JP2003270520A - Focus state detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a focus state detector which can change the spectral distribution of subject light for detecting the focus state and subject light for videos according to need by making it possible to exchange spectroscopic means for separating the subject light for detecting the focus state from the subject light for videos. <P>SOLUTION: A holder 26 is mounted with a plurality of spectral prisms 24A and 24D varying in spectral distribution and the spectral prisms to be used is changed over by rotating the holder 26. As a result, the spectral prism is changed over to the spectral prism of such spectral distribution as to increase the quantity of the subject light for videos when the image picked up by an imaging device for videos is dark and conversely the spectral prism is changed over to the spectral prism of such spectral distribution as to increase the quantity of the subject light for detecting the focus state when the subject light for detecting the focus state is insufficient, by which the conduction of photographing in an always optimum state and the detection of the focus state is made possible. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus state detecting device, and more particularly to a focus state of a photographing lens for separating a subject light for focus state detection from a subject light for image incident on an image pickup device for image of a camera body. The present invention relates to a focus state detection device for detecting a.

[0002]

2. Description of the Related Art Conventionally, a focus detection method called a wobbling method has been known as one of focus detection methods for video cameras and the like. This wobbling method periodically vibrates the focus lens or the image sensor (wobbling).
Then, the focus state is detected from the state of fluctuation of the focus evaluation value at that time.

However, this wobbling method has a drawback that the image quality is deteriorated by wobbling of an image pickup device or the like.

Therefore, in order to eliminate such a drawback of the wobbling method, Japanese Unexamined Patent Publication No. 8-502227 discloses that
Image sensor for focus state detection that separates the object light for focus state detection from the image light for image incident on the image sensor for video and provides the separated object light for focus state detection separately from the image sensor for video It is proposed to detect the focus state by irradiating the focus element on the optical axis and wobbling the image sensor for focus state detection in the optical axis direction.

[0005]

However, when the focus state is detected by separating the subject light for detecting the focus state from the subject light for video as in Japanese Patent Laid-Open No. 8-502227, only the separated amount is detected. There is a drawback that the amount of subject light incident on the image pickup device for images becomes small and the image to be shot becomes dark.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a focus state detection device capable of changing the spectral distribution of the focus state detection subject light and the image subject light as needed. To aim.

[0007]

The invention according to claim 1 is
In order to achieve the above-mentioned object, the focus state detection subject light is separated by the spectroscopic means from the image subject light incident on the image pickup device of the camera body through the photographing lens, and the focus state detection subject light is focused. In the focus state detection device that is incident on the state detection image pickup device and detects the focus state of the photographing lens based on the high frequency component of the image picked up by the focus state detection image pickup device, the spectroscopic means is detachable. Alternatively, it is possible to switch the light amount distribution of the focus state detection subject light separated from the image subject light by switching to a spectroscopic means having a different spectral distribution, and a focus state detection device. I will provide a.

In order to achieve the above-mentioned object, the invention according to claim 2 can be switched to a transmitting means for transmitting all of the image subject light in place of the spectroscopic means. To provide a focus state detecting device.

Further, in order to achieve the above-mentioned object, the invention according to claim 3 is characterized in that the spectroscopic means to be replaced have the same air conversion length, and the focus state detection according to claim 1 or 2. Provide a device.

In order to achieve the above object, the invention according to claim 4 is characterized in that a plurality of spectroscopic means having different spectral distributions are provided so as to be switchable by a switching means. Alternatively, a focus state detection device according to item 3 is provided.

According to a fifth aspect of the invention, in order to achieve the object, the switching means is configured by disposing the plurality of spectroscopic means on a concentric circle of a rotatably supported holder. The focus state detection device according to claim 4, wherein the spectroscopic means to be used is switched by rotating the holder.

In order to achieve the above-mentioned object, the invention according to claim 6 is a driving means for driving the switching means,
A control means for controlling the drive means so that a predetermined amount of light of the video subject light is incident on the video imaging element based on the image captured by the video imaging element. A focus state detection device according to claim 4 or 5 is provided.

In order to achieve the above object, the invention according to claim 7 is a driving means for driving the switching means,
A control unit that controls the drive unit so that a predetermined amount of focus state detection subject light is incident on the focus state detection image sensor based on an image captured by the focus state detection image sensor. The focus state detection device according to claim 3 or 4 is provided.

