DE102008028121A1 - Lens's centering error determining method, involves measuring displacement of energy center of gravity of image of blind on sensor during rotation of lens, and determining error of lens from value of displacement of centre of gravity - Google Patents

Abstract

The method involves supporting a lens (100) on a lens retainer, and rotating the lens through a drive roller (216). A light source (220) is focused on a blind (224), and another blind (226) is arranged behind the formed blind in a light direction. An image-giving sensor (232) e.g. charge-coupled device camera, is arranged behind a third blind (230) in the direction. A displacement of an energy center of gravity of an image of the latter blind on the sensor is measured during the rotation of the lens, and a centering error of the lens is determined from the value of the displacement. An independent claim is also included for a device for determining a centering error of a lens through optical scanning of a lens surface.

Description

Field of the invention

The The invention relates to a method for determining the centering error a lens by means of a device for optical probing the Lens surface.

A lens 100 (please refer 1A ) has a centering error (also called decentering the lens) when geometric axis 102 and optical axis 104 tilted against each other. The geometric axis 102 a lens 100 is defined by the symmetry axis of the lens edge 106 , The optical axis 102 arises z. B. in lenses 100 , whose two lens surfaces 108 . 110 Spherical surfaces are, from a straight line through the two centers of curvature of the spherical lens surfaces.

The centering error of a single lens surface K (see 1B ) with respect to the desired state K 'is defined by the center of curvature Δb or by the tilt Δθ = Δb / r (r = surface radius) of the vertex normal with respect to the geometric axis B. The crest normal is a normal on the surface at the intersection with the geometric axis B.

centering arise during edge processing of a lens. He is a manufacturing defect.

State of the art

In a known device of the aforementioned type ( DE 3407074 C2 "Device for measuring the distance and the tilting") an optoelectronic scanning device is described in which a light beam at an angle not equal to 90 degrees impinges on a surface to be touched. In this case, a point-shaped light source is focused on the desired position of the surface by an optical system and reflected in a further optical system. The further optical system focuses the reflected light beam into a spatial filter plane. An evaluation circuit detects the lateral deflection of the light spot. This makes it possible to determine a tilt or positional shift of the surface to be touched. The evaluation circuit has a uniaxial position-sensitive photodetector for this purpose.

Also in another known device ( US 4,936,676 "Surface Position Sensor"), such a device is disclosed, but with features for the different treatment of highly reflective or diffuse surfaces. The evaluation circuit described also has for this purpose only a single-axis position sensitive photodetector (PSD).

task

task The invention is the determination of the centering error of individual lenses as well as of cemented components by op tical probing of the lens surface to realize time-saving.

solution

These Task is by the inventions with the characteristics of the independent Claims solved. Advantageous developments The inventions are characterized in the subclaims. The wording of all claims hereby by reference to the content of this description. The invention also includes all meaningful and especially all mentioned Combinations of independent and / or dependent Claims.

in the Below individual process steps are described in more detail. The steps do not necessarily have to be in the specified Order to be performed, and the procedure to be described may also have other, unspecified steps.

at the inventive method for determining the centering error of a lens by means of an optical device Touching the lens surface is the first to be tested lens stored on a lens mount.

In In a further step, the lens is rotated by a drive.

A Light source is focused on a circular first aperture.

In Light direction behind the first aperture, a second aperture is arranged. This second aperture has a larger aperture on as the first aperture.

In In a next step, the light is at an angle with a first optical system on the surface of the focused lens to be tested.

From the surface of the lens to be tested becomes the Reflected light into a second optical system.

Of the Focus of the light on the lens surface is in the second optical system on a circular third aperture displayed.

In the light direction behind the third diaphragm, an imaging sensor is arranged such that the sensor is in the plane of a real image of the second aperture.

When The next step is a shift of energy focus the image of the second aperture on the imaging sensor during measured the rotation of the lens. Because is a tilt of the Surface of the lens to be tested the axis of rotation of the lens before (see below), so leads this to a periodic change in the surface angle and displacement of the surface in the direction of the major axis Z of the facility (see below). This can be due to the resulting Displacement of the energy focus of the image of the second aperture be recognized on the imaging sensor.

Finally becomes from the size of the shift of the energy focus the centering error of the lens to be tested determined. at The rotation of the lens is the magnitude of the energy center shift a measure of the tilt of the lens relative to its axis of rotation.

