Patent Description:
More precisely the invention relates to an optical device comprising a lens and a control member configured such that a motion of the control member produces a change in the optical power provided along an optical axis of the lens. The invention also relates to an optometric equipment comprising such an optical device.

Document <CIT> describes an optical device as just mentioned.

Such an optical device further comprises a framework, a motor and a driving member, such as a worm screw: said motor includes an output shaft whereon said driving member is affixed, and the motor and the control member (e.g. a toothed wheel) are mounted in the framework such that the driving member and the control member mechanically cooperate.

Thus, by appropriate control of the motor, it is possible to activate the driving member and move the control member (e.g. rotate the toothed wheel) to a position where the lens provides a particular optical power.

Motors used in this context (usually electric motors) are however generally designed with an axial play in the position of their output shaft to ensure proper functioning in a wide range of temperatures.

This axial play however results in an inaccurate positioning of the driving member relative to the framework and thus in an imprecise control of the motion of the control member from the motor.

This is problematic in particular when no information is available as to the actual position of the control member, for instance when motion control is based on an encoder determining the angular position of the output shaft. Further prior art can be found in <CIT> and <CIT>.

In this context, the invention provides an optical device as defined in claim <NUM> comprising a lens and a control member configured such that motion of the control member produces a change in the optical power provided along an optical axis of the lens, the optical device further comprising a framework, a motor and a driving member, said motor including an output shaft rotatively coupled to said driving member, the motor and the control member being mounted in the framework such that the driving member and the control member mechanically cooperate, characterised in that the driving member is rotatably mounted in the framework and in that the optical device comprises biasing means for maintaining the driving member in a predetermined axial position along the output shaft axis and relative to the framework.

The driving member is thus precisely positioned and can therefore accurately control motion of the control member, which results in an accurate control of the optical power provided by the optical device.

The optical device may also include one or several of the following features:.

The invention also provides an optometric equipment as defined in claim <NUM>, (e.g. a refractor) comprising an optical device.

Illustrative embodiments of the present invention are described in detail below with reference to the attached drawing Figures, wherein.

<FIG> represents elements of an optical device <NUM> constructed in accordance with the teachings of the invention.

Such an optical device <NUM> includes at least a lens <NUM>; <NUM>; <NUM>, at least a motor <NUM>; <NUM>; <NUM> and at least a transmission system <NUM>; <NUM>; <NUM> configured to move at least a portion of the lens <NUM>; <NUM>; <NUM> and thereby change the optical power provided along an optical axis X of the lens <NUM>; <NUM>; <NUM> when the motor <NUM>; <NUM>; <NUM> is operated.

In the present example, the optical device <NUM> includes:.

These elements are mounted in a framework <NUM> of the optical device <NUM> such that the lens <NUM> having a variable spherical power, the first cylindrical lens <NUM> and the second cylindrical lens <NUM> have the same optical axis X (as schematically represented in <FIG>). Reference can be made to document <CIT> for further details on this aspect.

As shown in <FIG>, the optical device <NUM> also includes a control circuit <NUM> designed to control motion of the motor(s), here of the first motor <NUM>, of the second motor <NUM>, and of the third motor <NUM>, such that the lens or combination of lenses <NUM>, <NUM>, <NUM> provides a sought optical power, as explained in document <CIT>.

The optical device <NUM> can thus be used to provide a predefined optical correction to an eye of a person (when this eye is situated along the optical axis X). The optical device <NUM> can thus be included in an optical equipment, such as a refractor (or phoropter), to be used for instance when subjecting a patient to a subjective refraction test.

In the present embodiment, each motor <NUM>; <NUM>; <NUM> includes an encoder for determining an angular position of the output shaft <NUM>; <NUM> of the concerned motor <NUM>; <NUM>; <NUM> and for transmitting an item of information representing this angular position to the control circuit <NUM> (based on which the control circuit <NUM> can precisely control the position of the concerned output shaft <NUM>; <NUM>).

The first transmission system <NUM> and the second transmission system <NUM> will now be described with reference to <FIG>. The third transmission system <NUM> is constructed in a manner identical to the second transmission system <NUM> and will not therefore be further described.

Each transmission system <NUM>; <NUM> comprises a driving member <NUM>; <NUM> rotatively coupled to the output shaft <NUM>; <NUM> of the corresponding motor <NUM>; <NUM> and a control member <NUM>; <NUM> designed so as to produce, when moving, a change in the optical power provided along an optical axis X of the concerned lens <NUM>; <NUM>.

