shape outer portion <NUM> of the light head <NUM> positioned between the light sources <NUM> and the annular shape lens <NUM>, and in the inner round portion <NUM> of the light head <NUM> positioned between the light sources <NUM> and inner round housing lens <NUM>.

The annular shape lens <NUM> and the housing lens <NUM>, and the collimators <NUM> if provided, may take on any form for spreading and/or bending the light emitted by the light sources <NUM>, <NUM>.

As shown for example in <FIG>, the inner round housing lens <NUM> of the housing lens <NUM> has a top face <NUM> formed as a stepped surface, for example a plurality of Fresnel wedges, that bends individual portions of the light beams <NUM>, and a bottom face <NUM> formed as a generally planar surface. The inner round housing lens <NUM> redirects, for example as by converging, the first beam of light <NUM> emitted by the first zone <NUM> of light sources <NUM> to the region of interest <NUM> to contribute light and thus illumination to the illumination pattern <NUM>. The annular shape lens <NUM> has a top face <NUM> formed as a stepped surface, for example a plurality of Fresnel wedges, that bends individual portions of the light beams <NUM>, and a bottom face <NUM> formed as a wavy or curved surface. The annular shape outer housing lens <NUM> of the housing lens <NUM>, meanwhile, has a top face <NUM> formed as a wavy or curved surface and a bottom face <NUM> formed as a generally planar wedge-shaped surface, where a generally planar wedge-shaped surface refers to a generally planar surface that is not perpendicular to the direction of travel of the light beam emitted by the light sources <NUM> and collimators <NUM>, for example. Rotation of the annular shape lens <NUM> and its wavy surface <NUM> relative to the annular shape outer housing lens <NUM> and its wavy surface <NUM> results in beam spreading (focusing) of the light beam, while simultaneously bending (aiming) of the light beam is achieved by the wedge-shaped surfaces <NUM>, <NUM> of the annular shape lens <NUM> and the annular shape outer housing lens <NUM>. The lenses <NUM>, <NUM> redirect, for example as by converging, the second beam of light <NUM> emitted by the second zone <NUM> of light sources <NUM> to the region of interest <NUM> to contribute light and thus illumination to the illumination pattern <NUM>. Further details of the top and bottom face features and characteristics that may be suitable for the annular shape lens <NUM> ("upper lens") and the housing lens <NUM> ("lower lens") can be found in <CIT>, published as <CIT>, and titled "Refractive Lens Array Assembly".

The motion transfer member <NUM> movably interacts with the boss <NUM> of the annular shape lens <NUM> to rotate the annular shape lens <NUM> about the rotation axis A-A. In the illustrative embodiment, the rotation axis A-A constitutes the central axis of the light head <NUM> including the central axis of the housing base <NUM> and the central axis of the housing cover <NUM>. The rotation axis A-A of the annular shape lens <NUM> need not be the same as (coincide with) the central axis of the light head <NUM> itself, or the same as (coincide with) the central axis of the housing base <NUM> and/or the housing cover <NUM>. Thus, for example, the rotation axis A-A of the annular shape lens <NUM> may be offset from the central axis of the housing base <NUM> and/or housing cover <NUM>, particularly where the light head <NUM> includes additional or alternate type control elements, handles, connection brackets, contours, among others.

The driving source <NUM> and the motion transfer member <NUM> impart motion to the boss <NUM> of the annular shape lens <NUM>. In the illustrative embodiment, the driving source <NUM> includes a handle <NUM>. It will be appreciated that the light head <NUM> may incorporate alternate or additional types of driving sources. In one form, the driving source <NUM> may include a lever depending downward from the bottom of the light head <NUM> in a manner like that of the illustrative handle <NUM> and operatively coupled to the motion transfer member <NUM>. In another form, the driving source <NUM> may be a slider that is slidable relative to a bottom surface of the light head <NUM> and operatively coupled to the motion transfer member <NUM>. In still another form, the driving source <NUM> may include a rotary motor or linear motor operable for example by control elements in a surface the light head <NUM> and operatively coupled to the motion transfer member <NUM>, or even a rotary motor or linear motor that is operable by a handle of the light head <NUM>. In the illustrative embodiment, the motion transfer member <NUM> includes a lever <NUM>. As was briefly noted above, the motion transfer member <NUM> may take on other forms. For example, the motion transfer member <NUM> may include a gear assembly whereby the driving source <NUM> imparts movement to a rotary gear or rack and the rotary gear or rack, in turn, impart motion to the annular shape lens <NUM>. It will be appreciated that the motion transfer member <NUM> may be a series of levers and/or gears and/or gear trains, or any other type of motion transfer mechanism and/or articulating assembly capable of conveying motion from the driving source <NUM> to the annular shape lens <NUM>.

