JP3397758B2 - Imaging device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup device such as a video camera capable of picking up a moving image or a still image.

[0002]

2. Description of the Related Art In a digital color camera, an object image is exposed for a desired time on a solid-state image sensor such as a CCD or a CMOS sensor in response to a release button being pressed, and an image signal obtained from this is converted into a digital signal. After that, predetermined processing such as YC processing is performed to obtain an image signal of a predetermined format. This digital image signal is recorded in the semiconductor memory. Then, the recorded image signal can be read out at any time, reproduced as a signal that can be displayed or printed, and output to a monitor or the like to visualize the recorded image.

The exposure form of the object image is such that an RGB color filter having a set of 2 × 2 pixels is formed on a solid-state image pickup element to impart wavelength selectivity to each pixel, whereby an object image is formed. , A method of separating each of the RGB images, a method in which the solid-state image sensor does not have wavelength selectivity, an optical filter having wavelength selectivity is inserted into the photographing optical system, and this is switched in time series, Further, a method is known in which a color separation optical system is added to the rear of the image pickup optical system and an image is captured by using different image pickup elements for different wavelength ranges.

A general digital color camera adopts many of the above-mentioned methods, and Japanese Patent Laid-Open No. 9-172649 discloses examples of the above-mentioned methods, and Japanese Patent Laid-Open Nos. 7-84177 and 7-1231818 disclose the above-mentioned methods. It is an example of disclosure of the method.

[0005]

However, in any of the above methods, since the imaging optical system is commonly used for each wavelength range, good optical performance over the entire visible range is achieved. Need to have. In general, the photographic optical system uses the refraction of light with optical glass or transparent resin for optics as its imaging principle, so the refractive index changes depending on the wavelength, but this does not reduce the image performance. An optical design method called eraser is used. As a result, it is difficult to construct a high-performance photographing optical system with a single lens, which has been an obstacle to downsizing of the imaging optical system.

An object of the present invention is to provide a compact image pickup device having high image performance.

[0007]

In order to achieve the above object, the present invention provides an image pickup device having at least first and second image pickup areas, and a photographing optical system for forming an object image on the image pickup device. In the image pickup apparatus having the image pickup device, the photographing optical system corresponds to at least the first and second image pickup regions
And a second imaging system for light of a second wavelength and a focal length of the first imaging system for light of a first wavelength and a second imaging system for forming light of a second wavelength. The focal length of the first imaging system is set to be the same, and the focal length of the first imaging system for light having a wavelength other than the first wavelength and the second for light having a wavelength other than the second wavelength. The imaging device is set so that the focal length of the imaging system is different.

According to the present invention, in an image pickup apparatus having an image pickup device having a plurality of image pickup regions and a photographing optical system for forming an object image on the image pickup device, the photographing optical system has the plurality of image pickup regions. Is provided with a plurality of image forming systems that respectively form object images, and the focal lengths of the plurality of image forming systems are
An imaging device that is set to be the same for the wavelength of light of a predetermined wavelength of each imaging system, and is set to be different for light of a wavelength other than the predetermined wavelength of each imaging system It is what

Further, according to the present invention, an image pickup device having first and second image pickup areas, a photographing optical system for forming an object image on the image pickup device, and image processing for processing an output signal of the image pickup device. in the image pickup apparatus and means, the photographing optical system becomes provided with a first and a second imaging system, said first and second imaging system object image each before Symbol first and second the A first image signal formed by an object light component having a first spectral distribution and a second image signal formed by an object light component having a second spectral distribution, which are formed on an imaging region and are formed from the first and second imaging regions. With each of the above, with respect to the representative wavelength of the spectral distribution of the first image signal, the focal lengths of the first and second imaging systems are made different, with respect to the representative wavelength of the spectral distribution of each image signal. The image pickup apparatus has the same settings.

According to the present invention, the first image pickup section and the second image pickup section for respectively receiving at least the first wavelength component of the subject light and the second wavelength component different from the first wavelength component.
And an image pickup section for guiding the first and second wavelength components of the subject light received by the first and second image pickup sections to the first and second image pickup sections respectively through different optical paths. A first optical system and a second optical system, wherein the first optical system and the second optical system have a focal length with respect to the first wavelength component of the first optical system and the second optical system. The imaging device is configured so that the optical system has the same focal length with respect to the second wavelength component.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

FIGS. 17A, 17B and 17C are diagrams showing the overall structure of a digital color camera according to the present invention. 17A is a front view, FIG. 17C is a rear view, and FIG.
17B is a cross-sectional view at the position of arrow A shown in the back view of FIG. 17C.

In FIGS. 17 (a), 17 (b) and 17 (c), reference numeral 1 is a camera body, and 2 is a window located behind the color liquid crystal monitor 4 and formed of a white diffuser. 5 is a main switch, 6 is a release button, 7, 8 and 9 are switches for the user to set the state of the camera, in particular 9 is a play button and 13 is a display of the number of remaining shots. Reference numeral 11 is a viewfinder eyepiece window through which the object light incident on the prism 12 from the viewfinder front frame 3 exits. Reference numeral 10 is an imaging system, and 14 is a connection terminal for connecting to an external computer or the like for transmitting and receiving data.

A schematic configuration of the signal processing system will be described. 14
FIG. 3 is a block diagram of a signal processing system. This camera is a CCD
Alternatively, it is a single-panel digital color camera using a solid-state image sensor 120 such as a CMOS sensor.
Are driven continuously or in a single shot to obtain an image signal representing a moving image or a still image. Here, the solid-state image sensor 120
Is an image pickup device of a type that converts exposed light into an electric signal for each pixel, accumulates electric charges according to the amount of light, and reads the electric charges.

It should be noted that FIG. 14 shows only the portions directly related to the present invention, and the illustration and description of the portions not directly related to the present invention are omitted.

As shown in FIG. 14, the image pickup apparatus includes an image pickup system.
An image processing system 20, which is an image processing means, a recording / reproducing system 30, and a control system 40 are provided. Furthermore, the imaging system 10
Includes a photographing lens 100, a diaphragm 110 and a solid-state image sensor 120, the image processing system 20 includes an A / D converter 500, an RGB image processing circuit 210 and a YC processing circuit 230, and the recording / reproducing system 30 includes:
The control system 40 includes a recording processing circuit 300 and a reproduction processing circuit 310, and a system control unit 400, an operation detection unit 410, and a drive circuit 420 for the solid-state imaging device.

