DE3019671A1 - Semi-automatic focus control for camera - has initial focus set manually with subsequent fine focus from servo drive connected to detectors - Google Patents

Abstract

A semi-automatic focus control for an SLR camera has an initial manual control (2) to set the focus approximately and a servo-controlled fine focus (5) for automatic control. The servo drive only extends for a short range and the combination provides a rapid focus setting with a simple lay-out. Both manual and servo controls move the taking lens axially, but on different threads. The servo-motor (5) has a feedback control from the focus detectors (19) in the base of the camera housing. A selector switch disengages the automatic control for a manual control for special effects, e.g. soft focus pictures and to operate in poor visibility with subsequent flash exposure.

Description

Camera with automatic baluster adjustment

The invention relates to a semi-automatic setting device, which is able to accurately focus according to the output signal of a focus detector after a rough focus adjustment done by hand.

Various types of automatic focus adjusters have already been proposed for single lens reflex cameras.

These have conventional automatic focusing devices a multitude of disadvantages, because automatically focused over the entire area will.

Thus, in these conventional devices, the shift is of the focusing mechanism in Direction of the optical axis u, rUw a few centimeters, and a lot of space is required in these constructions.

Furthermore, due to the large displacement, it is difficult to adjust the tur shortening the focusing time (focusing time). If the focusing time is shortened, this results in difficulties in obtaining a to achieve high accuracy in focusing.

Further, objects other than the object to be photographed are confusing in front of and behind the object to be photographed, so is conventional fully automatic focusing devices often target these other undesirable Objects in focus.

It is the object of the invention to provide a very convenient and effective device to create completely all of the disadvantages of conventional automatic focusing devices avoids. The invention is based on the idea that a rough focus can easily be done by hand in a sufficiently short period of time.

Furthermore, a camera with an automatic focusing device is intended creating an erroneous focus on peripheral objects around the object to be photographed avoids. The camera to be created should be an automatic one Have a focus device that adjusts the focus time (focus time) effectively shortened. Furthermore, this camera is intended to be an automatic focusing device with a compact and simplified structure. This camera should also be a have automatic focusing device that solves the above problem, without the need to change the conventional interchangeable lenses.

According to one embodiment of this invention, the device a photographic optics, a manual focusing device for shifting at least part of the photographic optics along the optical axis by hand, an automatic focusing device and a focusing detector on, the area in which by means of the automatic focuser can be focused, kept to the minimum required, and automatic Focusing device by means of the measurement signal of the focus detector is controlled.

Furthermore, the automatic focusing device has a device for moving the fastening part of the camera along the optical axis and for Measuring this displacement, as well as a device for limiting the motor drive for automatic focusing on the two end points of the shift on.

The invention has the following advantages: (1) Because the coarse focus (Focusing) is done by hand - and then fine focusing automatically is carried out, the erroneous focus adjustment on peripheral objects around the object to be photographed can be significantly reduced.

(2) Because the coarse focus, which takes a relatively long time While it can be done by hand, it is possible not only to do it automatically Focusing (AF mode; automatic focus) can be carried out without any practical hindrance, but also the amount of displacement of the objective or the lenses along the optical axis so that the structure compact and simple can be held.

(3) Since the displacement required for focusing is small, the focusing can be carried out quickly and therefore precisely.

(4) Even when the rough focus is far from the focus position deviates, excessive energy consumption of the motor by the inventive Control circuit. avoided, and the direction of the deviation can be easily determined by the Photographers are watched.

(5) As the shift adjusting part for automatic focus adjustment is designed so that it is at a central point after taking the picture of the shift range returns, the focus can be adjusted in either direction be carried out safely.

(6) As a manual coarse focusing device on the lens thread mount is present, while the automatic focusing device on the mounting part attached to the camera, all types of conventional interchangeable lenses can be used can be used without any modification.

The invention is described below using exemplary embodiments Described in more detail with reference to the drawing. 1 shows schematically a semi-automatic focusing device ' Fig. 2 schematically the release button mechanism, Fig. 3 shows an embodiment of the focus control circuit (Focus control circuit) J Fig. 4 shows a second embodiment of the focus control circuit, and FIG. 5 shows a third embodiment of the focus control circuit.