The lever <NUM> is movable relative to a fulcrum <NUM> of the light head <NUM> at a pivot slider portion <NUM> of the lever <NUM>. The lever <NUM> is configured to transfer motion from the driving source <NUM> at a first end <NUM> of the lever <NUM> into rotational motion of the annular shape lens <NUM> about the rotation axis A-A at a second end <NUM> of the lever <NUM> in response to movement of the lever <NUM> relative to the fulcrum <NUM>. Referring to <FIG> and <FIG>, the handle <NUM> is rotatably mounted coaxially to a hub <NUM> of the light head <NUM>. The first end <NUM> of the lever <NUM> is movably coupled to a bushing <NUM> of the handle <NUM> and the second end <NUM> of the lever <NUM> is movably coupled to the annular shape lens <NUM>. The lever <NUM> is configured to transfer rotational motion of the handle <NUM> at the first end <NUM> of the lever <NUM> into rotational motion of the annular shape lens <NUM> at the second end <NUM> of the lever <NUM>, which, as afore described, results in beam spreading (focusing) of the second beam of light <NUM>, while simultaneously bending (aiming) of the second beam of light <NUM>. Further details of a light head incorporating a rotating wave lens assembly can be found in <CIT>, and titled "Light Head with Rotating Lens Assembly and Method of Operating Same".

As shown in <FIG> and <FIG>, the light head <NUM> also includes a sensor <NUM> configured to sense or detect movement of the driving source <NUM> that corresponds to the spreading of the second beam of light <NUM>. In the illustrative embodiment, where the driving source <NUM> includes the handle <NUM>, the sensor <NUM> senses or detects rotation of the handle <NUM> and generates an output signal for processing by the control system <NUM>. The sensor <NUM> may comprise any type of sensor suitable for detecting or sensing movement in the driving source <NUM> where the movement is representative of the beam spreading of the second beam of light <NUM>. It will be appreciated that beam spreading of the second beam of light <NUM> could be sensed by means other than sensing movement in the driving source <NUM>. For example, a sensor may be provided that senses adjustment of the spread of the second beam of light <NUM> by, for example, sensing relative motion of the lenses <NUM>, <NUM> that are in the light emitting paths LP2 of the light sources <NUM> that emit the second beam of light <NUM>, or by sensing movement of the motion transfer member <NUM> such as the lever <NUM>, or by sensing other conditions indicative of beam spreading.

Referring to <FIG>, <FIG>, and <FIG>, the control system <NUM> is configured to vary power to the first zone <NUM> of light sources <NUM> and the second zone <NUM> of light sources <NUM> in response to adjustment of the beam spread of the second beam of light <NUM> by the optical system <NUM>. Each light head <NUM> is communicatively coupled with the control system <NUM> which includes control elements integrated into the light head housing, handle, or support structure. <FIG> shows an exemplary control system <NUM>. The control system <NUM> may include a main processor 90a including any suitable microprocessor, control processing unit (CPU), control circuitry, or the like. A controller 90b may be communicatively coupled between the processor 90a and components in the light head <NUM> for adjusting the components based on instructions received from the processor 90a. For example, the controller 90b may be configured to adjust a total visible flux of the light sources <NUM>, <NUM>, where the total visible flux refers to the radiant power of the light sources <NUM>, <NUM> that is weighted by the sensitivity of the human eye. The common unit of the total visible flux is lumens. A memory 90c may also be provided as part of the control system <NUM>. The memory 90c may contain stored data pertaining to operation of the light head <NUM> that is used by the processor 90a in providing instructions to the controller 90b. For example, the memory 90c may be configured to store data pertaining to total visible flux to be provided to the light sources <NUM>, <NUM> as a function of adjustment of spread of the second beam of light <NUM> for example as sensed by the sensor <NUM>, where the adjustment of the spread of the second beam of light <NUM> may be by, for example, relative motion of the lenses <NUM>, <NUM> that are in the light emitting paths LP2 of the light sources <NUM> that emit the second beam of light <NUM>, and where the relative motion of the lenses <NUM>, <NUM> may be imparted by, for example, movement of the driving source <NUM> such as the handle <NUM>, or movement of the motion transfer member <NUM> such as the lever <NUM>, or other means. The memory 90c may include one or more look-up tables that store power values that correspond to, for example, beam spread, distance between the light head <NUM> and the region of interest <NUM>, handle rotation, light head tilt angle, among others.