According to the present invention, the spectroscopic means for separating the focus state detection subject light from the video subject light is detachably or switchably provided, and the spectroscopic means having different spectral distribution is exchanged for the video image. It is possible to switch the light amount distribution of the focus state detection subject light separated from the subject light. Therefore, when the image picked up by the image pickup device for images is dark, it is changed to a spectroscopic unit of spectral distribution that increases the amount of the subject light for image incident on the image pickup device for images, and conversely for focus state detection. If the amount of subject light is insufficient, change to a spectroscopic distribution spectral unit that increases the amount of focus state detection subject light that is incident on the focus state detection image sensor, so that you can always shoot in optimal conditions. The focus state can be detected.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the focus state detecting device according to the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram of a television camera system to which the focus state detecting device according to the present invention is applied. As shown in the figure, this television camera system is composed of a camera body 10 and a taking lens 12.

The camera body 10 is provided with an image pickup device (hereinafter referred to as "image pickup device for image"), a required circuit, etc. for photographing a video image for broadcasting and outputting a video signal of a predetermined format or recording it on a recording medium. It is equipped. The taking lens 12 is detachably attached to the mount portion of the camera body 10.

The focus lens group 16, the zoom lens group 18, the iris 20, the relay lens group 22 and the like are arranged in the optical system of the taking lens 12, as is generally known. The relay lens group 22 includes a front relay lens 22A and a rear relay lens 22B. The front relay lens 22A and the rear relay lens 2 are included in the relay lens group 22.
Between 2B, a spectral prism 24A for splitting the subject light
Are arranged.

As shown in FIG. 2, the spectral prism 24A is held by a disc-shaped holder 26.
The holder 26 includes three spectral prisms 24A, 24
B and 24C and one optical member 24D are arranged at intervals of 90 degrees on a concentric circle centered on the rotation axis 26A.

The rotary shaft 26A of the holder 26 is supported by a bearing 28 fixed in the taking lens 12, as shown in FIG. Further, the gear 26 is provided on the outer periphery of the holder 26.
B is formed, and the drive gear 30A is meshed with the gear 26B. The drive gear 30A is fixed to the output shaft of the spectral prism switching motor 30, and the holder 26 is rotated by driving the spectral prism switching motor 30. Then, by rotating the holder 26, the spectral prism arranged on the optical axis O of the taking lens 12 is switched.

A rotation amount detection gear 32A is meshed with the gear 26B of the holder 26, and the rotation position of the holder 26 is detected by detecting the rotation amount of the rotation amount detection gear 32A with the holder potentiometer 32. To be done. The signal processing unit 34 uses the spectral prisms 24A to 24C or the optical member 24D (the spectral prism arranged on the optical axis O) currently used based on the rotational position information of the holder 26 output from the holder potentiometer 32. 24A to 24C or the optical member 24D) is detected. Then, the detected spectral prism 24A currently in use
24C or the optical member 24D is displayed on the display 54.

The holder 26 is rotated based on the operation information of the spectral prism switching controller 56. The spectroscopic prism switching controller 56 is configured to select a spectroscopic prism to be used, for example, and outputs the selection information to the signal processing unit 34. As shown in FIG. 4, the signal processing unit 34 loads the spectral prism selection information output from the spectral prism switching controller 56 into the CPU 46 via the A / D converter 44. The CPU 46 selects the spectral prism 24 selected based on the loaded spectral prism selection information and the rotational position information of the holder 26 from the holder potentiometer 32.
A control signal is output to the spectral prism switching motor drive circuit 36 via the D / A converter 69 so that A to 24C or the optical member 24D is arranged on the optical axis O, and the spectral prism switching motor 30 drives the spectral prism switching motor 30. , Rotate the holder 26.

The three spectroscopic prisms 24A to 24C are composed of two prisms, a first prism 24a ₁ , 24b ₁ and 24c ₁ and a second prism 24a ₂ , 24b ₂ and 24c ₂ , respectively, and are emitted from the front relay lens 22A. The separated subject light is branched into image subject light and focus state detection subject light. More specifically, the front relay lens 22A
The subject light emitted from the first is the first prism 24a.
_{1 to} 24c ₁ and the first prism 24a ₁ to
24c ₁ half mirror surfaces 24a ₃ , 24b ₃ , 24c
_{At 3} it is split into reflected and transmitted light. Then, the transmitted light travels along the optical axis O as image light for an image and is emitted from the second prisms 24a _{2 to} 24c ₂ . On the other hand, the reflected light travels along the optical axis O ′ orthogonal to the optical axis O as the focus state detection subject light, and the first prisms 24a _{1 to} 24a.
It is emitted from c ₁ .

