JP2001078214A - Image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a small-sized image pickup device capable of obtaining high image performance. SOLUTION: This image pickup device is provided with an image pickup optical system 100 and an image pickup element 120 with a plurality of image pickup areas and projects a plurality of images corresponding to image pickup areas onto the image pickup element 120. The image pickup optical system 100 has image forming systems, and the image forming systems have optical filter means 54a, 54b, 54c whose transmissivity is smaller as the distance from an optical axis of the image forming systems themselves gets larger.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art In a digital color camera, a solid-state image sensor such as a CCD or a CMOS sensor is exposed to an object image for a desired time in response to a press of a release button, and a single screen obtained from this is frozen. An image signal representing an image is converted into a digital signal and subjected to predetermined processing such as YC processing to obtain an image signal in a predetermined format. A digital image signal representing a captured image is recorded in a semiconductor memory for each image. The recorded image signal is read out at any time, reproduced into a displayable or printable signal, output to a monitor or the like, and displayed.

One of the techniques for reducing the thickness of a digital color camera is disclosed in Japanese Patent Application Laid-Open No. Hei 10-145802. In Japanese Patent Application Laid-Open No. H10-145802, a shooting screen is divided into a plurality of regions, and an image forming optical system is provided for each region to form a partial image of an object. At this time, one object image is formed for one imaging optical system, and an object image corresponding to the number obtained by dividing the shooting screen is projected on a single image sensor.

By arranging a plurality of imaging areas in a small island shape,
By providing a small imaging system for each, it is possible to reduce the thickness of the imaging device.

[0005]

In general, increasing the area of the entire image sensor lowers the production yield, and there is a practical upper limit to the size of the image sensor due to cost constraints. When the imaging area is arranged in a small island shape as disclosed in the above-mentioned Japanese Patent Application Laid-Open No. H10-145802, and in order to obtain a high-definition image in addition to the reduction in thickness, the spatial frequency that can be expressed by the photoelectric conversion output of the imaging element In order to increase the pixel pitch, at least the pixel pitch of the image sensor must be reduced based on the sampling theorem.

At the same time, an imaging optical system for forming an object image on an imaging device is required to maintain high contrast up to a higher frequency.

[0007] The imaging performance of the imaging system is expressed by a response function called OTF, and if the above characteristics are expressed by OTF characteristics,
The response curve maintains a high response from low frequency to high frequency, and has no value again after the response has dropped to zero.

The fact that the response turns to a negative value after dropping to zero is a phenomenon called false resolution which depends on the aberration characteristics of the photographing optical system. Black parts become white, and white parts become black, and black and white inversion occurs. An imaging system that produces spurious resolution tends to have a low response in a moderate frequency range, has no sharpness in the entire image, and has unnatural details, and is the most unsuitable for photographing people or landscapes. Is appropriate.

A method of improving the aberration characteristic of the photographing optical system to reduce the problem of false resolution includes increasing the number of constituent lenses, making the lens aspherical, using anomalous dispersion glass, and combining a diffractive optical element. There are two ways: increasing the degree of freedom in design by using some methods such as using, and reducing the imaging light flux.

The above-mentioned directionality that increases the degree of freedom of design complicates the configuration of the photographing optical system, and is not suitable for a thin photographing apparatus.

On the other hand, the directionality using the above-mentioned thin luminous flux has good compatibility with a thin photographing device. However, if the light beam is narrowed down to a certain degree or more, there arises a problem that the contrast in the high frequency range is reduced 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 central bright spot several times. This is because the intensity of diffraction fringes due to peripheral waves emitted from the edge of the aperture opening relatively increases. This can be understood from the fact that, for example, when the aperture diameter is reduced to /, the edge of the aperture is also reduced to ２, whereas the aperture area is reduced to /.

Therefore, it has conventionally been difficult to realize an imaging optical system for obtaining a high-definition image corresponding to a small pixel pitch with a simple configuration.

An object of the present invention is to provide a small-sized imaging device capable of obtaining high image performance.

[0014]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention comprises a photographing optical system and an image pickup device having a plurality of photographing areas, and the plurality of photographing optical systems are provided through the photographing optical system. In an imaging apparatus for projecting a plurality of images corresponding to an imaging region on the imaging device, the imaging optical system has a plurality of imaging systems, and the imaging systems have a distance from an optical axis of the imaging system itself. The photographing apparatus is provided with an optical filter means whose transmittance becomes smaller as the value becomes larger.

