JPH0444870B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a solid-state imaging camera that can obtain a high-resolution imaging output signal especially when imaging a stationary object, and is used in a so-called electronic still camera or the like. This is what we provide.

(Technical Background of the Invention) In recent years, so-called solid-state imaging devices using charge transfer devices such as CCDs have been put into practical use, and various solid-state imaging cameras using them have been proposed. However, the light-receiving surface structure of a solid-state image sensor is
As schematically shown in the figure, a large number of minute light-receiving elements P are arranged regularly but discretely within the light-receiving surface S, so even if this light-receiving surface is aligned with the image forming surface, The incident light image reaching the light-insensitive area Q is not used as a video signal at all.

As an attempt to increase the resolution of a solid-state imaging camera using such a solid-state imaging device, there is a method called spatial pixel shifting when the subject is stationary or moves very slowly. This method uses the first
Another one corresponding to the light-receiving element P is placed in the light-insensitive area Q in the figure.
This is a method of arranging picture elements equivalently. For example, as shown in FIG. 2, once the video signal from the light receiving element P is taken into the image memory in a normal state,
By deflecting the light image to be captured by a small angle, the light image that has reached the light-insensitive area between the adjacent light receiving elements P is brought onto the adjacent light receiving elements P as shown by the arrow X. Then, in this state, the image signal from the light receiving element P is taken into the image memory again, and then both video signals are combined on the image memory to obtain a video signal having twice the number of picture elements. According to this, the resolution in the horizontal direction is doubled in principle. In this case, if a mechanical movable means is used to deflect the optical image, it will take some time for the deflection, so it is preferable that the object to be imaged is a stationary object.

This method of spatial picture element shifting is, for example, the third
As shown in the figure, an optical axis deflecting means 12 for deflecting the lens optical axis O by a small angle is arranged in front of the imaging lens 10, and a frame memory 16 for recording the imaging output signal obtained from the solid-state imaging device 14.
achieved by. According to this configuration, the object is first imaged in the initial state of the optical axis deflection means 12, that is, in a state without optical axis deflection, the imaging output signal is recorded in the frame memory 16, and then the optical axis deflection means 12 is operated and the imaging lens Imaging is performed again with the optical axis toward 10 tilted by δ. When the incident light ray to the imaging lens 10 is tilted by δ, the outgoing light ray is also tilted by δ, and as a result, the imaging plane, that is, the solid-state image sensor 14
On the light-receiving surface of , the image moves by a distance d d = f tan δ (1) expressed by the following equation (1). Here, f indicates the image distance from the imaging lens to the solid-state image sensor, and becomes equal to the focal length of the imaging lens when the object distance from the subject to the lens is infinite.

By the way, in the above-mentioned conventional spatial pixel shifting method, a spherical glass or a wedge-shaped prism arranged at an angle with respect to the optical axis is used as the optical axis deflecting means 12 shown in FIG. Since the optical axis deflection effect was obtained by rotating around the axis, the locus of image movement on the imaging plane due to the optical axis deflection becomes circular. Therefore, for example, when the purpose is to improve the resolution in the horizontal direction, only one point in the circular scanning trajectory can be used. Furthermore, a decisive drawback of the conventional method is that, as is clear from equation (1), the amount of movement of the image as an optical axis deflecting means changes depending on the image distance f, in other words, the object distance. On the other hand, in solid-state imaging cameras, once the solid-state imaging device to be used is determined, the appropriate amount of image movement is determined from its light-receiving surface structure. It may be possible to use it only under an object distance of . Therefore, the above method cannot be applied to, for example, a normal television camera in which the object distance varies.

(Objective of the Invention) In view of the above technical background, an object of the present invention is to maintain the moving direction of the image constant (for example, horizontal direction) and to maintain the same amount of image movement even when the object distance changes. The objective is to obtain a high-resolution imaging output signal by using a spatial pixel shifting method using optical axis deflection means that can maintain the image quality.

(Structure of the Invention) As described in the claims, the structure of the present invention includes an optical axis deflecting means consisting of two wedge-shaped prisms having approximately equal apex angles on the imaging optical axis, thereby achieving high resolution. The present invention is characterized in that it is a solid-state imaging camera that can obtain an imaging output signal.

Next, the optical axis deflecting means which constitutes the main part of the present invention will be explained.

