DE1081306B - Photoelectric exposure meter or controller for photographic or cinematographic cameras - Google Patents

Description

The invention relates to a light meter or regulator for photographic or cinematographic Recording cameras.

It is known to have one or more factors influencing exposure on the directional springs of the im To allow the circuit of the photo element lying measuring mechanism to act.

This method is structurally simpler than the known methods of the whole rotatable measuring mechanism or the regulation of the photocurrent by electrical resistors.

The principle of the directional spring influence also includes others that have not yet been recognized Advantages, the recognition of which according to the invention for the application of this principle in connection with nuclear magnetic measuring mechanisms leads.

The known exposure regulators with means for influencing the photocurrent work according to the so-called fixed value method, whereby one uses variable resistors or diaphragms in front of the photo element.

A constant working point of the measuring mechanism is used here. That is why the scale characteristic is uninteresting with this method. The non-linear relationship between the Luminance and the photocurrent are determined by a special characteristic of the rheostat or compensated for by appropriate control of the photo element diaphragm.

The fixed value method has the disadvantage that for a high initial light sensitivity of the exposure meter or regulator must be worked with a very small fixed photocurrent value. This gets one has a very small pointer deflection for all values, and on the other hand must always be close the zero point can be worked, where friction errors and other discontinuities strongly in the measurement result enter. However, if a large fixed current value is used in order to avoid these deficiencies, see above this is done at the expense of the initial sensitivity to light.

The shortcomings of the fixed value method are avoided by such arrangements that are based on the full pointer deflection principle work, so do not have any means that affect the photocurrent. Known methods for this are the tracking pointer principle or the method of adjusting the measuring mechanism, which is rotatably mounted in its entirety. When applied of these methods, however, the scale characteristics of the measuring mechanism must no longer apply an operating point is worked, can be influenced so that for each interval of the to be measured Luminance results in a sufficiently large change in the pointer deflection. With external magnetic measuring mechanisms this is possible by arranging additional poles.

Photoelectrisctier light meter

or regulator for photographic or

cinematographic recording cameras

Applicant:

VEB Feinmeß Dresden,
Dresden-N23, Kleiststr. 10

Erich Hahn, Dresden,
has been named as the inventor

If you want to because of the small dimensions, in particular Use a nuclear magnetic measuring mechanism for built-in exposure meters or exposure regulators, influencing by additional poles is not possible.

In the case of the magnetic core measuring mechanism, the induction in the air gap proceeds according to the sine function (homogeneous Field and uniform air gap provided).

By changing the angle between the zero position of the moving coil and the direction of magnetization of the core, the scale characteristics known to be changed within wide limits. Depending on the choice of the angle between Zero position of the coil and the direction of magnetization of the core can reduce the maximum induction in the Air gap and thus the maximum sensitivity of the measuring mechanism at every point in the angular range of the Pointer deflection. However, as with the external magnet mechanism, it is not possible to use the scale progression to be designed in such a way as it is necessary from the photocurrent characteristics of the photo element results in the usual internal resistance of the measuring mechanism of approx. 1000 to 3000 Ω, namely high initial sensitivity, then a sharp decrease in sensitivity and after the end of the pointer deflection it increases again an increase in sensitivity.

In order to achieve high initial light sensitivity of the exposure meter or regulator, the The maximum sensitivity of the measuring mechanism must be placed at the start of the scale. Because of the sinusoidal This results in the course of the induction in the air gap at the end of the scale a strong compression of the intervals.

009-508 / 126

Ks are various measures to admit the strong compression of the intervals at the end of the scale avoid, such as grindings on the core magnet or unequal magnetization, tlm one of the sinusoidal shape to achieve different field distribution. However, these measures bring a noticeable effect in any case Loss of the initial sensitivity of the measuring mechanism.

The invention consists in that in a light meter or regulator with a moving coil measuring mechanism, its pointer deflection according to one or more exposure factors by pivoting the counter bearing of the directional spring is influenced around the axis of the moving coil, "as a measuring mechanism a core magnet system and its pointer is used in the entire measuring range with a setting mark fixed to the housing in such a position of the measuring mechanism coil is brought to congruence, this wctisich in the area of Maximum induction is located. "This enables all the advantages of the fixed-value method and the full-scale method exploited and their disadvantages avoided.