The term "control system" encompasses all apparatus, devices, and machines for processing data, including by way of example a programmable processor, a computer, or multiple processors or computers. The apparatus can include, in addition to hardware, code that creates an execution environment for the computer program in question, e.g., code that constitutes processor firmware, a protocol stack, a database management system, an operating system, a runtime environment, or a combination of one or more of them. In addition, the apparatus can employ various different computing model infrastructures, such as web services, distributed computing and grid computing infrastructures.

<FIG> and <FIG> show respective side cross section views of the light head <NUM> emitting a relatively smaller beam of light <NUM> and a relatively larger beam of light <NUM>. Each beam of light <NUM>, <NUM> is formed by a composite of the first beam of light <NUM> emitted by the first zone <NUM> of light sources <NUM> and the second beam of light <NUM> emitted by the second zone <NUM> of light sources <NUM>. In the illustrative embodiment, a single lens element <NUM> (for example Fresnel wedge lens, the inner round housing lens <NUM>) is in the path of the first beam of light <NUM> of the first or inner zone <NUM> of light sources <NUM>, and two-part lens elements <NUM>, <NUM> (for example "wave lenses," the annular shape lens <NUM> and the annular shape outer housing lens <NUM>) are in the second beam of light <NUM> of the second or outer zone <NUM> of light sources <NUM>. <FIG> shows the wave lenses <NUM>, <NUM> in their neutral orientation which generates a relatively smaller second beam of light <NUM> and relatively smaller pattern size <NUM>. <FIG> shows the wave lenses <NUM>, <NUM> in their beam spread orientation which generates the relatively larger second beam of light <NUM> and relatively larger pattern size <NUM>. In the illustrative embodiment, the first beam of light <NUM> from the first zone <NUM> is not spread by the wave lenses <NUM>, <NUM> but rather is bent or redirected by the single lens element <NUM>. In the illustrative embodiment, each composite beam of light <NUM>, <NUM> is round shape although other shapes are contemplated, as would occur for example when the light head <NUM> may be tilted relative to the region of interest <NUM>.

The lower portions of <FIG> and <FIG> show respective top-down views of the illumination pattern <NUM> generated by the composite beams of light <NUM>, <NUM> at the region of interest <NUM>. The <FIG> illumination pattern <NUM> has a pattern size <NUM> that is relatively larger than the pattern size <NUM> of the <FIG> illumination pattern <NUM> owing to the spreading of the second beam of light <NUM> by the optical system <NUM>, more particularly by the relative movement between the annular shape lens <NUM> and the annular shape outer housing lens <NUM> of the optical system <NUM>.

The cross hatch patterns (checkered patterns) shown in the lower portions of <FIG> and <FIG> indicate a surface density of the radiant flux, also referred to herein as the magnitude of illumination, also referred to as illuminance, of the composite beams of light <NUM>, <NUM> at for example the region of interest <NUM>. The common unit of illuminance is the lux, also defined as one lumen per square meter. In <FIG> and <FIG>, the cross hatch patterns are identical, indicating that the magnitude of the illuminance at the region of interest <NUM> in <FIG> is substantially the same as the magnitude of the illuminance at the region of interest <NUM> in <FIG>.

Also in <FIG> and <FIG>, the lines <NUM>, <NUM> from the light head <NUM> to the region of interest <NUM> represent light rays with the amount of rays or lines per light source <NUM>, <NUM> indicating the relative total visible flux <NUM>, <NUM>, or radiant power, emitted by the light sources <NUM>, <NUM>. Thus, in <FIG> the total visible flux <NUM>, represented by three lines in <FIG>, of the light sources <NUM> is the same as the total visible flux <NUM>, also represented by three lines in <FIG>, of the light sources <NUM>. On the other hand, in <FIG>, the total visible flux <NUM>, represented by two lines in <FIG>, of the light sources <NUM> is relatively less than the total visible flux <NUM>, represented by nine lines in <FIG>, of the light sources <NUM>. It will be appreciated that <FIG> and <FIG> are not to scale to allow better visualization and understanding of the invention.