The image pickup system 10 is an optical processing system that forms an image of light from an object on the image pickup surface of the solid-state image pickup device 120 through the aperture 110 and the image pickup lens 100, and adjusts the light transmittance of the image pickup lens 100. The solid-state image sensor 120 is exposed with a subject image having an appropriate light amount. As described above, the solid-state image sensor 120 is a CCD or C
An image pickup device such as a MOS sensor is applied, and by controlling the exposure time and the exposure interval of the solid-state image pickup device 120, an image signal showing a continuous moving image or an image signal showing a still image by one exposure is obtained. You can

FIG. 1 is a detailed view of the image pickup system 10. First, the diaphragm 110 has three circular openings 110a, 110b, 11 as shown in FIG.
0c, from each of which the light entrance surface 100e of the taking lens 100
The object light incident on the three lens parts 10 of the taking lens 100 is
Three object images are formed on the image pickup surface of the solid-state image pickup device 120 after being emitted from 0a, 100b, and 100c. The diaphragm 110, the light incident surface 100e, and the imaging surface of the solid-state imaging device 120 are arranged in parallel. In this way, the power on the incident side is weakened, the power on the exit side is increased, and the diaphragm is provided on the incident side, whereby the curvature of the image plane can be reduced. Although the light incident surface 100e of the taking lens 100 is a flat surface here, it may be formed of three spherical surfaces or three rotationally symmetric aspherical surfaces.

Each of the three lens portions 100a, 100b, 100c has a spherical spherical portion having a circular diameter as shown in FIG. 5 when the photographing lens 100 is viewed from the light exit side, and this spherical portion has a low wavelength region of 670 nm or more. Infrared cut filter with transmittance
Further, a light-shielding film is formed on the plane portion 100d shown by hatching. That is, the photographing optical system is composed of a photographing lens 100 and an aperture 110, and three lens units 100a, 100b, 1
Each of 00c is an imaging system.

In the present embodiment, the first image pickup area of the present invention is the image pickup area 120a, and the second image pickup area is the image pickup area 120b.
Alternatively, the imaging region 120c corresponds to it. The first imaging system is the lens unit 100a, and the second imaging system is the lens unit 100b or the lens unit.
100c corresponds. Further, the first object image corresponds to the object image formed inside the image circle 51a, and the second object image corresponds to the object image formed inside the image circle 51b or the image circle 51c. Also, the first image signal is
The R image signal or the B image signal corresponds to the G image signal and the second image signal.

When the taking lens 100 is made of glass, a glass molding method is used, and when it is made of resin, injection molding is used.

FIG. 2 is a front view of the solid-state image pickup device 120. The three image pickup areas 120a and 12 are made to correspond to the three object images formed.
It is equipped with 0b and 120c. Each of the imaging areas 120a, 120b, and 120c is a 2.24 mm × 1.68 mm area formed by arranging 800 × 600 pixels with a vertical and horizontal pitch of 2.8 μm, and the overall size of the imaging area is 2.24 mm × 5.04 mm. , And the diagonal dimension of each imaging area is
2.80mm. In the figure, 51a, 51b and 51c are image circles in which an object image is formed. The image circles 51a, 51b and 51c are circular shapes determined by the aperture of the diaphragm and the size of the spherical surface on the exit side of the taking lens 100, and the image circles 51a and 51b and the image circles 51b and 51c.
Have overlapping parts.

In FIG. 1, portions 52a, 52b and 52c indicated by hatching are shown in a region sandwiched between the diaphragm 110 and the taking lens 100.
Is an optical filter formed on the light incident surface 100e of the taking lens 100. The optical filters 52a, 52b, and 52c are formed in a range that completely includes the aperture openings 110a, 110b, and 110c, as shown in FIG. 4 when the photographing lens 100 is viewed from the light incident side.

The optical filter 52a has a spectral transmittance characteristic for transmitting mainly green light shown by G in FIG.
52b has a spectral transmittance characteristic indicated by R that mainly transmits red, and the optical filter 52c has a spectral transmittance characteristic indicated by B that mainly transmits blue. That is, these are primary color filters. Lens part 100a, 100b, 100c
As the product of the characteristics of the infrared cut filter formed on the image circle 51a, the object image formed on the image circle 51a is the green light component, the object image formed on the image circle 51b is the red light component, the image circle 51c is formed. The image of the object being formed is due to the blue light component.

On the other hand, the three imaging regions 12 of the solid-state imaging device 120
Optical filters 53a, 53b, 53 also on 0a, 120b, 120c
c is formed, and their spectral transmittance characteristics are also equivalent to those shown in FIG. That is, the imaging area 120a is for green light (G), the imaging area 120b is for red light (R),
The imaging region 120c is sensitive to blue light (B).

Since the light reception spectrum distribution of each image pickup region is given as the product of the spectral transmittance of the pupil and the image pickup region, the combination of the pupil and the image pickup region is selected according to the wavelength region. In other words, the object light that has passed through the aperture 110a of the diaphragm is mainly focused on the imaging area 12
The object light that is photoelectrically converted at 0a and has passed through the aperture 110b of the diaphragm is mainly photoelectrically converted at the imaging area 120b, and the aperture of the diaphragm is further
Object light that has passed through 110c is mainly photoelectrically converted in the imaging region 120c. That is, the imaging area 120a displays the G image and the imaging area 120a
b outputs the R image, and the imaging area 120c outputs the B image. As described above, when an optical filter for color separation is multiply used in the pupil of the image pickup optical system and the image pickup element, color purity can be increased. It has 2 optical filters of the same kind.
This is because the transmission characteristics rise sharply when the material is rotated, and the red (R) and blue (B) overlaps disappear. It should be noted that the optical filters 52a and 52a are arranged so that the signal levels in the respective imaging regions are appropriate in the same accumulation time.
It is preferable to set the transmittance of b, 52c or the optical filters 53a, 53b, 53c.