In an arrangement according to the invention, the measurement is always adjusted to the same position of the coil in the air gap, ie always the same working point in the air gap ^; -used. This means that you are independent of the intrinsic characteristics of the measuring mechanism. ^l "

The torque of the straightening springs is proportional to the twist angle and thus also the twist angle proportional to the current flowing through the moving coil. The sensitivity is in all Points equal to the maximum sensitivity in the direction of magnetization.

The two straightening springs of the Kernmagnetmeßwerkes are connected according to the invention by a bracket and thus adjusted together. The pivoting movement of this bracket is achieved by adjusting the the exposure influencing setting elements (aperture, exposure time, film speed) generated, whereby expediently these adjusting members on the bracket via a differential gear known per se works.

In order to adapt to the different characteristics of the photo elements, the movement of the adjusting elements is not transmitted directly, but with the interposition of a correction curve.

Only a small deflection range is required to set the pointer to the mark fixed on the housing of the pointer to be visible. The invisible part of the deflection area can be prevented by pointer stops be suppressed. This makes it possible to accommodate a larger number of intervals or to enlarge the intervals, the pivoting angle of the bracket connecting the straightening springs to make greater than 90 ° without the risk of the coil overshooting the neutral zone addition and thus a stop in the opposite direction.

As in the measuring mechanisms used for the exposure meters or controllers, the resistance of the moving coil generally has the size of 1000 to 3000 Ω, increases with increasing brightness The photocurrent increases more than it corresponds to the scale characteristic proportional to the current. To this one To compensate for errors, the resistance of the outer circle of the photo element can be increased to such an extent that that, for the geometric series of brightness values, there is an approximately linear increase in the photocurrent results, for example by a series resistance of about 15 to 25 kΩ.

However, according to a further feature of the invention, the exposed light to be measured can also be used Reduce the area of the photo element by means of a diaphragm so that the geometric A series of brightness values to be measured results in a linear increase in the photocurrent. The aperture will controlled by a curve which is coupled to the bracket connecting the straightening springs. Through this is compared to the fixed value principle

ίο working aperture control still has the following advantage in addition to the advantages already outlined above:

With the aperture control, which works according to the fixed value principle, the photocurrent is used for all measured values is reduced to a value equal to the initial measured value. That means that if with small photocurrent fixed value, so high initial sensitivity is worked, the opening of the Photo element diaphragm becomes extremely small at high brightness. Is the fixed photocurrent value about 2 μΑ and the illuminance on the photo element about 5000 Ix, the diameter is the opening about 1 mm. The change in diameter for the next level of brightness to be measured is then only about 0.2 mm. So it is a matter of orders of magnitude that are within the tolerances of the devices go under. In addition, in the case of the small diameters, there are also the scattering due to the inhomogeneous ones Photosensitivity of the surface of the photo element.

If a large fixed photocurrent value is used, the conditions with regard to the aperture are reduced cheaper at high brightness, but the initial sensitivity to light is missing here.

The known fixed value method with photo element diaphragm therefore has deficiencies in addition to the deficiencies mentioned at the beginning nor that of the limited scope of measurement.

In the arrangement according to the invention, this deficiency is also eliminated by the opening of the photo-element diaphragm with increasing brightness only needs to be reduced so far that, as already, mentions an increase in the photocurrent for the increase in the brightness to be measured in a geometric series results in arithmetic series, consequently the scope of measurement is not restricted in any way.

Two exemplary embodiments of the inventive concept are shown in the drawing.

Fig. 1 shows a semi-automatic light meter for a cinematographic recording camera without a photo-element shutter;

2 shows a semi-automatic exposure regulator for a cinematographic recording camera with additional photo element aperture.

In the embodiment according to FIG. 1, the lens aperture setting is 1, the frame rate setting 2 as well as the setting 3 to take into account the film speed over a in its effect known differential gear, consisting of gears 4, 5, 6 and 7, with a cam disk 8 coupled. This acts on a pin 9 which is attached to a bracket 10. The bracket 10 that the Directional springs 13 of the measuring mechanism coil 14 connects, has lugs 12 on which the directional springs are mounted are. In the drawing, only the front straightening spring 13 and the front extension 12 is visible, since the rear The spring and the rear approach are covered by the measuring mechanism.

On a bolt 15 attached to the measuring mechanism 11, a spring 16 is mounted which is attached to the on the measuring mechanism or on the bracket 10 arranged pins 17 and 18 is supported. This spring makes the bracket 10 or

the pin 9 attached to it is printed on the cam 8.

19 with the photo element and 20 with a series resistor.