Especially advantageous is the combination of the reflective imaging device with the imaging sensor. This combination of reflex imaging device with an imaging sensor that allows for the method according to the invention also methods of image processing can be applied. Therefore, the third behind Aperture arranged imaging sensor preferably a CCD area camera.

The Adjustment settings, in particular in the direction of the main axis Z (see below) is facilitated by the imaging sensor.

Advantageous is also that of the lens to be inspected the lens data need not be known.

From It is particularly advantageous that the procedure for determining the centering error is relatively fast. The invention allows it, that due to the design-related set-up, for example, three Lenses can be measured in less than five minutes. The measurement of three lenses of the same design can already be realize in less than a minute. In previously known devices, however required the centering error measurement of three different lenses Due to long set-up times approx. 30 minutes for execution.

For the invention, there are other applications, such. B. measuring of surface heights.

In an advantageous embodiment of the invention, the second aperture on the form of a gap. Also, the second aperture in another advantageous embodiment, the shape of a Have cross.

• a) einer Linsenaufnahme, auf der die Linse gelagert wird;
• b) einem Antrieb, der die Linse dreht;
• c) einer Lichtquelle und Mitteln, die Lichtquelle auf eine kreisförmige erste Blende der Vorrichtung zu fokussieren;
• d) einer zweiten Blende, die in Lichtrichtung hinter der ersten Blende angeordnet ist, d1) wobei die zweite Blende eine größere Blendenöffnung als die erste Blende aufweist;
• e) einem ersten optischen System, welches das Licht unter einem Winkel auf die Oberfläche der zu prüfenden Linse fokussiert;
• f) einem zweiten optischen System, in welches das Licht von der Oberfläche der zu prüfenden Linse reflektiert wird;
• g) einer dritten Blende 230, auf welche der Fokus des Lichtes auf der Linsenoberfläche 206 durch das zweite optische System (228) abgebildet wird;
• h) einem bildgebenden Sensor, der in Lichtrichtung hinter der dritten Blende angeordnet ist; h1) wobei der bildgebende Sensor in der Ebene eines reellen Bilds der zweiten Blende angeordnet ist;
• i) Mitteln, eine Verlagerung eines Energieschwerpunktes des Bilds der zweiten Blende auf dem bildgebenden Sensor während der Rotation der Linse zu messen; und
• j) Mitteln, aus der Größe der Verlagerung des Energieschwerpunktes den Zentrierfehler der zu prüfenden Linse bestimmt.

The object is also achieved by a device for determining the centering error of a lens by optical scanning of the lens surface with:

• a) a lens mount on which the lens is stored;
• b) a drive which rotates the lens;
• c) a light source and means to focus the light source on a circular first aperture of the device;
• d) a second diaphragm, which is arranged in the light direction behind the first diaphragm, d1) wherein the second diaphragm has a larger aperture than the first diaphragm;
• e) a first optical system which focuses the light at an angle on the surface of the lens to be tested;
• f) a second optical system in which the light is reflected from the surface of the lens to be tested;
• g) a third aperture 230 on which the focus of the light on the lens surface 206 through the second optical system ( 228 ) is mapped;
• h) an imaging sensor disposed in the light direction behind the third aperture; h1) wherein the imaging sensor is arranged in the plane of a real image of the second diaphragm;
• i) means for measuring a shift of an energy center of gravity of the image of the second aperture on the imaging sensor during rotation of the lens; and
• j) means, determined from the size of the displacement of the energy center the centering error of the lens to be tested.

Further Details and features will become apparent from the following description of preferred embodiments in connection with the dependent claims. Here, the respective features alone or in combination with each other be realized. The possibilities to solve the task are not limited to the embodiments.

The Embodiments are schematic in various figures shown. Identical reference numbers in the individual figures designate the same or functionally identical or with regard to their functions corresponding elements. In detail shows:

1A a schematic representation of a lens with centering error;

1B a schematic representation of Definition of the centering error of a lens;

2 the optical design (schematic) for the Zentrierfehlermessung a lens;

3 the principle of lens recording when measuring lenses with only one centering error (surface tilt error);

4 The principle of lens recording when measuring lenses with two Zentrierfehlern (surface tilt error).

The optical setup for the centering error measurement on a lens 100 with two centering errors (surface tilt errors) is in 2 shown schematically. The measuring device 200 includes two separate optical systems (measuring heads) 202 and 204 for the respective measurement of the centering error of the specimen surfaces 206 respectively. 208 , The measuring arrangement 200 has a major axis "Z".