Fig. 1 shows schematically the relationship between the described semi-automatic focusing device and photographic optics etc. Here 1 denotes a taking lens, 2 a threaded mount, 3 a tube, 4 a fastening part or a »connection socket at the Sweragehause and 5 part of the Kam.eragehuses. A screw mount thread 6 for moving the connector mount along the optical Axis is attached between the connection socket 4 and the camera housing 5. A Motor 7 has a gear which is mounted on its shaft and with the connection socket thread 6 is engaged. The connection socket 4 is along the optical axis by means a gear 8 and the connection socket thread 6 shifted. A swing-back mirror 9 is partially or entirely a semi-transparent mirror. 10 is a swing back mirror for the optical distance measuring system, 11 a focusing screen, 12 a shutter, 13 a film surface, 14 a pentaprism, 15 an eyepiece, 16 a reflection mirror for displaying viewfinder information, 17 a display component, for example a Light emitting diode to display viewfinder information.

A deflection element 18 for the optical distance measuring system shares the Luminous flux from the swing-back mirror to two photoelectric transducers 19, 19 'on.

27 is a member for measuring a fine displacement of the terminal socket 4. In this exemplary embodiment, the component 27 has a variable resistance used.

With the above arrangement, the Taking lens 1 with the threaded mount 2.

The connection socket 4 is along the optical axis by means of automatic focusing mechanism finely shifted the photoelectric Measurement converter 19s 19 'as focus detectors and the motor 7 as focus actuator for performing focusing.

Needless to say, the construction described can of course also be modified, for example the focusing mechanism can also be provided on the interchangeable lenses.

Fig. 2 shows an embodiment of the release button mechanism. 5 is the camera body, 21 is a release button, 22 is a fixed pin, which is shown in an elongated hole 23 is inserted, the ausgebil det in part of the release head and the one in the release release direction (upwards in this version: - example) is acted upon by a spring 24. 25 is an AF (auto-focus) system switch and 26 a record switch, both of which are normally open. The recording switch can be carried out conventionally, for example, the light measurement at a first stage and the AE operation (automatic exposure control) and the shutter release triggered at a second stage.

If the release button is pressed directly down in the above structure, this will trigger an ordinary recording. If the release button is pushed to the left and then pressed down, it will take a picture with automatic Focus released.

When the shutter release button is pushed to the AF side, It is impossible to focus, so the photographer can quickly take an ordinary picture switch to the right side by pushing the release button back.

Fig. 3 shows an embodiment of the focusing or. Focus control circuit. A block A represents the focus detection circuit and the motor drive circuit, a block B the front and rear endpoint detection circuit and a block C represents the voltage supply circuit. In the block A are 19 and 19 ' the already mentioned photoelectric transducers, for example CdS components. 43 is a constant voltage diode, 46 and 49 are arithmetic amplifiers, 52 is a Differential amplifier, 69 a power amplifier, 70 a capacitor, 7 a motor, 47 and 50, respectively, are log compression diodes, 44 a resistor, Vcc a positive voltage source, Vee a negative voltage source. The CdS converter 19 or

19 'are biased with a constant voltage via the constant voltage diode 43 and the resistor 44 are supplied and change according to the incident light flux their resistance value. The change in potential corresponding to this change in resistance is the input signal for the differential amplifier 52. via the from the computing amplifier 46 and the diode 47 built up logarithmic amplifier or from the computing amplifier 49 and the diode 50 constructed logarithmic amplifier.

Therefore, the output signal of the differential amplifier corresponds to from the comparison of the incident light conditions on the transducers 19 and 19 ' resulting focus information.

In this case there is no information about the brightness or the contrast of an object, but this information can in the focus information by using another focus detecting means can be obtained so as to add the front and rear focus signals obtain.

The signals of the front and rear Poussierun "are over Analog switches 65 and 42 applied to the input of the power amplifier, so as to the to generate the necessary power for the selective rotation of the reversible motor 7.

When the control input to analog switches 65 and 42 is high Level, the motor rotates in a direction in which the focus deviation is eliminated in accordance with the image design using photographic optics, and stops at the position at which it is in focus.

The block B is the detection circuit, the front and the detects the rear end point of the displacement range of the frame and the motor 7 stops when the socket reaches the front or rear end point.