The measuring tool pointer 21, which must be brought into line with a mark 22 fixed to the housing, is shown in FIG its rash, which is visible in the viewfinder of the camera, is limited by stops 23 and 24.

The mode of operation of the arrangement is as follows: frame rate and film sensitivity are set in front of the Measurement set by means of members 2 and 3 and act on the cam disc via the differential gear 8, which thus receives the corresponding basic setting. When measuring, turning the lens aperture ring 1 of the measuring tool pointer 21 with the mark 22 brought to coincide. The aperture ring 1 acts on the cam 8 via the differential gear.

By rotating the cam 8, the bracket 10 is moved, and this influences the directional springs 13 the position of the measuring mechanism coil 14. The slope of curve 8 is the characteristic of the photo element 19 adapted.

The embodiment shown in FIG. 2 shows a semi-automatic exposure regulator aperture arranged in front of the photo element.

As in the exemplary embodiment according to FIG. 1, the bracket 10 is rotatably mounted on the core magnet system 11 which the directional springs 13 are attached. The attached to the bracket 10 pin 9 is form-fitting with a Cam 25 connected. In front of the photo element 19, a diaphragm 27 is rotatably mounted about a bolt 26, which carries a pin 28 which is pressed against the cam disk 25 by a spring 29. Of the Adjustment ring 30 for the lens diaphragm is connected via a coupling rod 31 to a disk 32 which carries the film speed values. The disk 32 is connected to the adjusting disk 33 via a friction clutch, not shown in detail, which in turn is rigidly connected to the cam 25. The unequal distances of the lens aperture values on the setting ring 30 are through ■ Corresponding position of the coupling points 35 and 34 of the coupling rod 31 in uniform angles of rotation the disk 32 translated.

The mode of operation of the arrangement is as follows: The film speed is achieved by twisting the Adjusting disk 33 is specified as a reference variable for the exposure controller in relation to disk 32. at the measurement is made by turning the aperture setting ring 30 of the measuring tool 21 with the fixed to the housing Brand 22 brought to cover. During this adjustment process, the aperture adjustment ring is turned 30 via the coupling rod 31, the disk 32, the adjusting disk 33 and finally the curve 25 rotated. This takes over the pin 9 with the bracket 10, which over the directional springs 13 the position of the Measuring tool 21 influenced. At the same time the pin 28 slides along the curve 25, so that the front of the Photo element 19 mounted aperture 27 covers the photo element more or less. The slope of the curve is coordinated in such a way that only as much of the area of the photo element is covered as for It is necessary to achieve a photocurrent proportional to the angle of rotation of the bracket.

Claims (6)

Patent claims: 1. Photoelectric exposure meter or controller for photographic or cinematographic use Recording camera with a moving coil measuring mechanism whose pointer deflection corresponds to an or several exposure factors by pivoting the counter bearings of the straightening springs around the axis of the Moving coil is influenced, characterized in that a core magnet system (11) is used as the measuring mechanism and its pointer (21) with a setting mark fixed to the housing in the entire measuring range (22) in such a position of the measuring mechanism coil is brought to cover where it is in the area the maximum induction of the air gap. 2. Photoelectric exposure meter or controller according to claim 1, characterized in that that the two directional springs (13) of the measuring mechanism are connected by a bracket (10), which is of the setting elements influencing the exposure is controlled via a correction curve (8) which serves to compensate for the different characteristics of the photo elements. 3. Photoelectric exposure meter or controller according to claim 1 and 2, characterized in that that the setting elements influencing the exposure via a differential gear the correction curve (8) and the bracket (10) connecting the two straightening springs (13) act. 4. Photoelectric exposure meter or controller according to claim 1 to 3, characterized in that that the pointer deflection of the measuring mechanism is limited by stops (23 and 24) on both sides and the pivot angle of the bracket (10) are greater than the limited deflection range. 5. Photoelectric exposure meter or controller according to claim 1 to 4, characterized in that that the pivot angle of the bracket (10) is greater than 90 °. 6. Photoelectric exposure meter or controller according to claim 1 or one or more of the following claims, characterized in that the surface exposed to the light to be measured of the photo element is reduced so far by a diaphragm (27) that the geometric Grading of the brightness values to be measured results in a linear increase in the photocurrent, whereby the diaphragm is controlled by a curve (25) that connects with the directional springs (13) Bracket (10) is coupled. 1 sheet of drawings © 0Oi 508/126 4.