FR2605209A1 - Apparatus for measuring an ocular parameter of a subject wearing a glasses frame - Google Patents

Abstract

The invention relates for example to measuring the mounting height to be adhered to when fitting a corrective lens on to a glasses frame. The apparatus according to the invention comprises for this purpose a feeler 17, to which is connected an index, an observation unit 20, which is mounted movably, and a measurement scale, which, itself also mounted movably, opposite the aforementioned index, is linked in movement with the observation unit 20, the said observation unit 20 being adapted to allow observation of corneal reflection on the eye of the patient in question. Application not only to measuring a mounting height, but also pupillary distance.

Description

"Apparatus for measuring an ocular parameter
on a subject wearing a spectacle frame "
The present invention relates generally to the mounting of lenses on a spectacle frame, and it relates more precisely to the case where, in the case of corrective lenses, and for example corrective lenses with progressively variable focal power, this mounting must cutter performed in a particularly precise manner, taking into account both the geometric outline of the circles or surroundings of the spectacle frame to be fitted as well as the morphological characteristics of the subject concerned.

 For the subject to have an optimal vision in near vision, it is important, in fact, that at least a substantial portion of the corresponding near vision zone of the corrective lenses is preserved during the trimming of these necessary for their adaptation to the geometry of the circles or entourages to be fitted, and it is therefore important that the distance, commonly known as the mounting height, separating the lower part of these circles or entourages from the viewing axis in far vision of the subject even sufficient.

 At the same time, for the good comfort of the subject during his passage from his far vision to his near vision, it is necessary to take into account his pupillary distance.

 With regard to the mounting height, which is in practice the most difficult to raise, various measuring devices have already been proposed.

 As described for example in the French patent which, filed on March 15, 1977 under No. 77 07641, was published under No. 2,384,232, it may be a kind of false lens, which is to be implanted in the circle or entourage to be fitted and in a recess of which is movably mounted a strip which it is up to the practitioner to move until an opening which is practiced there for this purpose is at the level of the pupil of the eye concerned with the subject for a distant vision of it.

 Although this measurement device is by itself very simple, and that, from this point of view, it gives satisfaction, its implementation involves the execution of fairly delicate operations, namely, the implementation of the 'together in the circle or surrounding glasses frame concerned, then the displacement of a strip, so that this implementation is relatively involved.

 In addition, it is preferably necessary to have two separate measuring devices, one for each of the circles or surrounds of the spectacle frame concerned.

The measuring device also described in the French patent which, filed on November 3, 1982 under
No 82 18385, was published under No 2.535.194, is also particularly simple, since it is reduced to a plate that the operator, in practice a practitioner, such as an optician or optometrist, must superimpose on the circle or entourage of spectacle frame to be equipped, and which has, in addition to a measurement scale, a slot to be aligned with the pupil of the subject for far vision thereof.

 However, for its implementation, this measuring device presupposes satisfactory ambient lighting, sufficient in any case for the production, on the observed eye, through the slit which it comprises, of a luminous line.

 It also presupposes a certain dexterity on the part of the practitioner, who in a way must perform his measurement on the fly.

 The subject of the present invention is an apparatus which, generally speaking, suitable for measuring an ocular parameter on a subject wearing a spectacle frame, allows, with regard to the mounting height, the measurement of which it is more particularly intended, to advantageously obviate the drawbacks succinctly set out above, and which also has other advantages, and in particular that of being able to also allow, if desired, the measurement of the pupillary distance d 'such a subject.

 This device is generally characterized in that it comprises a shoemaker, a feeler, of which an index finger is integral, and which, carried by said shoemaker, is applied against the inner contour of one of the circles or circles of the spectacle frame with which the subject concerned is equipped, at a chosen point in this circle or circle, an observation block which, under the control of a moving command available to the operator, is mounted in said case , and a measurement scale, which also mounted mobile in the case, opposite the integral index of the probe, is linked in movement to the observation block, said observation block comprising, interposed obliquely on a track suitable for allowing the operator to see the subject's eye live, a semi-transparent slide, with, at the back of the latter, that is to say on the side of this slide semi-transparent opposite the subject, a light source capable of forming a reflection on the cornea of said eye it thereof, and a reflector, which, disposed in a substantially conjugate position with respect to this eye, is capable of returning to the semi-transparent plate, and by the latter, to the operator, an image of said source bright.