Here, each of the spectral prisms 24A to 24C.
Are formed such that the image subject light and the focus state detection subject light have different spectral distributions, and each divides the image subject light and the focus state detection subject light by a predetermined light amount. For example, the first spectral prism 24A has a one-to-one correspondence between the light quantity of the subject light for video and the light quantity of the subject light for focus state detection.
The second spectral prism 24B branches the light amount of the image subject light and the light amount of the focus state detection subject light at a ratio of 2: 1. In addition, the third spectral prism 24C
Divides the light quantity of the image subject light and the light quantity of the focus state detection subject light at a ratio of 3: 1.

On the other hand, the optical member 24D allows the subject light emitted from the front relay lens 22A to pass through without branching. That is, the focus state detection subject light is not separated and all is used for the image subject light.

The spectroscopic prisms 24A to 24C and the optical member 24D are all formed to have the same air-equivalent length so that even if they are replaced, the image forming position is not displaced.

The display 54 displays the spectral prisms 24A to 24C currently in use and the spectral distribution of the spectral prisms 24A to 24C.

The image subject light that has passed through the spectral prisms 24A to 24C or the optical member 24D travels along the optical axis O, and passes through the rear relay lens 22B to the photographing lens 12.
It is injected from the rear end side. Then, the light is incident on the imaging unit 14 of the camera body 10.

Although the configuration of the image pickup unit 14 is omitted,
The subject light that has entered the imaging unit 14 is separated into three colors of red light, green light, and blue light by, for example, a color separation optical system, and enters the image pickup surface of the image pickup device for each color. As a result, a color image for broadcasting is shot. The focus plane P in the figure shows an optically equivalent position on the optical axis O of the taking lens 12 with respect to the image pickup surface of each image pickup device.

On the other hand, the focus state detection subject light reflected by the half mirror surfaces 24a _{3 to} 24c ₃ of the spectral prisms 24A to 24C travels along an optical axis O'which is perpendicular to the optical axis O, and is relayed. The light enters the focusing state detection imaging unit 40 via the lens 38.

The focus state detecting image pickup section 40 is a beam splitter 42 which divides the focus state detecting object light into three equal parts.
And the three focus state detection image pickup devices A, B and C on which the focus state detection subject light that has been split into three equal parts by the beam splitter 42 is incident.

The beam splitter 42 is composed of three prisms 42A, 42B and 42C as shown in FIGS. As described above, the spectral prism 2
The focus state detection subject light separated from the image subject light by 4A to 24C proceeds along the optical axis O ', and is first incident on the first prism 42A. Then, the half mirror surface 42a of the first prism 42A splits the light into reflected light and transmitted light. Of these, the reflected light is incident on the first focus state detecting image pickup device A, and the transmitted light is the second prism 4
It is incident on 2B.

The transmitted light incident on the second prism 42B is further split into reflected light and transmitted light by the half mirror surface 42b of the second prism 42B. Of these, the reflected light is the second
The transmitted light which is incident on the image sensor B for detecting the focus state is
It is incident on the prism 42C. And the third prism 4
The transmitted light incident on 2C is transmitted through the third prism 42C and is incident on the third focus state detecting image pickup device C.

As described above, the beam splitter 42 splits the focus state detecting subject light separated from the image subject light into three equal parts, and divides each of the divided focus state detecting subject lights into the focus state detecting image pickup device A. , B, and C. It should be noted that each of the focus state detecting image pickup devices A, B, and C does not need to pick up a color image, and in the present embodiment, is a CCD that picks up a monochrome image.

FIG. 3 shows each focus state detecting image pickup device A,
The optical axes of the subject light incident on B and C are shown on the same straight line.

As shown in the figure, the focus state detection subject light incident on each of the focus state detection image pickup devices A, B and C has the shortest optical path length of the first focus state detection image pickup device A, and The optical path length of the image sensor B for 2-focus state detection is the longest. The optical path length of the third focus state detection image pickup device C is an intermediate length between the optical path lengths of the first focus state detection image pickup device A and the second focus state detection image pickup device B.
That is, the image pickup surface of the first focus state detection image pickup element A and the image pickup surface of the second focus state detection image pickup element B are equidistant from each other with respect to the image pickup surface of the third focus state detection image pickup element C. Are arranged in parallel with. The image pickup surface of the third focus state detecting image pickup device C is in a conjugate relationship with the focus surface P of the camera body 10, and the taking lens 12
The optical path length for the subject light incident on the camera body 10
It coincides with the image pickup surface of the image pickup device for video provided in.
That is, the third focus state detection image pickup device C is arranged at a position optically equivalent to the image pickup device provided in the camera body 10, and the first focus state detection image pickup device is provided at positions equidistant from the front and rear. An image pickup surface of the image pickup element A and an image pickup surface of the second focus state detecting image pickup element B are arranged.