Turning now to <FIG> in conjunction with <FIG> and <FIG>, rotation of the handle <NUM> imparts motion to the lever <NUM> which, in turn, rotates the annular shape lens <NUM> relative to the annular shape outer housing lens <NUM> to spread the second beam of light <NUM>, where <FIG> shows the relatively smaller pattern size <NUM> and <FIG> shows the relatively larger, i.e. spreaded, pattern size <NUM>. As the pattern size of the illumination pattern <NUM> changes, either by increasing or decreasing pattern size, the control system <NUM> changes the total visible flux <NUM>, <NUM> of the light sources <NUM>, <NUM>, for example by varying the power to the light sources <NUM>, <NUM>, to maintain the magnitude of the illuminance substantially constant, as indicated by the same cross hatch pattern in <FIG> and <FIG>.

Substantially constant magnitude illuminance refers to an illuminance of the illumination pattern <NUM> including a first illuminance (in units of lux) at the illumination pattern <NUM> having the first pattern size <NUM> (for example <FIG>) and a second illuminance (in units of lux) at the illumination pattern <NUM> having the second pattern size <NUM> (for example <FIG>), where the second illuminance is no more or no less than preferably <NUM> percent different (+ / - <NUM> percent) from the first illuminance, more preferably <NUM> percent different (+ / - <NUM> percent) from the first illuminance, and most preferably five percent different (+ / - <NUM> percent) from the first illuminance.

It will be appreciated that substantially constant magnitude illuminance may refer to the illuminance of the illumination pattern <NUM> at any portion of the illuminance pattern <NUM>, for example, the center of the illumination pattern <NUM>, a certain radial distance from the center of the illumination pattern <NUM>, a periphery of the illumination pattern <NUM>, or even a combination and/or an average of one or more of the foregoing. Thus, in one form, substantially constant magnitude illuminance may refer to an illuminance of the illumination pattern <NUM> including a first illuminance (in units of lux) at a center of the illumination pattern <NUM> having the first pattern size <NUM> (for example <FIG>) and a second illuminance (in units of lux at) a center of the illumination pattern <NUM> having the second pattern size <NUM> (for example <FIG>), where the second illuminance is no more or no less than preferably <NUM> percent different (+ / - <NUM> percent) from the first illuminance, more preferably <NUM> percent different (+ / - <NUM> percent) from the first illuminance, and most preferably five percent different (+ / - <NUM> percent) from the first illuminance.

In another form, substantially constant magnitude illuminance may refer to an illuminance of the illumination pattern <NUM> including a first illuminance (in units of lux) at a certain radial distance from the center of the illumination pattern <NUM> having the first pattern size <NUM> (for example <FIG>) and a second illuminance (in units of lux) at a certain radial distance from the center of the illumination pattern <NUM> having the second pattern size <NUM> (for example <FIG>), where the second illuminance is no more or no less than preferably <NUM> percent different (+ / - <NUM> percent) from the first illuminance, more preferably <NUM> percent different (+ / - <NUM> percent) from the first illuminance, and most preferably five percent different (+ / - <NUM> percent) from the first illuminance.

In another form, substantially constant magnitude illuminance may refer to an illuminance of the illumination pattern <NUM> including a first illuminance (in units of lux) at a center of the illumination pattern <NUM> having the first pattern size <NUM> (for example <FIG>) and a second illumination (in units of lux) at a certain radial distance from the center of the illumination pattern <NUM> having the second pattern size <NUM> (for example <FIG>), where the second illuminance is no more or no less than preferably <NUM> percent different (+ / - <NUM> percent) from the first illuminance, more preferably <NUM> percent different (+ / - <NUM> percent) from the first illuminance, and most preferably five percent different (+ / - <NUM> percent) from the first illuminance.

In yet another form, substantially constant magnitude illuminance may refer to an illuminance of the illumination pattern <NUM> including a first illuminance (in units of lux) that is an average of an illuminance at a center and an illuminance at a certain distance from center of the illumination pattern <NUM> having the first pattern size <NUM> (for example <FIG>) and a second illuminance (in units of lux) that is an average of an illuminance at a center and an illuminance at a certain radial distance from center of the illumination pattern <NUM> having the second pattern size <NUM> (for example <FIG>), where the second illuminance is no more or no less than preferably <NUM> percent different (+ / - <NUM> percent) from the first illuminance, more preferably <NUM> percent different (+ / - <NUM> percent) from the first illuminance, and most preferably five percent different (+ / - <NUM> percent) from the first illuminance.

