DE19530027A1 - Automatic measuring of lens parameters using parallel radiation beam - Google Patents

Abstract

The measurement is carried out in steps. First the parallel radiation beam (SB) penetrates through the front surface of the lens (LX), and following the reversal of the lens, through its rear surface, and impinges after leaving the rear surface of the lens or after the reversal of the lens from its front surface, on a diaphragm (RB). The light passing through the diaphragm impinges on the radiation receiver (EE), which produces a first or a second measurement signal value, determining the distance between the back lens and the image. The parallel radiation beam impinges firstly on a diaphragm (RB) and then penetrates the front surface of the lens under test. The light leaving the rear surface of the lens impinges on the radiation receiver, which produces a third measurement value, determining the focal length.

Description

The invention relates to a method for automatic measurement of lens parameters according to the preamble of the first Patent claim and a device for carrying out the method according to the preamble of the fifth claim.

Lens parameters are used with spectacle lens which is also known as vertex-sizer-meter are determined.

The known devices usually provide readings for Lint, Sphere, Cylinder, Addition and Prism. By way of example, DE-PS 29 34 263 is mentioned here, in which a method and an apparatus for automatic measurement of the vertex values in the main sections toric Eyeglass lenses is described.

In the GERMAN OPTIKERZEITUNG, Heidelberg, No. 9/1980 is the Measuring principle of the automatic crimpmeter Metrolens 11 explained.

However, the known vertex-measuring instruments do not deliver all measured values which are of interest for a lens.

It is therefore the object of the invention, a method and a Device for automatic measurement of lens parameters which provides the measurement of additional lens parameters allows, which are important for the selection of lenses.

This object is achieved by the characterizing Part of the first claim and by the characterizing part of the fifth claim.  

In the method according to the invention for automatic measurement of lens parameters is the lens to be measured, which is a Front surface and a back surface possesses, of a preferential wise monochromatic parallel beams interspersed. The light beam is through a ring aperture in the immediate limited near the lens. The light bundle falls last to a radiation that is spatially resolved at least in one axis receiver, which generates a measured signal value.

According to the invention penetrates in a first and second method stepped the parallel beam through the front surface of the Lens and after turning the lens through its back surface and falls after emerging from the back surface of the lens or after Turning the lens from its front surface onto an aperture. The through the aperture falling light then falls on the Radiation receiver, which a first and after turning the Lens generates a second Meßsignalwert. Hereby the Determination of the two primary readings front and back Back focus.

In the third method step, the parallel rays fall bundle first on a panel and then penetrates through the front area of the lens. The emerging from the back surface of the lens Light then falls on the radiation receiver, which one generates another measured signal value. Through this process step the determination of the primary measured value focal length takes place.

In a fourth method step takes place advantageously a thickness measurement. This measured value is also a primary measured value.

These process steps may also be in a different order done without any influence on the procedure.

With the primary measured values can now advantageously further Secondary measured values are determined by the measured signal values be combined with each other to produce at least another lens parameter.  

An inventive device for carrying out the invention proper method for the automatic measurement of lenses At least in addition parameters require an inventive Blendenschwenkeinrichtung which an aperture before optional or swings behind the lens to be measured.

Alternatively, in the device according to the invention for management of the method for the automatic measurement of lenses parameters in front of and behind the lens to be measured, one each Aperture be attached, which alternately parts of the parallel Hide the beam.

Advantageously, the two diaphragms are used as liquid crystal Arrays executed.

It is also advantageous if on the device a lens turn device is attached.

It is very useful if in the device a device for Thickness measurement is appropriate.

To simplify the determination of the measured values, it is very useful if in the device a device for storage the measured values is present.

The calculation is facilitated if in the device a Device for billing the measured values with each other is.

To represent the determined values, it is advantageous if on the device a device for selective display at least one measured value is present.

The invention will be explained in more detail below by way of example with reference to FIGS. 1-3 of the drawings, wherein further essential features and the better understanding explanatory and possible embodiments of the invention are described thought.

Showing:

Figure 1 is a sketch for determining the vertex refractive power and the rear focal distance.

Fig. 2 is a sketch of the ring diaphragm used;

Figure 3 is a sketch of the alternative determination of the back focal distance.

Figure 4 is a sketch for the determination of the focal length. and

Fig. 5 is a device sketch.