The two wedge-shaped prisms are located on the imaging optical axis of the solid-state imaging camera and are configured to rotate by equal amounts in opposite directions about the optical axis. That is, by rotating two wedge-shaped prisms with the same apex angle in opposite directions to each other around the optical axis, the prisms act as variable apex angle prisms only in a predetermined image movement direction (generally horizontal direction), and By controlling the rotation using the focus position information of the solid-state imaging camera, the zoom magnification information of the zoom lens used, or both information, it is possible to always move the image by a constant amount regardless of changes in the object distance. It becomes possible. Therefore, by using the optical axis deflecting means, the resolution of the imaging output signal in the horizontal scanning direction of the solid-state imaging camera can be effectively increased.

FIGS. 4a, 4b, and 4c are explanatory diagrams of the operating principle of the optical axis deflecting means. The wedge-shaped prisms 20A and 20B each have an apex angle θ and are interposed on the optical axis O. At the position shown in FIG. 4a, the apex angles of the respective prisms cancel each other out, and no optical axis deflection occurs. In the position shown in Fig. 4b, the prism 20A is rotated counterclockwise about the optical axis, and the prism 20b is rotated clockwise by an angle ψ, and the combined apex angle of both prisms changes only in the horizontal direction. Accordingly, the optical axis O is deflected horizontally by an angle δ. Further, the maximum deflection angle δmax is obtained at the position shown in FIG. 4c, and this maximum deflection angle δmax is expressed as δmax=2θ(n-1) (2). However, n is the refractive index of the prism.
In addition, in Fig. 4b, the horizontal deflection angle δ during the process of rotation of both prisms is determined by the rotation angle of each prism as |ψ| (if prism 20A is ψ and prism 20B is -ψ, δ=θ sinψ …(3) It can be expressed as:

Therefore, the above equation (1) expressing the amount of image movement becomes d=f tan(θ sinψ) ...(3) where θ is constant at the apex angle of the prism, so the rotation angle ψ is expressed as the image distance. By controlling according to changes in f (which uniquely corresponds to the object distance), it is possible to keep the image movement amount d constant. Utilizing this fact, the object of the present invention can be achieved by manually or automatically adjusting the prism rotation angle ψ according to the object distance so that the image movement amount d in equation (3) is constant. , high resolution of the imaging output signal can be achieved.

FIG. 5 shows an example of a drive system for rotating wedge-shaped prisms 20A and 20B at equal angles in opposite directions around the optical axis. The gears are rotated.

(Description of Embodiments) FIG. 6 is a system block diagram showing the overall system of the solid-state imaging camera of the present invention, in which 40 is an optical axis deflecting means, 42 is an imaging lens, and 44 is a solid-state imaging device. Further, 50 is a video process amplifier that appropriately amplifies and shapes the output from the solid-state image sensor 44, 52 is an A/D converter, 54 is a frame memory as an image memory, and 56 is a D/A converter, from which high-resolution images are generated. An output signal is obtained. Reference numeral 60 designates a synchronization signal generating section that generates clock pulses and television synchronization signals to be supplied to each circuit, 62 a frame memory drive circuit, and 64 a solid-state image sensor drive circuit. 70 is a system control unit 72,
An imaging lens distance setting detection section 74 is a drive and deflection angle detection section for the optical axis deflection means.

Next, the operation of the solid-state imaging camera of the present invention having the above configuration will be explained.

Drive of optical axis deflection means and deflection angle detection section 74
constitutes a servo system that rotates the motor M shown in FIG.
Does the wedge-shaped prism stop at the position shown in Figure 4 a (hereinafter referred to as the A position)?
Two types of information are received: (1) information on whether to stop at the position shown in FIG. Based on these two types of information supplied from the system control unit 70, the optical axis deflection means driving and deflection angle detection unit 74 rotates the motor M to move the wedge-shaped prism A,
Or stop at position B. Motor M
Although it takes a certain amount of time for the motor M to rotate, the drive and deflection angle detection section 74 sends information to the system control section 70 informing that the motor M is in the middle of rotating.

The imaging lens distance setting detection section 72 has a function of converting zoom magnification information (in the case of a zoom lens) and focus position information of the imaging lens 42 into electrical signals and sending them to the system control section 70 .

