Patent Description:
More precisely the invention relates to an optometry device.

Optometry devices are used by eye care professionals, in particular optometrists and ophthalmologists, to assist them in assessing characteristics of an individual's vision.

In particular, a refraction apparatus is an optometry device adapted to generate a variable correction and used during a test known as "subjective refraction" in order to determine the necessary correction for compensating an individual's ametropia.

Document <CIT> describes an optometry device for testing an individual's eye comprising an imaging module adapted to produce a first image at a variable distance for the individual's eye, a beam splitter arranged to combine the first image and a second image for the individual's eye and a screen facing the beam splitter.

Document <CIT> describes a visual function test apparatus comprising an optotype disc, a beam splitter arranged to combine a first image and a second image for the individual's eye and a diffusing plate at the level of the beam splitter (Fig. <NUM>).

In this context, the invention provides an optometry device according to claim <NUM>.

This makes it possible to project the light beam produced by the screen as a broad virtual image (representing any desired background), upon which the first image is superimposed, thus simulating a realistic situation.

The optometry device may also include one or several of the following optional features (which are to be understood as non limiting):.

The following description will be made in light of the appended figures, where:.

The optometry device of <FIG> includes a casing <NUM> mounted on a stand <NUM> so that the optometry device may be placed on a table, for instance.

In the present embodiment, the casing <NUM> encloses an acuity module <NUM>, a scene module <NUM>, a refraction module <NUM> and a sensor module <NUM>. The casing <NUM> also encloses a driving module <NUM> adapted to move some parts of other modules, in particular some parts of the refraction module <NUM> (as further explained below) and/or some parts of the sensor module <NUM>.

As visible in <FIG>, the casing <NUM> includes a wall <NUM> situated opposite the acuity module <NUM> and having a window <NUM> (possibly closed by a transparent material, such as a transparent plastic) through which an individual can look into the casing <NUM>, as further explained below.

The acuity module <NUM> includes a screen <NUM>, a pair of mirrors <NUM>, <NUM>, a lens <NUM> and a further mirror <NUM>.

The screen <NUM> (for instance an LCD screen) produces a light beam along a screen axis S (this screen axis S being vertical in the present case). As further explained below, this light beam is meant to produce an image of an object, such as an optotype, for an individual using the optometry device.

Mirrors <NUM>, <NUM> are disposed at a right angle with respect to each other; in addition, mirror <NUM> is disposed at an angle of <NUM>° with respect to the screen axis S. Thanks to this arrangement, the light beam produced by the screen <NUM> is successively reflected by mirror <NUM>, then by mirror <NUM>, such that it is directed towards the lens <NUM> along a lens axis L (the screen axis S and the lens axis L being parallel to each other).

Lens <NUM> is here an achromatic lens, having a focal length between <NUM> and <NUM>, for instance.

The further mirror <NUM> is positioned at <NUM>° on the lens axis L, opposite mirror <NUM> with respect to the lens <NUM>, such that the light beam reflected by mirror <NUM> along the lens axis L crosses the lens <NUM> and is then reflected on the further mirror <NUM> and directed therefrom to the individual's eye E (through window <NUM>) along an optical axis O of the optometry device.

The distance between the lens <NUM> and the screen <NUM> (along the optical path just described) is less than the focal length of the lens <NUM>, such that the screen <NUM> is situated between the object focal plane of the lens <NUM> and the lens itself.

On the other hand, the casing <NUM> and the acuity module <NUM> are designed such that the individual's eye E is situated in the image focal plane of the lens <NUM> (when the individual positions his head H against a dedicated part of the casing <NUM>).

The acuity module <NUM> is thus designed to produce an image (representing an object, such as an optotype) for the individual's eye E.

In addition, mirrors <NUM>, <NUM> are held on a base <NUM> which is slidably mounted on a support <NUM> of the acuity module <NUM> such that mirrors <NUM>, <NUM> are movable along the (vertical) screen axis S. (The screen <NUM>, the lens <NUM> and the further mirror <NUM> are fixedly attached to this support <NUM>.