In the apparatus for carrying out the method according to the invention it is a modified according to the invention Automatic Lensmeter with which a series of spectacle lens data, their determination with conventional vertex measuring instruments not or only partly possible.

The following measured variables are determined in detail:

1. rear cut s₁ 2. front cut s₂ 3rd focal length f 4. Center thickness d 5. Rear vertex power S₁ 6. front vertex power S₂ 7. refractive power D 8. refractive index n 9. rear surface power value D₁ 10. front surface power D₂ 11. rear surface radius R₁ 12. front surface radius R₂

In addition, of course, with the device according to the invention In principle, the determination of prismatic and cylindrical effect as well as additions possible. This can doing so with one of the known methods according to the prior art the technology happened.

The measured quantities 1-4 can be determined with the aid of the invention Device can be measured directly and therefore below referred to as primary readings.

The measured quantities 5-12 are explained in more detail with the help of the following calculated relationships from the primary measured values and are therefore referred to below as secondary readings.

Primary readings and secondary readings together give the complete set of measurement results.

If the mentioned calculations are done in the device, so it is necessary that the device has a computer unit with appropriate Memory and input and output options contains.

The rear and the front cut s₁ and s₂ can be determined with an arrangement whose principle is shown in Fig. 1 using a first method. The ring diaphragm RB used in this case is shown in FIG .

From the left side, an axis-parallel beam (SB) impinges on the lens (L _x ) to be measured. Immediately behind the lens (L _x ) is located as close as possible to the apex plane, a ring diaphragm (RB) with a narrow, annular gap, with the radius (r _o ).

Both the lens (L _x ) and the ring diaphragm (RB) are centered on the optical axis (OA).

In principle arbitrary selectable distance (a) is located the receiver plane with a photosensitive diode array (EE).  

The annular shutter (RB) described here and below does not necessarily have to be circular, as shown in FIG . There are in principle other forms conceivable -. Square, ellipse, triangle etc. -

The following for a circular aperture (RB) If necessary, then the considerations would have to Be adapted to circumstances.

If an axis-parallel beam (SB) hits the optical axis (OA) centered arrangement, so is by Ideally located in the apex plane annular aperture (RB) an annular beam (measuring beam) hidden.

Depending on the optical effect of the lens (L _x ) to be measured, this annular beam then flows more or less divergently or convergently toward the receiver plane (EE) and hits there with a correspondingly changed radius (r).

As can be read geometrically with reference to FIG. 1, the following relationship then applies:

With
s₁ = rear cut
r _o = radius d. ring diaphragm
a = distance ring diaphragm (RB) - receiver plane (EE)
= Distance of the measuring beam from the optical axis in the receiver plane.

The distance (r) can be measured in a known manner by means of a diode array (EE), (r _o ) and (a) are devices constant, s₁ can thus be calculated.

In a second method, a somewhat modified measuring arrangement is selected. The arrangement is shown in FIG .

In this case, between the ring diaphragm (RB) and the receiver plane (EE) an auxiliary lens (O) with focal length (f _o ) is introduced so that the image-side focal plane of this lens (O) coincides exactly with the receiver plane (EE).

It can be easily understood from Fig. 3 that, because of the geometric similarity of the triangles F _o , H _o , R and F _x , B, R _o, the following relationship holds:

in which:
s₁ = rear cut
r _o = radius of the ring diaphragm (RB)
r = distance of the measuring beam (SB) from the optical axis (OA) in the receiver plane (EE)
f _o = focal length of the auxiliary objective (O)
F _o = front focal point of the auxiliary objective (O)
F _x '= rear focal point of the sample glass (L _x )
H _o = position of the front main plane of the auxiliary objective (O)
B = position of the ring stop (RB) on the optical axis (OA)
R _o = position of the aperture ring on the ring diaphragm (RB)
R = hypothetical point of intersection of one of F _o coming to the measuring beam (SB) parallel beam with the front main plane of O.

The determination of the front cut s₂ takes place in principle in the same way as the determination of the rear cut wide. However, for this purpose, the spectacle lens (L _x ) must be reversed.

The focal length f can be determined with an arrangement whose principle is shown in FIG. 4.

Similar to the second cut-width method (see above) an axis-parallel beam (SB) from the left on the Meß arrangement.

