JPH1013730A - Video camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize sufficient focal accuracy even when contrast of an object is low by properly selecting a visual light video signal and an infrared ray video signal. SOLUTION: An output S1 of a visual light CCD 5 is given to a visual light image signal processing circuit 7, in which a visual light video signal S3 is obtained, and on the other hand, an output S2 of an infrared ray CCD 4 is given to an infrared ray image signal processing circuit 8, in which a infrared ray video signal S4 is obtained and they are fed to a video changeover control section 9 and an automatic focus control means 10. The video changeover control section 9 gives usually the visual light video signal S3 to a view finder 11 and a recorder 12, but when the infrared ray video signal S4 is more effective than the visual light video signal S3, the infrared ray video signal S4 is fed to both or one of the view finder 11 and the recorder 12 automatically. The comparison of the effectiveness of the visual light video signal S3 and the infrared ray video signal S4 is conducted based on a signal C1 from an automatic focus control means 10 and either of the signals is selected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video camera and an electronic still camera, and more particularly to an improvement in an autofocus function thereof.

[0002]

2. Description of the Related Art In general, a consumer video camera has an autofocus function for automatically focusing on a subject because of its convenience. The principle is that a part of the imaging optical system is moved in a direction in which the high frequency component included in the video signal increases, or the relative distance between the imaging optical system and the image sensor is changed, and the high frequency component of the video signal is Focusing is determined based on the maximum value, and there is a so-called hill-climbing method or a method called video AF. In addition, in addition to this, 1. A so-called sonar system in which the distance to the subject is measured from the time of arrival of the reflected ultrasonic wave, and the imaging optical system is moved for focusing. 2. It has another imaging optical system that moves together with the shooting optical system, and the pupil division lens and the line sensor at the focal point detect the focus shift and move the imaging optical system to focus. A method called a so-called phase difference detection method. 3. It has an imaging optical system for autofocus and a line sensor separately from the optical system for shooting, projects infrared light onto the subject, detects the infrared light image on the subject with the line sensor, and measures the distance to the subject. A so-called triangulation method. However, there is no need for autofocus-specific parts, even if the focal length of the photographic optical system extends to the telephoto side, the focusing accuracy does not decrease, and the focusing area in the screen is associated with zooming. The so-called video AF described above is mainly used because it does not change due to a change in the focal length.

[0003]

SUMMARY OF THE INVENTION As explained above,
The so-called video AF has many features, but the illuminance of the subject is low, or even if the illuminance is sufficient, the subject cannot be focused without a certain level of contrast,
There is a problem that the focusing accuracy is reduced. For example, in a candle service at a wedding reception, the bride and groom ignite the candles at each table and turn around in a venue where lights are turned off. At that time, the spot illumination is turned off immediately before the ignition, and the spot illumination is applied simultaneously with the ignition. Before the ignition is too dark, the contrast cannot be detected for the bride and groom who are the subjects, and the autofocus continues to be lost. However, the moment the candle is lit and the bride and groom are illuminated, the screen is out of focus, and then the contrast of the subject is detected to focus on the bride and groom. In addition, even when the lighting is down, there is a case where the autofocus continues to be lost because small lights and emergency exit signs are present in the venue. In order to prevent such unsightly shooting, it is conceivable to stop the auto focus function and shoot with manual focus. However, it is difficult to manually focus while looking through the electronic viewfinder in a dark venue.