 Thus, the apparatus according to the invention implements, in a manner known per se, in particular in pupillometers more specially adapted for measuring the single pupillary distance of a subject, the observation of a corneal reflection from a source bright on the concerned eye of such a subject.

 But, as regards, according to the invention, the measurement of an ocular parameter which is not necessarily the pupillary distance of a subject, this light source equips an observation block mounted mobile, with, for appreciate the movement, a measurement scale itself mounted mobile opposite an index secured to a probe.

 With regard to the measurement of a mounting height, it is therefore sufficient, for the operator, after having placed the probe in contact with the lower part of the inner contour of the circle or surrounding concerned with the spectacle frame to be fitted, with move the observation block until it obtains an overlay of the image it sees of the light source with the corneal reflection of it on the subject's corresponding eye for far vision of this subject, and read, opposite the index linked to the probe, on the measurement scale linked to the observation block, the desired mounting height.

 A single operation, in this case moving the observation block, is thus advantageously sufficient to measure this mounting height.

 Preferably, the feeler thus equipping the apparatus according to the invention is pivotally mounted on the housing, around an axis orthogonal to the axis of the observation path, carrying with it the index which is associated with it, and there is further provided, at the disposal of the operator, a trigger, commonly known as a trigger, which is also pivotally mounted on the housing, around an axis orthogonal to the axis of the observation path, and which, inside said housing, carries a brake to which said probe is likely to be subjected, in practice by means of a strip, which, carrying said index, is coupled to it, and in cooperation with elastic means recall that permanently request said trigger in the direction for which said brake is active.

 At rest, the probe is blocked by this brake.

 It is enough for the operator, to release it, and thus make the device operational, to act accordingly on the trigger.

 It then suffices, its observation being made, to release the trigger in its turn, so that, the brake becoming active again, the index linked to the probe is locked in the position which is its during this observation, and that, therefore, the measurement made of the desired mounting height is somehow "frozen" within the device itself.

 The operator can then advantageously raise this mounting height at leisure.

 Preferably, also, the semi-transparent blade that comprises the observation block of the apparatus according to the invention carries a reticle to be aligned, too, with the corneal reflection of the light source on the subject's concerned eye.

 Thus, any parallax error, due to the fact that from one subject to another the distance separating from the eye of such a subject the circle or entourage of the spectacle frame which he wears varies in notable portions, in practice from single to double, is advantageously and systematically avoided.

These characteristics, as well as others, and their advantages, will also emerge from the description which follows, by way of example, with reference to the appended schematic drawings in which
Figure 1 is a perspective view of the apparatus according to the invention
Figure 2 is, on a different scale, a sectional elevation view, one of the two shells constituting the housing of this device being assumed removed
Figure 3 is, on a different scale, an exploded perspective view of all the components of the apparatus according to the invention
Figure 4 is, also on a different scale, a partial view, in elevation-section, of the apparatus according to the invention, illustrating the implementation thereof
Figure 5 is, operator side, a rear view which also illustrates the implementation.

 As illustrated in these figures, and more particularly in Figures 4 and 5, it is, in general, to ensure the measurement of an ocular parameter on a subject wearing a spectacle frame.

 In FIG. 5, the subject is shown diagrammatically by its two eyes 10G, 10D, and, in FIG. 4, by only one of them, in this case the right eye 10D.

 In conjunction, in FIG. 5, the spectacle frame concerned is only represented by its single face 11, and, in FIG. 4, it is only represented by only one of the circles or circles around it, in l 'its right circle or circle 12D.

 It is, more particularly, to measure the mounting height H & respect when installing a corrective lens, and for example a corrective lens with gradually variable focal power, in such a circle or entourage.

 This distance H is the distance separating the low point of the interior contour of the circle or surrounding 12D concerned from the line of sight in far vision VS of the subject.