The driving member <NUM>; <NUM> is mounted with respect to the output shaft <NUM>; <NUM> of the corresponding motor <NUM>; <NUM> so as to be connected or affixed to the output shaft <NUM>; <NUM> such that the driving member <NUM>; <NUM> and the output shaft <NUM>; <NUM> are coupled when rotating (i.e. when the corresponding motor <NUM>; <NUM> operates) around the output shaft axis. The driving member <NUM>; <NUM> may however in practice be mounted with respect to the output shaft <NUM>; <NUM> so as to move in translation with respect to the output shaft <NUM>; <NUM> along the axis of the output shaft <NUM>; <NUM>.

In the present embodiment, the driving member <NUM>; <NUM> is a worm screw. This worm screw <NUM>; <NUM> is here affixed to the output shaft <NUM>; <NUM> with the axis of the worm screw <NUM>; <NUM> extending along the axis of the output shaft <NUM>; <NUM>, such that rotation of the output shaft <NUM>; <NUM> (when operating the motor <NUM>; <NUM>) results in rotation of the worm screw <NUM>; <NUM> (around the axis of the worm screw <NUM>; <NUM>).

In the present embodiment, the control member <NUM>; <NUM> is a toothed wheel. This toothed wheel <NUM>; <NUM> meshes with the worm screw <NUM>; <NUM> such that rotation of the worm screw <NUM>; <NUM> (around the axis of the worm screw <NUM>; <NUM>) produces a rotation of the toothed wheel <NUM>; <NUM> around the axis of the toothed wheel <NUM>; <NUM> (the axis of the toothed wheel <NUM>; <NUM> being perpendicular to the axis of the worm screw <NUM>; <NUM>, i.e. perpendicular to the axis of the output shaft <NUM>; <NUM> of the motor <NUM>; <NUM>, and/or being situated at a distance from the axis of the worm screw <NUM>; <NUM>).

<FIG> show details of the first transmission system <NUM>.

As visible in <FIG>, in the present embodiment, the framework <NUM> comprises a frame <NUM> and a sleeve <NUM>. The frame <NUM> is for instance made of a plastic material, such as polyether ether ketone (PEEK). The sleeve <NUM> is for instance made of metal, e.g. stainless steel.

The sleeve <NUM> is for instance received in a complementary recess <NUM> formed in the frame <NUM> and retained in this complementary recess <NUM> thanks to a ring <NUM> affixed to the frame <NUM> by means of screws <NUM>.

The sleeve <NUM> defines a through aperture <NUM> through which the output shaft <NUM> of the motor <NUM> and the driving member <NUM> extend. The through aperture <NUM> comprises a first cylindrical portion <NUM> for partly accommodating the motor <NUM> and a second cylindrical portion <NUM> for accommodating a rolling bearing at least (here two rolling bearings <NUM>, <NUM>).

The sleeve <NUM> forms a ring-shaped wall <NUM> at an axial end of the second cylindrical portion <NUM> for a bearing <NUM> to abut, as further explained below.

The frame <NUM> defines a cavity <NUM> communicating with the recess <NUM>. In the present embodiment, the cavity <NUM> comprises (sequentially along an axis of the cavity <NUM>, from a portion situated near the recess <NUM> to a portion situated away from the recess <NUM>):.

The first cylindrical portion <NUM> accommodates in the present example a spring washer <NUM>. The frame <NUM> has a ring shaped wall <NUM> (connecting the first cylindrical portion <NUM> and the second cylindrical portion <NUM>, i.e. formed by the difference in diameter between the first cylindrical portion <NUM> and the second cylindrical portion <NUM>).

The spring washer <NUM> is thus held (axially) between the wall <NUM> and the outer race of the rolling bearing <NUM> and presses the rolling bearing assembly <NUM>, <NUM> against the wall <NUM> formed in framework <NUM> (here in the sleeve <NUM>).

A further rolling bearing <NUM> is accommodated in the cavity at the level of the third cylindrical portion <NUM>. The rolling bearing <NUM> is able to translate axially under the force of the spring washer <NUM> and is mounted tight on the driving member <NUM>.