Further, the image pickup apparatus of the present invention comprises: a photographing optical system;
An imaging device having a plurality of imaging regions, wherein the imaging optical system projects a plurality of images corresponding to the plurality of imaging regions onto the imaging device via the imaging optical system. A photographing apparatus comprising an imaging system having an optical filter means whose transmittance decreases as the distance of the image system from the optical axis increases, and an imaging system not having the optical filter means. It is.

Further, according to the present invention, there are provided a plurality of imaging units for respectively receiving different wavelength components of subject light, and a large distance from an optical axis for guiding the subject light to each of the plurality of imaging units. An image pickup apparatus having a plurality of optical systems having a filter function of decreasing the transmittance as the number of filters increases.

Further, the present invention has a plurality of imaging units for respectively receiving different wavelength components of the subject light, and a plurality of optical systems for guiding the subject light to the plurality of imaging units, respectively. At least one of the plurality of optical systems has a filter function of decreasing transmittance as the distance from the optical axis increases, and at least one of the other optical systems increases the distance from the optical axis. Accordingly, the imaging apparatus does not have a filter function of decreasing the transmittance according to the above.

[0018]

Embodiments of the present invention will be described below in detail with reference to the drawings.

(First Embodiment) First, the overall configuration of a digital color camera using the present invention and a signal processing system will be described.

FIGS. 17A, 17B, and 17C are views showing the overall configuration of a digital color camera according to the present invention. 17A is a front view, FIG. 17C is a rear view, and FIG.
FIG. 18B is a cross-sectional view at the position of arrow A shown in the back view of FIG.

In FIGS. 17 (a), (b) and (c), reference numeral 1 denotes a camera body, and 2 denotes an illumination light take-in window which is located behind the color liquid crystal monitor 4 and is made 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 playback button, and 13 is a display of the remaining number of images that can be taken. Reference numeral 11 denotes a finder eyepiece window, from which object light incident on the prism 12 from the finder front frame 3 exits. Reference numeral 10 denotes an imaging system, and 14 denotes a connection terminal for connecting to an external computer or the like to transmit and receive data.

The schematic configuration of the signal processing system will be described. FIG.
FIG. 2 is a block diagram of a signal processing system. This camera uses a CCD
Alternatively, it is a single-chip digital color camera using a solid-state image sensor 120 such as a CMOS sensor.
Is driven continuously or sporadically to obtain an image signal representing a moving image or a still image. Here, the solid-state imaging device 120
Is an imaging device of a type that converts exposed light into an electric signal for each pixel, accumulates charges corresponding to the amount of light, and reads out the charges.

FIG. 14 shows only parts directly related to the present invention, and illustrations of parts not directly related to the present invention are omitted.

As shown in FIG. 14, the image pickup apparatus has an image pickup system.
10, an image processing system 20, which is an image processing means, a recording / reproducing system 30, and a control system 40. Furthermore, the imaging system 10
Includes a photographing lens 100, an aperture 110, and a solid-state imaging device 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. The control system 40 includes 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 stop 110 and the image pickup lens 100, and adjusts the light transmittance of the image pickup lens 100. Then, the solid-state imaging device 120 is exposed to a subject image having an appropriate amount of light. As described above, the solid-state imaging device 120 is a CCD or C
An imaging device such as a MOS sensor is applied, and by controlling the exposure time and exposure interval of the solid-state imaging device 120, an image signal representing a continuous moving image or an image signal representing a still image by one exposure is obtained. Can be.

Next, the imaging system 10 will be described. In the present embodiment, the image pickup lens system 100 serving as the image pickup optical system of the image pickup system 10, the optical filter means according to the present invention, the transmittance distribution type filters 54a, 54b, 54c described below.
It has.

FIG. 1 is a detailed view of the image pickup system 10. First, the stop 110 has three circular openings 110a, 110b, 11 as shown in FIG.
0c, from each of which the light incident surface 100e of the taking lens 100
The object light that has entered the three lens units 10 of the taking lens 100
The three object images are formed on the imaging surface of the solid-state imaging device 120 by emitting light from 0a, 100b, and 100c. The stop 110, the light incident surface 100e, and the imaging surface of the solid-state imaging device 120 are arranged in parallel. As described above, the curvature of the image plane can be reduced by weakening the power on the incidence side, increasing the power on the emission side, and providing the stop on the incidence side. Note that, here, the light incident surface 100e of the photographing lens 100 is a plane, but it may be constituted by three spherical surfaces or three rotationally symmetric aspheric surfaces.

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

When the photographic lens 100 is made of glass, a glass mold manufacturing method is used, and when the photographic lens 100 is made of resin, injection molding is used.

