JPH07107355A - Image pickup device adaptable to low illuminance - Google Patents

Abstract

PURPOSE:To selectively switch a low illuminance photographing state and a normal photographing state by attaching and detaching an infrared ray cut filter to an optical system provided with a lens group photographing an object according to the level of a luminance signal. CONSTITUTION:In an image pickup device 1 adaptable to low illuminance, an infrared ray cut filter 11 and a dummy glass 12 are selectively and freely attachably and detachably provided between a lens group 2 and a solid-state image pickup element 4. A low illuminance photographing time when an object H and the surroundings of the object H are dark and a normal photographing time when the object H and the surroundings of the object H are bright are decided according to the luminance level of the luminance signal separated from the output side of the solid-state image pickup element 4. Based on this decision result, only the dummy glass 12 is inserted at the time of the luminance level at which the low illuminance photographing is performed and only an infrared ray cut filter 11 is inserted at the time of the luminance level at which a normal photographing is performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to a video camera or the like, and an infrared light cut filter is inserted / removed in / from an optical system having a lens group for photographing an object according to the level of a luminance signal to perform low-illuminance photographing. The present invention relates to a low-illuminance compatible imaging device configured to selectively switch between a normal state and a normal photographing state.

[0002]

2. Description of the Related Art Generally, a camera-integrated magnetic recording / reproducing apparatus (hereinafter referred to as a video camera) is often used as a portable device, and is also installed at an appropriate place for monitoring purposes. .

5A and 5B are views for explaining a conventional video camera. FIG. 5A is a view showing the entire structure, and FIG. 5B is an enlarged view showing a camera section in the video camera.

A conventional video camera 10 shown in FIG.
At 0, the camera unit 110 for photographing the subject H and the magnetic recording / reproducing unit 120 for recording and reproducing the photographed subject H on the magnetic tape T in the tape cassette TK are provided in the video camera housing 10.
It is configured so that it is housed in one unit. Also, FIG.
As shown in (B), the camera unit 110 includes an optical axis between a lens barrel 112 holding a lens group 111 for photographing the subject H and a solid-state image sensor 113 for forming a subject image through the lens group 111. An infrared light cut filter 114 is inserted above K. This infrared light cut filter 114 is for removing harmful infrared light emitted from the subject H and the periphery of the subject H in the case of normal shooting in a bright state. It is always installed between the element 113 and the element 113.

[0005]

[Problems to be Solved by the Invention]
While the conventional video camera 100 shown in (A) and (B) is often used as a portable device, it is also used for monitoring and the like by being installed in an appropriate place and used for normal shooting for shooting bright scenes. The infrared cut filter 114 is permanently installed between the lens group 111 and the solid-state image sensor 113 that make up the camera unit 110, although it is configured to be used for low-light shooting for shooting dark scenes. Therefore, when the subject H and the periphery of the subject H are relatively bright, the subject H can be favorably imaged on the solid-state imaging device 113.

On the other hand, for surveillance purposes, a video camera 100 is installed in a bank, a convenience store or the like, and the video camera 100 must be operated even at night. 11
The infrared light cut filter 114, which is permanently installed between the solid-state image sensor 113 and the solid-state image sensor 113, adversely affects the image of the subject H on the solid-state image sensor 113, and in order to compensate for this, the sensitivity of the video circuit system is compensated. Since the video signal is amplified so as to increase the image quality, noise components are included in the video signal, which causes a problem such as an image with a poor S / N ratio when shooting a dark scene. There is.

Further, although not shown, Japanese Patent Laid-Open No. 4-28
Although Japanese Patent No. 6479 discloses an infrared solid-state image pickup device having a high sensitivity to an infrared light region, this infrared solid-state image pickup device is configured exclusively for photographing a dark scene, and a bright scene. There is a problem that another image pickup device is required to take a picture.