By moving the base <NUM> carrying mirrors <NUM>, <NUM> (for instance thanks to an electric motor <NUM> and associated mechanism, which are not shown in <FIG>), the length of the optical path between the screen <NUM> and the lens <NUM> can be modified.

Thanks to this, the acuity module is adapted to produce the image of the object at a variable distance for the individual's eye E.

The various elements of the acuity module <NUM> just described are enclosed in a housing <NUM> shown in <FIG> (but not represented in <FIG> for the sake of clarity).

The scene module <NUM> comprises a screen <NUM>, a mirror (here a concave mirror) <NUM> and a beam splitter <NUM>. The scene module <NUM> also comprises a housing <NUM> enclosing the screen <NUM>, the mirror <NUM> and the beam splitter <NUM>.

The screen <NUM> may be a video display, for instance an LCD display.

The housing <NUM> has a first aperture <NUM> and a second aperture <NUM>, both situated on the optical axis O of the optometry device and meant to allow light directed to the individual's eye E to pass.

The first aperture <NUM> is made in a wall of the housing <NUM> facing the acuity module <NUM>, while the second aperture <NUM> is made in a wall of the housing <NUM> facing the individual's eye E.

The beam splitter <NUM> is positioned on the optical axis O. The light beam produced by the acuity module <NUM> (here, reflected by the further mirror <NUM> of the acuity module <NUM>) is thus transmitted towards the individual's eye E across the first aperture, the beam splitter and the second aperture.

The screen <NUM>, the beam splitter <NUM> and the mirror <NUM> are aligned along a direction (here a vertical direction) perpendicular to the optical axis O. The screen <NUM> and the mirror <NUM> are furthermore positioned on either sides of the beam splitter <NUM>, which is itself positioned at <NUM>° with respect to the optical axis.

Thanks to this construction, a light beam produced by the screen <NUM> is transmitted from the screen <NUM> to the mirror <NUM> across the beam splitter <NUM> (as shown e.g. by ray R<NUM> in <FIG>), reflects on the mirror <NUM> towards the beam splitter <NUM> (ray R<NUM>) and reflects on the beam splitter <NUM> so as to be eventually directed along the optical axis O, towards the individual's eye E (ray R<NUM>). This light beam thus also exit the scene module <NUM> via the second aperture <NUM>.

The (here concave) mirror <NUM> has a focal length making it possible for the individual using the optometry device to view the image generated by the screen <NUM> at a distance larger than <NUM> (or larger than <NUM>).

The beam splitter <NUM> thus not only makes it possible to transmit the light beam produced by the acuity module <NUM>, but also to add in the same direction (optical axis O) the light beam initially produced by the screen <NUM> of the scene module <NUM>, i.e. to combine the image produced by the acuity module <NUM> with another image generated by the screen of the scene module <NUM>.

As visible on <FIG>, the width of the screen <NUM> of the scene module <NUM> (as measured here along the optical axis O) makes it possible to generate a light beam which extends substantially along the whole length of the beam splitter <NUM> and which is therefore visible from the individual's eye E over a rather wide angle α, generally an angle α of <NUM>° or more, preferably an angle α of <NUM>° or more.

In comparison, the image of the object generated by the acuity module <NUM> (as visible on the further mirror <NUM> from the individual's eye E) covers a rather narrow angle β of <NUM>° or less.

In view of this, in the present embodiment, the area of the first aperture <NUM> is clearly smaller than the area of the second aperture <NUM>.

In the present embodiment, elements of the scene module <NUM> are positioned such that the (virtual) image produced by the screen <NUM> of the scene module <NUM> is in the distance for the individual's eye E (i.e. corresponds to distance vision for the individual).

According to a possible implementation, the screen <NUM> may be movable (for instance by motorized movement on a linear guide) from the position shown in <FIG> to another position (shown in dotted lines under reference <NUM>') in order to image the image produced by the screen <NUM> at a variable distance for the individual's eye E.

Thanks to the construction of the optometry device presented above, the scene module <NUM> could be removed (for instance if mounted by detachable means in the casing <NUM>) or not included in some products, without affecting the operation of the acuity module <NUM> and of other modules <NUM>, <NUM> described below.

