JPH0614133B2 - Focus information detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is a focus used in an image pickup apparatus in which a subject image is formed on a photoelectric conversion surface by an optical system including an image pickup lens to obtain a video signal. The present invention relates to an information detection device.

[Conventional technology]

Conventionally, as one of the focus information detecting devices of this type, there is a device using a detecting means based on image shift. FIG. 1 shows an example of the operation principle. In the figure, 1 is a subject, and an optical image of the subject 1 is formed as an image 3 by a lens 2 on a photoelectric conversion surface such as an image pickup device or an image pickup tube installed at a focus position F0. In this case, at the non-focus position F1 in front of the focus position, the light flux 4 that has passed through the upper half area of the lens 2 and the light flux 5 that has passed through the lower half area of the lens 2 respectively pass through the positions shown in the figure. Therefore, the non-focus position F1
In, there is a deviation of 1 between 4 and 5. Further, at the non-focus position F2 behind the focus position F0, the
The positional relationship between and is reversed to 6 and 7.

As a means for obtaining the information of the displacement amount 1, as shown in FIG. 1, the small lens groups 8a, 8b,
Install multiple ... Thus, the small lens groups 8a, 8b, ...
A pair of photoelectric conversion elements 9a, 10a, 9b, 10b ... Are installed with the center of each lens as a boundary, and the light flux passing through the lower region of the lens 2 is made incident on the photoelectric conversion elements 9a, 9b. The light flux passing through the upper region of the lens 2 is made incident on the elements 10a, 10b, .... Then, the focus information detector 11 reads the photoelectric conversion outputs in the order of the photoelectric conversion elements 9a, 9b ..., Obtains the time-series image information 4 or 6 and the photoelectric conversion elements 10a, 10b.
The photoelectric conversion output is read in this order, the time-series image information of 5 or 7 is obtained, and the spatial deviation amount of the obtained image information of both is signal-processed to output focus information from the output terminal 12. .

As described above, the conventional focus information detection device requires a plurality of small lens groups, and each of these small lens groups requires a pair of photoelectric conversion elements, so that the configuration of the detection system is extremely complicated. In addition, the alignment of the small lens group and the photoelectric conversion element group was very troublesome. Therefore, there is a problem that the cost is inevitable.

On the other hand, in a microscopic photographic device, etc., a light-shielding plate having an aperture arranged near the pupil position of an optical system is stepped so that the aperture crosses the pupil in a plane perpendicular to the optical axis with a point outside the pupil as the center. Conventionally, a technique has been proposed in which the lens is continuously rotated and the focus is adjusted by adjusting the lens position so that the image position does not move due to this rotation (JP-A-57-179810). According to the technique described in this publication, since the plurality of small lens groups as described above with reference to FIG. 1 are not required, the configuration of the detection system is remarkably complicated, and the small lens group and the photoelectric conversion element group are combined. There is no problem itself that alignment of is very time-consuming. However, in the technique disclosed in the publication, when an operator visually focuses the microscopic device, the depth of focus is so deep that it is difficult to discriminate whether or not it is in a strictly focused state with a low magnification. This is intended to enable proper focus state recognition even when is selected, and focus detection itself is not inherently a function of the apparatus itself. Further, since it is a method of continuously rotating the light shielding plate in a stepwise manner, it is indispensable to include a mechanically movable member, which causes harmful vibrations and wear of the movable portion. There is an unavoidable problem. Further, the configuration including such a mechanically feasible member as an essential element becomes an obstacle to downsizing of the device.

