JPH0810911B2 - Imaging device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a still video camera, and more particularly, to an autofocus type still video camera equipped with an electronic viewfinder.

[Conventional technology]

Conventionally, for example, using a solid-state imaging device such as CCD (electrically coupled device), to convert the image of the subject into an electronic signal,
A "still video camera" for recording a still image signal of a subject on a recording medium such as a small magnetic disk has already been put to practical use.

The finder of such a still video camera is often an optical one, but instead of this, a small CRT is used.
It is known that a (cathode ray tube) or a so-called electronic viewfinder (hereinafter referred to as EVF) using liquid crystal is used.

The feature of the still video camera using EVF is that the screen to be shot can be viewed as it is without parallax without taking the form of a single-lens reflex camera with a mirror in the shooting optical path. In addition, if it has a playback function, it can also be used to view playback images.

[Problems to be solved by the invention]

However, when such a EVF is equipped in a still video camera, if the subject is dark, for example, unless a strobe is used, the brightness of the shooting lens,
Alternatively, depending on the sensitivity of the image pickup system including the signal processing circuit.
There are cases where the subject cannot be observed.

In view of the above cases, the present invention has an object to provide a still video camera of this type, which makes it possible to observe an object even in a dark environment without using special illumination light or the like.

In particular, the present invention is a still video of this kind provided with a so-called autofocus mechanism of irradiating a near infrared ray to a subject and receiving the reflected light with a light receiving element as a position detection sensor to measure the distance to the subject. It tries to adapt to the camera.

[Means for solving problems]

Therefore, in the present invention, this type of imaging device is
An autofocus means for performing an autofocus operation using an infrared light emitting element, an image pickup means for converting a subject image into an electric signal, and an electronic viewfinder for displaying the output of the image pickup means for observing the subject. An infrared cut filter arranged in the optical path of the image pickup means for cutting infrared light incident on the image pickup means; and the infrared light emitting element in the autofocus means when the subject is dark. By providing light for observing the subject even during a period other than the autofocus operation, and by providing control means for removing the infrared cut filter from the optical path of the image pickup means in association with this, the automatic operation is performed when the subject is dark. By making it possible to observe the subject illuminated by the infrared light emitting element in the focusing means with the electronic viewfinder. , It is intended to achieve the above purpose.

[Action]

With the above configuration, even in a dark place where it cannot be photographed without using a strobe, the EVF operates as a viewfinder of a so-called infrared camera when observing a subject with the EVF, and matches the wavelength on the near infrared side. Since the subject image is obtained, the subject can be clearly observed.

〔Example〕

 The present invention will be described below based on examples.

(Outline) The present invention is a still video camera having an EVF and a near-infrared ray autofocus system, and is capable of performing CC when photographing and when observing a subject in a visible light region.
Insert an infrared cut filter in the optical path of the solid-state image sensor such as D, when observing a subject in a dark case where it cannot be photographed without using a strobe as described above, remove the infrared cut filter from the optical path, In addition, the (near) infrared light emitting element (IRED) used for autofocusing illuminates the subject.

FIG. 2 shows an example of a wavelength-sensitivity characteristic curve a of a CCD used in a solid-state image sensor and a wavelength-transmittance curve b of an infrared cut filter. That is, without the infrared cut filter, the central sensitivity of the CDD is near 800 to 900 nm, and the light on the longer wavelength side than 800 nm is cut by passing through the infrared cut filter.

In a general still video camera, for colorization, correction is performed to obtain characteristics close to the luminosity through the R (red), G (green), and B (blue) color filters. I'm using it.

(Structure) FIG. 1 shows a block-like exploded explanatory view of the main part of the still video camera of the present embodiment based on the above principle. In the figure, 1 and 2 are photographing lenses, and an arrow A indicates the optical axis thereof. Reference numeral 3 denotes a lens driving mechanism for driving the taking lens 1 to focus a subject, 4 denotes a diaphragm mechanism, 5
Is a drive mechanism for the diaphragm mechanism 4. The diaphragm mechanism 4 is
It has a function of adjusting the amount of light with which the CDD array 11 as a solid-state image sensor is irradiated.