The images picked up by the focus state detecting image pickup devices A to C are output to the signal processing section 34, and the signal processing section 3
Reference numeral 4 denotes each focus state detection image pickup device A to A, as will be described later.
The focus state of the taking lens 12 is detected based on the video signal acquired from C. Then, a control signal is output to the focus motor drive circuit 48 based on the detected focus state and the position data of the focus lens 16 fetched from the focusing potentiometer 52, and the focus motor 50 is driven to perform AF control of the taking lens 12. To do.

Normally, the focus of the taking lens 12 is controlled by manual focus (MF) (MF
Mode), AF control is performed only when an AF switch (not shown) is turned on (AF mode). Where A
The F switch is turned on once pressed, and is automatically turned off when the taking lens 12 is focused. Therefore,
AF control is performed only once, and when the taking lens 12 is in focus, the AF mode is restored again.

Next, the focus state in the signal processing unit 34
The detection process of will be described. As shown in FIG.
Focusing state detection image pickup devices A to C
Each image is output as a video signal in a specified format.
High pass filters 70A to 70C and A / D converter 7
2A to 72C, gate circuits 74A to 74C, adder 76
Image sharpness (image contrast
Evaluation value V indicating_A, V _B, V_CConverted to the signal of
It is input to the CPU 46.

Here, the process for obtaining the evaluation values V _{A to} V _C will be described. The focus state detecting image pickup devices A to C in the present embodiment are all C for picking up a monochrome image.
Since it is a CD, each focus state detecting image pickup device A to
The video signal output from C is a luminance signal indicating the luminance of each pixel forming each screen.

The video signals output from the focus state detecting image pickup devices A to C are first passed through the high pass filter 70A.
Is input to 70 C and its high frequency components are extracted. The signals of the high frequency components extracted by the high pass filters 70A to 70C are converted into digital signals by the A / D converters 72A to 72C. Then, of the digital signals for one screen (for one field) of the image captured by each of the focus state detecting image pickup devices A to C, only the digital signal corresponding to the pixel within a predetermined focus area (for example, the central portion of the screen) Are extracted by the gate circuits 74A to 74C, and the values of the digital signals in the extracted range are added by the adders 76A to 76C. As a result, the sum of the values of the high frequency components of the video signal in the predetermined focus area is obtained, and the obtained value is an evaluation value V _A that indicates the level of sharpness of the image in the predetermined focus area. It becomes V _C.

The focus state detecting image pickup devices A to C
Each circuit such as a gate circuit 74A to 74C is provided with various synchronization signals from a synchronization signal generation circuit (not shown) to synchronize the processing of each circuit. Further, the CPU 46 is supplied with a vertical synchronization signal (V signal) for each field of the video signal from the synchronization signal generation circuit.

The CPU 46 detects the current focus state of the taking lens 12 with respect to the image pickup surface (focus surface P) of the image pickup device based on the evaluation values V _{A to} V _C obtained as described above.

Next, the taking lens 1 by the CPU 46
A method of detecting the focus state of No. 2 will be described.

FIG. 5 is a diagram showing how the focus value of the taking lens 12 is plotted on the horizontal axis and the evaluation value on the vertical axis, and how the evaluation value changes with respect to the focus position when a certain object is photographed. Curves S _A , S _B , and S _C show evaluation values obtained from the focus state detection image pickup devices A, B, and C with respect to the focus position, respectively.

Here, the third focus state detecting image pickup device C
Is located at the same position as the image pickup device for video, the position F3 where the evaluation value of the curve S _C is maximum (maximum) is the focus position in FIG.

When the focus position of the photographing lens 12 is set to the in-focus position F3, the evaluation values obtained from the focus state detecting image pickup devices A to _C correspond to the position F3 of the curves S _{A to} S _C. The values are V _A3 , V _B3 , and V _C3 . As shown in FIG. 5, in this case, the evaluation value V _A3 obtained from the first focus state detection image sensor A and the evaluation value V _B3 obtained from the second focus state detection image sensor B become the same value, Only the evaluation value V _C3 obtained from the 3-focus state detection image sensor C has different values (V _A3 = V _B3 , V _A3 ≠ V _C3 , V _B3 ≠).
V _C3 ). Therefore, as described above, the evaluation value V _A3 obtained from the first focus state detection image pickup device A and the evaluation value V _B3 obtained from the second focus state detection image pickup device B are the same value, and the third focus state detection is performed. When the evaluation value V _C3 obtained from the image pickup device C for use is different from these values, the taking lens 12
It can be seen that the focus position of is set to the focus position F3.