The image processing system 20 forms a color image in each of the plurality of image pickup regions of the solid-state image pickup device 120 based on the selective photoelectric conversion output obtained from one of the plurality of images. At this time, since the peak wavelength of the relative luminous efficiency is 555 nm, signal processing is performed using the G image signal including this wavelength as the reference image signal.

When the pixel pitch of the solid-state image sensor is fixed, for example, RG in which a set of 2 × 2 pixels is formed on the solid-state image sensor is used.
Compared with the method adopted in general digital color cameras that form a B color filter to give wavelength selectivity to each pixel and separate the object image into RGB images, The image size becomes 1 / √3, and the focal length of the taking lens becomes approximately 1 / √3 accordingly.
Therefore, it is extremely advantageous for thinning the camera.

The optical filters 52a, 52b and 52c,
Regarding the spectral transmittance characteristics of the optical filters 53a, 53b, 53c, although R and B are almost separated as shown in FIG. 6,
R and G and G and B overlap each other.

Therefore, the red light image circle 51
Even if b is on the imaging area 120c that photoelectrically converts blue light, conversely, even if the image circle 51c of blue light is on the imaging area 120b that photoelectrically converts red light, these images are output from the imaging area. It never becomes. However, in the part where the image circle 51b of red light overlaps the imaging region 120a that photoelectrically converts green light, and in the part where the image circle 51a of green light overlaps the imaging region 120b that photoelectrically converts red light, it is originally blocked. The images of different wavelengths to be superimposed are slightly overlapped. That is, since the selectivity of the object image is given by the product of the spectral transmittance characteristics of the optical filter 52a and the optical filter 53b and the spectral transmittance characteristic of the optical filter 52b and the optical filter 53a, the R image signal and the G image signal Crosstalk is small, but does not completely reach zero.

Therefore, the taking lens 100 is further provided with the characteristic of reducing the transmittance in the wavelength region of the overlapping portion of R and G. For this, an optical filter technology called a color purity correction filter may be used.

This color purity correction filter is an optical filter in which a predetermined amount of rare earth metal ions are contained in a base material made of transparent synthetic resin or glass.

Examples of rare earth metal ions include one or more of neodymium ions, praseodymium ions, erbium ions, and holmium ions. At least neodymium ions are preferably used as essential ions. Note that these ions are usually 3
Valuable ions are used. The content of metal ions is usually 0.01 with respect to 100 parts by mass of the base material of the photographing lens 100.
To 40 parts by mass, preferably 0.04 to 30 parts by mass.

As shown in FIG. 7, the color purity correction filter has a characteristic that it selectively absorbs light in a predetermined wavelength range between peak wavelengths of the RGB color components and reduces the amount of transmission. By this action, the red light image circle 51
b is applied to the imaging area 120a that photoelectrically converts green light,
Then, crosstalk due to the image circle 51a of green light being applied to the imaging region 120b for photoelectrically converting red light hardly occurs.

Further, the photographing lens 100 is also provided with a photochromic characteristic which is a phenomenon that reversibly returns to a colorless state when light is darkened and the irradiation of light is stopped. this is,
This is because the storage time control range of the solid-state image sensor 120 is limited, so that when the field is extremely bright, the amount of light reaching the solid-state image sensor is suppressed and the brightness range that can be captured is expanded.

As the photochromic glass, for example, phosphate-based photochromic glass (trade name: Reactolite Rapide) manufactured by Chance-Pilkinton Co., which is practically used for spectacles, may be used.

FIG. 8 is a diagram showing the spectral transmittance characteristics of the photochromic glass used in the taking lens 100.
In the figure, the solid line shows the characteristics after irradiation with sunlight for 20 minutes, and the broken line shows the characteristics when there is no irradiation. When the camera is carried around outdoors in fine weather, the photographing lens 100 itself is darkened by the light flux incident on the photographing lens 100 from the diaphragm 110, and the amount of light incident on the solid-state image sensor 120 can be suppressed to about 1/2. As a result, the storage time can be doubled and the control limit on the high brightness side is raised.

The screen size of each imaging area 120a, 120b, 120c is 2.24 mm × 1.68 mm from the pixel pitch of 2.8 μm and the number of pixels of 800 × 600 as described above, and the diagonal size of the screen is 2.80 mm.
Becomes Generally, the shooting angle of view θ of a small camera is in the diagonal direction.
The easiest setting is 70 °. When the shooting angle of view is 70 °, the focal length is determined from the diagonal dimension of the screen, which is 2.0 mm in this case.

When a person or the like is to be photographed, the virtual subject distance D [m] is taken based on the fact that the height of a person is around 170 cm and that 1 to 3 people are often photographed together. It can be defined as a function of the angle θ [°] as shown in equation (1).

[0040]

[Outside 2] Substituting 70 ° for θ in equation (1) gives D = 2.0m. Therefore, if the imaging system 10 is configured so that the best focus is achieved when the subject distance is 2 m, the lens extension from the infinity position is 0.002 mm, and the lens extension mechanism is described in relation to the permissible circle of confusion diameter described later. There is no problem in practical use even as a fixed-focus imaging optical system that does not have any.

The focal length f of a plano-convex lens placed in the air is represented by the refractive index n and the radius of the spherical surface r.

[0042]

[Outside 3] Can be expressed as Therefore, tentatively, the photographing lens 10
If the refractive index n of 0 is 1.5, the focal length of 2.0mm is r
It will be 1.0 mm.

If the image sizes of the red, green, and blue object images are made uniform, it is not necessary to correct the image magnification in the subsequent signal processing, which is convenient because it does not extend the processing time. For this reason, the lens parts 100a, 100 for the peak wavelengths 530 nm, 620 nm, and 450 nm of the transmitted light of the RGB optical filter
b, 100c are optimized and each image magnification is set constant. This can be achieved paraxially by making the distance from the principal point position of each lens unit to the solid-state image sensor uniform.

In the case of glass having a _d -line (587.6 nm) refractive index n _d = 1.5 and an Abbe number ν _d = 60, the wavelengths are 530 nm, 620 nm and 450 nm.
The refractive indices in are about 1.503, 1.499, and 1.509, respectively. Assuming that the radius of the spherical surface of the lens parts 100a, 100b, 100c
When r is uniformly set to -1.0 mm, the focal lengths at these wavelengths are given by the equation (2) as follows.

