JPS6238674A - Electronic camera with automatic focusing device - Google Patents

Abstract

PURPOSE:To attain high class camera by fixing a rear-group lens system of a lens system in a camera main body and arranging the rear-group lens system so as to be vibrated for wobbling and replacing a lens at the front-group lens system. CONSTITUTION:An image pickup optical system consists of the rear-group lens system 11 and a front-group lens system 12, the system 11 is fixed to a camera main body 10 and the system 12 is provided freely attachably and detachably to the system 11. A focus information detecting means 17 generates a focus information detecting signal based on an output of a photoelectric transducing means 15. A drive means 13 moves the lens system 11 or a photoelectric transducing means 15 based on said detection signal. A shutter control means 18 opens a shutter 14 when a focus information detection signal is detected and after the movement is finished, the shutter 14 is closed. Thus, the replacement of lens is applied only at the lens system 11 and the lens system 11 is subject to position modulation in the optical axis direction and the focusing is detected by the wobbling system.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention captures a still image, records it on an image recording device, and
Regarding electronic cameras dedicated to still images that can be played back,
More specifically, the present invention relates to an automatic focus adjustment device for an electronic camera with interchangeable lenses.

[Prior Art] Since an electronic camera uses an image sensor such as a CCD, this image sensor can be used as an automatic focus adjustment device. The wobbling automatic focus adjustment device performs automatic focus adjustment by vibrating the lens system in the optical axis direction, and uses the imaging optical system and image sensor of an electronic camera for automatic focus adjustment as well as imaging. It is not necessary to provide a device. Therefore, the electronic camera can be made small in size and is also advantageous in terms of cost. Further, since the wobbling automatic focusing device vibrates the lens system or the image sensor in the optical axis direction, problems arise in electronic cameras that use interchangeable lenses.

[Problems to be Solved by the Invention] Therefore, in this invention, the rear group lens system of the imaging lens system, which is an imaging optical system, is fixed in the camera body, and this rear group lens system can be vibrated for wobbling. The objective of the lens exchange is to make electronic cameras more sophisticated by making it possible to replace only the front group lens system of the imaging lens system with the camera body. Therefore, the imaging optical system is of the TTL type, which is also used for autofocus, and is configured so that only the front group lens system can be detachably attached to the camera body as an interchangeable lens.

[Means and operations for solving the problems] In order to achieve the above object, the present invention, as shown in FIG. An imaging optical system includes a front lens group 12 that is detachably attached to a group lens system 11, and a subject light image is formed on a photoelectric conversion light receiving surface by the imaging optical system to obtain a video output signal. a photoelectric conversion means 15; a shutter 14 disposed in the optical path between the imaging optical system and the photoelectric conversion means 15; and a focus information detection unit that generates a focus information detection signal based on the output of the photoelectric conversion means 15. means 17, a driving means 13 for moving the rear group lens system 11 of the imaging optical system or the photoelectric conversion means 15 to a focus position based on the focus information detection signal, and the focus information detection means 17. While detecting the focus information detection signal, the shutter 1
4 and a shutter control means 18 for closing the shutter 14 after the movement of the imaging optical system or the photoelectric conversion means 15 is completed by the driving means 13. Therefore, since the rear lens group of the imaging lens system is disposed on the camera body side, only the front lens group is replaced when replacing lenses. The position of the rear group lens system is modulated in the optical axis direction, and focus detection is performed by a so-called wobbling method.

[Embodiment] Hereinafter, embodiments of the present invention will be explained in detail with reference to FIGS. 2 to 9. In FIGS. 2 and 3, a lens mount section 2o is provided on the front surface of the electronic camera body 10 for detachably attaching the front group lens system 12 to the camera body 10. A lens mount portion 21 disposed at the base of the front group lens system 12 can be fitted into the lens mount portion 21 .

Furthermore, two guide rails 22.22 are provided vertically on the inner wall of the front surface of the electronic camera body 10, and a slider 23 is slidably disposed on the guide rails 22.22. . The slider 23 is elastically biased inward of the electronic camera body 10 by a tension spring (not shown), and the output shaft of the motor 43 is attached to a contact surface 23A connected to the side of the slider 23. When the cam surfaces of the eccentric cam 43B attached to the eccentric cam 43A collide with each other to rotate the motor 43, the slider 23 can be moved in the optical axis direction by the cam surface of the eccentric cam 43B. At the center of the slider 23, a bobbin 26 in which a wobbling coil 47 is disposed is supported by a damper 25, and the rear group lens system 11 is fixed to the bobbin 26. Further, around the coil 47 of the bobbin 26, there is an annular magnet that forms a so-called voice coil type magnetic enclosure.・24 is fixed. Furthermore, behind the rear group lens system 11, a shutter 14 and a CCD type photoelectric conversion means 15 are sequentially arranged.