On the other hand, when the focus position of the taking lens 12 is set to a position F2 closer to the focus position F3, the evaluation values obtained from the focus state detecting image pickup devices A to C are the curves S _A. The values V _A2 , V _B2 , and V _C2 correspond to the position F2 of S _C. As shown in FIG. 5, in this case, the relationship between the evaluation value V _A2 obtained from the first focus state detection image sensor A and the evaluation value V _B2 obtained from the second focus state detection image sensor B is the first focus state. Image sensor A for state detection
The evaluation value V _A2 obtained from the above is larger than the evaluation value V _B2 obtained from the second focus state detection image pickup device B (V
_A2 > V _B2 ). Therefore, when the evaluation value V _A2 obtained from the first focus state detection image pickup device A is larger than the evaluation value V _B2 obtained from the second focus state detection image pickup device B as described above, It can be seen that the focus position is set closer to the focus position F3, that is, the front focus state.

Further, the focus position of the taking lens 12 is
When the focus position is set to a position F4 on the infinity side of the position F3
In this case, the evaluation obtained from each of the focus state detecting image pickup devices A to C
Value is each curve S_A~ S_CValue corresponding to position F4 of
V_A4, V_B4, V_c4Becomes As shown in FIG.
Evaluation obtained from the first focus state detection image sensor A
Value V _A4And the second focus state detecting image sensor B
The relationship between the evaluation values is from the first focus state detection image sensor A
Obtained evaluation value V_A4Second focus state detection imager
Evaluation value V obtained from child B_B4Becomes larger (V_A4<
V_B4). Therefore, in this way, for the first focus state detection
Evaluation value V obtained from the image sensor A_A4Is the second focus
Evaluation value V obtained from the image sensor B for state detection_B4Less than
If not, the focus position of the taking lens 12 is in focus.
State set to infinity side of the position F3, that is, rear
You can see that it is in a pin state.

By the way, when the focus position of the taking lens 12 is set to a position F1 which is further closer than the position F2, the evaluation value obtained from the first focus state detecting image pickup device A as shown in FIG. V _A1 and the evaluation value V _B1 obtained from the second focus state detection image sensor B have the same value, but in this case, the evaluation value V _C1 obtained from the third focus state detection image sensor C also has the same value (V _A1 = V _B1 = V _C1 ). Therefore, when the evaluation values V _{A1 to} V _C1 obtained from the focus state detecting image pickup devices A to _C are all the same, the focus position of the taking lens 12 is significantly deviated from the in-focus position F3 ( It is understood that it is in a state where it is greatly blurred.

The focus position of the photographing lens 12 is
Even if it is set to the position F5 which is further infinity than F4
It is the same. That is, the first focus state detecting image sensor
Evaluation value V obtained from A_A5And second focus state detection imaging
Evaluation value V obtained from element B _B5Are the same, but in this case
In the case of evaluation, the evaluation obtained from the third focus state detecting image pickup device C
Value V_C5Becomes the same value (V_A5= V_B5= V_C5). According to
As described above, from the focus state detecting image pickup devices A to C,
Obtained evaluation value V_A5~ V_C5If all are the same value,
The focus position of the lens 12 is significantly displaced from the in-focus position F3.
It can be seen that it is in a depressed state (a state where it is greatly blurred).

Next, a focus control processing procedure in the television camera system configured as described above will be described with reference to the flowchart shown in FIG.

First, the CPU 46 performs necessary initial setting (step S10), and then performs necessary processing other than AF such as aperture control and zoom control of the taking lens 12 and setting of a spectral prism to be used (step S12). . That is, the iris 20 of the photographic lens 12 is controlled based on the iris control signal given from the camera body 10, and the zoom of the photographic lens 12 is controlled based on zoom demand data from a zoom demand (not shown). In addition, a control signal is output to the spectral prism switching motor drive circuit 36 based on the spectral prism selection information from the spectral prism switching controller 56, and the selected spectral prisms 24A to 24A.
The holder 26 is rotationally controlled so that C or the optical member 24D is arranged on the optical axis O.

Here, the photographer selects the spectral prism to be used based on the brightness of the image picked up by the image pickup section 14 and the like. For example, when the image captured by the image capturing unit 14 is dark, a spectral prism that increases the light amount of the subject light for video is selected. When the AF is unnecessary, the optical member 24D is set to be arranged on the optical axis O.

Next, the CPU 46 turns on the AF switch.
Confirm OFF (step S14). Then, when the AF switch is ON, the following AF control is performed. When the AF switch is off, MF control is performed.