 In practice, this line of sight in far vision VS is a horizontal.

 In practice, too, 'the mounting height H should normally be assessed by taking into account the depth S of the groove 13, commonly known as a bezel, which the circle or surround 12 presents for receiving the glass which is to equip it.

 The apparatus 15 used according to the invention for measuring such a mounting height H generally comprises a housing 16, which is intended to be manipulated by the operator, that is to say & say the practitioner, optician or optometrist for example, called upon to carry out this measurement, a feeler 17, of which an index 18 is integral, and which, carried by said housing 16, is to be applied against the inner contour of the circle or surrounding 12D concerned, at a selected point thereof, in practice, as indicated above, at the bottom point of this interior contour, an observation block 20 which, under the control of a displacement control 21 at the disposal of the operator, and as shown schematically in broken lines in FIG. 2, is mounted movably in the housing 16, and a measurement scale 22, which, too, is movably mounted in the housing 16, facing the index 18 secured to the probe 17, is linked in movement to the observation block 20, said observation block 20 itself comprising, interposed obliquely on an observation path VO, specified below, suitable for allowing the operator, shown diagrammatically by an eye 28 in FIG. 4, to see live the eye 10D concerned of the subject, a semi-blade transparent 19, with, at the rear thereof, that is to say on the side of this semi-transparent blade 19 opposite the subject, a light source 23 capable of forming a reflection on the cornea of said eye 10D of that -this, and a reflector 24, which, disposed in a substantially conjugate position with respect to this eye, is capable of returning towards the semi-transparent plate, and, by the latter, towards the operator, along the line of sight VP of the latter, an image of said light source 23.

 In the embodiment shown, the housing 16 forms, at its upper part, a generally parallelepipedal box 25, on the front of which, and projecting from which, the observation block 20 is movably mounted, and, at its lower part , it forms, to facilitate handling, a handle 26.

 In practice, for a better ergonomic adaptation, this handle 26 extends slightly obliquely towards the rear relative to the box 25.

 In practice, also, the case 16 is formed of two shells 27A, 27B suitably facing one another and suitably secured to one another.

 In FIG. 2, only the shell 27A is visible, the shell 27B having been assumed to be removed.

 Such an embodiment in two shells of the housing 16 falling within the skill of the art, it will not be described in detail here.

 it will suffice to indicate that, internally, for their relative attachment to one another, at least one of these shells has, from place to place, projecting, own pins each respectively & engaging with additional wells provided for this purpose on the other of these.

 In practice, the shells 27A, 27B thus constituting the housing 16 are not necessarily identical to each other.

 On the contrary, the shell 27B for example may constitute only a cover, the stacking of the various components of the apparatus 15 according to the invention then preferably taking place in the shell Z7.

 The observation block 20 itself comprises a housing 29, which is generally rectangular in shape, with its lower front edge cut down by a chamfer, and which, according to arrangements of the same type as the previous ones, is also formed of two shells 30A, 30B suitably facing one another and suitably secured to one another.

 These two shells 30A, 30B jointly form, at the front, a passage 31, the lower part of which, corresponding to the chamfer cutting down the affected edge of the assembly, is at least partly obscured by the semi-transparent blade 19, and, at the rear, a passage 32.

 These two passages 31, 32 jointly form the observation path VO mentioned above.

 In addition, they enclose transversely both the semi-transparent strip 19 and the reflector 24.

 Preferably, and as shown, the semi-transparent blade carries a reticle 34, which is only visible in FIG. 5 alone.

 It is for example a simple line, which, continuous, or, as shown, interrupted, extends substantially orthogonally to the axis of the observation path VO, assumed here defined by the line of sight in far vision VS of the subject, and, more precisely, orthogonally to the vertical plane containing such an axis.

Preferably also, and as shown, the reflector 24, which is arranged at the top of the observation block 20, above the observation path
VO, is a cylindrical reflector whose generatrices are parallel to the reticle 34 and which therefore, like this one, are orthogonal to the axis of this observation path VO.

 It may, for example, be a plate of stainless steel or of suitably bent metallized synthetic material.

 Anyway, it is arranged in a substantially conjugate position relative to the eye to be observed.