[0004]

Means for Solving the Problems The present invention has been made in view of such a problem.
"A photographing optical system, a dichroic mirror for separating an image formed by the photographing optical system into a visible light image and an infrared light image, and a visible light for photoelectrically converting the visible light image separated and formed by the dichroic mirror. An image sensor, an infrared image sensor for photoelectrically converting an infrared image separated and formed by the dichroic mirror, and a visible light image signal processing circuit for converting an output of the visible light image sensor into a visible light video signal And an infrared light image signal processing circuit that converts the output of the infrared light image sensor into an infrared light image signal, based on the high-frequency component of the visible light image signal or the infrared light image signal, Move a part of the photographing optical system in a direction in which the high-frequency component increases, or change the relative distance between the photographing optical system and the visible light image sensor or the infrared light image sensor to focus. Auto focus control means for performing operations and infrared An infrared light radiating means for illuminating the object and illuminating a subject by operating the infrared light radiating means when focusing by the visible light image signal is difficult, and performing a focusing operation by the infrared light image signal And a video camera equipped with a mode for performing

According to a second aspect of the present invention, there is provided an image-taking optical system comprising:
A dichroic mirror for separating an image formed by the photographing optical system into a visible light image and an infrared light image, a visible light image sensor for photoelectrically converting the visible light image separated and formed by the dichroic mirror, and the dichroic An infrared light image sensor for photoelectrically converting an infrared light image separated and formed by a mirror, a visible light image signal processing circuit for converting an output of the visible light image sensor to a visible light image signal, An infrared light image signal processing circuit for converting an output of the imaging device for use into an infrared light image signal, and the high frequency component increases based on the high frequency component of the visible light image signal or the infrared light image signal. Autofocus control for moving a part of the photographing optical system in the direction in which the photographing optical system is moved or changing a relative distance between the photographing optical system and the visible light image sensor or the infrared light image sensor to perform a focusing operation. Means and an infrared light pattern projected on the subject An infrared light emitting means, and when focusing by the visible light image signal is difficult, the infrared light emitting means is operated to project the infrared light pattern on a subject, and the infrared light image signal And a mode for performing a focusing operation. ”.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a photographing optical system. In this example, a focus lens 1a is driven by a focus motor 2 and moves in the optical axis direction to perform a focusing operation. A prism 3 having a dichroic mirror 3a that reflects infrared light and transmits visible light is provided near the focal point of the imaging optical system 1. This prism 3 separates an infrared light beam and a visible light beam. Then, the light is incident on the CCD 4 for infrared light and the CCD 5 for visible light, respectively. Reference numeral 6 denotes an optical low-pass filter provided between the prism 3 and the visible light CCD 5.

The output S1 of the visible light CCD 5 is converted into a visible light image signal S3 by a visible light image signal processing circuit 7 and sent to an image switching control section 9 and an auto focus control means 10. On the other hand, the output S2 of the infrared light CCD 4 is converted into an infrared light image signal S4 by the infrared light image signal processing circuit 8, and sent to the image switching control section 9 and the auto focus control means 10.
The video switching control unit 9 normally uses the visible light video signal S3
Is sent to the viewfinder 11 and the recording device 12,
If the infrared light image signal S4 is more effective than the visible light image signal S3, the infrared light image signal S4 is automatically sent to the viewfinder 11 and / or the recording device 12.
Here, various methods can be considered for comparing and judging the validity of the visible light video signal S3 and the infrared light video signal S4. In this example, the video signal S3 and the infrared light video signal S4 are determined by the signal C1 from the autofocus control means 10. Is switched.

That is, the auto focus control means 10
Then, the high-frequency components are extracted from the visible light image signal S3 and the infrared light image signal S4 while moving the focus lens 1a at a predetermined pitch, and the differences ΔS3 and ΔS4 of the high-frequency components before and after the movement are obtained. If the difference is a positive value, the focus lens 1 is further moved in the same direction by one pitch.
is moved, and if the difference is a negative value, control is performed to reverse the moving direction. Then, the visible light video signal S
3. Which signal of the infrared light image signal S4 is to be used for this control is determined by comparing the magnitudes of the differences ΔS3 and ΔS4 in an arbitrary moving step of the focus lens 1a, Adopt it. This is because generally, a signal having a larger difference is considered to be a signal having higher reliability. Therefore, by setting the value of the signal C1 to H or L in accordance with ΔS3 <ΔS4, ΔS3> ΔS4, the video switching control unit 9 can switch the video signal. Of course, this switching may be manually performed by the photographer.