Lens part 100a Representative wavelength 530nm: 1.988mm Lens part 100b Representative wavelength 620nm: 2.004mm Lens part 100c Representative wavelength 450nm: 1.965mm The permissible circle of confusion diameter is 3.0μm from the pixel pitch, and the F number of the taking lens Assuming F5.6, the depth of focus represented by these products is 16.8 μm, and it can be seen that the difference in focal length between 620 nm and 450 nm of 0.039 mm has already exceeded this. That is, although the paraxial image magnification is the same, the image may not be in focus depending on the color of the subject. Normally, the spectral reflectance of an object spans a wide wavelength range, so
In general, it is extremely rare to obtain a sharp focus.

Therefore, the radius r of the spherical surface of the lens portions 100a, 100b, 100c is optimized for each representative wavelength. That is, here, achromatic design for removing chromatic aberration in the entire visible region is not performed, and a design for each wavelength is applied for each lens. First, the formula (2) is transformed to obtain the formula (3).

R = (1-n) f (3) In equation (3), f = 2.0 and then n = 1.503, n = 1.499, n = 1.509
Substituting and calculating each radius, it becomes as follows.

Lens part 100a Representative wavelength 530nm: r = -1.006mm Lens part 100b Representative wavelength 620nm: r = -0.998mm Lens part 100c Representative wavelength 450nm: r = -1.018mm Image magnification difference at a high image height position To balance
By slightly adjusting the heights of the vertices of the lens units 100a, 100b, 100c, an ideal form can be obtained with respect to both sharpness and image magnification. Furthermore, an aspherical surface is used for each lens portion, and the field curvature is corrected well. The image distortion may be corrected in the subsequent signal processing.

Thus, the green color with the highest luminosity is 555 nm.
Of the reference G image signal by the object light including the wavelength of and the image signals by the red and blue object light respectively, and for the single wavelength (for example, the wavelength of green 555 nm with the highest visibility) in the imaging system, Different focal lengths (each lens section 100a-10
For 0c, different focal lengths are set for lights other than the spectral distributions having the respective representative wavelengths), and if the substantially same focal lengths are set for the representative wavelengths of the respective spectral distributions, these image signals are combined. By doing so, it is possible to obtain a color image in which the chromatic aberration is favorably corrected.
Since each image forming system is composed of one sheet, there is also an effect that the imaging system is made thin. Further, in general, achromatization requires a combination of two lenses having different dispersions, but the single-lens configuration has an effect of cost reduction.

The taking lens 100 is required to have a high contrast resolution up to a high spatial frequency band up to the same level as the pixel pitch. Since the imaging system 10 captures three object images for each wavelength range, when compared with an imaging system with the same number of pixels equipped with a mosaic optical filter such as a Bayer array, the focus of about 1 / √3 as described above. The same shooting angle of view is obtained at a distance. Therefore, high-contrast resolution of higher spatial frequency components must be realized. The wavelength-dependent optimization of each lens unit described above is a technique for suppressing chromatic aberration for this purpose.

In general, as a method of improving the aberration characteristics of the photographing optical system to make it difficult to cause false resolution and reducing the problem, the number of constituent lenses is increased, aspherical surface is used, and anomalous dispersion glass is used. There are two methods: increasing the degree of freedom in design by using several methods such as using multiple optical elements, and narrowing down the image forming light beam.

The above-mentioned direction of increasing the degree of freedom in designing complicates the structure of the photographing optical system even though the focal length becomes 1 / √3, and goes against the thinning of the photographing apparatus. It will not be appropriate. On the other hand, the directivity using the thin luminous flux has good compatibility with a thin imaging device.

When the image-forming light flux is narrowed down, the response function called OTF gradually and monotonously decreases in the low frequency component as shown by the solid line (b) in FIG. 10, and then takes a slightly negative value and then slightly again. It is a characteristic that takes a positive value. On the other hand, when a thick light beam is used without narrowing down the image-forming light beam, the characteristic of taking a negative value and then a positive value after being rapidly decreased in the low frequency component as shown by the broken line (a) in FIG. Becomes

The state in which the OTF takes a negative value represents the occurrence of false resolution, and corresponds to the state in which the negative-positive inversion phenomenon occurs in which the white portion becomes black and the black portion becomes white in the actual image. Therefore, it can be seen that a more natural image can be obtained by narrowing the image-forming light flux.

However, when the light flux is extremely narrowed down, the contrast of the high frequency region is lowered due to the influence of light diffraction. In such a situation, the point image is composed of a central bright spot and diffraction fringes surrounding the bright spot. This is because, as is well known, the intensity of diffraction fringes due to the peripheral wave emitted from the edge of the aperture is relatively increased.

In order to reduce the diffraction fringes, a filter having a transparent central portion and a density increasing toward the periphery may be added to the taking lens. This method is called apodization, and is a supplementary version of the Optical Technology Handbook (1975,
(Asakura Shoten), pages 172 to 174.

FIG. 9 is a diagram showing the transmittance distribution of a transmittance distribution type filter provided on the light incident surface 100e of the taking lens 100 at a position facing the aperture openings 110a, 110b and 110c. The transmittance distribution type filters are indicated by 54a, 54b and 54c in FIG. 1, and the positions where the transmittance is highest are the diaphragm apertures 110a and 110b,
The position where the transmittance is zero, which coincides with the center of 110c, is coincident with the edges of the aperture openings 110a, 110b, 110c. That is,
The transmittance distribution is highest at the center of the diaphragm, and decreases monotonically with distance from the center.

The transmittance distribution type filter is a photographing lens 100.
On the light incident side of, a thin film of Inconel, chromel, chrome or the like is formed by vapor deposition or sputtering. It is possible to obtain the characteristics shown in FIG. 9 by making the thickness of the thin film thin in the central portion and thickest in the peripheral portion. In addition, in forming such a thin film, the position control of the shield in the vapor deposition or sputtering process is continuously performed.