The lens to be tested 100 is on a lens holder 210 (Support ring) stored. The lateral surface (edge) 214 the lens 100 (please refer 3 ) is from the right by a spring-mounted drive roller 216 to a left V-shaped plant 218 pressed, which also to the lens holder 210 belongs. The V-parts are clamped to a dovetail rail with a screw and are also adjusted in height. The carrier of the V-shaped plant 218 can be adjusted for adjustment to a specific lens diameter. V system 218 and drive roller 216 are possible on the lower part of the cylindrical lens edge 214 to adjust the V-system 218 slightly higher than the drive roller 216 , whereby a lifting of the lens from the support ring 210 is avoided.

The drive roller 216 , which is driven by a motor, offset the lens 100 that are on the recording ring 210 is in a rotational movement.

The axis of rotation around which the lens 100 by the action of the drive roller 216 turns coincides with the geometric axis of the lens. It is not necessarily identical to the direction of the main axis Z of the measuring device 200 ,

she can coincide with the major axis Z as well as opposite the major axis Z tilted.

For determining the centering error of the lens surface 206 becomes a light source 220 in a first optical system 222 (Projector) of the measuring device 200 on a circular first aperture 224 focused. In the light direction behind the first panel 224 is a second aperture 226 with a larger aperture than the first aperture 224 arranged. The light from the projector 222 is at an angle to the surface 206 the lens to be tested 100 (Examinee) focused. The light gets off the surface 206 the lens to be tested 100 in a second optical system 228 (Receiver) reflected. In the second optical system 228 becomes a first focus of the light from the lens surface 206 on a circular third aperture 230 displayed. In the light direction behind the third aperture 230 will be in a real picture of the second aperture 226 a photoelectronic imaging sensor 232 (Preferably, a CCD matrix camera) arranged such that the sensor by means of a in the image of the second aperture 226 located surface 234 a shift of an energy center of light during the rotation of the lens 100 detects if the probed lens surface has a surface tilt error with respect to the geometric axis.

The shift of the energy focus of the light is caused by a shift of the tilted surface 206 in the direction of the major axis Z during the rotation of the lens 100 generated. This shift of the surface 206 detects the imaging sensor (CCD area camera), thereby enabling the determination of the displacement of the surface 206 the lens 100 in the direction of the main axis Z. The radius of the striking circle or the size of the displacement of the energy center is a measure of the centering error 236 the lens to be tested 100 ,

For measuring the centering error of the lens surface 208 the lens 100 is an identical but separate measurement of the centering error with the second optical system (measuring head) 204 executed.

At the in 3 shown lens holder (receiving ring) 210 is the lens 100 preferably on the surface 208 take. The spherical or plane lens surface 208 (but in this case not to be tested surface) of the lens 100 lies on the replaceable support ring 210 on. The bearing edges of the bearing rings used 210 For this purpose, they are precisely made of plastic. The support rings 210 must be chosen appropriately for the test specimens.

The Lens 100 should be as close to the edge on the ring 210 rest. Small lenses (Ø <40 mm) should be sucked in for secure support. The adjustable pressure (negative pressure) is to be adjusted so that the lens 100 through the drive roller 216 still rotate evenly. For larger heavier lenses, suction is not required.

The lateral surface (lens edge) 214 the lens 100 is located on the left V-shaped two-point system 218 (not shown).

The recording of lenses with two surface tilt errors to be measured is in 4 shown. This is the lens 100 with the plane surface 400 on the support ring 210 placed. The lateral surface (lens edge) 214 the lens 100 is like in 3 on the left arranged V-shaped two-point system 218 (not shown).

As described above, the measuring method is identical to that in FIG 2 However, it is described with the upper and lower measuring head 204 executed. It should be noted that the measurement with the upper measuring head 202 for the upper Linsenflä surface 206 and measuring with the lower measuring head 204 for the lower lens surface 208 two completely separate measurements.

The height adjustments along the main axis Z for both measuring heads 202 . 204 They are separated, because they are independent of each other. In a specific measurement process, you set the focus of the upper head 202 on the upper lens surface 206 and the focus of the lower head 204 on the lower surface 208 one. Thereafter, no more refocusing is required with a lens change within the same design.