Therefore, it is possible to automatically detect low-luminance photographing for photographing a dark scene and normal photographing for photographing a bright scene, and photograph a subject well under conditions suitable for each. A low-illuminance type imaging device is desired.

[0009]

The present invention has been made in view of the above problems, and a first invention is a lens group for photographing a subject, and an image pickup device for forming a subject image through the lens group. , An infrared light cut filter that is detachably provided on the incident side of the image pickup device, and a luminance signal that is separated from a video signal on the output side of the image pickup device, and the luminance signal level is a luminance for performing low-illuminance shooting. A determination circuit that determines whether the level is a brightness level for performing normal shooting, and based on the determination result of the determination circuit, the infrared light cut filter is removed when the brightness level is for performing low-illuminance shooting, while the normal shooting is performed. And a driving means for inserting the infrared light cut filter at the brightness level for performing the low illuminance correspondence type image pickup apparatus.

A second aspect of the present invention is a lens group for photographing a subject, an image pickup element for forming a subject image through the lens group, and selectively insertable / removable between the lens group and the image pickup element. The infrared light cut filter and the dummy glass provided in the image sensor and the luminance signal are separated from the image signal on the output side of the image sensor, and the luminance signal level is the luminance level for low-illuminance photographing or normal photographing is performed. Based on the determination result of the determination circuit and the determination circuit for determining whether the brightness level,
A low illuminance compatible device is provided with a driving means for inserting only the dummy glass at a brightness level for low-illumination shooting and inserting only the infrared light cut filter at a brightness level for normal shooting. Image pickup apparatus.

Further, according to a third aspect of the present invention, in the first and second low-illuminance type image pickup devices, when the infrared light cut filter is removed, the white balance shift of the video signal is automatically corrected. A low illuminance compatible type image pickup device characterized by comprising a white balance correction circuit.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a low illuminance type image pickup apparatus according to the present invention will be described in detail below with reference to FIGS.

FIG. 1 is a diagram for explaining a low illuminance type image pickup device according to the present invention, and FIG. 2 is a structure for switching an infrared light cut filter and a dummy glass which constitutes a main part of the low illuminance type image pickup device. FIGS. 3A and 3B are views for explaining the structure, FIG. 3A shows a rotating structure, FIG. 3B shows a linear moving structure, and FIG. 3 shows a level of a luminance signal in the low illuminance compatible imaging device. 4A and 4B are diagrams for explaining the operation of the low-illuminance compatible imaging apparatus, FIG. 4A is a diagram showing dark low-illumination shooting, and FIG. 4B is a diagram showing bright normal shooting. .

In the low illuminance type image pickup apparatus 1 according to the present invention shown in FIG. 1, a lens group 2 for photographing a subject H and an image pickup element for forming a subject image through the lens group 2 (hereinafter,
An infrared light cut filter 11 and a dummy glass 12 are selectively inserted into and removed from the solid-state image sensor 4),
The low-illuminance shooting in which the subject H and the periphery of the subject H are dark and the normal shooting in which the subject H and the periphery of the subject H are bright are determined by the brightness level of the brightness signal separated from the output side of the solid-state image sensor 4, On the basis of the determination result, only the dummy glass 12 is inserted at the brightness level for low-illumination shooting, while only the infrared light cut filter 11 is inserted at the brightness level for normal shooting, and It is characterized in that the time of normal photographing is automatically detected. In the following description, low-illuminance shooting means a state in which the subject H and the periphery of the subject H are dark when the subject H is shot, while normal shooting means the subject H.
It is assumed that the subject H and the periphery of the subject H are in a bright state at the time of shooting.