The driving member <NUM> comprises a first axial portion <NUM>, a second axial portion <NUM> and a threaded portion <NUM> separating (i.e. extending between, here along the axis of the driving member <NUM>) the first axial portion <NUM> and the second axial portion <NUM>.

The second cylindrical portion <NUM> has a diameter (second diameter as mentioned above) larger than the external diameter of the threaded portion <NUM> of the driving member <NUM> (for the cavity <NUM> to accommodate the driving member <NUM>).

The rolling bearings <NUM>, <NUM> are mounted on the first axial portion <NUM> of the driving member <NUM>. Precisely here, the first axial portion <NUM> of the driving member <NUM> is press fit into respective inner races of the rolling bearings <NUM>, <NUM>.

The further rolling bearing <NUM> is mounted on the second axial portion <NUM> of the driving member <NUM>. Precisely here, the second axial portion <NUM> of the driving member <NUM> is press fit into the inner race of the further rolling bearing <NUM>.

The driving member <NUM> is thus rotatably mounted in the framework <NUM> (rotating around an axis of the driving member <NUM>, corresponding here to the output shaft axis).

Thanks to the construction just described, as the rolling bearing assembly <NUM>, <NUM> is urged against the wall <NUM> of the framework <NUM> thanks to the spring washer <NUM> and the driving member <NUM> is press fit into inner races of the rolling bearings <NUM>, <NUM>, the driving member <NUM> is maintained in a predetermined axial position along the axis of the output shaft <NUM> (identical here to the axis of the driving member <NUM>) relative to the framework <NUM>.

The spring washer <NUM> may for instance be selected so as to exert, along the axis of the output shaft <NUM>, a biasing force greater than a force exerted by the driving member <NUM> on the control member <NUM> for driving the control member <NUM> into motion (for example, three times greater than said force exerted by the driving member <NUM> or more, here four times greater than said force exerted by the driving member <NUM> or more).

The stiffness of the spring is dimensioned/chosen so that the thermal expansions do not significantly influence the biasing force exerted by the spring washer <NUM> along the axis of the output shaft <NUM>.

For example, the force exerted by the driving member <NUM> on the control member <NUM> for driving the control member <NUM> into motion is between <NUM> N and <NUM> N, here <NUM> N; the biasing force exerted by the spring washer <NUM> along the axis of the output shaft <NUM> is between <NUM> N and <NUM> N, here <NUM> N.

Motion of the control member <NUM> (here by rotation) can thus be precisely controlled by corresponding motion of the driving member <NUM> (itself driven by the motor <NUM>). Control of the optical power (here of the spherical power) provided by the lens <NUM> along the lens axis X is thus improved.

In the present case, rotation of the control member <NUM> is converted into a translation movement by a screw arrangement (not shown), this translation movement producing the deformation of a deformable membrane (not shown) of the lens <NUM>, thus varying the spherical power of the lens <NUM>.

<FIG> show details of the second transmission system <NUM>.

As shown in <FIG>, the framework <NUM> also includes here a bushing <NUM> (in addition to the frame already mentioned). The bushing <NUM> is for instance made of metal, e.g. stainless steel.

The frame <NUM> defines a cavity <NUM> comprising (sequentially along an axis of the cavity <NUM>, from a portion situated near the motor <NUM> to a portion situated away from the motor <NUM>):.

The bushing <NUM> is here received in the cavity <NUM> at the level of the first cylindrical portion <NUM>. A portion of the bushing <NUM> has a cylindrical shape having a diameter corresponding to the fourth diameter mentioned above. The bushing <NUM> is for instance affixed to the frame <NUM> by means of a clip <NUM> cooperating with a groove <NUM> formed on the bushing <NUM>.

The bushing <NUM> defines a through aperture <NUM> through which the output shaft <NUM> of the motor <NUM> and an end of the driving member <NUM> extend.

The bushing <NUM> defines a first recess <NUM> partly receiving the motor <NUM> and a second recess <NUM> (situated axially opposite the first recess <NUM>) accommodating a rolling bearing <NUM>.

The second recess <NUM> defines a ring-shaped wall <NUM> against which the rolling bearing <NUM> abuts, as further explained below.

The second cylindrical portion <NUM> has a diameter (fifth diameter as mentioned above) larger than the external diameter of the threaded portion <NUM> of the driving member <NUM> (for the cavity <NUM> to accommodate the driving member <NUM>).

