DE1497538B2 - Automatic focusing device for optical devices - Google Patents

Description

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The invention relates to an automatic Hch again a direct current that occurs when the focusing device is unsharp for optical devices, provision is available anyway. It is therefore also possible, for example, to use cameras with a photoresist cell, not an arbitrary object in this known device be used by the imaging lens to be in focus jekt, rather you have to rely on with the light rays emanating from an object - very small objects with comparatively few images is applied, and with means for deriving points limit to a complete Ausmiteines Positioning of the Imnals that occur when the focus is focused, depending on the focus state from the photocurrent. to prevent pulse trains. It is known to do the

It is known for this purpose, through a grid, electron-emitting cathode of a vacuum

to break up the image into strips, the contrast of which on the io photocell itself becomes bitter,

is greatest when the grating is in the plane of focus. In contrast, it is the object of the invention to provide a

If the grating is set in motion, an automatic focusing device can be created at

Alternating current is generated in a photocell and can therefore be used with any objects,

the contrast can be measured, the maximum value of which can accordingly be used universally, i.e. both

is used for automatic focusing. A 15 can also be built into a camera, for example

Another known adjustment device is can.

that two raster-shaped test images are arranged in front of and behind the setting plane, which are alternately made accessible by a light-electrically conductive described type for an automatic focusing device of the one swinging slit diaphragm. The photo that the light receiving surface of the resistance cell currents are then switched against each other and by a number of fine contacting electrodes disappear with the same positive and negative impurities in fine individual resistance strips, the sharpness of the two test images. From this, a number of bridge circuits error signal can be grouped together for automatic, servo-controlled whether a device for lens adjustment can be derived. Moving the photoresistive cell back and forth is also known in advance, instead of a swinging slit diaphragm being seen, using the reversal points of movement in front of Foucault's cutting edge, which are known to lie behind the image plane, and that a Schald even shields the light if it is exactly in the arrangement of all unbalanced states in the focal point of a lens. If it is located in front of or behind the focal point, the two signals for the automatic adjustment of the objective of the halves of the beam are diverted to different degrees, whereby the location of the maximum bridge is shaded. So one uses here as a criterion which moods correspond to the setting level.
Adjustment to the same brightness, which is used by means of the known fact that photocells are detected, in which case the contrast of the respective parts of an image at a suitable error location of the two photocurrents is maximum, thus also generating a signal and to control a servo, the difference between the resistance values of the individual drives can be used (cf. for all the photoresistive strips of a bridge circuit on, for example, the German Auslegeschrift 1103 050, which is greatest and thus the bridge circuit on column 1). is most upset, with the result that the

These known arrangements are suitable, however, when the voltage in the bridge zero branch is greatest,

only for the manufacturer's lens adjustment and the like, because this bridge output voltage is

working with a precisely defined test object, the blurring of the image becomes increasingly smaller,

must become. because then the contrasts gradually disappear

It is also known (United States patent specification and all photoresistive strips of the respective

2 524 807), a rotating fine grid in about the 45 bridge circuits lit about evenly

To be arranged the focal plane of the lens to be adjusted, so that they have an approximately equal reflection

with the degree of fineness of the lattice chosen so that the bridge

is that the grid elements and their spacing will be roughly the same.

the narrowest, with the lens when using an es, is by simply moving back and forth Point-shaped object reachable rays of the photoresistive cell possible, the location of the

bundle cross-section (so-called minimum unsharp sharp image, whereby with the help of the following

circle). In the case of focus, the lowing circuitry covers an unbalanced one

therefore the grid elements of the rotating grid detected the state in each bridge circuit and

Image point of an object-side point light source, from this a control signal for automatic adjustment from each other, and it is derived at the 55 of the lens located behind it.

