DE2113142A1 - Device for electro-optical determination of the position of a lens - Google Patents

Description

PATENT LAWYERS
Pr. Rer. r-ΰί. Ρ ":: Τ": ΐ LOUIS ΟΙ 1 ΟΙ / -J

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8Ö00 N URN BERQ
KESSlERPLATZ 1

11 726 30 / he SIRA INSTITU (DE, Chisleburst, Kent / Great Britain

Device for electro-optical determination of the position of a lens

The invention relates to a device for the electro-optical determination of the position of a lens, which is a device for emitting a beam onto a surface of the lens to be centered and a receiver for the reflected from there Has radiation. It is intended in particular to determine the decentering of a lens.

In the manufacture of lenses, it is necessary to ^{align the mechanical axis "M w of} the cylindrical edge of the lens in such a way that it is aligned with its optical axis" 0 "(ie the line connecting the centers of curvature of the two radiation-transmissive or reflective surfaces of the lens) This coincidence, called MO coincidence, is achieved by machining the edge of the lens while the lens is moving rotates around its optical axis. As a result, it is still necessary before machining begins to align the optical axis with the axis of rotation "R ¹¹ (0-R coincidence)

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to bring, the axis of rotation "R" passing through the axis of rotation of the rotatable ropes holding the lens during processing is predetermined. If a lens surface is flat, it is optical axis is normal to this flat surface and goes through the center of curvature of the surface with limited Radius. It is said that a curved surface of a lens is centered with respect to an axis, for example the axis of rotation "R", if the center of curvature lies on this axis.

It has already been suggested that the 0-R-Koinsidenζ of a lens to be achieved by attaching the lens to a rotatable, annular holder is attached, which was first adjusted so that its mechanical axis coincides with the axis of rotation. Then the holder is rotated and the image or images * are reflected from one or both surfaces are observed visually. A reflected image is as long as possible

tilt when the optical axis does not coincide with the axis of rotation. Mr den pail the nutation of the picture or pictures will the glue heats up and the lens is then moved or adjusted a little by hand. This process is repeated until the Image or images appear stationary as the holder rotates. Then you leave the glue or the adhesive harden, whereupon the edge of the lens can be machined to create the M-O-Kpinzidenz. With this approach depends

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_; the accuracy of the centering largely depends on the skill and patience of the operator as well as on one's own

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shear off the adhesive or putty. There is also the risk of that the lens will be damaged during manual adjustment of its position on the holder.

To avoid the need for skill and relying on the patience of the operator became the device described in British Patent 1,147,521 developed. This device enables a lens to be centered automatically and does not require a particularly skilled person for operation. However, it is, for example, for smaller manufacturers. Ler optical instruments too expensive, which is why the invention has set itself the goal of an affordable one for this group of people To create device. In addition, the device according to the invention should be able to use them in conjunction with existing forms of rotatable lens holders, such as those described above, in which the lens by means of a putty or the like. Is attached to the holder to use. Close some forms of such lens holder suggested the use of an optical centering system which required postural responsive eotocells each side of the holder. Therefore, the inventive lake Device be designed such that it Ie-

is only to be arranged on one side of a lens holder, the holder itself of course not being part of the invention. The inventive device is designed so that it generates electrical signals which tion a measure for the decentering of the lens can display and serve a display

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instrument »for example a measuring instrument, a scribe or a cathode ray oscillograph to drive, whereby strain on the operator's eyes can be avoided.

In order to achieve the objects explained above, according to the invention proposed in a device of the type mentioned that the receiver both to receive one of a Lens surface directly reflected beam as well as to receive a through this one lens surface passing through, is set up on the inside on the other lens surface reflected beam and at least one radiation-sensitive Has element which signals the position of the reflected rays relative to a reference position generated which indicate the amount of Se centering one or both sides of the lens.

A so-called position-sensitive potentiometer that responds to the position of the incident beam or a corresponding photoelectric device for determining displacements of the image is preferably used as the receiver. Positionally sensitive Io to cells are described in "Instrument Practice" 1965, Vol. 19, page 733 and "Optica Acta", 1968, Vol. 15, Wr. 6,

Page 556, -559 * If the image (s) does not move when the lens holder is rotated according to the \ display of the recipient

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more, O-R coincidence is achieved and the lens can then to achieve the M-0 coincidence. The for

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Electro-magnetic radiation used for measurement can be visible Light, infrared or ultraviolet radiation.