One way to assess uniformity of illuminance across the illumination pattern <NUM> is by calculating the ratio of the diameter at which the illuminance reaches <NUM> percent (<NUM>%) of the maximum or central value (the illuminance at the center of the illumination pattern <NUM>), referred to as d50, over the diameter at which the illuminance reaches <NUM>% of the central value, referred to as d10. This ratio, referred to as d50/d10, is preferably greater than <NUM> and even more preferably greater than <NUM>. Thus, for example, in the illustrative embodiment the diameter of the center portion <NUM> (where for example the illuminance is <NUM> percent of the illuminance value at the center of the illumination pattern <NUM>) is greater than or equal to <NUM> percent (<NUM>%) of the diameter of the portion <NUM> (where the illuminance is <NUM>% of the illuminance value at the center of the illumination pattern <NUM>) yielding a d50/d10 of about <NUM>. Further, for example, where in the illustrative embodiment the diameter of the center portion <NUM> (where for example the illuminance is <NUM> percent (<NUM>%) of the illuminance value at the center of the illumination pattern <NUM>) is greater than or equal to <NUM>% of the diameter of the portion <NUM> (where the illuminance is <NUM>% of the illuminance value at the center of the illumination pattern <NUM>) yielding a d50/d10 of about <NUM>.

It will be appreciated that the natural tendency of the illuminance to decrease with increasing radial distance from the center of the illumination pattern <NUM> will also affect the illuminance across the illumination pattern <NUM>. The control system <NUM> may be configured to process for example empirical data inputs indicative of how "smoothly" the decrease occurs and, based on such empirical data inputs, adjust the power to the first and second zones <NUM>, <NUM> of light sources <NUM>, <NUM>. The control system <NUM> may be configured to adjust illuminance based one or both of empirical data inputs and the afore described d50/d10 ratio.

Thus, the rotation of the handle <NUM> mechanically moves the wave lenses <NUM>, <NUM> relative to one another to adjust the spread of the beam of light <NUM> from the outer zone <NUM> of light sources <NUM>, the control system <NUM> senses the rotation of the handle <NUM>, for example as by receipt of the output signal from the sensor <NUM>, and, based on this sensed handle rotation, the control system <NUM> adjusts the power to the inner and outer zones <NUM>, <NUM> of light sources <NUM>, <NUM> as needed to maintain a substantially constant illuminance in the illumination pattern <NUM> of the composite beam of light <NUM>, <NUM>, for example a substantially constant illuminance in the center of the illumination pattern <NUM> or a substantially constant illuminance at a certain radial distance from the center of the illumination pattern <NUM>, as the pattern size of the illumination pattern <NUM> changes from the first pattern size <NUM> to the second pattern size <NUM>.

The control system <NUM> is configured to change the total visible flux <NUM> and/or the total visible flux <NUM> based on an input, or inputs, representative of or indicative of a change in the beam spread of the second beam of light <NUM>, or a change in the pattern size of the illumination pattern <NUM> at the region of interest <NUM> from, for example, the first pattern size <NUM> to the second pattern size <NUM>, or the second pattern size <NUM> to the first pattern size <NUM>. In an embodiment, the control system <NUM> may be configured to sense rotation of the handle <NUM> for example by the sensor <NUM> and, depending on the sensed rotation, change the total visible flux <NUM>, <NUM> of the light sources <NUM>, <NUM>. For example, if clockwise rotation of the handle <NUM> results in spreading of the beam of light <NUM> from that which is shown in <FIG> to that which is shown in <FIG>, then the control system <NUM> increases the total visible flux <NUM> of the light sources <NUM> (from three lines in <FIG> to nine lines in <FIG>) while decreasing the total visible flux <NUM> of the light sources <NUM> (from three lines in <FIG> to two lines in <FIG>). Conversely, if counterclockwise rotation of the handle <NUM> results in narrowing of the beam of light <NUM> from that which is shown in <FIG> to that which is shown in <FIG>, then the control system <NUM> decreases the total visible flux <NUM> of the light sources <NUM> (from nine lines in <FIG> to three lines in <FIG>) while increasing the total visible flux <NUM> of the light sources <NUM> (from two lines in <FIG> to three lines in <FIG>).