 In other words, by construction, it is made so that the distance separating from the semi-transparent plate 19 the reflector 24 is substantially equal to that separating this semi-transparent plate 19 from the eye to be observed.

 In addition, the radius of this reflector 24 is preferably of the order of 8 nm, the average radius of the cornea of the human eye.

 In the embodiment shown, this reflector 24 extends only over a half of a cylinder, and, by its longitudinal edges, it is taken up with ribs 36 provided for this purpose on the shells 30A, 30B constituting the housing 29 of the observation block 20, at the top of it.

 For its mobility, the observation block 20 is integral with a leg 38, which is slidably mounted in the housing 16, and which carries a rack 39 with which meshes a pinion 40 which is integral in rotation with at least one control button 41 belonging to the moving control 21.

 In practice, for the sliding guide of this leg 38, the shell 27A of the housing 16 has, internally, projecting, suitably staggered along the corresponding sliding direction, lugs 43, which, in pairs, each extend respectively on either side of such a sliding direction.

 In practice, too, this sliding direction, which is parallel to the rear edge of the upper box 25 of the housing 16, extends obliquely, from the rear towards the front, relative to the lower handle 26 of this housing. 16.

 In the embodiment shown, the leg 38 belongs to a bracket 44 on the crosspiece 45 from which is attached the housing 29 of the observation block 20, the shells 30A, 30B constituting this housing 29 each comprising wings 46A respectively. 46B by which they enclose such a cross member 45, with pins 47 engaged with bores 48 of the latter.

 Of course, the shells 27A, 27D of the housing 16 form, jointly, at the upper part of the box 25 thereof, an opening 50 suitable for the passage of the crosspiece 45 of the bracket 44 thus carrying the observation block 20.

 In the embodiment shown, two control buttons 41 are provided, which are each arranged respectively on two opposite faces of the housing 16, one for a right-handed person, the other for a left-handed person, and which are each locked in rotation on the axis 52 of the pinion 40, the latter crossing for this purpose the shells 27A, 27B constituting this housing 16.

 In practice, the jamb 38 of the bracket 44 carrying the observation block 20 carries, back to back, two racks, namely, in addition to the rack 39 with which the preceding pinion meshes, a rack 53, which is not visible that in Figure 2, and with which meshes a return pinion 54, said return pinion 54, whose axis 55 is parallel to the axis 52 of the pinion 40, meshing together with a rack 56 linked to the scale measurement 22.

 The assembly forms a transmission of report 1 so that, to a displacement of the observation block 20, corresponds an equal displacement of the measurement scale 22.

 In practice, the measuring scale 22 is carried by a strip 58, which, in accordance with provisions of the type of the previous ones, is slidably mounted in the case 16, said strip 58 forming by its longitudinal edges lips by which it is engaged. with complementary grooves provided for this purpose on the shells 27A, 27B constituting this housing 16, and which, on one of its faces, its internal face, carries the rack 56, while on its opposite face, its external face , it carries the measurement scale 22.

 Preferably, and as shown, the probe 17 is pivotally mounted on the housing 16, around an axis orthogonal to the axis of the observation path VO.

 it has for this purpose, laterally, pins 60 by which it is articulated to the shells 27A, 27B constituting the housing 16.

 Preferably, and as shown, this probe 17 has, for contact with the inner contour of a circle or circle around the face 11 of the spectacle frame, a finger 61, which is pivotally mounted on its main part 62, around d 'an axis which is orthogonal to its own axis of articulation.

 In practice, to facilitate handling, this finger 61, which projects out of the housing 16, and more specifically out of the upper box 25 thereof, by means of the opening 50 thereof, this opening 50 extending in front for this purpose, door, laterally, available to the operator, two wings 63.

 A probe 17 thus formed is coupled to a strip 65 which carries the index 18 associated therewith and which is slidably mounted in the housing 16.

 For example, and as shown, this strip 65 forms, at its corresponding end, a yoke 66 by which it is engaged with a lug 67 provided projecting at the end of the current part 62 of the feeler 17 opposite its finger 61.