The optometry device may also include an illuminator <NUM>, which is here interposed between the acuity module <NUM> and the scene module <NUM>. The illuminator <NUM> may be mounted to the housing <NUM> of the acuity module, for instance.

The illuminator <NUM> may comprise at least one light source (for instance a plurality of light sources, such as LEDs) and a plaque of transparent plastic material adapted to scatter and diffuse light. The illuminator <NUM> is thus adapted to illuminate an area situated opposite the individual's eye E with respect to the beam splitter <NUM> and therefore to simulate ambient light for the individual. The level of this ambient light (i.e. the simulated luminosity) may be varied by varying the intensity of the light source(s).

The refraction module <NUM> is mounted in the casing <NUM> so as to be interposed between the scene module <NUM> and the individual's eye E (and hence between the acuity module <NUM> and the individual's eye E).

In the present embodiment, the refraction module <NUM> is located in the vicinity of the wall <NUM> of the casing <NUM> presenting the window <NUM>.

The refraction module <NUM> is for instance a visual compensation system as described in document <CIT>.

Such a refraction module is adapted to provide a variable optical correction for the individual's eye E looking therethrough.

Precisely, as shown in <FIG>, the refraction module <NUM> includes a lens <NUM> having a spherical power along the optical axis O, which spherical power is variable.

Said variable spherical power lens <NUM> has for instance a deformable surface (such as a deformable membrane). The shape of this surface (in particular the radius of curvature of this surface, and hence the spherical power provided by the lens) can be controlled by moving a mechanical part (such as a ring), which mechanical part may be driven by a first motor <NUM> of the refraction module <NUM>.

The refraction module also includes a pair of independently rotatable lenses <NUM>, <NUM> each having a cylindrical power along the optical axis O.

The two rotatable lenses <NUM>, <NUM> may each be rotated by action of a second motor of the refraction module <NUM> and of a third motor of the refraction module <NUM>, respectively.

The refraction module <NUM> includes a control unit <NUM> which is designed to generate controls for the first motor <NUM>, the second motor and the third motor, respectively, such that the combination of the variable spherical power lens <NUM> and the two cylindrical power lenses <NUM>, <NUM> provides a desired spherical correction and a desired cylindrical correction to the individual's eye E, as explained in document <CIT>.

The various elements of the refraction module <NUM> (such as the variable spherical power lens <NUM>, the cylindrical lenses <NUM>, <NUM>, the first motor <NUM>, the second motor, the third motor and the control unit <NUM>) are enclosed in a housing <NUM>.

In the present embodiment, the optometry device includes two visual compensation systems as mentioned above and shown in <FIG>, each such system being situated in front of one of the individual's eyes.

The driving module <NUM> may in this case include means to move each of the visual compensation system in a direction perpendicular to the optical axis O in order to adjust to the pupillary distance (PD) of the individual.

<FIG> shows a possible embodiment wherein the optometry device includes two refraction modules <NUM>, <NUM>' and each refraction module <NUM>, <NUM>' is provided with a shutter <NUM>, <NUM>'.

Each shutter <NUM>, <NUM>' is rotatably mounted about an axis <NUM>, <NUM>' (which is substantially parallel to the optical axis O) so as to be movable between a first (closed) position (shown in <FIG>), where the concerned shutter <NUM>, <NUM>' lies on the optical axis O (i.e. faces window <NUM>) and blocks vision with the concerned eye, and a second (open) position, where the concerned shutter <NUM>, <NUM>' is out of the optical axis O and does not impede vision with the concerned eye.

By controlling the position of the shutters <NUM>, <NUM>' independently and synchronized with the screen <NUM> of the acuity module <NUM> and/or the screen <NUM> of the scene module <NUM>, it is possible to produce an image for the right eye which is distinct from an image produced for the left eye, this being applicable to images produced by the acuity module <NUM> and to images produced by the scene module.

For instance, for a sequence of images displayed on the screen <NUM> of the acuity module <NUM> or on the screen <NUM> of the scene module <NUM>, odd images can be shown to one eye only (shutter <NUM> closed, shutter <NUM>' open) while even images are shown to the other eye only (shutter <NUM> open, shutter <NUM>' closed).