First, each focus state detecting image pickup device A,
The evaluation values V _A , V _B , and V _C obtained from _B and _C are loaded (step S16). Then, the fetched each focus state detection image pickup device A, B, C evaluation value V _A of, V _B, V
_C is compared (step S18), and it is determined whether or not the focus state is achieved (step S20).

Here, it is determined whether or not the in-focus state is achieved by
The difference [Delta] V _AB between the evaluation values V _B of the evaluation values V _A and the second focus state detection image pickup device B of the first focus state detection image pickup devices A
(ΔV _AB = V _A −V _B ) is obtained, and it is determined whether or not the difference is zero. Then, when the difference ΔV _AB between the evaluation values is zero, it is determined to be in focus, and when the difference ΔV _AB is not zero, it is determined to be out of focus.

The difference ΔV _AB between the evaluation values of the first focus state detecting image sensor A and the second focus state detecting image sensor B.
Even if is zero, the difference ΔV _AC between the evaluation values of the first focus state detection image pickup device A and the third focus state detection image pickup device C
(ΔV _AC = V _A −V _C ) is zero, the difference ΔV _BC (ΔV _BC = V _B −V _C ) between the evaluation values of the second focus state detection image sensor B and the third focus state detection image sensor C. Is also zero, it is determined to be a blurred state.

If the result of this determination is that it is in focus, there is no need for focus control, so focus control is not performed in this case, the AF switch is turned off (step S22), and AF control is terminated. . AF again
Focus is controlled in the MF mode until the switch is pressed.

On the other hand, if it is determined that the subject is not in focus, focus control is executed. That is, based on the evaluation value V _B of the evaluation values V _A and the second focus state detection image pickup device B of the first focus state detection image pickup devices A obtains the deviation direction of the focus (step S24), and the evaluation value Difference ΔV
_The focus lens group 16 is moved using _AB as a control amount (moving amount or moving speed). For example, if the focus shift direction is the infinity direction, the focus lens group 16 is moved to the close-up side by using the evaluation value difference ΔV _AB as the control amount (step S26), and if the focus shift direction is the close-up direction. For example, the focus lens group 16 is moved to the infinity side using the evaluation value difference ΔV _AB as the control amount (step S2).
8). Then, the above processing is repeated until the focus is achieved, that is, until the difference ΔV _AB between the evaluation values of the first focus state detection image pickup device A and the second focus state detection image pickup device B becomes zero. As a result, the focus of the taking lens 12 is focused on the subject, and the subject image is formed on the image pickup surface of the image pickup device of the image pickup unit 14.

Here, in this AF, if the focus state cannot be accurately detected unless the amount of the focus state detection subject light is increased, the photographer operates the spectral prism switching controller 56. Then, the spectral prisms 24A to 24A that increase the amount of the focus state detection subject light
Switch to 4C. On the other hand, when the light amount of the image subject light is small and the image is dark, the spectral prisms 24A to 24C are switched to increase the light amount of the image subject light. At this time, the photographer operates the spectral prism switching controller 56 based on the display on the display 54.

As described above, according to the television camera system of the present embodiment, the light amount of the focus state detecting subject light separated from the image subject light can be changed as necessary, and therefore, the image pickup section 14 takes an image. It is possible to effectively prevent the image from becoming dark and the AF from not operating due to the lack of sufficient focus state detection subject light.

In the above embodiment, the photographer sets the spectroscopic prism to be used, but the spectroscopic prism is automatically set based on the brightness information of the image picked up by the image pickup section 14. You may make it switch.
For example, the signal processing unit 34 acquires the brightness information of the captured image from the imaging unit 14, and the spectral prism switching controller 5 so that the brightness of the captured image maintains a predetermined range.
A control signal is output to 6, and the holder 26 is rotated to automatically switch the spectroscopic prism to be used.

Similarly, the spectral prisms may be automatically switched based on the brightness information of the image picked up by the focus state detecting image pickup section 40. For example, the signal processing unit 34 obtains the brightness information of the focus state detection image from the focus state detection imaging unit 40, and causes the spectral prism switching controller 56 to keep the brightness of the image within a predetermined range. A control signal is output and the holder 26 is rotated to automatically switch the spectroscopic prism to be used.

Further, instead of automatically switching the spectral prism, when it becomes necessary to replace the spectral prism, a display prompting replacement may be displayed on the display unit 54. For example, the signal processing unit 34 acquires the brightness information of the captured image from the imaging unit 14, and when the brightness of the captured image becomes equal to or lower than a predetermined brightness, issues a display command to the display 54 to urge the switching of the spectral prism. Output. Further, for example, the signal processing unit 34 acquires the brightness information of the focus state detection image from the focus state detection imaging unit 40, and when the brightness of the image becomes equal to or lower than a predetermined brightness, the display unit 54 separates the light. A display command that prompts switching of the prism is output.