On the other hand, as an automatic focus adjustment device for cine cameras, a refracting optical element is arranged near the image forming surface of an objective lens, and the refracting optical element is moved by changing its refraction direction at a constant cycle. The effect equivalent to vibrating in the front-back direction is obtained, and only when the image formed by the objective lens is imaged on this refractive optical element, when the image is seen from the back of this refractive optical element, the formed image is stationary. It is visible, and when this image is formed at a position displaced from the refractive optical element in the front-back direction, the image appears to vibrate, and a photoelectric element is arranged behind the refractive optical element to detect the image shake, There is also proposed a method in which the AC component of the output of this photoelectric element is amplified and rectified so that the objective lens is stopped at a position where this AC component is minimized (Japanese Patent Laid-Open No. 53-19028). Even the device disclosed in the publication does not require a plurality of small lens groups as described above with reference to FIG. 1, so that the configuration of the detection system is remarkably complicated and the positioning of the small lens group and the photoelectric conversion element group is performed. The problem itself, which is very time-consuming, does not occur. However, since it is indispensable to include a mechanically movable member for constantly moving the refracting optical element in a constant cycle, there is an unavoidable problem such as vibration generated from this mechanical portion and wear of the movable portion. . Further, as described above, the configuration including such a mechanically movable member as an essential element becomes an obstacle to downsizing of the device.

In any of the techniques described in any of the above-mentioned publications, the movement itself of the light shielding plate or the refraction optical element has nothing to do with the intensity of the incident light. Therefore, it is necessary to separately control the exposure amount in the apparatus. It is necessary to provide the means of. Further, in the latter case, it is necessary to specially provide a light receiving element as an element of the focus detection optical system separate from the photographing optical system, and therefore the configuration of the entire apparatus must be more complicated. .

Further, in a configuration in which a light shielding plate that continuously rotates in steps is inserted in the photographing optical system, there is a problem that securing the light amount of the photographing (imaging) optical system is hindered.

[Problems to be Solved by the Invention]

The present invention has been made to solve the above-mentioned conventional problems, and the first invention is for focus detection without providing a separate means for controlling the exposure amount in the apparatus. The second invention aims to achieve simplification and miniaturization of this type of device by making the optical element of the present invention also have a function of controlling the exposure amount, and the second invention is excellent in durability and small in size without causing vibration or wear. It is an object of the present invention to realize an apparatus of this type that is easy to realize and that does not substantially hinder the securing of the light amount of the imaging optical system.

[Means and Actions for Solving Problems]

In order to solve the above-mentioned problems, the device of the first invention of the present application inserts a light flux controlling means including at least a pair of light transmittance varying portions into an imaging optical system, and the light transmittance varying portions are used to transmit the light transmittance varying portions. The focus is detected by focusing by detecting the phase shift between the shifted images by driving the lens so as to change the ratio sequentially and repeatedly. An information detection report device, characterized in that the light transmittance of the light transmittance variable portion is adjusted in accordance with the incident light intensity. The change in the light transmittance is used both for detecting the phase shift of the image and for controlling the exposure amount, and simplification and miniaturization as this type of device can be achieved.

According to a second aspect of the present invention, a light flux controlling means including at least a pair of light transmittance varying portions is inserted in the image pickup optical system, and the light transmittance varying portions are driven so as to sequentially and repeatedly change the light transmittance. A focus information detection report device for detecting focus by detecting an image whose position is shifted according to the focus state of the image pickup optical system and detecting a phase shift between the shifted images. An image pickup device for obtaining the video signal related to the image pickup optical system is configured to also serve as the detection of the phase shift,
Moreover, while using a liquid crystal for the light transmittance variable portion,
After the focus is detected, the drive for changing the light transmittance of the light transmittance changing section is stopped, and the liquid crystal is used for the light transmittance changing section. In addition to essentially avoiding the vibration and wear problems peculiar to the movable mechanical element, after the focus is detected, the drive for changing the light transmittance of the light transmittance variable section is stopped so that the imaging optical It is less likely that the securing of the light amount of the system is substantially hindered.

〔Example〕

2 and 3 are diagrams showing a schematic configuration of an optical system in an embodiment of the present invention. In FIG. 2, the subject 21
The light image of is passed through the lens 22, passes through the pair of holes 24 and 25 of the light flux control plate 23 provided in the vicinity of the exit pupil of the lens 22, and is formed on the photoelectric conversion surface 27 of the image pickup element 26.
The pair of holes 24 and 25 are provided at symmetrical positions with respect to the center O of the light flux controlling plate 23. The portions other than the pair of holes are formed of a light shielding member. Thus, the pair of holes 24 and 25 are respectively formed in the upper region 2 of the lens 22.
An image formed by the light flux passing through 2a and the lower region 22b is formed on the photoelectric conversion surface 27. As a result of the above results, the image formed on the photoelectric conversion surface 27 does not cause an image shift when focused, but causes an image shift in the vertical direction when the subject is out of focus, as indicated by reference numerals 31 and 32 in FIG. .