Here, the transmittance distribution type filters 54a, 5
Although 4b and 54c are formed on the taking lens, they may be formed on a glass plate and arranged on the light incident side or the light emitting side of the taking lens 100.

FIG. 11 is a diagram showing the luminance distribution of a point image.
In the figure, the wavy line (a) shows the case where the transmissivity of the diaphragm aperture is constant, and the solid line (b) shows the case where the transmissivity of the diaphragm aperture is decreased from the center to the periphery. In contrast to the characteristics of (a), the characteristics of (b) show that there is no rebound at the skirt of the point image, and the image is clearly good. This is a manifestation of the diffraction fringe reduction effect by reducing the peripheral light flux by apodization.

Next, the positional relationship between the taking lens and the image pickup area will be described. Since the imaging system has three lens portions, the positions of the three object images relatively change according to the subject distance. As described above, each imaging region is 2.24 mm × 1.68 mm, and these are arranged adjacent to each other so that their long sides are in contact with each other. Therefore, the center interval between adjacent imaging areas is 1.
It is 68 mm. A YC processing circuit 230, which will be described later, performs signal processing on the assumption that the center of the object image and the center of the imaging area are coincident with each other. Assuming that an object image at a virtual subject distance of 2 m is formed on the imaging unit at the same interval as this, as shown in FIG. 12, the interval between the lens units 100a, 100b, and 100c of the taking lens 100 is 1.6.
It will be set to 783 mm. In the figure, arrows 55a, 55
b and 55c are three lens parts 100a, 100b of the taking lens 100,
Symbol representing a 100c imaging system with positive power, rectangle
56a, 56b and 56c are symbols representing the ranges of the imaging regions 120a, 120b and 120c, and L1, L2 and L3 are optical axes of the image forming systems 55a, 55b and 55c. Since the light incident surface of the photographing lens 100 is a flat surface and the lens portions 100a, 100b, 100c which are light emitting surfaces are spherical surfaces, a straight line passing through each spherical center and perpendicular to the light incident surface 100e is the optical axis.

At this time, since the image of the object at infinity is formed at the same interval as the lens portions 100a, 100b, 100c as shown in FIG. 13, the interval between the G object image and the R object image, and the R object image. The distance between the B and B object images is 1.6783 mm. Therefore, the center interval of the imaging area is slightly narrower than 1.68 mm, and this difference ΔY is 0.0
017 mm or 1.7 μm. It also has the highest visibility
Considering the movement of the B object image with the G object image as the reference, the difference ΔY
Is doubled to 3.4 μm. A short-distance object such as a person is located in the center of the shooting screen, and a long-distance object is often located in the periphery of the screen.Furthermore, in the periphery of the screen, the aberration of the shooting lens increases and the image performance deteriorates. From doing
If the maximum image spacing change is less than twice the pixel pitch,
It can be said that there are no practical problems. As described above, since the pixel pitch P of the solid-state image sensor 120 is 2.8 μm, ΔY <2 × P, and the color shift of the infinity image at this level is at an allowable level.

Further, the image interval also changes depending on the temperature change of the image pickup system 10. The linear expansion coefficient of the solid-state image sensor 120 is α _S ,
Assuming that the linear expansion coefficient of the taking lens 100 is α _L and the temperature change is ΔT, the imaging system 10 has an extremely small imaging magnification, so the image interval change amount ΔZ is the difference between the extension of the taking lens and the extension of the solid-state image sensor. , Can be expressed by equation (4).

ΔZ = 1.68 × (α _L −α _S ) × ΔT (4) where α _S = 0.26 × 10 ⁻⁵ , ΔT = 20 [°], and the taking lens 100 As made of low melting glass, α _L = 1.2
Assuming × 10 ⁻⁵ , ΔZ is calculated as 0.00032 [mm]. This is the change in the distance between the G and R object images, and the change in the distance between the R and B object images.

Considering the B object image as a change with respect to the G object image which is the reference image signal, the image interval is 1.68 × 2, so the image interval change amount is also ΔZ × 2 = 0.00063 [mm]. If the operating temperature range of the camera is 0 to 40 °, the deviation ΔT from the reference temperature of 20 ° is 20 °. At this time, if ΔZ × 2 is smaller than 1/2 of the pixel pitch, there is a practical problem. There is no. Generally, the linear expansion coefficient α _S of the solid-state imaging device 120 has a small value of about 0.26 × 10 ^−5, and therefore the linear expansion coefficient α _L of the taking lens 100 needs to be selected so as to satisfy the expression (5).

[0066]

[Outside 4] In addition, A is the interval between any two images of the R image, the G image, and the B image, and P is the pixel pitch.

Since the linear expansion coefficient α _L = 1.2 × 10 ⁻⁵ of the taking lens 100 used above satisfies the relationship of the equation (5),
It can be said that the material is suitable for this camera.

Further, in addition to the fluctuation of the image interval due to the change of the object distance or the temperature, the imaging areas 120a, 120b, 12 of the solid-state imaging device are
By shifting 0c by 1/2 pixel with respect to each other, a pixel shift method is used to increase the resolution with a small number of pixels. The 1/2 pixel shift amount is set for a virtual subject distance of 2 m.

As shown in FIG. 15, the image pickup area 120b for R pixel output and the image pickup area 120c for B pixel output are shifted by 1/2 pixel in the horizontal and vertical directions with respect to the image pickup area 120a for G image signal. Are arranged.

Even if this pixel shift is realized by slightly decentering the lens portions 100b and 100c of the photographing lens 100 with respect to the lens portion 100a, the image pickup area 120b of the solid-state image pickup element 120 is obtained.
And 120c may be slightly eccentric with respect to the imaging region 120a.

In an optical filter array such as a Bayer array, for example, a pixel provided with a red optical filter or a pixel provided with a blue optical filter is inserted between pixels provided with a green optical filter, so that aliasing distortion occurs. An optical low pass filter that suppresses is needed. However, by configuring so as to capture images having different spectral distributions for each imaging region in this way, it is possible to arrange pixels equipped with respective optical filters densely, and as a result, the effect of aliasing distortion is small and an optical low-pass filter is used. High-definition images can be obtained without the need. Therefore, it is possible to reduce the size of the imaging system and significantly reduce the cost.