Photocell on with corresponding pulses, as can be seen from the

lated photocurrent. If the setting is unsharp, the focusing device can be replaced with any ob-

the then correspondingly enlarged light spot can not be worked jekt.

more alternately completely covered and free- Below are two exemplary embodiments are given; the alternating current pulses disappear with the aid of the drawings in detail

therefore. But is it not just about NEN explained; it shows

a single point of light as the object, but around A b b. 1 shows an embodiment of the arrangement of FIG

any object with a corresponding number of electrodes on a photocell,

Individual light points, also in the case of Figs. 2A and 2B, create sectional views of this,
Focus each of these points of light an im- 65 A b b. 3 the electrical circuit of the photocell

pulse train, each in any phase relation- ship according to A b b. 1,

occur and are superimposed on one another. The A b b. 4 another embodiment of the arrangement

The result is therefore only the electrodes on a photocell, even with a sharp setting,

3 4

A b b. 5 the electrical circuit of the photocells - the contacts of the light receiving parts,

arrangement according to A b b. 4, whose width and spacing are the same as the

Fig. 6 is an embodiment of the automatic first embodiment; however, they are in here

Focusing device in which the photocell is in the form of a pattern with parallel stripes throughout

according to A b b. 1 is used, 5 is arranged. In the A b b. 4 and 5 mean Γ and 2 '

A b b. 7 a circuit arrangement for the front connections on the input side, 1-9 and 11 die

direction to A b b. 6, connections that connect to the other end of the

Fig. 8 the movement along the optical guide electrodes A are connected, T a transaxle of the photocell shown in Fig. 6, formator and 12 and 13 the output connections.

A b b. 9 is a graph showing the ίο the whole, as in A b b. 5 shown switched. Output sequence obtained in the meantime at terminals 3-10, if alternating current shows at the voltage, terminals 1 'and 2' are fed in, an output sequence

Fig. 10 is a graph showing the voltage between terminals 12 and 13 he output The amplifier's shows will hold up if some are not matched

Fig. 11 is a diagram showing the 15 resistors ... r ' are present, as the center output of the pulse shaper shows point. the secondary winding of the transformer T

A b b. 12 a further embodiment which is itself connected to the connection 12.

make focus adjustment device, in which the A b b. 6 shows an embodiment of the automatic

Photocell according to A b b. 4 is used, gene focusing device, in which the photo

A b b. 13 an embodiment of the with the front 20 resistance cell 5 according to A b b. 1 is used. In

Direction according to Fig. 12 connected electrical of Fig. 6 mean L the objective lens, V den

Systems, auger operation for focusing, F die

A b b. 14 is a diagram showing the image plane on which the lens L images and H a

Scanning state of the slit image on the photo-semitransparent mirror. The element S is the

conductive surface, and 25 photocell of A b b. 1, where C its more effective

Fig. 15 to 18 is the focusing effect for the case part, and C the effective area on surface

a checkerboard pattern to be photographed of F, which corresponds to C. Area C is smaller

Object. than the area F, so that when multiple objects

In Fig. 1 and 2, S denotes a photocell to be photographed that does not always

using a photoresistor S ', will have the same distance, only the

for example from CdS or CdSe. A denotes a generating part to be made the goal of the setting

Number of lead electrodes that can be adhered to S '.

Lead contacts P, P '. The latter are seen- E is a moving plate on which the photolich of its width and distance is roughly the same as the resistance cell S with that in A b b. 3 shown as the size of the electrical circuit as the diameter of the minimum blur circle is attached. The plate E is so ses the lens, so sized accordingly, arranged that it is about the axis NN ' within the and they are arranged in a suitable manner (according to the amount of TlJIl = Tl] C' ± Y with a frequency of different directions oriented), around which Rieh can oscillate several tens of Hertz. In doing so, the dependency on the function is to be reduced, which can be selected by the oscillation amplitude Y in such a way that the image width range of variation arising in the form of the object to be photographed is obtained. A switch SW is for detection

B is the base plate made of steatite or sintered quartz, the position of the movable plate E is provided,

and 1 to 9 are the terminals that are associated with the elec- To this, if Ή JJ is greater than Ή JJ ' , his

electrodes A connected and, for example, a contacts 14 and 15 connected to one another, furthermore

thin gold film are made. If Ή JJ is less than Ή JJ ' , its contacts 14 are the production 45

of the whole is done using known and 16 connected to one another, while if Ή JJ

Method, for example photo-etching or the like, after equal to Ή JJ ', the contacts are separated from one another