The rolling bearing <NUM> is mounted on the first axial portion <NUM> of the driving member <NUM>. Precisely here, an end portion of the first axial portion <NUM> of the driving member <NUM> is press fit into respective inner races of the rolling bearing <NUM>.

Another rolling bearing <NUM> is mounted on the second axial portion <NUM> of the driving member <NUM>. Precisely here, the second axial portion <NUM> of the driving member <NUM> is press fit into the inner race of the other rolling bearing <NUM>.

As visible in <FIG>, this rolling bearing <NUM> is accommodated in the cavity <NUM>, here in the third cylindrical portion <NUM> of the cavity <NUM>. The external diameter of the rolling bearing <NUM> corresponds here (in practice is equal to) the diameter of the third cylindrical portion (sixth diameter) so that the rolling bearing <NUM> may move (by translation along the axis of the driving member <NUM>, i.e. here the axis of the output shaft <NUM>) within the third cylindrical portion <NUM>.

A coil spring <NUM> is interposed between an end wall <NUM> of the cavity <NUM> (i.e. here an end wall of the third cylindrical portion) and the rolling bearing <NUM> (precisely here the outer race of the rolling bearing <NUM>).

In the present embodiment, a ring <NUM> is further interposed between the coil spring <NUM> and the rolling bearing <NUM>. The circular edge of the ring <NUM> (circular edge directed towards the rolling bearing <NUM>) contacts only the outer race of the rolling bearing <NUM>, which ensures that the force produced by the compressed coil spring <NUM> applies only on the outer race of the rolling bearing <NUM> and not on the inner race of the rolling bearing <NUM> (which would hinder rotation of the control member <NUM>).

As the coil spring <NUM> is compressed between the end wall <NUM> and the rolling bearing <NUM>, the coil spring <NUM> urges the assembly comprising the driving member <NUM> and the rolling bearings <NUM>, <NUM> towards the motor <NUM> up to abutment of the rolling bearing <NUM> against the wall <NUM>.

The driving member <NUM> is consequently maintained in a predetermined axial position along the axis of the output shaft <NUM> (identical here to the axis of the driving member <NUM>) relative to the framework <NUM>.

The coil spring <NUM> may for instance be selected so as to exert, along the axis of the output shaft <NUM>, a biasing force greater than a force exerted by the driving member <NUM> on the control member <NUM> for driving the control member <NUM> into motion.

Claim 1:
Optical device (<NUM>) comprising a lens (<NUM>; <NUM>) and a control member (<NUM>; <NUM>) configured such that motion of the control member (<NUM>) produces a change in the optical power provided along an optical axis (X) of the lens (<NUM>; <NUM>),
the optical device (<NUM>) further comprising a framework (<NUM>), a motor (<NUM>; <NUM>) and a driving member (<NUM>), said motor (<NUM>; <NUM>) including an output shaft (<NUM>) rotatively coupled to said driving member (<NUM>), the motor (<NUM>; <NUM>) and the control member (<NUM>) being mounted in the framework (<NUM>) such that the driving member (<NUM>) and the control member (<NUM>) mechanically cooperate,
the driving member (<NUM>) being rotatably mounted in the framework (<NUM>),
characterised in that the optical device (<NUM>) comprises biasing means (<NUM>) for maintaining the driving member (<NUM>) in a predetermined axial position along the output shaft axis and relative to the framework (<NUM>),
the framework (<NUM>) comprising a frame (<NUM>) defining a cavity (<NUM>) comprising a first cylindrical portion (<NUM>) having a first diameter, a second cylindrical portion (<NUM>) having a second diameter smaller than the first diameter, and a third cylindrical portion (<NUM>) having a third diameter smaller than the second diameter,
the driving member (<NUM>) comprising a first axial portion (<NUM>), a second axial portion (<NUM>) and a threaded portion (<NUM>) separating the first axial portion (<NUM>) and the second axial portion (<NUM>),
wherein the biasing means include a spring washer (<NUM>) held between an outer race of a rolling bearing (<NUM>) and a ring-shaped wall (<NUM>) connecting the first cylindrical portion (<NUM>) and the second cylindrical portion (<NUM>), and
wherein a further rolling bearing (<NUM>) is mounted on the second axial portion (<NUM>) of the driving member (<NUM>) and is accommodated in the cavity (<NUM>) at the level of the third cylindrical portion (<NUM>).