It will be appreciated that the control system <NUM> may be configured to increase and/or decrease the total visible flux <NUM>, <NUM> of the respective light sources <NUM>, <NUM> according to any suitable input(s) and need not be limited to, for example, sensed rotation of the handle <NUM> or other driving source <NUM>. For example, the control system <NUM> may be configured to increase and/or decrease the total visible flux <NUM>, <NUM> of the respective light sources <NUM>, <NUM> according to sensed movement of the annular shape lens <NUM>, or movement of the annular shape lens <NUM> relative to the annular shape outer housing lens <NUM>. In another form, the control system <NUM> may be configured to increase and/or decrease the total visible flux <NUM>, <NUM> of the respective light sources <NUM>, <NUM> according sensed movement of the lever <NUM> and, based on such sensed movement, change the total visible flux <NUM>, <NUM> of the light sources <NUM>, <NUM>. In another form, the driving source <NUM> may be a rotary motor rather than the handle <NUM> and the control system <NUM> may be configured to increase and/or decrease the total visible flux <NUM>, <NUM> of the respective light sources <NUM>, <NUM> according sensed rotary motion of the motor and change the total visible flux <NUM>, <NUM> based on such sensed rotary motion. In yet another form, the motion transfer member <NUM> may be a gear train rather than the lever <NUM> and the control system <NUM> may be configured to increase and/or decrease the total visible flux <NUM>, <NUM> of the respective light sources <NUM>, <NUM> according to a sensed particular movement in the gear train and change the total visible flux <NUM>, <NUM> according to such particular gear movement.

In the illustrative embodiment, as the size of the illumination pattern <NUM> is changed from the relatively smaller pattern size <NUM> in <FIG> to the relatively larger pattern size <NUM> in <FIG>, or vice versa, the control system <NUM> changes the total visible flux <NUM>, <NUM> of the light sources <NUM>, <NUM> to maintain the magnitude of the illuminance substantially constant. Referring to <FIG>, the control system <NUM> controls the total visible flux <NUM> of the first zone <NUM> of light sources <NUM> (three rays or lines) to be about the same as the total visible flux <NUM> of the second zone <NUM> of light sources <NUM> (three rays or lines). Thus, in <FIG>, the control system <NUM> controls the first or inner zone <NUM> of light sources <NUM> to produce the same total visible flux as the second or outer zone <NUM> of light sources <NUM>, although with differing number of light sources <NUM>, <NUM> (in the illustrative embodiment <NUM> light sources <NUM> in the inner zone <NUM> and <NUM> light sources <NUM> in the outer zone <NUM>, see <FIG> and <FIG>), and the inner and outer zones <NUM>, <NUM> produce the same illuminance since both zones <NUM>, <NUM> also emit respective pattern sizes of the same size, pattern size <NUM>. Referring to <FIG>, the control system <NUM> controls the total visible flux <NUM> of the first zone <NUM> of light sources <NUM> (two rays or lines) to be relatively less than the total visible flux <NUM> of the second zone <NUM> of light sources <NUM> (nine rays or lines). Thus, in <FIG>, the control system <NUM> controls the second or outer zone <NUM> of light sources <NUM> to produce more total visible flux <NUM> than in <FIG> but substantially the same illuminance as in <FIG> since the pattern size <NUM> in <FIG> is larger than the pattern size <NUM> in <FIG>. Thus, for example, the illuminance at the center of the illumination pattern <NUM> in <FIG> will be no more or no less than preferably <NUM> percent different (+ / - <NUM> percent) from the illuminance at the center of the illumination pattern <NUM> in <FIG>, more preferably <NUM> percent different (+ / - <NUM> percent) from the illuminance at the center of the illumination pattern <NUM> in <FIG>, and most preferably five percent different (+ / - <NUM> percent) from the illuminance at the center of the illumination pattern <NUM> in <FIG>.

The control system <NUM> may be configured to compensate for less illuminance or greater illuminance in the illumination pattern <NUM>, or portions thereof, at the region of interest <NUM> by adjusting the total visible flux <NUM>, <NUM> of, i.e. balancing the radiant power to, the respective first and second zones <NUM>, <NUM> of light sources <NUM>, <NUM>. For example, in <FIG>, the control system <NUM> may control the first or inner zone <NUM> of light sources <NUM> to produce for example half the illuminance at the relatively smaller pattern size <NUM> at the region of interest <NUM> and control the second or outer zone <NUM> of light sources <NUM> to likewise produce for example half the illuminance at the region of interest <NUM>. For the relatively larger pattern size <NUM> of <FIG>, the control system <NUM> may control the second or outer zone <NUM> of light sources <NUM> to produce substantially all the illuminance at the portion <NUM> surrounding the center portion <NUM> of the illumination pattern <NUM>. It will be appreciated that with respect to the cross section view shown in <FIG> and <FIG> there are more light sources <NUM>, <NUM> than shown; that is, for the example light head <NUM> described herein the light head <NUM> is round with <NUM> light sources <NUM> in the inner zone <NUM> and <NUM> light sources <NUM> in the outer zone <NUM>.