54, 55 and 56 are divider resistors connected in series, to provide a reference voltage when the connection socket on the front or on the rear end point is. 59 and 60 are. Comparator. One of the input ports of the comparator 59 is connected to the connection point of the resistors 54 and 55. The other input terminal is with one of the input terminals of the comparator 60 as well as with the tap of the resistor 27 for detecting the position of the connection socket connected. The other input terminal of the comparator 60 is with connected to the junction of resistors 55 and 56. The two end connections of the resistor 27 are connected to the voltage sources Vcc and Vee, respectively.

64 is a (logical) OR element with two input connections, the are connected to the output terminals of the comparators 59 and 60, respectively. The exit of the OR element 64 is connected to the control input of the analog switch 65. which consists of an FET, etc. One connection of the analog switch is to earth and the other terminal connected to the output terminal of the differential amplifier 52.

The one at the tap of the variable resistor 27 for measuring the terminal socket position The voltage present is compared with the reference voltages by means of the comparators 59 and 60 for the anterior and posterior endpoints compared. When the position of the connector socket reaches the front or the rear end point, either gives the comparator 59 or the comparator 60 outputs a high level output signal.

The outputs of the comparators 59 and 60 are with a resistor 62 and an LED 63 or a resistor 67 and an LED 68 are connected. Achieved the connection socket the front or the rear end point, so light up either LED 63 or LED 68 will light up and indicate the position of the connector socket at.

Furthermore, the output signal of the OR element is high level at the same time, so that the analog switch 65 turns on and blocks the focus detection signal.

For example, if the socket is at the front end point, then so there is a signal at circuit point 61 high level that is im Viewfinder across resistor 62 and LED 63 is displayed so that the photographer standardized by the impossibility of adjusting the distance by advancing it forwards will.

With this display, the photographer can decide whether to use the taking lens move forward or switch from AF mode to manual mode. In this case, the output signal of the OR element 64 takes a high level to switch through the analog switch and the voltage supply of the motor switch off.

If the connection socket is at the rear end point, there is a signal high at node 66 to indicate the location of the socket to indicate the rear end point via the LED 68 and the resistor 67. Similar As described above, the power supply for the motor is switched off.

When the AF operation is interrupted, the tap of the is the connector socket position measuring resistor 27 is connected to the input terminal of a comparator 71. The output terminal of the comparator 71 is connected to the input terminal of the power amplifier 69 connected via an analog switch 36 and a resistor 72. Switches the Analog switch 36 by (since the analog switch 42 is opened), so is therefore the motor 7 according to the tap voltage of the terminal socket position measuring resistor 27 driven so that the socket backwards and forwards shifted and the motor is driven until the value of the tap voltage is zero will. If the connection socket has reached the midpoint of its displacement range , the tap voltage of the resistor 27 becomes zero.

C represents the power supply circuit. 33 is a PNP transistor, 37 and 76 are inverters, 39 an AND gate with two inputs, 40 an RS flip-flop, 73 a rectifier, 74 a capacitor, 75 a differential amplifier, 32 and 41, respectively are resistors and 25 is the AF system switch shown in FIG.

The emitter of the transistor 33 is connected to the voltage source Vcc and the collector is connected to the corresponding points of each circuit. The base is connected to the ground through the resistor 32 and the AF system switch 25. Further is the base of transistor 33 with the Q or the inverse Q output of the RS flip-flop 40 connected via resistor 41. The connection point of switch 25 and des Resistor 32 is connected to the control input of the analog switch 36 as well as to the input of the inverter 37 is connected. The output connection of the inverter 37 is connected to the control input of the analog switch 42 and to the S input terminal (preparation input) of the RS flip-flops connected. Furthermore, the connection point of the resistor is 32 and of the switch 25 is connected to one of the input terminals of the AND gate 39. The output connection of the AND element is connected to the R input connection RX des.RS flip-flops 40 connected.

The rectifier 73 sets the voltages at the two end points into the absolute voltages and applies these absolute voltages to the differential amplifier 75. The capacitor 74 is connected between the two input connections, in order to prevent a voltage spike in the rectifier 73. The output terminal of the differential amplifier 75 is connected to the other input terminal of the AND gate 39 connected.

When the AF system switch 25 is closed, depressing of the trigger, the analog switch 36 is opened as previously explained and at the same time the analog switch 42 is switched through by the inverter 37.