Reference numeral 6 denotes an infrared cut filter which can be thrown in (indicated by a solid line) / retracted (indicated by a chain line 6a) in the photographing optical path A and is normally disposed in the optical path A. Reference numeral 7 denotes an aperture (photographing aperture), and 8 and 9 respectively denote a front blade and a rear blade of the shutter.

The front blade 8 of the shutter is controlled by the tensioning member 12 and the electromagnet 13, and the rear blade 9 is controlled by the electromagnet 14. Further, when the subject is observed by the EVF, both blades 8 and 9 keep the aperture 7 open as illustrated. Further, 10 indicates the color filter.

On the other hand, 15 is a near-infrared light emitting element (IRED), 16 is its projection lens, and arrow B shows the projection optical path thereof. Further, 17 is a light-receiving lens, and 18 is a position sensor composed of a silicon photodiode or the like. (Shown) is focused on the position sensor 18 for distance measurement and auto focusing is performed.
15, the light projecting lens 16, the light receiving lens 17, and the position sensor 18 form a distance measuring optical system for autofocusing.

Reference numeral 19 denotes an optical element such as a convex / concave / flat lens for converting the light of the near-infrared light emitting element 15 for distance measurement into dispersed light suitable for illuminating a subject. The light projecting lens 16 is retracted out of the optical path B (indicated by a solid line), and is inserted into the optical path B (indicated by a chain line 19a) as necessary, as will be described later. It is configured so that the subject can be illuminated.

Reference numeral 20 denotes a lever in which the infrared cut filter 6 is provided at one end of two arms extending from the pivot point 20a at an angle to each other and the optical element 19 is provided at the other end of the arm. The coil spring 22 is biased counterclockwise around the pivot point 20a. Reference numeral 21 denotes an electromagnetic plunger serving as a driving member for rotating the lever 20 in the clockwise direction against the biasing force. By energizing the electromagnetic plunger 21, the infrared cut filter 6 is moved from the photographing optical path A. The optical element 19 is retracted to the position 6a,
It is configured to be inserted at the 19a position.

Reference numeral 31 is a signal processing circuit for making the subject signal obtained from the image pickup device 11 suitable for a television signal, for example, and 32 is a recording circuit for making the signal suitable for magnetic recording. . Further, 33 is a magnetic head, 34 is a magnetic disk as a recording medium, and 35 is the magnetic disk 34.
2 shows a spindle motor for rotating the.

The image signal from the signal processing circuit 31 is added to the EVF drive circuit 36 so that it can be observed by the EVF monitor 37.

(Operation) Next, the operation will be described.

FIG. 3 is a flow chart showing a flow of main items of a series of operation sequence of the still video camera having the configuration of FIG. That is, in step 51, the operation of the camera is started, and the distance to the subject is measured by the near infrared light emitting element 15, the position sensor 18, and the like. Then step 52
Then, based on the distance information, the lens driving mechanism 3 drives the taking lens 1 to automatically focus the subject. Next, in step 53, photometry is performed by means (not shown), and in step 54, it is judged from the photometric information whether or not auxiliary light is necessary for photographing. When the auxiliary light is not required (N), the subject can be observed through the EVF monitor 37 with natural light. (Step 55).

Here, in step 56, when the release button or the like is pressed to start the photographing operation, in step 57, the aperture 4,
Each blade (8, 9) of the shutter travels from closed to open to closed, and the image pickup device 11 is exposed and an image signal is transferred. Then, in step 58, the data is recorded on the magnetic disk 34. Here, the magnetic head 33 is sequentially moved to the next track (step 5
9), in step 60, if continuing (Y), step 5 again
If the process returns to 1 and does not continue (N), the operation ends.

On the other hand, if auxiliary light is required for shooting in step 54 (Y), the process proceeds to step 61, and the position of the shooting lens 1 is corrected according to the wavelength of the light beam emitted by the infrared light emitting element 15. That is, in step 52 described above, the position of the taking lens 1 is adjusted according to the wavelength of visible light, but in step 61, the illumination light of the subject is the (infrared) light flux due to the near infrared ray emission blocking 15. Therefore, even if the subject distance is the same, the image forming position is displaced, and the displacement is corrected here.