The control system <NUM> may be configured to power balance, or compensate, based on two different effects occurring at the region of interest <NUM>. The first effect is that the spreading of the light emitted by the outer zone <NUM> of light sources <NUM> decreases the illuminance of the illumination pattern <NUM> at the region of interest <NUM>. The control system <NUM> compensates for such decreased illuminance effect by increasing the total visible flux <NUM> of the outer zone <NUM> of light sources <NUM>. Thus, power to the outer zone <NUM> of light sources <NUM> is increased to compensate for the loss of illuminance (power density) in the illumination pattern <NUM> of the beam of light <NUM> that would otherwise occur from spreading the light from the outer zone <NUM> of light sources <NUM>. Increased power to the outer zone <NUM> of light sources <NUM> by itself however results in a second effect referred to as a "hot spot" in the center portion <NUM> of the beam of light <NUM>, since in this illustrative embodiment the light emitted by the inner zone <NUM> of light sources <NUM> is not subject to beam spreading. Thus, the hot spot in the illustrative example may include for example a magnitude of illuminance at the center portion <NUM> being relatively higher than a magnitude of illuminance at the portion <NUM> surrounding the center portion <NUM>. The control system <NUM> compensates for such hot spot effect by decreasing the total visible flux <NUM> from the inner zone <NUM> of light sources <NUM> and increasing the total visible flux <NUM> from the outer zone <NUM> of light sources <NUM> even further. The net effect is that the magnitude of the illuminance of the illumination pattern <NUM> is maintained substantially constant as the size of the illumination pattern <NUM> changes, and a substantially uniform illuminance is maintained across the illumination pattern <NUM> (i.e. minimization of the hot spot effect).

As described above, the illuminance of the illumination pattern <NUM> also naturally decreases radially outwardly from the center of the illustrative pattern <NUM> toward the perimeter of the illumination pattern <NUM>. The control system <NUM> is configured to adjust power to the zones <NUM>, <NUM> of light sources <NUM>, <NUM> to maintain the decrease low, that is, where the d50/d10 ratio is greater than <NUM>, and more preferably greater than <NUM>. When the d50/d10 ratio is greater than <NUM>, and more preferably greater than <NUM>, the illumination across the illumination pattern <NUM> may be said to be substantially uniform.

Thus, the control system <NUM> is configured to turn down the light output or total visible flux <NUM> from the inner zone <NUM> for the larger pattern size <NUM> shown in <FIG> relative to the light output or total visible flux <NUM> from the inner zone <NUM> for the smaller pattern size <NUM> shown in <FIG>. The inventors have found that this prevents creating a noticeable "hot spot" in the center portion <NUM> of the relatively larger pattern size <NUM> from the beam of light <NUM> emitted by the inner zone <NUM> of light sources <NUM>, which beam of light <NUM> is not spread but rather merely bent or redirected by the inner round housing lens <NUM>. In addition, for the larger pattern size <NUM>, the control system <NUM> is configured to increase the light output or total visible flux <NUM> from the outer zone <NUM> of light sources <NUM> so that the composite beam <NUM> formed by both the inner and outer zones <NUM>, <NUM> of light sources <NUM>, <NUM> has similar light density on the surface (illuminance) while also providing substantially uniform illuminance across the illumination pattern <NUM>, that is, the illumination, or brightness, drops off smoothly from the center portion <NUM> of the beam to the edge.

Referring now to <FIG>, there is shown a flowchart <NUM> of a method of operating a light head of a medical device support system, such as the afore described light head <NUM> of the medical device support system <NUM> of <FIG>, in accordance with an embodiment of the invention. At step <NUM>, first and second beams of light are emitted by respective first and second zones of light sources, for example the first and second zones <NUM>, <NUM> of light sources <NUM>, <NUM>, wherein the first and second beams of light form an illumination pattern having a pattern size at a region of interest, such as the illumination pattern <NUM> at the region of interest <NUM>. At step <NUM>, a beam spread of the second beam of light is adjusted by an optical system, for example the optical system <NUM>, in the path of the second beam of light to change the pattern size of the illumination pattern at the region of interest from a first pattern size to a second pattern size, for example the above described first and second pattern sizes <NUM>, <NUM>. At step <NUM>, power to the first and second zones of light sources is varied for example by the control system <NUM>, in response to adjustment of the beam spread of the second beam of light by the optical system to maintain a substantially constant magnitude of illuminance at the region of interest as the pattern size of the illumination pattern at the region of interest is changed from the first pattern size to the second pattern size.