 In addition, in the embodiment shown, this strip 65 is, for its guidance, slidably engaged in a groove 69 provided, ê for this purpose, opposite the measurement scale 22, on the external face of the strip 58 carrying this measurement scale 22.

 Of course, on the rear edge of the housing 16, and more precisely on the rear edge of the lower handle 26 thereof, the two shells 27A, 27B constituting this housing 16 jointly form a window 70 allowing the simultaneous observation of the measurement scale 22 carried by the strip 58 and the index 18 carried by the strip 65, FIG. 5.

 Preferably, and as shown, the probe 17 is also subjected to elastic means which permanently urge it in pivoting downwards.

 In the embodiment shown, these elastic means consist of a torsion spring 71, the median torsion part of which is engaged on a lug 72 provided for this purpose projecting from the internal face of the shell 27A of the housing 16, with the lower part of the handle 26 thereof, and which, by one wing, bears on the corresponding transverse wall of this shell 27A, while by the other, it bears on the lower edge of the strip 65 coupled to the probe 17, by being engaged in a groove 73 provided for this purpose on said edge of this strip 65.

 Preferably, finally, and as also shown, the apparatus according to the invention comprises, at the disposal of the operator, a trigger 75, commonly known as a trigger, which is pivotally mounted on the housing 16, and which, at inside of it, carries a brake 76, in this case a simple buffer of elastic material, to which the probe 17 may be subjected, according to methods described in more detail below, and in cooperation with elastic return means which permanently urge said trigger 75 in the direction for which said brake 76 is active.

 In practice, the brake 76 thus carried by the trigger 75 is arranged in line with the strip 65 coupled to the probe 17, for action thereon, and, so that it has access to this strip 65, the strip 58 on which it is slidably mounted and has, at its base, a notch 78.

 In the embodiment shown, the trigger 75 extends, transversely, over almost the entire internal volume of the housing 16, and, to leave, however, in it, a free passage to the leg 38 of the bracket 44 carrying the observation block 20, it has, in its middle zone, a recess 79.

 In practice, in this embodiment, the trigger 75 has, laterally, for its articulation with the shells 27A, 27B constituting the housing 16, pins 80, and, for operator action, it forms, at its upper part, a key 81 accessible to said operator by means of a passage 82 which, for this purpose, forms the shells 27A, 27B constituting the housing 16.

 The elastic return means associated therewith are constituted, in the embodiment shown, by a spring 84, which, bearing on a lug 85 provided for this purpose projecting from the shell 27A, bears on its lower part.

 A switch being also provided on the supply circuit of the light source 23, this switch is in practice under the control of the trigger 75.

 In the embodiment shown, this trigger 75 carries, for this purpose, at its lower part, a contact blade 87 which, normally separated from an autonomous current source 88, a simple battery for example, for the rest position of the assembly, is applied to this autonomous current source 88 when an action is exerted on the trigger 75.

 Another contact blade 89, carried, like the autonomous current source 88, by the housing 16, ensures, jointly with the previous contact blade 87, and electrical conductors 90 shown diagrammatically in broken lines in FIG. 2, the service of the light source 23.

 This light source 23, a simple diode for example, being, in practice, carried by the crosspiece 45 of the bracket 44 carrying the observation block 20, being for example placed at the end of this crosspiece 45, the electrical conductors 90 are preferably each respectively arranged for their protection in grooves 91 provided, laterally, over its entire height, on the leg 38 of this bracket 44.

 Finally, for contact with a circle or circle around the face 11, the housing 16 of the device according to the invention carries, projecting, at the front of its upper box 25, a support member 92.

 In practice, in the embodiment shown, this support member 92 is in the form of a frame, and, by a sole 93 in the form of a bracket, it is engaged with the shells 27A, 27B constituting the housing. 16, this sole 93 passing through a slot 94 which these shells 27A, 27B form jointly for this purpose.

 In the embodiment shown, the support member 92 has, projecting, pins 95 adapted to firm the seat on the circle or frame of spectacle frame to which it must be applied.