In contrast to the kerf measurement, however, the ring diaphragm (RB) with the radius (r _o ) is located in front of the spectacle lens (L _x ) to be measured during the focal length measurement.

In this way it is achieved that an axis-parallel distance r _o incoming axis-parallel beam (SB) is deflected by the action of the lens (L _x ) in the image-side main plane so that this beam through the optical axis (OA) in focus (F _x ) of the spectacle lens (L _x ) would cut. However, this does not happen because the beam is previously deflected by an auxiliary lens (O). This auxiliary lens (O) has the focal length (f _o ) and is brought into the beam path so that its rear focal plane coincides exactly with the receiver plane (EE) (diode array).

Because of the geometric similarity of the triangles H, F _x , B, and O, F _o , R, the following relationship now holds:

in which:
f _x = focal length of the spectacle lens (L _x )
r _o = radius of the ring diaphragm (RB)
f _o = focal length of the auxiliary objective (O)
H _o = position of the image-side main plane of the spectacle lens (L _x )
F _x '= rear focal point of the spectacle lens (L _x )
B = intersection of the measuring beam with the bildsei term main plane of the lens (L _x )
O = position of the object-side main plane of the auxiliary objective (O)
F _o = object focal point of Hilfsobjek tive (O)
R = hypothetical point of intersection of one of F _o coming to the measuring beam (SB) parallel beam with the object-side main plane of (O).

r _o and f _o are again known device constants, while r can be determined in a known manner as a measured value with the aid of a diode array located in the receiver plane (EE). With the aid of the specified relationship 3, this results in the focal length f of the spectacle lens (L _x ).

The center thickness d can be either with a commercial Dickentaster determined, and via a keyboard in the device can be entered, or the device itself can be a device for thickness measurement, the measured values directly be stored.

As mentioned in Section 1, the so-called secondary readings can be calculated from the primary readings. The following relationships apply:
(Prerequisite is that all four parameters (s₁, s₂, f and d) are available.)

Rear vertex refractive index S₁

Front vertex power S₂

Refractive index D

Refractive index n

Rear surface power D₁

Front surface value D₂

Rear surface radius R₁

Front surface radius R₂

The above statements are now based on a Example, with the dimensions in square Brackets stand. The following values are the primary measured values measured:

s₁ = 0,1429 [m]
S₂ = 0.1500 [m]
f = 0.1477 [m]
d = 0.004 [m]

From this the following formulas are calculated according to the above formulas Secondary values:

S₁ = 7.00 [dpt]
S₂ = 6.67 [dpt]
D = 6.77 [dpt]
D₁ = 12.62 [dpt]
D₂ = 6.05 [dpt]
n = 1.5536
R₁ = 0.044 [m]
R₂ = -0.091 [m]

It has been described above, as first the cut wide (s₁ and s₂) and then the focal length (f) are measured.

This is a technical problem in so far as for the Determination of the focal length (f) a slightly different measuring arrangement is required as for the determination of the cutting width (s₁ and s₂).

In the first case, the ring diaphragm (RB) must be in front of the lens (L _x ) to be tested, otherwise it must be behind it (compare Fig. 3 or Fig. 4).

So there must be a possibility, the position the ring diaphragm (RB) depending on the intended measurement change. In principle, this can be done by a corresponding Swing mechanism can be achieved.

Another possibility is, for example, the ring aperture (RB) with the help of an LCD array and generate these by a corresponding electrical wiring on or to be switched off.

One can then each such a ring diaphragm (RB) in front of and behind the lens to be measured (L _x ) position and depending on the intended measurement (focal length or focal length) once the front and once the rear ring diaphragm (RB) activate while the other diaphragm (RB) is switched transparent.

Such a measuring arrangement is shown in FIG. 5. The measuring arrangement serves as a device for carrying out automatic measurements of lens parameters.