the vapor deposition. are. Connections 1, 2, 3 and 10 correspond to 1, 2,

Fig. 3 shows the electrical circuit, the 3, 10 in Fig. 3. G is the gear wheel for twisting contacts P and P ' a number Wheatstone 50 of the lens L, while M is a servo motor or shear bridges together with the respectively between - form a combination of a motor, a mechanical photoresist group r-r '" . nisch reversible rotary drive device and therefore, if voltage can be between the terminals of an electromagnetic clutch. The terminals 1 and 2 is applied and some is not the Arrangement is made so that, if bridges are equalized by voltage, a positive voltage is applied to terminals 17 and 18, which or negative voltage is generated at terminals 4-9. The connections .4-9 of the objective lens L takes place, while when applying are connected to the connection 10 via diodes Ό , a voltage to the connections 17 and 19 so that when the N achweisstrom is moved back from the connection lens L.

sen 3 and 10 is removed, the output voltage 60 A b b. 7 shows an embodiment of the electrinings of the respective bridges without mutual see circuitry, which is assigned to the mechanical part described above. can. So if alternating current is supplied to the terminals, the photoelectric light receiving part, which is fed to sen 1 and 2, is always given in the drawing by a dashed line around an output voltage between 3 and 10, if a 65 is given on the moving plate E (A b b. 6) There is a matching deficit in one of the bridges. provided, and the resistors r-r '" correspond to Fig. 4 and 5 show a further embodiment - those in Fig. 3. Between the connections 1 form for the arrangement of the electrodes, where P, P' and 2 an oscillator is connected, the alternating current

of several kilohertz delivers. An amplifier V operating in C mode, a pulse shaper and an automatic gain control R (with a time constant of several tens of microseconds) are connected to the output connections 3 and 10, as shown.

The element SW (14, 15 and 16) is the switch corresponding to the one in Fig. 6, and TrI and Tr 2 are the transistors of a bistable multivibrator. U is a voltage source (battery), while ml and ml are the field windings of the in A b b. 6 or the solenoid of the magnetic coupling, in each case the connections 17, 18, 19 to those in A b b. 6 correspond.

If, for example, the images of two objects of a scene are generated at k and K ' in the vicinity of the photocell S , which oscillates between + y and - y (A b b. 8), the one in A b b. 9 generated output voltage between the terminals 3 and 10. Since the contrast of the respective parts of the image at the point of their sharp image is maximal, the difference in the resistances rr "'is maximal, and the output voltage generated between the terminals 3 and 10 is maximal. The output thus obtained is provided by the C- Amplifier amplified, clipped at a certain height CL (A b b. 10) and rectified, giving negative pulses X ₁ and X ₉ (Fig. 11) If, as shown, the output voltage produced by the figure at k is greater than is that of the image at k!, the latter will not influence the pulse shaper (Figs. 9 to 11), so that the output pulse is only generated by the image at k and has no relation to the image at k ', for example the background .

The pulses Z ₁ and X ₂ are then fed to the switch SW , so that, since the contact 14 is connected to the contact 16 in this case, they reach the base of the right transistor TrI . The transistor Tr 2 thereby becomes non-conductive if it was previously conductive, while it remains non-conductive if it was previously non-conductive. The left transistor TrI therefore becomes conductive, so that a voltage is applied between the terminals 17 and 18, the lens L is moved forward by the gear G and the image at point k is thus shifted towards point 0 (abscissa). Then, if the relationship between the number of vibrations of the moving plate E and the reciprocating speed of the lens L is appropriately selected, the lens L repeats the back and forth motion to keep the image slightly in front of or behind the position of the image plane F. , to bring about the automatic focusing.

Fig. 12 shows an embodiment of the automatic focusing device, in which the cell according to A b b. 4 and the circuit arrangement according to A b b. 5 are used. In the drawing, L denotes the objective lens, L ' denotes the worm drive for adjusting it, F denotes the image plane of the lens L and H denotes a semitransparent mirror.

S is the photocell of A b b. 4, and C is its effective part, which corresponds to C in the image area F. In this embodiment, too, C is made smaller than the image area F for the reasons given above. E is the element that carries the circuitry shown in A b b. 5 is framed by a dashed line and connected to the connections 1, 2 and 13. W is a turntable which is rotated by the electric motor M ' and has a gap si for scanning. LR is a relay lens for re-imaging the intermediate image generated on the disk W by the objective onto the light receiving part C. In this case, only the light passing through the gap si is imaged at the corresponding point of the photocell,

ίο so that the image falling on C as a whole is scanned through the gap si in accordance with the rotation of the disk W.