Further features, details and gate parts of the invention emerge from the following description of preferred exemplary embodiments with reference to the drawing.

Pig · 1A and 1B schematically a device in which a photocell is used and requires successive operations to center the lens are first, the one reflected from a surface of the lens to be centered Beam (Fig. 1A) and then the beam reflected from the other surface (Fig. 1B) is scanned will;

Pig. 2. schematically a device for centering

a lens that uses two photocells so that they reflect off both surfaces Beams can be scanned simultaneously and

Pig. 3 is a block diagram of a signal processing unit for use in the devices

according to Fig. 1 and 2 »

In Fig. 1A, a light beam 10 emits from a source 12 and arrives via a lens system 14 and a beam cable 16 on the front surface 20 of a lens 18 to be centered, the

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is adhesively attached to a rotatable lens holder 32. That Light reflected from the surface 20 is passed through the beam splitter 16 onto a position-sensitive potentiometer 22 via a lens system 24 reflects »whose two ropes are adjustable along their axis. In addition, the photocell has an adjustable one Device for generating slight movements in a plane perpendicular to its axis.

As shown in Fig. 1B, a rope of light enters the beam 10 through the front surface 20 of the lens 16 and becomes inside on the rear surface 26 of the lens 18 reflected through the lens and then imaged on the position-sensitive photocell 22 after reflection on the beam rope 16 to become.

Since the light reflected from the front surface 20 is combined by the system 24- into a focal point which differs from the Differs focus of the light reflected from the inner surface of the rear side 26 due to the refraction by the lens 18, the position of the cables of the optical system 24 and the position of the photocell 22 are adjusted in such a way that the photo cell 22 incident light is focused there when the amount is measured by which one of the lens surfaces 20 or 26 is decentered.

A chopper or interrupter 11 is arranged in the path of the beam 10, so that the photocell 22 receives an alternating current signal

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generated.

In use, the position of the cables of the optical system 24 and the position of the photocell are adjusted so that the beam is focused on the photocell, which beam is reflected either from the front surface 20 or the inside of the rear surface 26 of the lens. The holder 32 is rotated, whereupon the signals generated by the photocell 22 indicate the amount by which the centering of the respective surface deviates. If the surface is not centered, the cement or the like, with which the lens 18 is attached to the holder 32, is heated and the lens 18 is displaced so that the surface to be tested is displayed as indicated by the signals generated by the photocell 22 is centered. Since the accuracy with which the lens is displaced depends on the skill of the operator, it may be necessary to change the position of the lens in relation to the holder several times in order to obtain an exact centering of the surface to be tested.

If one surface is centered, the position of the elements of the optical system 24 and the position of the photocell 22 are changed so that the light reflected from the other surface to be centered is focused accordingly on the photocell 22. The second surface is also centered on this as explained above. ■

Once both surfaces are centered, the edge of the lin-

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se are ground to generate the M-O-Koinζidenζ.

The above with reference to Pig. 1A and 1B Device requires a plurality of successive steps to adjust the lens with respect to the holder, while the following referring to Pig. 2 device to be described enables simultaneous centering of the two lens surfaces.

The device described in FIG. 2 has the same parts as the device according to Pig. 1A and 1B, but additionally comprises a beam splitter 16 for reflecting the light reflected from the inner surface of the rear side 26 of the lens 18 via an optical system 24 'onto a second, position-sensitive photocell 22'. The additional beam splitter 16 * allows light reflected from the front surface 20 of the lens 18 to reach the position-sensitive photocell 22 through the optical system 24, which in this exemplary embodiment uses fixed parts. By using two position-sensitive photocells 22, 22 'and two optical systems 24 * 24' assigned to them, signals are obtained which indicate the amount by which both surfaces are decentered. The signals from these two photocells can be given to display instruments, for example measuring instruments with a central zero point or a cathode ray scanner, as will be described below with reference to FIG. 3, so that the operator can place the lens in relation to the holder as described above

while observing the instruments that indicate the position of the lens, the two surfaces of which are being centered. According to the specification in the device according to the Pig. 1A and 1B may also require several relocation processes here before the lens is exactly centered and so a subsequent grinding of its edge to generate the M-O coincidences is made possible.

The optical systems used in the devices according to FIG. 1A, 1B and 2 used, can be designed to accommodate the refraction of different lens surfaces allow the lens 18 generated optical effects.