For this purpose, the measuring arrangement has a radiation source ( 1 ). The light emitted by the radiation source ( 1 ) is parallelized by a first lens ( 2 ) and imaged by a second lens ( 3 ) onto a diaphragm ( 4 ). The divergent light beam coming through the aperture ( 4 ) is then formed by a further lens ( 5 ) into a parallel beam. A filter disc ( 6 ) ensures that the beam limiting diaphragm ( 7 ) a monochromatic parallel beam ( 24 ) falls. (This could also be achieved by an expanded laser beam (eg He-Ne with lambda = 543 nm).)
This monochromatic parallel beam ( 24 ) then strikes an LCD array ( 8 a). If the LCD array ( 8 a) is active, it acts as a ring diaphragm and leaves only a circular ring of the monochrome matic parallel beam ( 24 ). On the other hand, if the LCD array ( 8a ) is switched off, it acts only as a transparent plane plate and the monochromatic parallel beam ( 24 ) strikes directly on the lens ( 9 ) to be tested. Behind the lens to be tested ( 9 ), a second LCD array ( 8 b) is arranged. If this LCD array ( 8 b) is active, it acts as a ring diaphragm and only lets through a circular ring of the radiation beam coming from the lens ( 9 ) to be tested. But if it is switched off, it only acts as a transparent plane plate. Both LCD arrays ( 8 a, 8 b) are always active only alternately in order to carry out the neces- sary process steps for determining the Primärmeßwerte can. (so)

Behind the second LCD array ( 8 b), an auxiliary objective ( 10 ) is arranged, which deflects the beam passing through them onto a receiver plane ( 11 ), in which a light-sensitive diode array ( 22 ) is located. The diode array ( 22 ) can be arranged one-dimensionally. Then, the diode array ( 22 ) but should be rotatable so that a Meßwertaufnahme is possible at different angles. Advantageously, however, the diodes on the array ( 22 ) are arranged two-dimensionally, so that no rotating device for the array is necessary. This also has the advantage that the measured value determination can be done faster.

The measured values obtained by the diode array ( 22 ) are either passed directly to a computer ( 14 ) via an interface ( 15 ) or are first buffered in a memory ( 13 ). The computer ( 14 ) is also connected to the two LCD arrays ( 8 a, 8 b) via the interface ( 15 ).

Measurements determined by the computer ( 14 ) are displayed on a screen ( 17 ) by means of an image screen driver ( 16 ) or forwarded to other devices (eg a printer) via a data transmission line ( 23 ). The input of the desired screen display, the measuring sequence steps and the possibly desired additional data input takes place via an input station ( 18 ) (eg a keyboard).

If the light beam is to fall on the lens ( 9 ) to be measured from the other lens side, then in principle it is possible to leave the lens ( 9 ) to be measured and to turn the measuring arrangement. But it is easier if only the lens ( 9 ) is rotated.

For this purpose, the lens ( 9 ) by a lens rotating device ( 19 ) is rotated out of the beam path (this is easier by turning the lens by hand). The lens rotating device ( 19 ) has a lens holding device ( 19 a) in which the lens to be measured ( 9 ) is held and which is rotatable. In the out-rotated position ( 9 a) of the lens rotation device ( 19 ) opposite the region of the lens ( 9 ) in a by a motor ( 21 ) rotatable receptacle ( 21 a). So that lenses ( 9 ) can be rotated with different diameters, both the lens rotating device ( 19 ) and the motor ( 21 ) with the rotatable receptacle ( 21 a) in the z-direction adjustable bar.

Between the Linsendrehvorrichtung ( 19 ) and the rotatable on acquisition ( 21 a) a Mittendickenmeßanordnung ( 20 ) is arranged. This Dickenmeßanordnung consists of two Meßtastern ( 20 a, 20 b), which are brought to the measurement in the correct Z-axis position and are brought to the lens ( 9 ) until they have a contact with this.

The Mittendickenmeßanordnung ( 20 ), the Linsendrehvorrichtung ( 19 ) and the mounting arrangement for the motor ( 21 ) with the rotatable receptacle ( 21 a) are connected via data lines to the interface ( 15 ) of the computer ( 14 ), so that this all necessary movements can control. In addition, the measured value of the center thickness measuring arrangement ( 20 ) passes into the computer ( 14 ) or into the memory ( 13 ) via the data lines.

The determined measured values, the so-called primary measured values, are stored in the memory ( 13 ). From the primary measured values, the secondary measured values can then be calculated in the computer ( 14 ) as described above.

The described devices (rotation of the lens, thicknesses measuring device, aperture replacement device) are only as to see possible embodiments.

From the known state of the art there are so many different design possibilities of these facilities, that a complete enumeration of the different ext design possibilities of the inventive idea impossible appears.