 At rest, that is to say when no action is exerted on the button 81 of the trigger 75, the brake 76 carried by this trigger 75 presses against the corresponding transverse wall of the housing 16, under the bias of the spring 84, the strip 65 carrying the index 18 associated with the probe 17.

 This strip 65 is thus thus locked in position in the housing 16, and it is therefore the same for the probe 17.

 At the same time, the light source 23 is switched off.

 Grasping the housing 16 of the device according to the invention by its lower handle 26, the operator comes to apply against the circle or entourage of spectacle frame to be fitted, in this case a straight circle or entourage 12D, the member d 'support 92 that has for this purpose projecting this housing 16, after having properly oriented the finger 61 of the probe 17 according to the proper geometric contour of such a circle or circle 12D.

 The operator must then press the key 81 of the trigger 75, this operation being able to be carried out just as well before applying the support member 92 against the circle or surrounding 12D concerned.

 By thus acting on the trigger 75, the operator releases the strip 65, and the latter, under the stress of the elastic means constituted by the spring 71 to which it is subjected, moves upwards, carrying with it the probe 17 to which she is harnessed.

 This movement continues until, by the finger 61 which it comprises, this probe 17 comes, by pivoting about its axis, into contact with the low point of the inner contour of the circle or circle 12D.

 The index 18 associated therewith is then stopped in position relative to the housing 16.

 Jointly, the light source 23 being supplied, it is the source of a corneal reflection on the corresponding eye 1OD of the subject concerned, and, through the observation path VO, this corneal reflection can be observed by the operator.

 This corneal reflection has been shown diagrammatically by a point R in FIG. 5.

 Simultaneously, the operator sees, in the form of a single light line, the image T that this cylindrical reflector 24 gives of this light source 23.

 it is then necessary, that by acting on one or other of the control buttons 41, it moves the observation block 20 until it obtains an alignment of the corneal reflection R of the source light 23 and the image T of this light source 23 with the reticle 34 carried by the semi-transparent blade 19.

 This alignment being obtained, the operator releases the trigger 75.

 Under the stress of the spring 84 constituting its elastic return means, this trigger 75 then again locks in position in the housing 16 the strip 65 carrying the index 18.

 The desired mounting height H is then read directly on the measurement scale 22, in line with this index 18.

 By construction, in fact, it is systematically taken into account, for the constitution of the measurement scale 22, not only of the depth g of the bezel 13 that usually includes the circles or surrounds of a spectacle frame for mounting a lens, but also the offset h formed between them, in line with such a circle or frame of spectacle frame, the aiming axis in far vision VS of the subject and the aiming axis VP of the operator due to the fact that the light source 23 is necessarily offset transversely with respect to the assembly.

 Although more particularly intended for the measurement of a mounting height, according to the process described above, the apparatus according to the invention may as well be suitable for measuring the pupillary distance of a subject.

 It suffices for this, by arranging it, no longer vertically, as previously, but horizontally, to proceed, in one direction, to a first measurement on the side of a first of the eyes of this subject, and, in the opposite direction, to a second measurement on the other side of these.

 Of course, the support member projecting from the housing of the device according to the invention must be adapted accordingly.

 For this purpose, this support member is preferably removable, so that, depending on the measurement to be made, there is substituted for it a support member more suitable for the latter.

 The present invention is moreover not limited to the embodiment described and shown, but encompasses any variant.

 In particular, assuming that, for a group of subjects, the distance separating from the eyes of such a subject the face of the spectacle frame which he wears is substantially of the same order for all, it is possible, in a simplified version of the device according to the invention, to eliminate any reticle on the semi-transparent plate reflecting the light source towards the operator, which makes easier the alignment which the latter must ensure during his observation.