Generally, in a television camera, when the imaging lens 42 is a zoom lens, the zoom magnification and focus position are fixed according to the intention of the cameraman who images the subject. These electrical signals of zoom magnification information and focus position information are sent to the lens distance setting detection section 72 or the system control section 70, and calculate the rotational position ψo of the optical axis deflection means 40 based on the above-described principle. This calculation is
This is done based on the above equation (3), and since the zoom magnification and focus position are related to the image movement amount d and the image distance f in equation (3), respectively, these specific values can be calculated as the imaging lens distance. By capturing the data in the setting detection unit 72, it is possible to obtain the rotation angle ψo of the wedge-shaped prism necessary to keep the image movement amount d constant. That is, the image distance is determined in relation to the object distance from the imaging lens to the subject, and furthermore,
At this time, the rotation angle ψo required to move the image by 1/2 of the pixel interval between the light receiving elements P on the solid-state image sensor surface is calculated.

The function that calculates this rotation angle ψo is
As described above, the information on the rotation angle ψo as a calculation result may be provided in either the lens distance setting detection section 72 or the system control section 70, and the information on the rotation angle ψo as a calculation result is transmitted from the system control section 70 to the drive of the optical axis deflection means and the deflection angle detection section 74. sent to.

The frame memory 54 as an image memory is for combining two imaging output signals, but the data in the frame memory 54 is driven by a frame memory drive circuit 62 to convert the recorded image data into a television signal. The output signal of the D/A converter 56 is the output of the solid-state imaging camera system of the present invention, but to aid understanding, the output signal of the D/A converter 56 is displayed on a monitor. FIG. 7 shows the correspondence between the screen position at the time of output and the data inside the frame memory.

One data position inside the frame memory is shown as one ○ or × dot on the screen, and the contents of the memory data are related to the output of the image sensor, and the brightness and darkness of the screen is determined. It is worshiped. Also,
It goes without saying that the positional relationship between 0 and x within the image sensor is such that they are separated by a distance corresponding to the amount of movement d of the image in equations (1) and (3) above.

In this frame memory, the data at the position marked with a circle records an image when the wedge-shaped prism is in the A position, for example. Also, ×
The data at the marked position is data recorded as an image at the B position. When reading signals from the frame memory, reading is performed in the order of 〇×〇×.... Regarding the recording of the image signal, it is determined by the system control whether the image data (digital amount) supplied from the A/D converter 52 is recorded at a location corresponding to the ○ mark position or at a location corresponding to the x position. controlled by a signal from section 70,
The system control 70 includes a wedge-shaped prism A
There is information instructing whether to set the position 1 or the position B, and based on this information, a command can be issued to the frame memory 54 as well. Note that the number of data in one horizontal line of the frame memory is 2N when the number of horizontal pixels of the solid-state image sensor is N and one pixel is digitized as one data. By writing, the N pieces of data marked with O are recorded, and during the second writing, the N pieces of data marked with × are recorded.

Next, a procedure for controlling the system shown in FIG. 6 to obtain a video signal with twice the horizontal resolution as the output video signal of the D/A converter 56 will be explained with reference to FIG.

When the cameraman determines the zoom magnification and focus position of the zoom lens, the system control section 70 calculates the necessary rotation angle ψo of the optical axis deflection means 40 from this information and outputs it to the drive and detection section 74.
As a result, the drive and detection section 74 starts operating, the motor M rotates, and the motor stops at position A or B. This may be either position; for example, the one with the smaller rotation angle of the motor may be selected.

Depending on whether the motor M is stopped at the A position or the B position, recording is performed twice in two cases, and the process in this case is as shown in the figure. The reason why the motor is divided into two cases is because the motor needs to rotate a lot because it has been devised so that it passes through only one place marked with *.If the start is always set to the A position, the motor must rotate repeatedly. When recording data, it is necessary to rotate the motor twice for one recording, which is disadvantageous in terms of time.

The present invention is not limited to the example described above, and may be implemented with various modifications. For example, in the above example, the imaging lens is a zoom lens and frame memory is used, but in the case of a lens that is not a so-called zoom lens and has a unique focal length, the image distance f in equation (3) corresponds to It is sufficient to control the rotation angle of the wedge-shaped prism using only the focus position information. Further, the frame memory may be changed to other image memory, such as field memory or line memory, and the purpose of the present invention can be sufficiently achieved by implementing the present invention without departing from the scope of the claims. be able to.