Further, when the optical member 24D is switched to, the focus state detection subject light is not incident on the focus state detection image pickup unit 40, so AF control is not performed and MF is not performed.
It is preferable to be dedicated.

Further, in the present embodiment, the holder 26 is driven and rotated by the spectral prism switching motor 36, but it may be manually rotated without providing a drive mechanism. Further, the switching mechanism of the spectral prism is not limited to this, and another mechanism may be adopted.

FIG. 7 is a block diagram of a television camera system employing a plug-in type spectral prism switching mechanism.
FIG. 8 is a front view showing the structure of the holder. As shown in the figure, the spectral prisms 24A to 24C and the optical member 24D are fixed to the lower end portion of a block-shaped holder 60A, and the holders 60A to 60D are formed on the lens barrel portion 12A of the taking lens 12. It is set on the taking lens 12 by being inserted into the formed insertion port 12a, and is arranged on the optical axis O. Holder 60 inserted in the insertion port 12a
A to 60D are top plates 62A to 6 fixed to the upper ends thereof.
The 2D is fixed to the taking lens 12 by screwing the 2D to the lens barrel section 12A with screws 64A to 64D.

Further, the recognition of the spectral prism set on the taking lens 12 is performed by the photo interrupters 66A to 66D installed in the taking lens 12. That is, as shown in FIG. 8, each of the spectral prisms 24A to 24A.
Light shielding plates 68A to 68D are installed at positions below C and the optical member 24D at different positions, and photo interrupters 66A to 66B are installed in the taking lens 12 at the same intervals as the installation intervals of the light shielding plates 68A to 68D. is set up.

When the spectral prism is set on the taking lens 12, the light shielding plate 68A attached to the spectral prism
-68D are the corresponding photo interrupters 66A-66.
Shade D. The signal processing unit 34 detects which spectroscopic prism is set based on the light shielding information from the photo interrupters 66A to 66D. For example, when the first spectral prism 24A is set on the taking lens 12, the light blocking plate 68A attached to the first spectral prism 24A blocks the photo interrupter 66A, so that the signal processing unit 34 causes the photo interrupter 66A.
By inputting the light-shielding signal from the photographing lens 12
It is detected that the first spectroscopic prism 24A is set to. Then, the signal processing unit 34 displays the detection result on the display 54.

As described above, the photographer may manually replace and use the spectral prisms to be used.

In the present embodiment, the number of spectroscopic prisms that can be selected is four including the optical members, but the number is not limited to this number and may be increased or decreased as necessary. .

Further, the controller 5 for switching the spectral prism
6 may be attached to the taking lens 12 or may be installed separately from the taking lens 12.
In addition, when it is installed separately from the taking lens 12, it may be controlled wirelessly.

Further, in the present embodiment, the spectral prisms 24A to 24C and the optical member 24D to be used have the same air-converted length, but different air-converted lengths may be used. In this case, since the image forming position is displaced due to the spectral prism used, a mechanism for correcting the image forming position displacement is provided. That is, for example, the image forming position is corrected by the optical lens in association with the switching of the spectral prism. Further, the positions of the image pickup unit 14 and the focus state detection image pickup unit 40 are moved back and forth in association with the switching of the spectral prism.

Further, in the present embodiment, the spectral prism is used as the means for dispersing the subject light, but the means for dispersing the subject light is not limited to this.
For example, a half mirror may be used for spectral separation.

In the above-described embodiments, the case where the present invention is applied to the television camera system has been described as an example, but the present invention is not limited to this and is also applied to a video camera or a still camera for taking a still image. can do.

Further, in the above embodiment, the first focus state detecting image pickup device A and the second focus state detecting image pickup device B are provided.
In addition to the above, a third focus state detecting image pickup device C is installed, but at least a pair of focus state detecting image pickup devices (first focus state detecting image pickup device A and second focus state detecting image pickup device B). ) May be installed, and the third focus state detection image sensor C may not be installed.

[0078]

As described above, the spectroscopic means for separating the focus state detecting subject light from the video subject light is detachably or switchably provided, and by exchanging the spectroscopic means having different spectral distributions. It is possible to switch the light amount distribution of the focus state detection subject light separated from the image subject light. As a result, when the image picked up by the video image pickup device is dark, the spectroscopic distribution is changed so that the light amount of the image subject light incident on the video image pickup device is increased, and conversely the focus state detection is performed. If the amount of subject light for use is insufficient, you can always shoot in an optimal state by changing to a spectral distribution spectral unit that increases the amount of subject light for focus state detection that enters the image sensor for focus state detection. Also, the focus state can be detected.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a television camera system to which a focus state detection device according to the invention is applied.