Of course, if the disc W is placed close to the cell, the relay lens LR can be omitted.

The part B1, which is framed by a dash-dotted line in the drawing, is a block which is designed and arranged in such a way that it is within the amount Ή, 'S! = Ή, ϋ '+ y can oscillate in the direction indicated by the arrow at a speed of several tens of periods per second.

y is here equal to the adjustment stroke of the lens or slightly greater.

SW is the switch for determining the position of the block Bl, if 77.37 is smaller than 77, U ', the connections 14 and 16 are connected to each other, while if 77.37 is greater than Ή, Ό' , the Connections 14 and 15 are connected to each other and the remainder of the connection is isolated.

G is the gear wheel for rotating the lens L, M is a combination of a servo motor or a motor and a mechanical reverse rotary drive and an electromagnetic clutch for driving the gear wheel G, the arrangement being such that the lens L is moved forward when voltage is applied to terminals 17 and 19, while lens L is returned when voltage is applied to terminals 17 and 18.

Fig. 13 shows an example of a circuit for the mechanical part according to Fig. 12, with the part framed by a dashed line in Fig. 13 being arranged on the part E shown in Fig. 12 and r and r ^{1 being} those in A b b. 5 correspond. An oscillator O is connected to the primary side of the transformer T , which generates, for example, alternating current of several kilohertz and supplies it to the connections 1 'and 2', while the output-side connections 12 and 13 have the C amplifier V, the pulse shaper I and the automatic gain control R are turned on with a time constant of tens of microseconds as shown. SW is the switch that corresponds to the one in Fig. 12, and TrI and Tr2 are transistors which, together with other electrical elements, form a bistable multivibrator. U is the battery, ml and m2 are the field windings of the servomotor shown or the magnet windings of the magnetic coupling, and the connections 17, 18 and 19 correspond to those in Fig. 12.

With this arrangement, the light rays from the object are collected by the lens L, divided by the semitransparent mirror H , i.e. mapped partly onto F and partly onto the pane W. The image at W is scanned through the slit Sl and mapped onto C from there.

Fig. 14 shows the movement of the figure SV 's

Slit 5 / on the surface of C. The shapes of the electrode A to A b b. 4 and the movement of the gap S1 are combined in this embodiment in such a way that the image section delimited by the gap falls simultaneously on many small sections of the electrode arrangement, that is to say it is finely divided by these. The movement process corresponds to that shown in Figs. 8 to 11.

A b b. 8 accordingly shows the position of the photocell 5 in relation to the image of the object. The cell 5 oscillates between 4- y and -y about the position on the optical axis which corresponds to the position of the image plane F.

There may now be two objects in front of or behind this position whose sharp images are at k and at k ' . An output voltage is obtained at the connections 12 and 13 again corresponding to A b b. In other words, the contrast of the respective images is at its maximum at the sharp image points, so that the difference between the respective photoresist groups r and r 'is at its maximum, the electrical bridge receives its greatest adjustment deficit and the output voltage generated between the terminals 12 and 13 is at its maximum will. The output voltage obtained in this way is amplified (A b b. 10) by the C amplifier, cut off at a certain level CL and rectified, so that the negative pulses X1 and X 2 are obtained. In this case, influenced if that is by the imaging at k obtained output voltage greater than the output voltage by the imaging at k ', not the latter, the output signal of the pulse shaper, so that the image in k, such as a person as the subject of the image, but generates the output pulse of the pulse shaper, while the image at k ', for example the background, does not cause any output signal. The pulse then passes to the switch SW, in which case the contact 14 is connected to the contact 15, so that the pulses X ₁ and X are fed to the base of the left transistor Tr 1. If this was initially conductive, it becomes non-conductive, while, if it was initially non-conductive, it remains so, so that at least the right transistor Tr 2 is conductive, voltage is applied between the terminals 17 and 19 and the lens L is moved forward. If the position of the image were in the inverted position against the photocell S , the lens L would be moved backwards. Therefore, when the relationship between the rocking motion of the block Bl and the speed of the back and forth motion of the lens L is appropriately selected, the lens L repeats the back and forth motion to move the image of the object slightly behind and in front of the position of the diaphragm, respectively F , which enables the automatic focus to be achieved.