A high level signal is also applied to the S input of the RS flip-flop while a low level signal is applied to the R input via the AND gate 39 is applied so that a low level signal is applied to the Q or inverse Q output terminal of the RS flip-flop is created. This signal is passed to the base of transistor 33 the resistor 41 placed so that the transistor 33 remains switched on. Is this RS flip-flop by resetting the connection socket to the center position Backed up, the power supply is maintained even when the AF system switch is turned off.

The resistor for measuring the connector socket position is designed so that the tap voltage is zero when the terminal socket is at the midpoint of the displacement range is, and that a negative or a positive voltage is output when the Connection socket is not at the center. This voltage is converted into an absolute value implemented by the rectifier 73 and via the differential amplifier 75 and the Inverter 76 is applied to one input terminal of AND gate 39. Therefore takes the Q or inverse Q output of the RS flip-flop 40 only goes high when the AF system switch 25 is opened, photography is ended and the frame is set has returned to the center of the displacement range. At the same time goes the transistor 33 in the blocking state, so that the voltage supply is interrupted at the individual points of the circuit.

In the focus control circuit described above, the motor is continuously rotated until the focus Detector signals of the photoelectric The transducers 19 and 19 'coincide with one another. The coarse focus deviates by hand so far from the focus that the automatic fine focus adjustment is impossible, the power supply for the motor is interrupted, the direction in which the coarse focus should be corrected indicates the connector socket is moved back to the center of the displacement area, even if the The picture has been taken so that fine focusing is consequently possible.

Even if the photographer turned the AF system switch due to a faulty AF operation etc. should shift to the manual side, d. H. the AF system switch 25 is switched off, the voltage supply is continued by the flip-flop 40, to slide the socket back to the midpoint of its range of displacement.

Fig. 4 shows a second embodiment of the focus control circuit, in which only the displacement of the connection socket over the two end points of the displacement range is prevented, while with the in Fig.

The first embodiment shown, the power supply for the Motor 7 completely interrupted at the two end points of the displacement range will.

If the front end point is determined, the second Embodiment only prevents the motor from pushing the connector socket forward and allows the motor to slide the connector socket backwards.

If, on the other hand, the rear end point is averaged, it is only prevented that the motor pushes the connector backwards, but allows the motor the connection socket slides forward.

The components provided with the same reference numerals as in FIG. 3 4 are the same components with the same connections.

Analog switches 77 and 79 consist of field effect transistors etc. The control inputs of the analog switches are connected to the output connections of the comparators 59 or 60 connected.

One of the output connections of the above analog switch is marked} 1assa and the other output terminal connected to the cathode of a diode 78. The anode the diode 78 is connected to the output terminal of the differential amplifier 52. One output connection of the analog switch 79 is the other output connection with ^^ cup connected to the anode of a diode 80. The cathode of diode 80 is connected to the output Terminal of the differential amplifier 52 connected.

As described above, lies at the leading end point a high level signal at node 61 so that the analog switch 77 switches through. As a result, by means of the diode 78, a signal for the further Forward movement of the connection socket 4 prevented; only the backward movement the connection version is permitted. Correspondingly lies when reaching the rear Endpoint a high level signal at node 66 so that the analog switch 79 is switched through, so that this results in the backward movement of the connection socket prevented and only forward movement is allowed.

For the restriction at the front and rear endpoints is not always a position measurement by means of the variable resistor 27, as described above is necessary, but it can also be a conventional end circuit as shown in Fig. 5 can be used.

Fig. 5 shows a third embodiment of the focusing device. Components which are the same as those in FIGS. 3 and 4 have the same reference numerals. 81 is a front limit switch that normally connects node 82 to the Connection point 83, in particular Vcc. Therefore, the output stage enables of a transistor 84 in the differential amplifier 52 the forward movement of the terminal socket, since the emitter is connected to Vcc.

At the front end point, the limit switch 81 is switched over, see above that the node 82 is connected to OSSE 85. This will make the emitter of transistor 84 grounded, allowing the socket to move further forward leading rotation of the motor prevented and at the same time the LED connected to Vcc 63 is powered through resistor 62 to reach the front The end point.

Correspondingly, a rear limit switch 86 is over a switching point 88 connected to Vee. Because this causes the emitter of a transistor 89 to be connected to Vee is, the backward movement of the socket is made possible.

At the rear end point, the limit switch 86 is switched over and node 87 is connected to ground 90.

Furthermore, the connection becomes a further backward movement leading rotation of the motor via the transistor 89 prevented and at the same time the LED 68 connected to Vee powered through resistor 67 to achieve of the rear end point.