That is, as shown in FIG. 1, in the low illuminance type image pickup apparatus 1 according to the present invention, a lens barrel 3 holding a lens group 2 for photographing a subject H and a subject image are formed through the lens group 2. Optical axis K between the solid-state imaging device 4 and the image
An infrared light cut filter 11 and a dummy glass 12, which form the main part of the present invention, are provided on the top of the drive means 10 (10A or 10B) so that they can be selectively inserted and removed. As described above, in the embodiment, the infrared light cut filter 11 is used.
Is provided so as to be freely inserted and removed between the lens group 2 and the solid-state image sensor 4, but not limited to this, an infrared ray is provided in front of the lens group 2 on the incident side of the solid-state image sensor 4 or in the lens group 2. A method is also conceivable in which only the light cut filter 11 is detachably provided.

Further, in the lens group 2, a lens group including a front lens and a plurality of convex surfaces, concave surfaces, and flat surfaces is arranged with their optical axes K aligned.

Further, on the incident surface side of the solid-state image pickup device 4, an image pickup surface in which a plurality of pixels are independently and regularly arranged is formed, and on the image pickup surface corresponding to the pixels of the image pickup surface. A known color filter array is integrally formed with a film, and a known optical low-pass filter for suppressing spurious signals is attached to the color filter array so as to face the color filter array. Description of a known optical low-pass filter is omitted. The infrared light cut filter 11 and the dummy glass 12, which form the main part of the present invention, are provided on the front side (incident side) or the rear side (emission side) of a known optical low-pass filter, and of course the solid-state image sensor. 4 is provided on the incident side. Further, the solid-state image pickup device 4 having the above structure is formed of a silicon material or the like which is not only sufficiently sensitive to the visible light region but also sufficiently sensitive to the infrared light region.

Further, the infrared light cut filter 11 is
The infrared region is formed by using glass so as to cut a wavelength of 750 nm or more, for example, and is generally radiated from the subject H and the periphery of the subject H during normal shooting when the subject H and the periphery of the subject H are bright. It is designed to remove harmful infrared light. However, as described later, during low-illuminance shooting in which the subject H and the periphery of the subject H are dark, it is necessary to form a subject image on the solid-state image sensor 4 by infrared light emitted from the subject H and the periphery of the subject H. In this case, if the infrared light cut filter 11 is attached, the infrared light will be cut off, so that the subject image cannot be formed well, and therefore, in the present invention, in such a dark low-illuminance shooting, the red light is red. Outside light cut filter 11
By separating from, the subject image can be favorably formed on the solid-state imaging device 4 by infrared light.

On the other hand, the dummy glass 12 is made of transparent glass having a thickness substantially equal to that of the infrared light cut filter 11, and is replaced with the infrared light cut filter 11 when the infrared light cut filter 11 is detached. By inserting the dummy glass 12 into the solid-state image sensor 4, the subject image through the lens group 2 can be formed on the solid-state image sensor 4 with the same optical path length as when the infrared light cut filter 11 is used. Therefore,
The optical path length from the lens group 2 to the solid-state image sensor 4 can always be kept constant.

Here, the driving means 10 for selectively inserting and removing the infrared light cut filter 11 and the dummy glass 12 is a driving means 10A adopting a rotating structure as shown in FIG. 2A. , Or the drive means 10B adopting the linear movement structure as shown in FIG. 2B is applied. That is, in the drive means 10A adopting the rotating structure,
As shown in (A), the fan-shaped support plate 1 in which the infrared light cut filter 11 and the dummy glass 12 rotate about a shaft 13
4 is arranged along a circular arc on the radius R, and the motor 1 is attached to the gear 15 integrally provided on the fan-shaped support plate 14 with the shaft 13 aligned.
By engaging the gear 16a fixed to the shaft of 6,
The fan-shaped support plate 14 can be rotated in the directions of the arrows Z ₁ and Z ₂ , and the infrared light cut filter 11 and the dummy glass 12 can be rotated.
And are selectively and alternately inserted on the optical axis K. On the other hand, the driving means 10 adopting the linear movement structure
In B, the infrared light cut filter 11 and the dummy glass 12 are arranged in a line in the rectangular frame 17, and the gear portion 18a fixed to the shaft of the motor 18 is meshed with the rack portion 17a formed at one end of the rectangular frame 17. By making the rectangular frame 1
7 can be moved linearly in the directions of the arrows X ₁ and X ₂ ,
The infrared light cut filter 11 and the dummy glass 12 are selectively and alternately inserted on the optical axis K.