Furthermore, since the optical axis deflecting means used in the present invention has a constant moving direction of the image on the light-receiving surface of the solid-state image sensor, the amount of image movement is not limited to only two positions (for example, A position and B position); It is also possible to further increase the resolution by shifting the spatial picture elements multiple times. Furthermore, if one set of image signals is recorded between a and c in FIG. By considering the composition of the images, it becomes theoretically possible to record four sets of image signals, that is, to capture images for four screens during 360° rotation of the wedge-shaped prism.

Furthermore, if the motor for rotationally driving the wedge-shaped prism is a pulse motor, the prism rotational position can be detected by counting motor drive pulses, and there is no need to separately provide a position detecting member around the prism.

(Effects of the Invention) As explained above, according to the present invention, two wedge-shaped prisms having approximately equal apex angles, which are rotated by equal amounts in opposite directions around the optical axis, are used as optical axis deflecting means. Since the spatial pixel shifting method has been realized using the spatial pixel shifting method, the resolution can be improved by using the spatial pixel shifting method for cameras where the object distance can take an arbitrary value, such as regular television cameras and still cameras. can be sufficiently improved.

Furthermore, when a zoom lens is used as an imaging lens, the conventional method of spatial pixel shifting cannot be applied, and therefore the effect cannot be expected, but according to the present invention, the method shown in the embodiment shown in FIG. By controlling the rotation angle of the wedge-shaped prism using the zoom magnification information, it is possible to increase the resolution of the imaging output signal without any difficulty, as in the case of an imaging lens having a unique focal point.

In the above, the camera that can be expected to improve resolution by the present invention is limited to a so-called still image camera that images a stationary subject. If shuttering is allowed, it is possible to obtain an imaging output signal with sufficiently high resolution even for slight movements by performing imaging twice in a very short period of time.

[Brief explanation of drawings]

Figure 1 is a structural diagram of the light-receiving surface of a solid-state image sensor, Figure 2
The figure is an explanatory diagram of the method of spatial pixel shifting, Figure 3 is a diagram of the principle configuration for realizing the method of spatial pixel shifting, and Figures 4 a, b, and c are lights used in the solid-state imaging camera of the present invention. FIG. 5 is a structural diagram showing an example of a drive system for rotating the wedge-shaped prism; FIG. 6 is a block diagram showing the overall system of the solid-state imaging camera of the present invention; FIG. 7 8 is an explanatory diagram showing the data arrangement in the frame memory, and FIG. 8 is a flowchart showing the procedure for obtaining a video signal with double resolution according to the present invention. 10...Imaging lens, 12...Optical axis deflection means, 14
...Solid-state image sensor, 16...Frame memory, 20
A, 20B... Wedge-shaped prism, 30... Gear train, 40... Optical axis deflection means, 42... Imaging lens,
44... Solid-state image sensor, 50... Video process amplifier, 52... A/D converter, 54... Frame memory, 56... D/A converter, 60... Synchronization signal generation section, 62... Frame memory drive circuit, 64...
Solid-state image sensor drive circuit, 70... system control unit,
72... Imaging lens distance setting detection section, 74... Optical axis deflection means drive and deflection angle detection section, S... Light receiving surface,
P...Photodetector, Q...Light-insensitive area, O...Lens optical axis, δ...Deflection angle, θ...Wedge-shaped prism apex angle, ψ
...Same prism rotation angle, M...Motor.

Claims (1)

[Scope of Claims] 1. Two wedge-shaped prisms with approximately equal apex angles are provided on the optical axis of the imaging optical system so as to rotate by equal amounts in opposite directions about the optical axis, and A solid-state imaging camera characterized in that a high-resolution image signal is obtained by combining imaging output signals obtained by imaging at a plurality of rotational positions of a prism. 2. The solid-state imaging camera according to claim 1, wherein the rotation of the two wedge-shaped prisms is controlled by focus position information from the solid-state imaging camera. 3. The solid-state imaging camera according to claim 1, wherein the rotation of the two wedge-shaped prisms is controlled by focus position information and zoom magnification information from the solid-state imaging camera.