Next, a circuit built into such an electronic camera body 10 will be explained using FIG. 4. In FIG. 4, the output terminal of the photoelectric conversion means 15 is connected to the input terminal of a video processor 30 that generates a desired video signal such as NTSC, and a video output signal S is output from the output terminal of the video processor 30 to an image (not shown). The signal is sent to a recording circuit, etc. This video processor 30 includes a synchronization signal generation circuit 31
Signal processing is performed based on various synchronization signals of the vertical and horizontal rings sent from the photoelectric conversion means 15, and photoelectric conversion operation is similarly performed based on various synchronization signals of the photoelectric conversion means 15. ing. The video processor 30 and the synchronization signal generation circuit 31 constitute the video signal generation section 16. The video output signal S generated at the output end of the video signal generation section 16, ie, the output end of the video processor 30, is converted into a focus information detection signal G by the focus information detection means 17. That is, from the video output signal S, after only the brightness signal A is separated and extracted by the brightness signal separation circuit 32 as shown in FIG. High frequency components of several hundred KHz of signal A are extracted. This horizontal synchronization period component of signal B is removed by analog gate 34 to become signal C. That is, the analog gate 34 prohibits the transmission of the signal B during the H level period of the horizontal blanking pulse D sent from the synchronization signal generation circuit 31, in other words, removes the component of the horizontal synchronization period.

The signal C is subjected to envelope detection by the detection circuit 35 and becomes a signal E. This signal E is provided with focus information by sequentially passing through a band pass filter (hereinafter referred to as rBPFJ) 36 and a sampling hold circuit (hereinafter referred to as "88 circuit") 37, as will be described in detail later. A detection signal G is obtained. This focus information detection signal G is determined by the focus detection circuit 41 as to whether or not the focus is in focus, and if the result of the determination is that the focus is in focus, a focus signal H1 and a motor stop signal H3 are sent out. It is supposed to be done. Note that the control end of the SH circuit 37 includes a sampling pulse generation circuit (hereinafter abbreviated as "SP generation circuit").
A sampling pulse F sent out from 40 is supplied.

On the other hand, according to the focus information detection signal G, the rear group lens system 1
1 (see FIGS. 1 to 3) is provided with a driving means 13 for driving the lens to a focusing position. This driving means 13
is a signal obtained by DC amplifying the focus information detection signal G by a DC amplifier 42 to rotate a motor 43;
The rotation of No. 3 is controlled to be stopped by a switch circuit 44 that is closed by a motor stop signal H3.

Further, an oscillator 39 is provided which serves as a source for wobbling the rear group lens system 11, and the output terminal of this oscillator 39 is supplied with a drive signal to a wobbling coil 47 via a drive circuit 38. This coil 47 is controlled to stop wobbling by a switch circuit 56 which is closed by a wobbling stop signal H. The wobbling stop signal H1 sent from the focus detection circuit 41 triggers an OR gate 46. The above-mentioned wobbling stop signal H is provided through the OR gate 46, and the pull-up resistor 4 connected to the operating power supply element B is connected to the OR gate 46.
A shutter release signal H2 formed by a series circuit of 5 and a shutter release switch 60 is also supplied.

On the other hand, a shutter control means 18 is provided for controlling the opening and closing of the solenoid 55 of the shutter based on the wobbling stop signal H. This shutter control means 18 controls opening and closing of the shutter 14 (see FIGS. 1 to 3) based on the wobbling stop signal H. The wobbling stop signal H is generated when the focus signal H1 from the focus detection circuit 41 is inverted to H level, or when the shutter release switch 60 is opened with the shutter release and the shutter release signal H2 is generated.
is inverted to the H level when the signal is inverted to the H level. The pulse generation circuit 48 is triggered by the rising of the wobbling stop signal H to the H level, and a signal is generated from the output terminal of the pulse generation circuit 48 that maintains the H level for the time necessary for the photoelectric conversion means 15 to discharge charges. I is generated. Then, the L of this signal l
The variable pulse generation circuit 49 is triggered by the fall to the level, and an H level pulse signal J corresponding to the shutter time is generated. The pulse generation circuit 51 is triggered by the falling of the signal J to the L level, and the pulse generation circuit 51 is triggered to generate an H signal corresponding to the signal readout time in the photoelectric conversion means 15.
A level pulse signal K is generated. This signal is input manually to the pulse generating circuit 52 together with the wobbling stop signal H. This pulse generation path 52 is a so-called latch circuit formed of Nant gates 52C and 52D, a fall detection capacitor 52A, and a pull-up resistor 52B, as shown in FIG. The signal R generated at the output end of the pulse generating circuit 52 and the signal J are supplied to the solenoid 55 through respective diodes 53 and 54 forming an OR circuit. Further, the output signal of the oscillator 39 is transmitted to the drive circuit 38.
is converted into a drive signal M, and this drive signal M is supplied to the coil 47.

This drive signal M is short-circuited by a switch circuit 56 activated by the wobbling stop signal H.