Returning to FIG. 1, a luminance signal Y and a chroma signal C are superimposed on the output signal from the solid-state image pickup device 4 on which the subject image is formed, and thereafter, the output signal from the solid-state image pickup device 4 is changed. The Y / C separation circuit 20 separates the luminance signal Y and the chroma signal C. Here, in particular, the luminance signal Y serves as a control signal for selectively inserting / removing the infrared light cut filter 11 and the dummy glass 12 forming the main part of the present invention, and the output of the solid-state image sensor 4 On the side, the luminance signal Y at any point of time does not cause any problem. Furthermore,
The luminance signal Y separated by the Y / C separation circuit 20 is branched and input to the image processing circuit 21 and the determination circuit 22, while the chroma signal C separated by the Y / C separation circuit 20 is the image processing circuit. 21 is input. In the image processing circuit 21, the input luminance signal Y and chroma signal C are mixed again and output.

Next, in the judgment circuit 22, as shown in FIG. 3, the set level value Y ₀ preset on the black level side is set to 100% between the reference sync tip level and the white peak level. And the brightness level value Y ₁ (Y ₁₁ , Y of the brightness signal Y separated from the output of the solid-state image sensor 4).
₁₂ ). Here, as shown in the figure, with the set level value Y ₀ as a boundary, the sync tip level side is called the black level side, and the white peak level side is called the white level side. Further, as is apparent from FIG. 3, the brightness level value Y ₁₁ of the brightness signal Y indicates the level value at the time of low illuminance shooting, and the brightness level value Y ₁₂ of the brightness signal Y indicates the level value at the time of normal shooting. .

The set level value Y ₀ is preset to a brightness level value biased to the black level side as shown in the figure,
Since the set level value Y ₀ depends on the performance of the lens group 2 and the performance of the solid-state image pickup device 4, in the low illuminance compatible image pickup apparatus 1 according to the present invention, an appropriate setting biased to the black level side is set. The level value Y ₀ is set.

Therefore, in the judgment circuit 22, the brightness level value Y of the brightness signal Y separated from the output of the solid-state image pickup device 4 is obtained.
_{When 1} (Y ₁₁ , Y ₁₂ ) is equal to or smaller than the set level value Y ₀ , it is determined from FIG. 3 that it is the brightness level value Y ₁₁ for low-illuminance shooting. According to this determination result, it is determined that the subject H and the periphery of the subject H are dark, and the brightness level value Y ₁₁ is such that photographing in the visible light region is impossible, and that photographing in the infrared light region is necessary. To be done. On the other hand, when the brightness level value Y ₁ (Y ₁₁ , Y ₁₂ ) of the brightness signal Y separated from the output of the solid-state image sensor 4 is larger than the set level value Y ₀ , the brightness level for performing normal shooting from FIG. It is determined that the value is Y ₁₂ . According to this determination result, it is determined that the subject H and the periphery of the subject H are bright, and the brightness level value Y ₁₂ that allows image capturing in the visible light region is obtained, and that infrared light is harmful. .

Next, when it is judged in the judgment circuit 22 that the brightness level value Y ₁₁ is for low-luminance photographing, based on this judgment result, the driving circuit 23 connected to the output side of the judgment circuit 22 is used. 2A, the motor 16 of the driving means 10A or the motor 18 of the driving means 10B shown in FIG. 2B drives to drive the lens group 2 and the lens group 2 as shown in FIG. 4A. The infrared light cut filter 11 is removed from between the solid-state image sensor 4 and the dummy glass 12 is replaced by the infrared light cut filter 11 between the lens group 2 and the solid-state image sensor 4 accordingly. Is inserted. Of course, even when the infrared light cut filter 11 is detachably provided in front of the lens group 2 or in the lens group 2, the infrared light cut filter 11
Should be removed.