Next, the signal processing will be described.

As described above, as the solid-state image pickup device 120, an image pickup device having a total of 1.44 million pixels, which is 1800 pixels in the long side direction and 800 pixels in the short side direction, is effectively applied, and a red color is provided on the front surface thereof. Optical filters of three primary colors of (R), green (G), and blue (B) are arranged in each predetermined area.

As shown in FIG. 14, the image signals read from the solid-state image pickup device 120 are A /
It is supplied to the D converter 500. The A / D converter 500 is provided with, for example, 10 A according to the amplitude of the signal of each exposed pixel.
This is a signal conversion circuit for converting into a bit digital signal and outputting it, and subsequent image signal processing is executed by digital processing.

The image processing system 20 has a signal processing circuit for obtaining an image signal of a desired format from R, G, B digital signals.
G, B color signals are luminance signals Y and color difference signals (RY), (BY)
Convert to YC signal etc.

The RGB image processing circuit 210 is a signal processing circuit for processing an image signal of 1800 × 800 pixels received from the solid-state image sensor 120 via the A / D converter 500, and includes a white balance circuit, a gamma correction circuit, It has an interpolation calculation circuit for increasing the resolution by interpolation calculation.

The YC processing circuit 230 is a signal processing circuit for generating the luminance signal Y and the color difference signals RY, BY. High-frequency luminance signal generation circuit that generates high-frequency luminance signal YH, low-frequency luminance signal
Low-frequency luminance signal generation circuit for generating YL and color difference signal
It is composed of a color difference signal generation circuit that generates RY and BY. The luminance signal Y is formed by combining the high frequency luminance signal YH and the low frequency luminance signal YL.

Details of the RGB image processing circuit 210 will be described.

The RGB signals output from the A / D converter 500 for each of the R, G, and B areas are first subjected to predetermined white balance adjustment by the white balance circuit in the RGB image processing circuit 210. Further, a predetermined gamma correction is performed by the gamma correction circuit.

An interpolation calculation circuit in the RGB image processing circuit 210 generates an image signal having a resolution four times 600 × 800 pixels by interpolation processing, and converts the image signal from the solid-state image sensor 120 into a signal of high definition image quality. Then, the high-frequency luminance signal generating circuit, the low-frequency luminance signal generating circuit, and the color difference signal generating circuit in the subsequent stage are supplied.

Since the size of each RGB object image has already become the same depending on the setting of the taking lens 100, first, a calculation process for correcting the distortion aberration of the taking optical system is performed for each image signal by a known method. Subsequent interpolation processing, luminance signal processing, and color difference signal processing are based on the processing in a normal digital color camera. The interpolation process is as follows.

First, the G image signal from the image pickup area 120a, which is the reference image signal, is interpolated by the following equations (6) to (9).

G2i2j = Gij ………… (6) G2i (2j + 1) = Gij ・ 1/2 + Gi (j + 1) ・ 1/2 ………… (7) G (2i + 1) 2j = Gij ・ 1/2 + G (i + 1) j ・ 1/2 ………… (8) G (2i + 1) (2j + 1) = Gij ・ 1/4 + Gi (j + 1) ・1/4 + G (i + 1) j ・ 1/4 + G (i + 1) (j + 1) ・ 1/4 ………… (9) As a result, as shown in FIG. 16 G pixels are generated from the G pixels of
The G image signal of 0x800 pixels is converted into 1200x1600 pixels.

Next, the R from the image pickup area 120b corresponding to each position of the G image signal obtained by the above equations (6) to (9).
The pixel output is interpolated by the following equations (10) to (13).

R2i2j = R (i-1) (j-1) ・ 1/4 + R (i-1) j ・ 1/4 + Ri (j-1) ・ 1/4 + Rij ・ 1/4 ... ……… (10) R2i (2j + 1) = R (i-1) j ・ 1/2 + Rij ・ 1/2 ………… (11) R (2i + 1) 2j = Ri (j-1 ) ・ 1/2 + Rij ・ 1/2 ………… (12) R (2i + 1) (2j + 1) = Rij ………… (13) As mentioned above, the imaging area of the R object image and B The imaging area of the object image is
Since the layout is shifted by 1/2 pixel with respect to the G object image capturing area, the original output at address ij is (2
It is applied to i + 1) (2j + 1).

Similarly, in the same manner as the R pixel, the B pixel from the image pickup area 120c corresponds to the respective positions of the G image signal obtained by the above equations (6) to (9), and the following equations (14) to (14) Perform interpolation calculation in 17).

B2i2j = B (i-1) (j-1) ・ 1/4 + B (i-1) j ・ 1/4 + Bi (j-1) ・ 1/4 + Bij ・ 1/4 ... ……… (14) B2i (2j + 1) = B (i-1) j ・ 1/2 + Bij ・ 1/2 ………… (15) B (2i + 1) 2j = Bi (j-1 ) ・ 1/2 + Bij ・ 1/2 ………… (16) B (2i + 1) (2j + 1) = Bij ………… (17) With the above processing, the imaging areas 120a, 120b, 120c From each
The RGB signal of 600 × 800 pixels is converted to the RGB signal of 1200 × 1600 pixels with high definition.

The high-frequency luminance signal generating circuit in the YC processing circuit 230 is a known signal forming circuit for forming the high-frequency luminance signal YH from the color signal having the highest spatial frequency component among the color component signals. The low-frequency luminance signal generating circuit is a known signal forming circuit that forms a low-frequency luminance signal YL from a signal containing all R, G, B color components. The color difference signal generation circuit is a known calculation circuit that calculates the color difference signals RY and BY from high definition RGB signals.

The recording / reproducing system 30 is a processing system for outputting the image signal to the memory and outputting the image signal to the liquid crystal monitor 4, and is a recording processing circuit for writing and reading the image signal to and from the memory. 300 and playback processing circuit that plays back the image signal read from the memory and outputs it as a monitor
Including 310 and. More specifically, the recording processing circuit 300 includes a compression / expansion circuit that compresses YC signals representing a still image and a moving image in a predetermined compression format, and expands when compressed data is read. The compression / expansion circuit includes a frame memory and the like for signal processing. The YC signal from the image processing system 20 is stored in this frame memory for each frame, and each block is read out and compressed and encoded for each of a plurality of blocks. The compression coding is performed by, for example, performing two-dimensional orthogonal transformation, normalization, and Huffman coding on the image signal for each block.