FIG. 2 is a front view showing the structure of a holder.

FIG. 3 is a diagram in which the optical axes of the focus state detection subject light incident on the focus state detection image pickup devices A, B, and C are displayed on the same straight line.

FIG. 4 is a block diagram showing a configuration of a signal processing unit.

FIG. 5 shows the focus position of the taking lens on the horizontal axis and the evaluation value on the vertical axis, and the focus state detection image pickup devices A, B, C, and D for the focus position when a certain subject is photographed.
Figure showing the E evaluation value

FIG. 6 is a flowchart showing another embodiment of the processing procedure of focus control.

FIG. 7 is a block diagram of a television camera system in which a plug-in type spectral prism switching mechanism is adopted.

8 is a front view of the holder shown in FIG.

[Explanation of symbols]

10 ... Camera body, 12 ... Photographing lens, 12A ... Lens barrel section, 12a ... Insertion port, 14 ... Imaging section, 16 ... Focus lens group, 18 ... Zoom lens group, 20 ... Iris, 2
2 ... Relay lens group, 22A ... Front relay lens, 22
B ... rear relay lens, 24A to 24C ... spectroscopic prism, 24a ₁ ~24c ₁ ... first prism, 24a ₂ to 2
4c ₂ ... second prism, 24a ₃ ~24c ₃ ... half mirror surface, 24D ... optical member, 26 ... holder, 26A ... rotary shaft, 26B ... gear, 28 ... bearing, 30 ... spectral prism reversing motor, 30A ... driving gear , 32 ... Holder potentiometer, 32A ... Rotation amount detection gear, 34 ... Signal processing unit, 36 ... Spectral prism switching motor drive circuit, 38 ... Relay lens, 40 ... Focus state detection imaging unit, 42 ... Beam splitter, 42A ... 1st prism, 42B ... 2nd
Prism, 42C ... Third prism, 44 ... A / D converter, 46 ... CPU, 48 ... Focus motor drive circuit,
50 ... Focus motor, 52 ... Focus potentiometer, 54 ... Indicator, 56 ... Spectral prism switching controller, 60A-60D ... Holder, 62A-62D
... Top plate, 64A to 64D ... Screws, 66A to 66D ... Photo interrupter, 68A to 68D light shielding plate, 69 ... D / A
Converter, 70A-70C ... High-pass filter, 72A-
72C ... A / D converter, 74A to 74C ... Gate circuit,
76A to 76C ... Adder, A ... First focus state detecting image sensor, B ... Second focus state detecting image sensor, C ... Third
Image sensor for focus state detection, P ... Focus plane

Claims (7)

[Claims] 1. A subject state light for focus state detection is separated from a subject light for image incident on an image pickup device of a camera body through a photographing lens by a spectroscopic means, and the subject light for focus state detection is used for focus state detection. In the focus state detection device that detects the focus state of the photographing lens based on the high frequency component of the image captured by the focus state detection image sensor, the spectroscopic means is detachable or switchable. Is provided in
A focus state detection device, wherein the light amount distribution of the focus state detection subject light separated from the image subject light can be switched by exchanging with a spectral means having a different spectrum distribution. 2. The focus state detection device according to claim 1, wherein the focusing unit can be switched to a transmissive unit that transmits all of the image subject light in place of the spectroscopic unit. 3. The focus state detecting device according to claim 1, wherein the spectroscopic means to be replaced have the same air conversion length. 4. The focus state detecting device according to claim 1, wherein a plurality of spectroscopic means having different spectral distributions are provided so as to be switchable by a switching means. 5. The switching means is configured by disposing the plurality of spectroscopic means on a concentric circle of a rotatably supported holder, and the spectroscopic means to be used is switched by rotating the holder. The focus state detection device according to claim 4. 6. A drive means for driving the switching means, and the drive means such that a predetermined amount of light of the image subject light is made incident on the image pickup element based on the image picked up by the image pickup element. 6. The focus state detection device according to claim 4, further comprising: a control unit that controls the. 7. A drive unit for driving the switching unit, and a focus state detection subject light having a predetermined light amount is incident on the focus state detection image pickup device based on an image picked up by the focus state detection image pickup device. 6. The focus state detection device according to claim 4, further comprising: a control unit that controls the driving unit so as to control the focus state.