FIG. 4 specifically shows the configuration of the light flux controlling plate 23. In FIG. 4, 41 is a polarizer, 42 is a light shielding member, 43 is a liquid crystal layer, 44 is a transparent electrode, 45 is an analyzer, and these are laminated. The light shielding member 42 is provided with the pair of holes 24 and 25 described above, and the transparent electrodes 46 and 47 are fitted therein. 46a and 47a are electrodes for applying an alternating electric field to the transparent electrodes 46 and 47, respectively, and are led out to the outside by a lead wire or a thin film pattern. Incidentally, the polarizer 41 and the analyzer 4
The polarization angle is orthogonal to 5.

Thus, when an appropriate AC electric field is applied to the liquid crystal layer 43 through the transparent electrodes 46 and 47, the rotation of the incident light 48 and 49 in the polarization direction in the liquid crystal layer is minimized and the transmitted light is minimized. When no light streaming electric field is applied, the plane of polarization is rotated by 90 ° in the liquid crystal layer 43, and the transmitted light becomes maximum.

FIG. 5 is a block diagram showing the electrical configuration of the control system. In FIG. 5, the signal output from the photoelectric conversion surface 27 of the image pickup device 26 is supplied to the video processor 51, becomes an NTSC video signal as shown in FIG. 6A, for example, and is output from the output terminal 52. This video signal is also supplied to the vertical sync separator 53, and the vertical sync signal as shown in FIG. 6B contained in the video signal is separated and extracted. The separated and extracted vertical synchronizing signal is flip-flop circuit 54.
Trigger. The signal as shown in FIG. 6C output from the flip-flop circuit 54 is directly input to one of the AND gates 55, and the polarity is inverted by the inverter 56 to become a signal as shown in FIG. One input. A square wave pulse train is applied from the terminal 58 to the other inputs of the AND gates 55 and 57.
Thus, the AND gates 55 and 57 respectively output square wave pulse trains as shown in FIGS. 6E and 6F. The outputs of the AND gates 55 and 57 are transparent electrodes 46, which are fitted into the pair of holes 24 and 25 of the light flux controlling plate 23, respectively.
It is applied to 47 to switch the holes 24 and 25 to the light transmitting state or the light shielding state. In this embodiment, a pair of holes 24, 25
When the square wave pulse trains from the AND gates 55 and 57 are applied to the transparent electrodes 46 and 47, that is, when the liquid crystal layer 43 light streaming electric field is applied, the square wave from the AND gates 55 and 57 is generated. Pulse train has transparent electrodes 46, 4
7 is not applied, that is, when the AC electric field is not applied to the liquid crystal layer 43, the light transmitting state is achieved.

As a result, the holes 24 and 25 are formed for each field period of the video signal.
The light-transmitting state and the light-shielding state are switched. That is, as shown in FIG. 6, in the odd field period TA, for example, the hole 24 is in the light transmitting state and the hole 25 is in the light shielding state. On the contrary, in the even field period TB, the hole 24 is in the light shielding state and the hole 25 is in the light transmitting state. As described above, the image formed on the photoelectric conversion surface 27 is vertically displaced when it is out of focus. However, in this apparatus, in the odd field period TA, it is formed by the light flux passing through the upper half area of the lens 22. In the even field period TB, the image is formed by the light flux passing through the lower half region of the lens 22. as a result,
There is no phase shift between the video signal in the odd field period TA and the video signal in the even field period TB during focusing, but there is a phase shift during non-focusing.

Further, the phase shift direction is opposite when the focus position moves forward (to the lens side) with respect to the position of the photoelectric conversion surface 27 and when it moves backward.