Now, if the object has the checkerboard pattern shown in Figs. 15 and 16, the output voltage, as it would be obtained with the combination of a scanning gap and a single (ie unscanned) light receiving part in conventional devices, would not provide a useful value. Please refer to Fig. 17. There in diagram (i) the abscissa corresponds to the time, the vertical line to the position for sharp image generation, and the point 0 'corresponds to the gap position at time zero. The image coincides with the cleavage surface at time t when it is shifted from backward to front. However, as is clear from the diagram (U) , the amount of light arriving at the light receiving part is not related to the sharp image formation. In other words, regardless of whether the image is out of focus or in focus, the amount of light passing through the gap is brought to a constant mean value because of the length of the gap.
In the inventive device, however, is the light receiving portion of the photoconductor between the contacts P and P '(Fig. 4), and since the respective parts behave as independent lichtempfindliehe parts, the gap S is with regard to its function in small portions Sl 1, S 12 ... divided (A b b. 16), whereby the resistances between the respective electrodes are changed, as shown in the diagrams (Ui, iv) in Fig. 17. It can therefore, if the respective electrodes in the A b b. 5 are switched in the manner shown, the output voltage for focusing [s. the diagram (v)] between the terminals 12 and 13 can be obtained when AC voltage is applied to the terminals 1 'and 2'. As mentioned, this output voltage is then amplified and rectified. It is therefore possible to obtain the focus pulse even when the object is a checkerboard pattern.

The change in the amount of light received by the light receiving part is shown by the diagrams (i and Ui) in Fig. 18, while the change in the photoresist caused thereby is shown in the diagrams (H and iv). It can be seen from the diagrams that the scanning speed is small when the change in the amount of light corresponds to diagram (i) and the change in conductivity corresponds to diagram (U), while at a higher scanning speed the change in the amount of light corresponds to diagram (Ui) and the Change in conductivity according to diagram (Zv). In other words, the photoconductor needs a certain time to store and reduce the charge carriers caused by the light, so that the lower the scanning speed, the more advantageous the result that can be expected. With the device of the present invention, it is possible to reduce the scanning speed in inverse proportion to the number of parts of the divided photoconductor resistor, whereby a higher output voltage can be generated, which simplifies the amplifier. The in A b b. 3 shown electrical circuit arrangement can also in the embodiment according to A b b. 12 can be applied.
55

Claims (4)

Patent claims: 1. Automatic focusing device for optical devices, with a photoresistive cell, those resulting from the imaging lens to be focused with those resulting from an object Light beams is applied, and means for deriving a dependent on the focus state Signal, from the photocurrent, d a characterized in that the light receiving surface of the photoresist cell (C) by a number of fine contacting electro- 009 524/178 the (A) is divided into fine individual resistance strips (r, r ', ...), which are grouped together to form a number of bridge circuits (4 to 8) that a device (n, E, Bl) for moving the Photoresistive cell is provided, the movement reversal points being in front of or behind the image plane, and that a circuit arrangement (V, J, SW) detects all unbalanced states in the bridge circuits and derives a signal for automatic adjustment of the lens (L), the location corresponds to the maximum bridge detuning of the setting level. 2. Apparatus according to claim 1, characterized in that one point of the diagonals of all Bridge circuits are each connected to one another via a diode (D). 3. Apparatus according to claim 1 or 2, characterized in that the groups of strips (r, /. ..) of the individual bridge circuits are oriented in several directions (A b b. 1). 4. Apparatus according to claim 1 or 2, characterized in that the groups of strips (r, r '...) Of all bridge circuits are oriented in the same direction (A b b. 4) and that in front of the photoresistor (C) a slit diaphragm ( 5 /) is arranged with a gap oriented perpendicular to the strips, which is moved in the direction of the optical axis for scanning the image plane together with the photoresistor (C). For this purpose 2 sheets of drawings