It is also possible to use both lens surfaces 206 . 208 to measure simultaneously and the measurement results with the rotation angle of the lens 100 to combine. The result is the lens tilt error with the associated azimuths.

At the Measuring commutes the image of the second aperture on a CCD area camera associated with the display screen synchronously with the lens rotation. Based a scale becomes the sum of the images swept by the image Intervals as a measure of the centering error in angular minutes shown.

100

lens

102

geometric axis

104

optical axis

106

lens edge (Lateral surface)

108

lens surface

110

lens surface

200

Measuring device

202

Measuring head

204

Measuring head

206

lens surface

208

lens surface

210

lens holder (Support ring)

214

lateral surface (Lens edge)

216

capstan

218

V-shaped investment

220

light source

222

first optical system (projector)

224

first cover

226

second cover

228

second optical system (receiver)

230

third cover

232

imaging Sensor (CCD sensor)

234

Sensor interface in the picture of the second aperture

236

Flächenkippwinkel

240

plane surface a lens

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• DE 3407074 C2 [0005]
• US 4936676 [0006]

Claims (6)

Method for determining the centering error of a lens ( 100 ) by means of a device for optical scanning of the lens surface, comprising the following steps: a) the lens to be tested ( 100 ) is placed on a lens mount ( 210 ), b) the lens ( 100 ) is powered by a drive ( 216 ) turned; c) a light source ( 220 ) is placed on a circular first aperture ( 224 ) focused; d) in the light direction behind the first diaphragm ( 224 ) is a second aperture ( 226 d1), the second diaphragm ( 226 ) has a larger aperture than the first aperture ( 224 ) having; e) the light is at an angle with a first optical system ( 222 ) on the surface 206 the lens to be tested ( 100 ) focused; f) the light is emitted from the surface ( 206 ) of the lens to be tested in a second optical system ( 228 reflected); g) in the second optical system ( 228 ) the focus of the light on the lens surface ( 206 ) on a circular third aperture ( 230 ) shown; h) in the light direction behind the third diaphragm ( 230 ), an imaging sensor ( 232 ) arranged; h1) wherein the imaging sensor 232 in the plane ( 234 ) of a real image of the second aperture ( 226 ) is arranged; i) a shift of an energy center of gravity of the image of the second diaphragm ( 226 ) on the imaging sensor ( 232 ) during the rotation of the lens ( 100 ) is being measured; and j) from the magnitude of the shift of the energy center, the centering error of the lens to be tested ( 100 ) certainly. Method according to the preceding claim, characterized in that the second diaphragm ( 226 ) has the form of a gap. Method according to claim 1, characterized in that the second diaphragm ( 226 ) has the shape of a cross. Device for determining the centering error of a lens ( 100 ) by optical probing of the lens surface ( 206 ) with: a) a lens mount ( 210 ) on which the lens ( 100 ) is stored; b) a drive ( 216 ), the lens ( 100 ) turns; c) a light source ( 220 ) and means, the light source on a circular first aperture ( 224 ) of the device ( 200 ) to focus; d) a second aperture ( 226 ) in the light direction behind the first diaphragm ( 224 ), d1) the second diaphragm ( 226 ) has a larger aperture than the first aperture ( 224 ) having; e) a first optical system ( 222 ), which directs the light at an angle to the surface of the lens to be tested ( 100 ) focused; f) a second optical system ( 228 ) into which the light from the surface ( 206 ) of the lens to be tested ( 100 ) is reflected; g) a third aperture ( 230 ), to which the focus of the light on the lens surface ( 206 ) by the second optical system ( 228 ) is mapped; h) an imaging sensor ( 232 ) in the light direction behind the third diaphragm ( 230 ) is arranged; h1) wherein the imaging sensor ( 232 ) in the plane ( 234 ) of a real image of the second aperture ( 226 ) is arranged; i) means, a shift of an energy focus of the image ( 234 ) of the second diaphragm ( 226 ) on the imaging sensor ( 232 ) during the rotation of the lens ( 100 ) to eat; and j) means, from the magnitude of the displacement of the energy center, the centering error of the lens to be tested ( 100 ). Device according to the preceding claim, characterized in that the second diaphragm ( 226 ) has the form of a gap. Device according to claim 4, characterized in that the second diaphragm ( 226 ) has the shape of a cross.