Claims (19)

 1. Apparatus for measuring an ocular parameter on a subject wearing a spectacle frame, characterized in that it comprises a housing (16), a feeler (17), of which an index (18) is integral and which, carried by said housing (16), is to be applied against the interior contour of one of the circles or surrounds of the spectacle frame, at a chosen point thereof, an observation block (20), which, under the control of a movement control (21) available to the operator, is mounted mobile in said housing (16), and a measuring scale (22), which, too, is mobile mounted in the housing (16) , facing the index (18) integral with the probe (17), is linked in movement to the observation block (20), said observation block comprising, interposed obliquely on a clean observation channel (VO) to allow the operator to see live the subject's eye concerned, a semi-transparent blade (19), with, at the rear thereof, that is to say on the side of this semi blade -transparent ( 19) opposite the subject, a light source (23) capable of forming a reflection on the cornea of said eye thereof, and a reflector (24) which, disposed in a substantially conjugate position relative to this eye, is capable of returning towards the semi-transparent plate (19), and, by the latter, towards the operator, an image of said light source (23).  2. Apparatus according to claim 1, characterized in that the semi-transparent blade (19) carries a reticle (34) to be aligned with the corneal reflection of the light source (23) on the concerned eye of the subject and the image given from this light source (23) by the reflector (24).  3. Apparatus according to any one of claims 1, 2, characterized in that the reflector (24) is a cylindrical reflector of generators orthogonal to the axis of the observation path (VO).  4. Apparatus according to any one of claims 1 to 3, characterized in that the observation block (20) is integral with a leg (38), which is slidably mounted in the housing (16), and which carries a rack (39) with which meshes a pinion (40) which is integral in rotation with at least one control button (41) belonging to the movement control (21) available to the operator.  5. Apparatus according to claim 4, characterized in that two control buttons (41) are provided, each arranged respectively on two opposite faces of the housing (16).  6. Apparatus according to any one of claims 4, 5, characterized in that the leg (38) which is integral with the observation block (20) carries back to back two racks, one (39) with which meshes the pinion (40), of which at least one control button (41) is integral in rotation, the other (53) with which meshes a return pinion (54), said return pinion (54) meshing together with a rack ( 56) linked to the measurement scale (22).  7. Apparatus according to any one of claims 1 to 6, characterized in that the probe (17) is pivotally mounted on the housing (16), about an axis orthogonal to the axis of the observation path ( VO).  8. Apparatus according to claim 7, characterized in that the probe (17) is coupled a strip (65), which carries the index (18) associated therewith, and which is slidably mounted in the housing (16).  9. Apparatus according to claim 8, characterized in that, the measuring scale (22) being itself carried by a strip (58) slidably mounted in the housing (16), the strip coupled to the probe (17) is slidably engaged in a groove (69) of said strip (58) carrying said measuring scale (22).  10. Apparatus according to any one of claims 7 to 9, characterized in that, for contact with a circle or entourage of the subject's spectacle frame, the feeler (17) has a finger (61) which is pivotally mounted on its current part (62), around an axis which is orthogonal to its own axis of articulation.  11. Apparatus according to claim 10, characterized in that the finger (61) of the probe (17) laterally carries two wings (63) adapted to facilitate handling.  12. Apparatus according to any one of claims 7 to 11, characterized in that the probe (17) is subjected to elastic means (71) which urge it permanently in pivoting downward.  13. Apparatus according to any one of claims 1 to 12, characterized in that the housing (16) forms a handle (26 ?.  14. Apparatus according to claims 4 and 13, taken together, characterized in that the sliding direction of the leg (38) which is integral with the observation block (20) extends obliquely relative to the handle (26) .  15. Apparatus according to claim 7, characterized in that it comprises, at the disposal of the operator, a trigger (75), which is pivotally mounted on the housing (16), and which, inside that -this carries a brake (76) to which the feeler (17) is liable to be subjected, in cooperation with elastic return means (84) which permanently urge said trigger (75) in the direction for which said brake ( 76) is active.  16. Apparatus according to claims 7 and 15, taken together, characterized in that the brake (76) carried by the trigger (75) is arranged in line with the strip (65) coupled to the probe (17), for action on that -this.  17. Apparatus according to any one of claims 15, 16, characterized in that, a switch being provided on the supply circuit of the light source (23), said switch is under the control of the trigger (75).  18. Apparatus according to any one of claims 1 to 17, characterized in that, for contact with the subject's spectacle frame, the housing (16) carries, projecting, a support member (92).  19. Apparatus according to claim 18, characterized in that the support member (92) is removable.