91 is a reset contact composed of an element for measuring the the front and the rear position of the socket. The reset contact is designed so that a part 93 has contact with a contact tab 92, if for example the lens has been moved forward, to the engine for one Reverse motion to rotate. If the lens has been moved backwards, the contact tab has contact with a portion 94 to allow the motor to move forward of the connection socket until the return movement to the center point or

is completed to the zero potential position.

A focus adjusting device for a camera has been described above in which a coarse focusing by hand using a screw lens barrel takes place and a fine focus adjustment automatically by moving the camera connection mount is performed along the optical axis.

The above focusing device is designed so that the connection socket to a certain position, for example the center point of the displacement range is reset, and measuring devices for measuring the front and rear end points of the displacement range of the terminal socket are present to stop the motor from rotating if one of the endpoints averages will.

Claims (12)

P a t e n t a n s p r ü c Ii e 1. Camera with semi-automatic focusing device as well as with a) a photographic optics, which an image of an object on a certain Designs the focal plane in the camera, and b) a hand-held focusing device, which moves at least part of the photographic optics along the optical axis, to get a sharp image of an object in the area between a close-up area and to design an infinite area on the plane, characterized by c) an automatic focusing device with a motor (7), the at least one. Part of the photographic optics (1) over a certain distance along the optical Axis can move, being the object distance range over which the distance the shift is sharply adjustable, narrower than the object distance range is selected, can be sharpened by means of the manual focusing device (2) is, and d) by a focus detector (8, 19, 19 '), which the condition measure the image drawn on the focal plane (13) of the photographic optics (1) can, wherein the detector is a motor control circuit for controlling the motor drive has, and this control circuit drives the motor (7) in accordance with the output signal of the detector regulates that the part of the photographic optics (7) through the automatic focusing device for focusing is slidable in the field the displacement distance is shifted. 2. Camera with semi-automatic focusing device according to claim 1, in that the automatic focusing device is designed to have a lens mount t2 holding the photographic optics (1), 3) to move along the optical axis. 3. Camera with semi-automatic focusing device according to claim 2, in that the lens mount is removable on one Connection version of a camera housing (5) is attached, and that the automatic Focusing device moves the connection socket (4) along the optical axis. 4. Camera with semi-automatic focusing device according to claim 1, characterized by the fact that the hand-held focusing device uses the Clt3eXtive mount moves forward and backward by means of a screw thread. 5. Camera with semi-automatic focusing device according to claim 1, g e k e n n n z e i c h n e t by a measuring device for measuring the size of the Displacement, which is the amount of displacement of the photographic optics (1) caused by the automatic focusing device is slidable into an electric one Size implements. 6. Camera with semi-automatic focusing device according to claim 5, characterized in that the measuring device for measuring the size the displacement has a sliding resistor (27), the resistance value of which corresponds accordingly the displacement of the part of the photographic optics (1) that is affected by the automatic focusing device is slidable. 7. Camera with semi-automatic focusing device according to claim 1, indicated by an end detection circuit (B) which sends a signal emits when the part of the photographic optics (1) passed through the automatic focusing device is displaceable, has reached an end point of its range of displacement. 8. Camera with semi-automatic focusing device according to claim 7, g e k e n n n n z i c h n e t by a limiting device that prevents that the motor shifts the photographic optics beyond the shift range, when it receives the signal from the endpoint detection circuit. 9. Camera with semi-automatic focusing device according to claim 8, characterized in that the limiting device is designed in such a way is that it cuts off the power supply to the motor when the endpoint detection circuit generates a signal. 10. Camera with semi-automatic focusing device according to claim 7, characterized in that a display device indicates that a signal is received from the endpoint detection circuit. 11. Camera with semi-automatic focusing device according to claim 1, g e k e n n n z e i c h n e t by a feed device that drives the motor (7) in such a way powered that upon completion of the auto focus process by means of the automatic focusing device that by means of the automatic Focusing device displaceable part of the photographic optics (1) is displaceable to a predetermined point within the displacement range. 12. Camera with semi-automatic focusing device according to claim 10, signed by a body that has the appropriate Circuit parts energized until the part of the photographic optics (1) passed through the automatic focusing device is slidable to a specific location returned within the displacement range after the automatic Focusing has been carried out by the automatic focuser is.