Therefore, in the initial state when operating power is supplied to each part of the circuit, the wobbling stop signal H1 sent from the focus detection circuit 41 is at L level and the shutter release signal H2 is also at L level because it is out of focus. Along with this, the wobbling stop signal H is maintained at the L level. Therefore, when the coil 47 is energized by the drive signal M based on the output of the oscillator 39, the rear lens group 1
1 vibrates in the optical axis direction. At this time, the rear group lens system 11
As shown in FIG. 7, if the amount of displacement is ±g, the signal C (analog gate 3
4) is amplitude-modulated at a frequency twice the frequency of the drive signal M, as shown by symbol CJ, when in focus. Further, in the case of the rear bin, the amplitude is modulated with the frequency of the drive signal M as shown by the symbol CO, and in the case of the front bin, the amplitude is modulated with the frequency of the drive signal M as shown by the symbol CU. At this time, the phases of Co and CU become signals that differ by 180 degrees depending on the movement of the lens in the front bin direction and the rear bin direction with the focus position as the boundary. Then, such a signal is subjected to envelope detection by a detection circuit 35, and a signal E, which is passed through a BPF 36 whose center frequency is equal to the frequency of the drive signal M, has a symbol EJ as shown in FIG.

It will be like EO and EU. This signal E is used as the drive signal M
When sampling and holding is performed with a sampling pulse F equal to the frequency of , the focus information detection signal G corresponding to the focus state is
will be obtained. As shown in FIG. 8, the focus information detection signal G obtained in this way has voltages in different directions on the front focus side and the rear focus side with the signal GJ obtained in the focused state as the boundary. value is obtained.

Therefore, the motor 43 is rotationally driven based on the focus information detection signal G, and the rear group lens system 11 is driven toward the in-focus position by the eccentric cam 43B and the like described above. After that, when the focus detection circuit 41 determines that the focus information detection signal G is in focus, the wobbling stop signal H1
and a drive stop signal H3 are generated, the switch circuit 44 is activated, and the drive of the motor 43 is stopped. At the same time, the wobbling stop signal H1 passes through the OR gate 46, actuating the switch circuit 56 to cut off the current to the coil 47, and triggering the pulse generating circuit 52 to generate an H-level pulse as the signal, thereby turning off the diode 54. The solenoid 55 is energized through the solenoid 55. Then, the shutter 14 is closed and the charge from the CCD type photoelectric conversion means 15 is discharged.

When this charge discharging is completed, the shutter 14 is opened for the exposure time set by the variable resistor 50 according to the signal J. Thereafter, the pulse generation circuit 51 is triggered by the falling of the signal J to the L level, and the rising signal of the signal K activates the solenoid 55 and the shutter 14 is closed. At the same time, the charges accumulated in the CCD type photoelectric conversion means 15 during the exposure time are read out.

This read signal is subjected to appropriate signal processing by the video processor 30 and sent as a video output signal S to an image recording circuit (not shown) or the like.

At this time, the video output signal S causes the wobbling drive of the rear group lens system 11 by the coil 47 and the motor 4 again after the focus information detection means 17 finishes reading out the accumulated charge.
3, the movement to the in-focus position is performed.

Note that the present invention is not limited to the above-described embodiments, and can be modified in various ways. That is, in the above embodiment, the rear group lens system 11 is wobbled, but the photoelectric conversion means 15 may be wobbled instead.

[Effects of the Invention] As described above, the present invention provides an electronic still camera that can obtain focus information by wobbling the rear group lens system forming the imaging means or the photoelectric conversion means, and can also easily exchange lenses. can get.

Therefore, there is no need to separately install an automatic focus adjustment device, and the lenses of the imaging optical system can be easily replaced.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram for explaining the present invention in detail. FIG. 2 is a schematic sectional view of an electronic camera showing an embodiment of the present invention. FIG. 3 is a perspective view as well. 5 is an electric circuit diagram showing details of the pulse generation circuit shown in FIG. 4, and FIGS. 6 to 9 are block circuit diagrams for explaining the operation of the electric circuit shown in FIG. 4. FIG. 10... Electronic camera body 11... Rear group lens system 12... Front group lens system 13... Drive means 14... Shutter 15 ...Photoelectric conversion means 17 ... Focusing information detection means 18 ... Shutter control means 1 Ward Atsushi 2 Ward Ma 5 Ward Ma 6 Ward also 7 Ward

Claims (1)

[Scope of Claims] An imaging optical system consisting of a rear group lens system provided on an electronic camera body and a front group lens system detachably provided with respect to the rear group lens system; a photoelectric conversion means for forming an image on a photoelectric conversion light-receiving surface by an imaging optical system to obtain a video output signal; a shutter disposed in an optical path between the imaging optical system and the photoelectric conversion means; and an output of the photoelectric conversion means. a focus information detection means for generating a focus information detection signal based on the focus information detection signal; and a drive for moving the rear group lens system of the imaging optical system or the photoelectric conversion means to a focus position based on the focus information detection signal. means, the shutter is opened while the focus information detection signal is detected by the focus information detection means, and the shutter is opened after the movement of the imaging optical system or the photoelectric conversion means is completed by the drive means. An electronic camera with an automatic focusing device, comprising: a shutter control means for closing;