When it is determined in the determination circuit 22 that the brightness level value Y ₁₁ is for low-luminance imaging, the brightness level of the brightness signal Y from the output of the determination circuit 22 is small based on the determination result. The value Y ₁₁ is AGC (Auto Gain Co
ntorol) circuit 24, the small luminance level value Y ₁₁ of the luminance signal Y is amplified in the AGC circuit 24, and then sent to the image processing circuit 21 where the image processing is performed.

Furthermore, when it is determined in the determination circuit 22 that the brightness level value Y ₁₁ is for low-illuminance shooting, the white balance correction circuit connected to the output side of the determination circuit 22 based on this determination result. Even if the infrared light cut filter 11 is detached by 25, the white balance is automatically corrected so as not to be lost, and then sent to the image processing circuit 21 where the image processing is performed. At this time, a memory table corresponding to the small luminance level value Y ₁₁ of the luminance signal Y is prepared in advance in the white balance correction circuit 25, and the white balance is corrected based on this memory table.

As described above, at the time of low-illuminance photographing in which the subject H and the periphery of the subject H are dark, the lens group 2 and the solid-state image pickup device 4 are used.
The infrared light cut filter 11 is automatically detached from between and, and the infrared light emitted from the subject H and the periphery of the subject H is sufficiently sensitive to the infrared light through the lens group 2 and the dummy glass 12. Since it reaches the solid-state image sensor 4, low-intensity infrared light imaging is possible. At this time, the dummy glass 12 is inserted between the lens group 2 and the solid-state image sensor 4 by replacing the infrared light cut filter 11, so that the optical path length from the lens group 2 to the solid-state image sensor 4 is always constant. Can be kept at Further, the low illuminance compatible image pickup apparatus 1 according to the present invention
When low-luminance shooting is performed using, the noise that occurs when the sensitivity of the video signal is increased by shooting while wearing the infrared light cut filter as in the related art does not occur, so that the SN ratio of the subject H is naturally high. Can be photographed, and a high-quality subject image without color misregistration can be obtained by correcting the brightness level and the white balance.

On the other hand, when it is determined in the determination circuit 22 that the brightness level value Y ₁₂ is for normal photographing, the result is determined through the drive circuit 23 connected to the output side of the determination circuit 22 based on the determination result. The motor 16 of the driving unit 10A shown in FIG. 2A or the motor 18 of the driving unit 10B shown in FIG. 2B drives to drive the lens group 2 and the solid-state imaging as shown in FIG. 4B. Infrared light cut filter 11 between element 4 and
And the dummy glass 12 is removed from between the lens group 2 and the solid-state image sensor 4.

As described above, during normal photographing in which the subject H and the periphery of the subject H are bright, harmful infrared light emitted from the subject H and the periphery of the subject H is cut by the infrared light cut filter 1.
Since it is removed by 1, the subject H can be photographed well as in the conventional case.

In the low-illuminance type image pickup apparatus 1 according to the present invention configured as described above, a small light 30 is added in the vicinity of the front of the lens group 2 so that the object H and the object H can be detected.
Infrared cut filter 11 when the area around is completely dark
If you leave the camera and shoot at low illuminance, you can also shoot at zero illuminance.