A device according to the invention can also be used to measure centering errors of lenses. If the OR coincidence of a lens is set, then measuring sensors or gauges can attack the edge of the lens during its rotation to generate an output signal, for example in the form of two amplitudes and a phase difference, which indicates the error of the MO coincidence as a space vector. Such an output signal can be displayed or recorded. On the other hand, when the lens is mounted on it in MR coincidence, the output signals of the photocells indicate the failure of the OM coincidence.

The devices described above can be used in any way for centering lenses, ie they can be used in conventional edge grinding machines in which

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The lens is fixed to a holder by means of a putty or the like, or they can be used in machines which have a special, adjustable table or top, which store the lens for pivoting and shifting so that an O-R coincidence can be achieved without touching the lens.

3hFig.31st a device for processing the signals generated by the photocells 22, 22 is shown, whereby the photocells 22, 22 'can be types which are described on pages .556 to 559 of "Optica Acta" , 1968, Vol. 15, No. 6. If only one photocell 22 is used according to FIGS. 1A and 1B, the connections A, B of the photocell, which emit signals, the difference of which corresponds to the amount by which a surface of the lens is decentered along the X-axis, with a Connected amplifier, which is tuned to the frequency of the chopper or interrupter 11. Connections C, D of the photocell. 22 are correspondingly connected to an amplifier tuned to the interruption frequency in order to obtain an output signal which corresponds to the amount by which the lens surface is decentered along the Y-axis. The output signals of the tuned amplifiers are fed to the X and Y connections of a display device, which has a phase-coherent D emodulators and a low-pass filter for each axis direction, the output of which is then connected to an amplifier which feeds an instrument which indicates the amount to which the Linaan supervisor to be examined

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- 11 is flat relative to the respective axis is decentered.

One derived from all four connections of the potentiometer Reference signal is sent to the reference input of the phase coherent Demodulators for the X and Y channels of the aforementioned display device given so that the sign of the displayed centering error is known.

If the device according to Pig. 2 is used, two reflection channels (1) and (2) according to FIG. 3 are used. The outputs of these two channels can either be switched one after the other to the input of the display device, or a separate display device can be used for the second reflection channel .

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Claims (7)

211 3 U 2 Patent (protection) claims -1? Device for electro-optical determination of the position a lens which means for emitting a beam onto a surface of the lens to be centered and has a receiver for the radiation reflected therefrom, characterized in that the receiver (16, 22, 24) both for receiving a beam reflected directly from a lens surface (20) and for receiving a beam through this one lens surface (20) passing through, reflected on the inside on the other lens surface (26) Beam is set up and has at least one radiation-sensitive element (22) which is the position of the reflected rays compared to a reference position generated corresponding signals that the amount of decentering specify one or both sides of the lens. 2. Device according to claim 1, characterized in that the receiver has an optical system (24) and the radiation-sensitive element has a position-sensitive photocell (22), and the optical system and / or the photocell are adjustable between positions in which either of The front surface (20) of the lens {18} or the inside of the other surface - (26) the lens reflected 2113U2 - 13 -.
Beam is focused on the potocell. 3. Device according to claim 1, characterized in that the receiver has a first and a second optical system (24 »24 ') and the radiation-sensitive element has a first and a second position-sensitive photocell (22, 22), the first optical system (24) from the one surface (20) of the lens (18) reflected radiation on the first photocell (22) while the second optical system (24 ¹ ) focuses radiation reflected from the inner surface of the other surface (26) of the lens © on the second photocell (22 ·) focused. 4. Apparatus according to claim 3, characterized in that the receiver has a beam splitter ( 16 ) for separating the beam reflected from one surface (20) of the lens (18) from that reflected from the inside of the other surface (26) Having beam. 5. Device according to one or more of the preceding claims, characterized in that the device for emitting a beam (10) has a radiation source (12), an optical projection system (14) and a beam splitter (16), the beam splitter Splitter coming from the radiation source and coming through the projection system for imaging radiation to the lens (18) to be centered pass and lets radiation on the photosensitive 109841/1270 2113U2 Element. (22) reflected, which is reflected from one of the surfaces (20, 26) of the lens to be centered. 6. Device according to one or more of the preceding claims, characterized by a display device which is generated by the radiation-sensitive element (22) and indicating the amount of decentering of the surfaces (20,26). Signals. 7. Apparatus according to claim 6, characterized by a breaker or chopper (11) for the cyclical interruption of the radiation striking the lens (18), the display device has circles responsive to the breaker frequency. 109841/1270