Alternatively to the device for rotating the lens, in addition to the already mentioned possibility of rotation of the measuring arrangement as such a rotation in the beam path done. Similarly In particular, the motor for rotation in the lens rotation be contained device. The corresponding constructive Changes in the measurement setup are those in the field Specialist (Material Turning Devices).  

The thickness measuring device can also after the known prior art be executed so that only one Probe is necessary (eg in the room movable probe like for coordinate measuring machines, use of a reference system surface, etc.).

The aperture replacement device can, for. B. from a room movable gripper arm with attached to it aperture, from two aperture swivel mechanisms, etc.

In particular, it should be noted that the Dar position in FIG. 5 is a schematic representation, which does not allow conclusions about dimensions or number of components.

The auxiliary lens can, but does not have to be in the beam path be included. Its existence only facilitates the mathematical relationships in the evaluation of the signals the detector array.

Claims (11)

1. A method for the automatic measurement of lens parameters, wherein the lens to be measured (L _x ) with a front surface and a rear surface of a parallel beam (SB) is penetrated, in which the light beam by a brought into the beam path annular aperture (RB) in the immediate Near the lens (L _x ) is limited, the light beam last on a spatially resolving at least in one axis radiation receiver (EE), which generates a measurement signal value, characterized by the following method steps:

• 1. + 2. The parallel beam (SB) penetrates through the front surface of the lens (L _x ) and after turning the lens (L _x ) through its back surface and falls after emerging from the back surface of the lens (L _x ) or after inversion the lens (L _x ) from its front surface onto a diaphragm (RB) and the light falling through the diaphragm (RB) impinges on the radiation receiver (EE), which generates a first or second measured signal value (determination of the cutting widths); and
• 3. the parallel beam (SB) first falls on a diaphragm (RB) and then penetrates through the pre-surface of the lens (L _x ) and the light from the rear surface of the lens (L _x ) emerging light falls on the radiation receiver (EE), which generates a third measured signal value (determination of the focal length).

2. The method according to claim 1, characterized by the following method step:

• 4. there is a thickness measurement of the lens (L _x )

3. The method according to any one of claims 1-2, characterized by the following method step:

• 5. the measured signal values are combined with each other to produce at least one further lens parameter.

4. Apparatus for carrying out the method according to claim 1 of automatic measurements of lens parameters, wherein the lens to be measured ( 9 ) is penetrated by a parallel beam ( 24 ) and passing through the lens ( 9 ) light beam through a placed in the beam path annular aperture ( 8 b) is limited in the immediate vicinity of the lens ( 9 ) and the aperture ( 8 b) is constantly illuminated fully by the parallel beam ( 24 ), wherein the light beam passed through falls on at least in one axis spatially resolving radiation receiver ( 22 ), which generates a corresponding measurement signal, characterized in that on the device a diaphragm replacement device ( 8 a, 8 b) is mounted, which ensures that a diaphragm ( 8 a, 8 b) optionally in front of or behind the lens to be measured ( 9 ) is arranged. 5. Apparatus for performing automatic measurements of lens parameters according to claim 4, characterized in that on the device in front of and behind the lens to be measured ( 9 ) in each case a device ( 8 a, 8 b) is mounted, which alternately in front of or behind the to be measured lens ( 9 ) parts of the parallel beam ( 24 ) hides. 6. Apparatus for performing automatic measurements of lens parameters according to claim 5, characterized in that the two devices ( 8 a, 8 b) are designed as liquid crystal arrays. 7. Apparatus for performing automatic measurements of lens parameters according to any one of claims 4-6, characterized in that on the device a lens turning device ( 19 , 19 a, 21 , 21 a) is mounted. 8. Apparatus for performing automatic measurements of lens parameters according to any one of claims 4-7, characterized in that on the device, a device for thickness measurement ( 20 , 20 a, 20 b) is mounted. 9. An apparatus for performing automatic measurements of lens parameters according to any one of claims 4-8, characterized in that on the device, a device ( 13 ) for storing the measured values is present. 10. An apparatus for performing automatic measurements of lens parameters according to any one of claims 4-9, characterized in that on the device, a device ( 14 ) for offsetting the measured values is present together. 11. An apparatus for performing automatic measurements of lens parameters according to any one of claims 4-10, characterized in that on the device, a device ( 16 , 17 , 23 ) for selectively displaying at least one measured value is present.