Referring now to <FIG>, there is shown a flowchart <NUM> of a method of operating a light head of a medical device support system, such as the afore described light head <NUM> of the medical device support system <NUM> of <FIG>, in accordance with an embodiment of the invention. At step <NUM>, first and second beams of light are emitted by respective first and second zones of light sources, for example the first and second zones <NUM>, <NUM> of light sources <NUM>, <NUM>, wherein the first and second beams of light form an illumination pattern having a pattern size at a region of interest, such as the illumination pattern <NUM> at the region of interest <NUM>. At step <NUM>, a beam spread of the second beam of light is adjusted by an optical system, for example the optical system <NUM>, in the path of the second beam of light to change the pattern size of the illumination pattern at the region of interest from a first pattern size to a second pattern size, for example the above described first and second pattern sizes <NUM>, <NUM>. At step <NUM>, power to the first and second zones of light sources is varied for example by the control system <NUM>, in response to adjustment of the beam spread of the second beam of light by the optical system to maintain a substantially uniform illuminance across the illumination pattern as the pattern size at the region of interest is changed from the first pattern size to the second pattern size.

The inventors have found the power balancing of the first and second zones <NUM>, <NUM> of light sources <NUM>, <NUM> to be advantageous over other systems. In other systems, when a relatively large pattern size is generated for example by beam spreading, the same amount of light is spread over the relatively larger area; thus, the total visible flux is constant, but the illuminance decreases due to the larger area of the pattern size. In contrast, in the present embodiment, as the pattern size increases for example from the <FIG> pattern size <NUM> to the <FIG> pattern size <NUM>, the control system <NUM> varies the total visible flux <NUM>, <NUM> of the light sources <NUM>, <NUM>, or power to the light sources <NUM>, <NUM>, so that the illuminance at the illumination pattern <NUM> is maintained substantially constant, whether at a certain portion of the illumination pattern <NUM> or an average of the illuminance at multiple portions of the illumination pattern <NUM>. Thus, for example, the illuminance at the center of the illumination pattern <NUM> in <FIG> relative to the illuminance at the center of the illumination pattern <NUM> in <FIG> is maintained substantially constant. The control system <NUM> increases the light output (total visible flux) for the relatively larger pattern size <NUM>, as represented by more rays of light being emitted from the light sources <NUM> in the second or outer zone <NUM> (from three rays in <FIG> to nine rays in <FIG>), but produces substantially the same illuminance at the region of interest <NUM>, depicted by the same density of the cross hatch patterns at the bottom of <FIG> and <FIG>, which represents the composite beam <NUM> formed by contributions from both the inner and outer zones <NUM>, <NUM> of light sources <NUM>, <NUM>.

The inventors have also found that the beam spreading by the optical elements <NUM>, <NUM> of the light head <NUM> is advantageous over other systems since the optical elements <NUM>, <NUM> of the light head <NUM> provide a more consistent beam size, shape and uniformity with variations in distance from the light head <NUM> than the beams produced by the other systems where light is rigidly designed to form a desired beam at a specific distance. This is significant in many surgical lighting applications since surgical light heads typically are adjusted over a range of distances as the surgical team places the light head over a patient during a surgical procedure.

The inventors have also found that the light head <NUM> according to the present invention is advantageous over light heads for which some of the light sources are not used to produce a relatively smaller size pattern. The light head <NUM> according to the invention delivers light from a full diameter of the light head <NUM> when producing the relatively small pattern shown in <FIG>, thus providing better shadow control.

Claim 1:
A light head (<NUM>) for a medical device support (system <NUM>), comprising:
a first zone (<NUM>) of light sources (<NUM>) that is configured to emit a first beam of light (<NUM>) and a second zone (<NUM>) of light sources (<NUM>) that is configured to emit a second beam of light (<NUM>), wherein the first and second beams of light are configured to form an illumination pattern (<NUM>) having a pattern size at a region of interest (<NUM>);
an optical system (<NUM>) in a path of the second beam of light to adjust a beam spread of the second beam of light to change the pattern size of the illumination pattern at the region of interest from a first pattern size (<NUM>) to a second pattern size (<NUM>); and,
a control system (<NUM>) configured to vary power to the first and second zones of light sources in response to adjustment of the beam spread of the second beam of light by the optical system to maintain a substantially constant magnitude of illuminance at the region of interest as the pattern size of the illumination pattern at the region of interest is changed from the first pattern size to the second pattern size.