The reproduction processing circuit 310 is a circuit for converting the luminance signal Y and the color difference signals RY, BY into a matrix, for example, into an RGB signal. The signal converted by the reproduction processing circuit 310 is output to the liquid crystal monitor 4, and a visible image is displayed and reproduced.

On the other hand, the control system 40 includes a control circuit of each part for controlling the image pickup system 10, the image processing system 20, and the recording / reproducing system 30 in response to an external operation, and detects the pressing of the release button 6, Driving the solid-state image sensor 120, RGB image processing circuit 210
And the compression processing of the recording processing circuit 300 are controlled.
Specifically, the operation detection circuit 410 for detecting the operation of the release button 6, and controlling each part in response to the detection signal,
A system control unit 400 that generates and outputs a timing signal at the time of imaging, and a drive circuit 420 for the solid-state image sensor that generates a drive signal that drives the solid-state image sensor 120 under the control of the system control unit 400. Including.

Next, the operation of the image pickup apparatus according to this embodiment will be described with reference to FIGS. First, when the main switch 5 is turned on, the power supply voltage is supplied to the respective parts to bring them into an operable state. Next, it is determined whether the image signal can be recorded in the memory. At this time, the number of recordable images that can be photographed is displayed on the remaining number display 13 of the liquid crystal monitor 4 according to the remaining capacity. If the operator who saw the display can shoot,
Aim the camera at the field and press the release button 6.

When the release button 6 is pressed halfway,
The exposure time is calculated. When all the shooting preparation processing is completed, shooting is possible and the display is reported to the photographer. As a result, when the release button 6 is pressed to the end, the operation detection circuit 410 sends the detection signal to the system control circuit 400. At that time, the elapsed time of the exposure time calculated in advance is time-counted, and when the predetermined exposure time elapses, the timing signal is supplied to the drive circuit 420. As a result, the drive circuit 420 generates horizontal and vertical drive signals and sequentially reads each of the exposed 1600 × 800 pixels in the horizontal and vertical directions.

Each pixel read out is converted into a digital signal having a predetermined bit value by the A / D converter 500, and is sequentially supplied to the RGB image processing circuit 210 of the image processing system 20. The RGB image processing circuit 210 performs interpolation processing for quadrupling the pixel resolution while performing white balance and gamma correction on each of these, and the YC processing circuit 230
Supply to.

In the YC processing circuit 230, the high-frequency luminance signal generation circuit generates the high-frequency luminance signal YH of each pixel of RGB, and similarly, the low-frequency luminance signal generation circuit generates the low-frequency luminance signal.
Calculate YL respectively. High-frequency luminance signal YH as a result of calculation
Is output to the adder through the low pass filter.
Similarly, the low-frequency luminance signal YL is subtracted from the high-frequency luminance signal YH, passes through the low-pass filter, and is output to the adder. As a result, the difference YL between the high frequency luminance signal YH and the low frequency luminance signal YL
-YH is added to obtain the luminance signal Y. Similarly, the color difference signal generating circuit obtains and outputs the color difference signals RY and BY. The output color difference signals RY and BY are supplied to the recording processing circuit 300 as components that have passed through the low-pass filters.

Next, the recording processing circuit 300 which receives the YC signal
Compresses the respective luminance signal Y and color difference signals RY, BY by a predetermined still image compression method and sequentially records them in the memory.

When the respective images are reproduced from the image signals representing the still image or the moving image recorded in the memory, when the reproduction button 9 is pressed, the operation detecting circuit 410 detects the operation and the system control unit Supply detection signal to 400. As a result, the recording processing circuit 300 is driven. The driven recording processing circuit 300 reads the recorded contents from the memory and displays an image on the liquid crystal monitor 4. The operator
A desired image is selected by pressing a selection button or the like.

The above is a description of the embodiments of the present invention, but the present invention is not limited to the configurations of these embodiments, and the functions or embodiments described in the claims or the embodiments Any structure can be applied as long as the function of the structure can be achieved.

For example, in the above embodiments, the optical filters for color separation are the primary color filters of red, green, and blue, but the present invention replaces them with complementary colors of cyan, magenta, and yellow. It is also applicable by using a filter.

Further, in the above embodiments, the change in the interval due to the change in the object distance from the object image of the other luminosity (color) is described with reference to the object image of the highest luminosity (green). However, this is applicable to the present invention even when the object image with the highest visibility (green) is not used as a reference.

Further, the present invention is such that the scope of the claims or the whole or part of the configuration of the embodiment forms one device, but is combined with another device. Alternatively, it may be a component of the device.

[0102]

As described above, according to the present invention,
It is possible to provide a small-sized image pickup device having high image performance.

[Brief description of drawings]

FIG. 1 is a sectional view of an image pickup system of a digital color camera according to an embodiment of the present invention.

FIG. 2 is a front view of a solid-state image pickup device of the image pickup system of FIG.

FIG. 3 is a plan view of a diaphragm of the image pickup system of FIG.

FIG. 4 is a diagram showing a formation range of an optical filter of the image pickup system of FIG.

5 is a view of the taking lens of the image pickup system of FIG. 1 viewed from the light exit side.

6 is a diagram showing a spectral transmittance characteristic of an optical filter of the image pickup system of FIG.

7 is a diagram showing a spectral transmittance characteristic of a color purity correction filter of the image pickup system of FIG.

8 is a diagram showing a spectral transmittance characteristic of the photochromic glass of the image pickup system of FIG. 1. FIG.

9 is a diagram showing a transmittance distribution of a transmittance distribution type filter of the image pickup system of FIG.

10 is a diagram showing OTF characteristics of the taking lens of the image pickup system of FIG. 1. FIG.

11 is a diagram showing a luminance distribution of a point image of the image pickup system of FIG.

12A and 12B are diagrams for explaining the interval setting of the lens units of the image pickup system in FIG.

13 is a diagram for explaining the position of an image of an object at infinity in the image pickup system of FIG.

