DD141722A1 - DEVICE FOR SHARPENING - Google Patents

Description

Applicatio gsgeb iet

The invention relates to a device for focusing optical systems,

Charak teristik de r known technical solution s

In known devices for automatically focusing photographic cameras, lens screens, grids, slotted disks and the like are used to scan the object to be recorded. Like. Application, which are arranged in a Meßstrahlengang before photoreceptors and are offset by an electric motor drive means in rotating or oscillating motion (see, for example, DE-OS 1 547 182, 2 264 253, 2 356 978).

Such devices are very expensive. "Aim of Invention

The invention is intended to reduce the effort required for proper focus adjustment »

2 11 O

Essence of the invention

The object of the invention is to provide a device for focusing optical systems with a light modulator, soft at high interference. ensures a low demand for space and electrical energy and is therefore particularly applicable in photographic cameras «

According to the invention this object is achieved in that the light modulator is formed by a rigidly arranged, a moving grid simulating electro-optical Y / andler «, Preferably, the electro-optical converter consists of a liquid crystal system and the spatial frequency of the grid is through the arrangement the control electrodes of the system and their temporally successive control of a clock generator determined.

Ausführu n gsbeispiel

The invention will be explained in more detail below with reference to exemplary embodiments illustrated.

Pig · 1 light modulator according to the invention

Schematic measuring beam path with two-light modulators

Control circuit group arrangement Arrangement example of the control electrodes in a double light modulator Pig. 5a-c Top view of control electrode arrangement.

1 is located between two glass plates 1, 2, a surface electrode 3 "beam electrodes 4 and an optically active liquid 5" marked transparent electrodes are legbaro via terminals 6, 7 to a control voltage

FIG. 1 Fig * 2 Pig. 3 Pig. 4

211 053

In Fig, 2 are on both sides of a target focus plane 8 of a Meßstrahlenganges ever a light modulator according to Pig. 1 arranged. With 9 is an imaging optics and 10 denotes a photoreceiver. :

In order to scars as little external connections as possible for technological reasons, the control electrodes within the electro-optical Y / andlers can be combined into groups according to FIG. 3 and connected to outwardly guided terminals 11-14. By means of suitable clock circuits, rasters with different spatial frequencies can thus be simulated.

In Fig. 4, a double light modulator is shown, which consists of a liquid crystal system with the electrodes 3 »4 and another liquid crystal system with the control electrodes 15, 16 and the glass plate.

In the case of an electrode progression according to FIGS. 5a-c, rotating or "oscillating grids can be reproduced without the light modulator as such having to be moved by a drive device.

The mode of action is the following:

The Lichtdurciilässigkeit the liquid of liquid crystal systems can be known to be changed by generated between the surface electrode 3 and the beam electrodes 5 electric fields. When the field is applied, the liquid is transparent, in the absence of field it is opaque * So if one puts on the terminals 7 as shown in FIG. 1 temporally one after the other via a timing generator, not shown voltages, the liquid is 5 strips one after the other translucent. ,

4 21 ί 053

Due to this fact, if, according to Pig. 2 in the optically active liquid dependent on the image to be focused illuminance distribution, ζ. B. a chiaroscuro edge, projected, converted at applied control voltages, the local Beleuchtnngsstärkeverteilung in a temporal function. The degree of modulation of the electro-optical converter passing through the light stream is a puncture of the local steepness äes illuminance transition and. thus a puncture of the focus of the image. In the case of blurred adjustment, that is to say in the case of a flat brightness change in the image content, the change in the light current per unit of time is small; in the case of a steep brightness change, it is large. The photoreceiver 10 thus registers the same brightness distribution as behind a mechanically oscillating screen. The signals emitted by the photoreceptor are amplified in a known manner to drive a focus display or a lens-setting device.

In order to obtain a focus signal, which is also the sign after unambiguous, according to FIG. 2, two light modulators according to the invention, the z. B »according to Pig. 4a can be formed, rigidly arranged at the same distance in front of and behind the desired focus plane 8. The photoreceiver 10 is consequently subjected to a change of light mixture when the control electrodes of both liquid systems are driven with different frequencies. The signal leaving the photon receiver thus has the two fundamental frequencies as well as their harmonics. The respective degrees of modulation are a puncture of the existing defocusing. After filtering out the fundamental waves, the voltages are fed to a voltage discriminator ₉

ZIl U

at the output of which defocusing a positive or negative Pokussiersignal is removable ·

The light modulator must be arranged symmetrically to a corresponding target focal plane. It is therefore possible to form the liquid crystal system with its transparent electrodes as an integral part of the viewfinder lens. With such an arrangement, additional signals for the camera user can be made visible by z. B. a complete or partial blanking of the liquid crystal surface is done to indicate the end of the focus or Mchtmöglichkeit an exact focus.

As electro-optical converters with low control energy requirements can equally apply to systems whose altered light transmission based on the rotation of the polarization plane or on the basis of a controllable scattering effect.

Claims (5)

Pat entanspruch 1e device for focusing optical systems of preferably photographic cameras, in which a light modulator is arranged in a the illumination intensity distribution of the image of a male object photoelectrically evaluating Meßstrahlengang, characterized in that the light modulator of a rigidly arranged, a moving grid simulating electro-optical converter formed becomes· 2. Device according to item 1, characterized in that the electro-optical converter consists of a known liquid crystal system and that the spatial frequencies of the grid is determined by the arrangement of the transparent control electrodes and their temporally successive control of a clock generator » 3 · Device according to point 3, characterized in that the control electrodes are grouped together within the electro-optical converter » 4. Device according to item 1, characterized in that the electro-optical transducer is associated with a desired focus plane and is preferably an integral part of a viewfinder field lens « 5 · Device according to item 1, characterized in that in front of and behind a target sharpness level of the measuring beam path in each case a rotating or oscillating grid simulating electro-optical 'dealer is arranged. verifiable calculations.