The video signal output from the video processor 51 is envelope-detected by the envelope detector 59 as shown in FIG. 6G, and then the high-frequency component is removed by the LPF 60 as shown in FIG. 6H. The reason for providing the LPF 60 is that when a differential output of video signals is obtained, as will be described later,
This is to prevent the polarity of the differential output from fluctuating when a high-frequency component is present in the video signal, and it becomes impossible to determine which side the focus is off. LPF above
The output of 60 becomes one input of the difference circuit 61 and
By the V delay circuit 62, one vertical synchronizing signal period (1/60
Then, it becomes the other input of the difference circuit 61. Further, the output of the LPF 60 is supplied to the gradient detector 62 =, and either the positive gradient region or the negative gradient region of the signal is detected. The output of the gradient detector 62 = is given to the analog gate 63 as a control signal. Therefore, of the difference output from the difference signal 61 applied to the analog gate 63, only one of the positive slope region and the negative slope region passes. The signal passing through the analog gate 63 is supplied to the lens driving motor 65 as focus information via the envelope detector 64.

7 (a) and 7 (b) are waveform charts showing the operation when obtaining the focus information, 71 is a waveform showing an example of the video signal, and 72 is delayed by the 1V delay circuit 62. It is a signal waveform. As is well known, there is a strong correlation between the fields of the video signal, and no significant difference occurs in the signal waveform between adjacent fields except for a subject that moves extremely fast. Therefore, in the in-focus state, the phases of the image signals 71 and 72 are the same, and when the focus position is in the front direction of the photoelectric conversion surface 27, the phase of 71 is different from the phase of 72 as shown in FIG. When the focus position is delayed or, conversely, the focus position is rearward, the phase of 71 advances with respect to 72 as shown in FIG. 73
a, 73b and 74a, 74b are the difference circuit 61 and the signal 72.
Is a difference signal obtained by subtracting the signal 71 from. Now, when the positive polarity gradient region (region in the direction of the central arrow in FIG. 7) of the video signal is gated by the control signal from the gradient detector 62 ', the difference signal becomes 73a or 73b depending on the defocusing direction.
Becomes The magnitude of the difference signal 73a or 73b is the amount of focus shift. This difference signal 73a or 73b
The signal obtained by envelope detection of is the focus information.

In the above structure, for example, a liquid crystal divided into a plurality of holes is applied as the liquid crystal layer 43, and a voltage corresponding to the intensity of subject light (incident light) is applied to each liquid crystal. By doing so, light flux controlling plate 23 as the light transmittance varying portion
Since the light transmittance of the hole is adjusted according to the incident light intensity, the same effect as the conventional iris control can be obtained.

Further, by controlling the magnitude of the voltage applied to the liquid crystal to make the change between the light-transmitting state and the light-blocking state gentle, the same effect as the conventional iris control can be obtained.

As described above, in the present apparatus, such adjustment of the light transmittance of the light transmittance variable portion causes the change in the light transmittance of the light transmittance variable portion to detect the exposure amount in order to detect the phase shift of the image. It is also used for the control of, and simplification and miniaturization as this type of device can be achieved. Further, since the phase shift state is detected and the focus information is obtained by utilizing the correlation between the video signal of the field at a certain time and the video signal of the field immediately before that, the detection system can be simplified.

Furthermore, in addition to the above configuration, only when the focus is not detected, that is, when focus detection is desired, the holes of the light flux control plate are alternately switched to the light blocking state or the light transmitting state in synchronization with the field cycle or the frame cycle. If information is obtained and this switching is stopped after focusing, and both holes 24 and 25 are made to be in a transparent state, deterioration of image quality due to flicker noise due to this switching is focused. After that, it does not occur, and it is possible to secure a light amount of about twice as much as when switching is continued. As described above, this device is configured so that the image pickup device for obtaining the video signal for detecting the phase shift is also used for this detection, and the liquid crystal is used as the light transmittance adjusting member. Therefore, the structure is simplified, and problems such as deterioration in accuracy or performance and increase in size due to aging that are inevitable when using a movable mechanical element are essentially solved. still,
If the light flux control plate 23 is used only during focus detection and the light flux control plate 23 is moved to the outside of the optical path by a motor or the like during image pickup, the effective light flux can be further increased.