[0032]

According to the low illuminance type image pickup apparatus according to the present invention described in detail above, in the first aspect, the infrared light cut filter is detachably provided between the lens group and the solid-state image pickup element. , A low-illuminance shooting in which the subject and the surroundings of the subject are dark and a normal shooting in which the subject and the surroundings of the subject are bright are determined by the luminance level of the luminance signal separated from the output side of the solid-state image sensor, and based on the determination result. Since the infrared light cut filter is removed at the brightness level for low-illumination shooting while the infrared light cut filter is inserted at the brightness level for normal shooting,
During dark low-illumination shooting, infrared light emitted from a subject and the periphery of the subject reaches a solid-state image sensor having sufficient sensitivity to infrared light through a lens group, so that low-illuminance infrared light shooting is possible. Further, when low-illuminance shooting is performed by using the low-illuminance type imaging device according to the present invention, it occurs when the sensitivity is increased for a video signal by performing shooting with the infrared cut filter mounted as in the conventional case. Since no noise is generated, the subject can be photographed with a good SN ratio. Of course, during normal shooting in which the subject and the surroundings of the subject are bright, the infrared light cut filter removes harmful infrared light emitted from the subject and the surroundings of the subject.
As in the conventional case, the subject can be photographed satisfactorily.

According to the second aspect of the present invention, an infrared light cut filter and a dummy glass are selectively inserted and removed between the lens group and the solid-state image pickup device, so that dark low-illuminance shooting and bright normal shooting can be performed. Time is judged by the brightness level of the brightness signal separated from the output side of the solid-state image sensor, and only the dummy glass is inserted at the brightness level for low-illuminance shooting based on this judgment result, while the brightness for normal shooting is set. Since the configuration is such that only the infrared light cut filter is inserted at the time of the level, the same effect as in claim 1 can be obtained, and the optical path length from the lens group to the solid-state image sensor can always be kept constant here. .

Further, according to the third aspect, even if the infrared light cut filter is removed during dark low illuminance photography, the deviation of the white balance of the video signal is automatically corrected, so that there is no color deviation. A subject image of high image quality can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a low-illuminance type imaging device according to the present invention.

FIG. 2 is a diagram for explaining a switching structure of an infrared light cut filter and a dummy glass, which constitutes a main part of a low illuminance type imaging device according to the present invention.

FIG. 3 is a diagram showing the level of a luminance signal in the low illuminance type imaging device according to the present invention.

FIG. 4 is a diagram for explaining the operation of the low-illuminance type imaging device according to the present invention.

FIG. 5 is a diagram for explaining a conventional video camera.

[Explanation of Codes] 1 ... Imaging device for low illuminance, 2 ... Lens group, 4 ... Imaging device (solid-state imaging device), 11 ... Infrared light cut filter, 1
2 ... Dummy glass, 10 (10A, 10B) ... Driving means, 20 ... Y / C separation circuit, 22 ... Judgment circuit, 25 ... White balance correction circuit, Y ... Luminance signal.

Claims (3)

[Claims] 1. A lens group for photographing a subject, an image sensor for forming a subject image through the lens group, an infrared light cut filter detachably provided on an incident side of the image sensor, and the image sensor. A determination circuit that separates the luminance signal from the output-side video signal and determines whether the level of the luminance signal is a luminance level for low-illumination shooting or a luminance level for normal shooting; Based on the above, the infrared light cut filter is disengaged at the brightness level for low-illumination shooting, and the infrared light cut filter is inserted at the brightness level for normal shooting. Low illuminance compatible imaging device. 2. A lens group for photographing a subject, an image pickup element for forming a subject image through the lens group, and infrared light selectively and removably provided between the lens group and the image pickup element. A luminance signal is separated from a video signal on the output side of the image sensor and a cut filter and a dummy glass, and it is determined whether the level of the luminance signal is a luminance level for low-illuminance photographing or a luminance level for normal photographing. Based on the determination circuit and the determination result of the determination circuit, only the dummy glass is inserted at the brightness level for low-illuminance shooting, and only the infrared light cut filter is inserted at the brightness level for normal shooting. A low illuminance compatible image pickup apparatus comprising: a driving unit. 3. The low-illuminance type image pickup device according to claim 1, wherein when the infrared light cut filter is removed, a white balance of the video signal is automatically corrected. A low-illuminance compatible image pickup device comprising a correction circuit.