Next, in step 62, the infrared cut filter 6 is retracted from the photographing optical axis A to the position 6a by applying a drive signal to the electromagnetic plunger 21 and rotating the lever 20 clockwise, and at the same time, the optical element 19 is projected. It is moved so as to be inserted into the position 19a in the optical path B. By moving the optical element 19 to the position 19a, the subject is illuminated by the near infrared light emitting element 15.

Next, in step 63, EV under the lighting in step 62 above.
A subject can be observed by the F monitor 37.

Thereafter, in step 64, as in the case of step 56, when the release button or the like is pressed to start the photographing operation, in step 65, the rotation of the lever 20 by the plunger 21 is stopped, and the bias spring 22 causes the red spring 22 to rotate. Outer cut filter 6
Is again inserted into the photographing optical path A, and the optical element 19 is retracted out of the projection optical path B.

Next, in step 66, the taking lens 1 corrected in step 61 is corrected again to the position of visible light. In step 67, shooting with auxiliary light is performed, and the same operation as that described in step 57 is performed.

(Other Embodiments) FIG. 4 is an exploded perspective view of a main portion of another embodiment of changing the illumination light by the near infrared light emitting element 15.
The same (corresponding) constituent elements in FIG. 1 are designated by the same reference numerals. One end of the lever 23 is in contact with one end of the lever 20b, and the other end is provided with a drive pin 23a for driving the projection lens 16 along the projection optical path B. The tension coil spring 24 is arranged to bias the lever 23 and the lever 20 in one direction.

In this example, the distance L between the near-infrared light emitting element 15 and the light projecting lens 16 is maintained at a certain interval when the infrared cut filter 6 is arranged in the photographing optical path A. The light flux image from the light emitting element 15 formed by the optical lens 16 is aligned at a position near 3 m, for example. That is, in this state, autofocus or image pickup by the image pickup device 11 is possible.

Further, when the lever 20 is rotated clockwise by a drive member (not shown) to retract the infrared cut filter 6 from the photographing optical axis A and move it to the position 61a, the projection lens 16 via the lever 23 is moved.
Is also moved, the distance L to the light emitting element 15 is changed, and the light is dispersed to the subject. Therefore, the subject is illuminated by the scattered light instead of the spot-like light flux for distance measurement. The image quality of the observation image on the EVF monitor 37 is improved.

[Effects of the Invention] As described above, according to the present invention, by operating the so-called infrared camera by arranging the characteristics of the image sensor even in a dark place where a flash cannot be used, the EVF Can be observed, and since the subject image at that time is focused according to the near infrared wavelength, a clear image can be observed. Further, since the near-infrared light source used for autofocusing is used for the illumination, the structure can be simplified. Further, in actual photographing, an image photographed because it is performed with a visible light source such as a strobe has a characteristic that it is the same as that in a normal state.

[Brief description of drawings]

FIG. 1 is a block-type exploded perspective view of a main part of a still video camera according to the present invention, and FIG. 2 is a diagram showing wavelength-sensitivity of CCD and wavelength-transmission characteristics of an infrared cut filter,
FIG. 3 is a flow chart showing the main operation sequence of the still video camera in FIG. 1, and FIG. 4 is a perspective view of a main part of a part of another embodiment in FIG. 1,2 …… Shooting lens 6 …… Infrared cut filter 11 …… CCD (image sensor) 15 …… Near infrared light emitting element 16 …… Emitting lens 17 …… Receiving lens 18 …… Position sensor 19 …… Optical element 20,20b …… Lever 23 …… Lever

Claims (1)

[Claims] 1. An autofocus means for performing an autofocus operation using an infrared light emitting element, an image pickup means for converting a subject image into an electric signal, and an output of the image pickup means for observing the subject. An electronic viewfinder, an infrared cut filter arranged in the optical path of the image pickup means for cutting infrared light incident on the image pickup means, and the infrared ray in the autofocus means when the subject is dark. By providing the light emitting element to emit light for observing the subject even during the period other than the autofocus operation, and by providing the control means for removing the infrared cut filter from the optical path of the image pickup means, It is possible to observe the subject illuminated by the infrared light emitting element in the autofocus means in the dark in the dark by the electronic viewfinder. Imaging device, characterized in that the.