Further, as shown in FIG. 8, the light shielding member portion of the light flux controlling plate is replaced with transparent electrodes 81 and 82, and when focusing, the hole 2
It is also possible to increase the effective luminous flux by making not only the transparent electrodes 46 and 47 fitted in the Nos. 4 and 25, but also the transparent electrodes 81 and 82 in the light transmitting state. In FIG. 8, 83 and 84 are insulators such as glass, and 85 is electrodes for the transparent electrodes 81 and 82.

As shown in FIG. 9, during focus detection, focus detection is performed by the system of the half mirror 92 and the mirror 93 in the quick return mirror 91, the mirror 94, the field lens 95, the light flux control plate 23, the imaging lens 96, and the image pickup device 26. It can be said that the configuration in which the quick return mirror 91 is flipped up and the light flux is incident on the image sensor 97 to perform the image capture at the time of image capture after focusing is sufficient to secure a sufficient effective light flux.

It should be noted that the image shift state described above may be displayed on a TV monitor so that the degree of focusing can be observed.

〔The invention's effect〕

According to the first invention of the present application, an optical element for focus detection is provided with an exposure amount control function without providing a separate means for controlling the exposure amount in the device, and thus as an apparatus of this type. According to the second aspect of the present invention, the durability of the image pickup optical system is excellent, the size and size of the image pickup optical system are substantially secured, and the light amount of the image pickup optical system is substantially secured. It is possible to realize a device of this kind that is less likely to be disturbed.

[Brief description of drawings]

FIG. 1 is a diagram showing the operating principle of a conventional focus detection device, and FIG.
FIGS. 1 to 7 are views showing an embodiment of the present invention, FIG. 2 is a view showing a schematic configuration of an optical system, FIG. 3 is a view showing a state of image shift obtained by the optical system, and FIG. FIG. 5 is a diagram showing the structure of the light flux control plate, FIG. 5 is a block diagram showing the electrical configuration of the control system, FIG. 6 is a signal waveform diagram for explaining each part of the operation, FIGS. 7 (a) and 7 (b). ) Is a signal waveform diagram for explaining the operation of the focus information detection unit, FIG. 8 is a diagram showing a main part of another embodiment, and FIG. 9 is a diagram showing a configuration effective for sufficiently securing an effective luminous flux. Is. 24 ... Subject, 22 ... Lens, 23 ... Light flux control plate, 24, 25 ... Pair of holes, 26 ... Imaging element, 27
...... Photoelectric conversion surface, 41 ...... Polarizer, 42 ...... Light blocking member,
43 ... Liquid crystal layer, 44 ... Transparent electrode, 45 ... Analyzer,
46, 47 ... Transparent electrodes

Claims (2)

[Claims] 1. A light flux control means including at least a pair of light transmittance variable portions is inserted in an image pickup optical system, and the light transmittance variable portions are driven so as to sequentially and repeatedly change the light transmittance. A focus information detection device for detecting focus by obtaining an image whose position is shifted according to the focus state of the image pickup optical system and detecting the phase shift between the shifted images. A focus information detecting and recording device characterized in that the light transmittance of the variable portion is adjusted according to the intensity of incident light. 2. A light flux control means including at least a pair of light transmittance variable portions is inserted in an image pickup optical system, and the light transmittance variable portions are driven so as to sequentially and repeatedly change the light transmittance. A focus information detection report device for detecting focus by obtaining an image whose position is shifted according to a focus state of the image pickup optical system and detecting whether a phase shift between the shifted images is detected. The imaging device for obtaining the video signal according to is also configured to be used also for detecting the phase shift, and liquid crystal is used for the light transmittance varying unit, and it is detected that focusing is achieved. After that, the focus information detecting and reporting device is characterized in that the drive for changing the light transmittance of the light transmittance changing portion is stopped.