Normally, the autofocus control means 10 controls the focus motor 2 based on the visible light image signal S3 to perform an autofocus operation. When focusing cannot be performed, the focus motor 2 is controlled based on the infrared video signal S4, and the focus motor 2 is automatically switched to perform an autofocus operation.

Further, if focusing cannot be performed correctly based on the infrared light image signal S4, the auto focus control means 1
0 operates the infrared light emitting means 13 to illuminate the subject with infrared light, controls the focus motor 2 based on the infrared light image signal S4, and performs an autofocus operation.

Furthermore, even if the subject is illuminated with infrared light, if focusing based on the infrared light image signal S4 cannot be performed correctly, the infrared light emitting means 13 is operated to project an infrared pattern onto the subject. The focus motor 2 is controlled based on the infrared light image signal S4 to perform an autofocus operation. Here, as an example of the infrared pattern, a slit-shaped pattern 14 in a direction orthogonal to the main scanning direction of the image sensor can be used. In order to project such a pattern on a subject, a slit may be arranged on a substantially focal plane of the projection lens of the infrared light emitting means 13.
Although the above switching is performed automatically, it is needless to say that the switching may be manually performed by the operation of the photographer.

[0012]

As described above, according to the video camera of the present invention, even when the illuminance of the subject is low, the contrast of the subject is low, or the like, the video signal from which the high frequency component should be extracted for the focusing operation. By selecting the visible light image signal and the infrared light image signal appropriately, there is an effect that sufficient focusing accuracy can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a video camera according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 shooting optical system 2 focus motor 3 prism 4 infrared light CCD 5 visible light CCD 6 optical low-pass filter 7 visible light image signal processing circuit 8 infrared light image signal processing circuit 9 video switching control unit 10 auto focus control means DESCRIPTION OF SYMBOLS 11 View finder 12 Recording device 13 Infrared light emission means

Claims (2)

[Claims] An image pickup optical system, a dichroic mirror for separating an image formed by the image pickup optical system into a visible light image and an infrared light image, and a visible light image separated and formed by the dichroic mirror is photoelectrically converted. An imaging device for visible light, an infrared imaging device for photoelectrically converting an infrared light image separated and formed by the dichroic mirror, and a visible light for converting an output of the imaging device for visible light into a visible light video signal An image signal processing circuit; an infrared light image signal processing circuit for converting an output of the infrared light image pickup device into an infrared light image signal; and a high frequency component of the visible light image signal or the infrared light image signal. Originally, a part of the photographing optical system is moved in a direction in which the high frequency component increases, or the relative distance between the photographing optical system and the visible light image sensor or the infrared light image sensor is changed. Auto focus control means for performing a focusing operation by An infrared light radiating means for illuminating the subject with infrared light; and when it is difficult to focus on the visible light video signal, the infrared light radiating means is operated to illuminate the subject, and the infrared light video signal And a mode for performing a focusing operation. A photographing optical system, a dichroic mirror for separating an image formed by the photographing optical system into a visible light image and an infrared light image, and a photoelectric conversion of the visible light image separated and formed by the dichroic mirror. An imaging device for visible light, an infrared imaging device for photoelectrically converting an infrared light image separated and formed by the dichroic mirror, and a visible light for converting an output of the imaging device for visible light into a visible light video signal An image signal processing circuit; an infrared light image signal processing circuit for converting an output of the infrared light image pickup device into an infrared light image signal; and a high frequency component of the visible light image signal or the infrared light image signal. Originally, a part of the photographing optical system is moved in a direction in which the high frequency component increases, or the relative distance between the photographing optical system and the visible light image sensor or the infrared light image sensor is changed. Auto focus control means for performing a focusing operation by An infrared light emitting means for projecting an infrared light pattern onto a subject; and when focusing by the visible light image signal is difficult, the infrared light emitting means is operated to project the infrared light pattern on the subject. A video camera that emits light and performs a focusing operation based on the infrared light video signal.