This makes it possible to display stereoscopic images, for instance.

According to a possible embodiment, by displaying images on the screen <NUM> of the acuity module <NUM> at moments different than displaying images on the screen <NUM> of the scene module <NUM>, it also possible to show an image (such as an optotype) produced by the acuity module <NUM> for a given eye only and to show an image produced by the scene module <NUM> for both eyes.

The sensor module <NUM> comprises a beam splitter <NUM> situated on the optical axis O, tilted at <NUM>° with respect to the optical axis O so as to reflect light emerging from the individual's eye E towards a sensor <NUM> (situated above the optical axis O in the present case). Sensor <NUM> is for instance an image sensor, such a video camera, design to capture images of the individual's eye E.

A processing unit, which may be located in the sensor module <NUM> or elsewhere (e.g. in a distinct electronic apparatus), receives images captured by sensor <NUM> and analyses these images to deduce therefrom physiological or behavioural parameters relating to the individual, such as the gaze direction of the concerned individual's eye E.

In the present embodiment, the refraction module <NUM> and the sensor module <NUM> are positioned in the casing <NUM> such that a cartridge <NUM> carrying at least an optical element <NUM> can be inserted between the refraction module <NUM> and the sensor module <NUM>.

As shown in <FIG>, the cartridge <NUM> is here inserted from above through an opening <NUM> in the casing <NUM>.

When the cartridge <NUM> is positioned between the refraction module <NUM> and the sensor module <NUM>, the optical element <NUM> is located on the optical axis O such that the individual's eye E observes the beam splitter <NUM> of the scene module and the further mirror <NUM> of the acuity module <NUM> (each producing an image for the individual's eye E) through the optical element <NUM>.

Optical element <NUM> is for instance a coloured filter, a tinted filter, a polarizing filter or a prismatic lens.

The optometry device described above, although being compact, can simulate real situations thanks to the image generated by the scene module with a broad field of vision.

By simultaneous use of the acuity module <NUM> and of the scene module <NUM>, a high resolution optotype OPT may be displayed in the centre of an image having a broad field of vision.

When the screen <NUM> of the scene module <NUM> is a video display, the test performed using the optometry device can even simulate a moving environment, as in a real situation.

In addition, by enclosing the various elements in the casing <NUM>, as described above, the level of light perceived by the individual's eye E can be adjusted as desired; all kinds of ambient light can thus be simulated (in particular using illuminator <NUM>), from penumbra to dazzling.

A subjective refraction test (possibly using the refraction module <NUM>) can thus be carried out with a light level chosen by the professional, for instance to test photopic vision or mesopic vision.

A test can also be performed for a specific colour (for instance red, green or blue) by displaying images having only the concerned colour on the screen <NUM> of the acuity module and/or on the screen <NUM> of the scene module <NUM>.

Optical element <NUM> may be used for instance to demonstrate interest of using a particular additional filter in a given situation (simulated as described above).

Thanks to the combination of two images (here using the beam splitter <NUM> of the scene module <NUM>), the object OPT used in the vision test (corresponding to the high resolution image generated by the acuity module <NUM>, e.g. an optotype) is viewed by the individual in the middle of a broader scene SCN (for instance as a distant sign in a landscape), which makes the test more realistic, as in the exemplary view shown in <FIG>.

For instance, a dedicated subjective refraction test can be performed in a context simulating night driving.

Claim 1:
Optometry device for testing an individual's eye (E) comprising:
- an imaging module (<NUM>);
- a beam splitter (<NUM>) arranged to combine a first image and a second image for the individual's eye (E);
- a screen (<NUM>) facing the beam splitter (<NUM>);
characterised by
- a concave mirror (<NUM>) arranged in combination with the screen (<NUM>) to produce the second image to be visible by the individual's eye via the beam splitter (<NUM>),
wherein the screen is a video display and wherein the imaging module (<NUM>) is adapted to produce the first image at a variable distance for the individual's eye (E).