14 is a block diagram of a signal processing system of the digital color camera of FIG.

15 is a diagram showing a positional relationship between an image pickup area for R image and an image pickup area for B pixel with respect to an image pickup area for G image in the image pickup system of FIG. 1;

16 is an explanatory diagram of an interpolation process of the digital color camera of FIG.

FIG. 17 is a diagram showing an overall configuration of the digital color camera of FIG.

[Explanation of symbols]

1 Camera Main Body 2 Illumination Light Capture Window 3 Viewfinder Front Frame 4 Color LCD Monitor 5 Main Switch 6 Release Buttons 7, 8, 9 Switch 10 Imaging System 11 Viewfinder Eyepiece Window 12 Prism 13 Display of Remaining Number of Photographable 14 Connection Terminal 51a, 51b, 51c Image circles 52a, 52b, 52c Optical filters 53a, 53b, 53c formed on a taking lens Optical filters 54a, 54b, 54c formed on a solid-state image sensor Transmissivity distribution type filter 100 Taking lenses 100a, 100b , 100c Lens section 110 of photographing lens Aperture 120 Solid-state image sensor

Claims (22)

(57) [Claims] 1. An image pickup apparatus comprising: an image pickup device having at least first and second image pickup areas; and an image pickup optical system for forming an object image on the image pickup device, wherein the image pickup optical system is at least the first image pickup device. And a second imaging system for forming an object image corresponding to the second imaging region, and a focal length of the first imaging system for light of a first wavelength and a second imaging system. Is set so that the focal length of the second image forming system with respect to the light of the wavelength is the same, and the focal length of the first image forming system with respect to the light of the wavelength other than the first wavelength and the second The imaging device is set so that the focal length of the second imaging system with respect to light having a wavelength other than the wavelength is set to be different. 2. The image pickup device according to claim 1, wherein the light of the first wavelength is a representative wavelength of the light of the first spectral distribution, and the light of the second wavelength is the second spectrum. An image pickup device having a representative wavelength of distributed light. 3. An imaging device having an imaging device having a plurality of imaging regions and a photographic optical system for forming an object image on the imaging device, wherein the photographic optical system corresponds to the plurality of imaging regions. Object image
A plurality of image forming systems each of which forms a focal length of each of the plurality of image forming systems, and the focal lengths of the plurality of image forming systems are set to be the same for the wavelength of light having a predetermined wavelength of each image forming system. An image pickup apparatus, which is set to be different for light having a wavelength other than the predetermined wavelength of the image system. 4. The imaging device according to claim 3, wherein the light having the predetermined wavelength is a representative wavelength of light having a different predetermined spectrum. 5. An image pickup device having first and second image pickup areas, and a photographing optical system for forming an object image on the image pickup device,
In an image pickup apparatus having an image processing unit that processes an output signal of the image pickup element, the photographing optical system includes first and second image forming systems,
It said first and second imaging system is formed in each front Symbol first and second imaging region of the object image, from the first and second imaging area, the object light component of the first spectral distribution And a second image signal due to the object light component of the second spectral distribution, respectively , for the representative wavelength of the spectral distribution of the first image signal the first and the second An image pickup device characterized in that the focal lengths of the two image forming systems are made different and the representative wavelengths of the spectral distributions of the respective image signals are set to be the same. The imaging apparatus according to any one of 6. The method of claim 2, 4, 5, said object light of the first spectral distribution is object light spectral distribution including a peak wavelength of spectral luminous efficiency An imaging device characterized by. 7. A first image pickup section and a second image pickup section for respectively receiving at least a first wavelength component of subject light and a second wavelength component different from the first wavelength component, and the first image pickup section and the second image pickup section. 1, the first of the subject light received by the second imaging unit,
A first optical system and a second optical system for guiding the second wavelength component to the first and second imaging units through different optical paths, respectively, and the first optical system and the second optical system. The optical system of
The imaging device is configured such that the focal length of the optical system for the first wavelength component is the same as the focal length of the second optical system for the second wavelength component. 8. The image pickup device according to claim 7, wherein the first wavelength component is a representative wavelength of light having a first spectral distribution, and the second wavelength component is the first spectral distribution. An imaging device having a representative wavelength of light having a second spectral distribution different from that of. 9. The image pickup apparatus according to claim 7, wherein the first wavelength component is included in a spectral distribution including a peak wavelength of luminosity. 10. The image pickup device according to claim 7, wherein the first and second wavelength components are any two color components of red, green, and blue, respectively. A characteristic imaging device. 11. The image pickup device according to claim 7, wherein the first and second optical systems extract the first and second wavelength components, respectively. An image pickup device having a filter for. 12. The imaging device according to claim 7, wherein the first and second optical systems each have a single lens. 13. The image pickup device according to claim 12, wherein the single lens is integrally formed of a glass material or a resin material. 14. The image pickup device according to claim 13, further comprising a light-shielding film between the integrally formed single lenses. 15. The image pickup device according to claim 7, wherein the first and second optical systems each have a single lens including an infrared cut filter. A characteristic imaging device. 16. The imaging device according to claim 7, wherein each of the first and second optical systems has a photochromic glass. 17. The image pickup device according to claim 7, wherein the first and second optical systems each have a color purity correction filter. apparatus. 18. The imaging device according to claim 7, wherein the first and second optical systems each have a transmittance as the distance from the optical axis increases. An image pickup apparatus having a filter that reduces 19. The image pickup device according to claim 7, wherein the predetermined object distance D [m] is a function of the image pickup angle of view θ [°] of the plurality of optical systems. [Outer 1] , The subject image received by one of the plurality of image pickup units and the subject image received by another one of the plurality of image pickup units when the subject is at the predetermined subject distance and at infinity. The optical axis intervals of the plurality of optical systems are set such that the change in the interval between the corresponding positions is smaller than twice the pixel pitch of the imaging unit. 20. The image pickup device according to claim 7, wherein the first and second image pickup units are integrally formed. . 21. The image pickup device according to claim 7, wherein the first and second image pickup units are formed in a planar shape. . 22. The image pickup device according to claim 7, wherein the first and second optical systems each have a plurality of openings for taking in external light. Image pickup device.