FIG. 2 is a front view of the solid-state image pickup device 120. Three image pickup areas 120a and 120a corresponding to three object images to be formed are shown.
0b and 120c. Each of the imaging areas 120a, 120b, 120c is a 2.24 mm x 1.68 mm area in which 800 × 600 pixels having a vertical and horizontal pitch of 2.8 μm are arranged, and the entire imaging area has a size of 2.24 mm x 5.04 mm , And the diagonal dimension of each imaging area is
It becomes 2.80mm. In the figure, 51a, 51b, 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 stop and the size of the exit-side spherical portion of the photographing lens 100. The image circles 51a and 51b, and the image circles 51b and 51c
Have overlapping portions.

In FIG. 1, portions 52a, 52b, and 52c indicated by hatching in an area between the diaphragm 110 and the photographing lens 100.
Denotes an optical filter formed on the light incident surface 100e of the taking lens 100. The optical filters 52a, 52b, 52c are formed in a range completely including the aperture openings 110a, 110b, 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 of mainly transmitting green 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 parts 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 formed with a green light component, the object image formed on the image circle 51b is formed with a red light component, and formed on the image circle 51c. The object image is a 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 are formed, and their spectral transmittance characteristics are also the same as those shown in FIG. That is, the imaging region 120a is for green light (G), the imaging region 120b is for red light (R),
The imaging region 120c has sensitivity to blue light (B).

Since the light receiving spectrum distribution of each imaging region is given as the product of the pupil and the spectral transmittance of the imaging region, the combination of the pupil and the imaging region is selected according to the wavelength range. That is, the object light that has passed through the aperture 110a of the diaphragm is mainly
The object light photoelectrically converted at 0a and passed through the aperture 110b of the aperture is photoelectrically converted mainly at the imaging region 120b, and
The object light that has passed through 110c is mainly subjected to photoelectric conversion in the imaging region 120c. That is, the imaging area 120a stores the G image and the imaging area 120a.
b outputs an R image, and the imaging area 120c outputs a B image. As described above, by using multiple optical filters for color separation in the pupil of the imaging optical system and the imaging device, the color purity can be increased. This means that two optical filters of the same type
This is because, when the light is passed, the transmission characteristic sharply rises and the overlap between red (R) and blue (B) is eliminated. It should be noted that the optical filters 52a, 52a,
It is preferable to set the transmittance of b, 52c or the optical filters 53a, 53b, 53c.

In the image processing system 20, a plurality of imaging regions of the solid-state imaging device 120 form a color image based on a 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 a G image signal including this wavelength as a reference image signal.

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

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

Therefore, the red light image circle 51
Even if b is over the imaging region 120c for photoelectrically converting blue light, or conversely, even if the image circle 51c of blue light is over the imaging region 120b for photoelectrically converting red light, these images are output from the imaging region. Will not be. However, the portion where the red light image circle 51b covers the imaging region 120a for photoelectrically converting green light and the portion where the green light image circle 51a covers the imaging region 120b for photoelectrically converting red light are originally blocked. The images of different wavelengths to be superimposed are small but superimposed. That is, 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 product of the spectral transmittance characteristics of the optical filter 52b and the optical filter 53a. Crosstalk is small but not completely zero.

Therefore, the photographic lens 100 is further provided with a characteristic of reducing the transmittance in the wavelength region of the overlap portion between R and G. For this, an optical filter technique 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 is contained in a base material made of a transparent synthetic resin or glass.

The rare earth metal ion includes one or more of neodymium ion, praseodymium ion, erbium ion, holmium ion and the like, and it is preferable to use at least neodymium ion as an essential ion. Incidentally, these ions are usually 3
Valent ions are used. The content of the metal ion is usually 0.01 part with respect to 100 parts by mass of the base material of the photographing lens 100.
To 40 parts by mass, preferably from 0.04 to 30 parts by mass.

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

Further, the photographic lens 100 is provided with a photochromic property, which is a phenomenon of being darkened by light and reversibly returning to a colorless state when light irradiation is stopped. this is,
This is because, since the storage time control range of the solid-state imaging device 120 is limited, the amount of light reaching the solid-state imaging device when the field is extremely bright is suppressed, and the luminance range in which photography can be performed is expanded.

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

FIG. 8 is a diagram showing the spectral transmittance characteristics of the photochromic glass used for the photographing lens 100.
, The solid line shows the characteristics after irradiating sunlight for 20 minutes, and the dashed line shows the characteristics when no irradiation was performed. When the camera is carried around outdoors in fine weather or the like, the luminous flux incident on the photographic lens 100 from the aperture 110 darkens the photographic lens 100 itself, and the amount of light incident on the solid-state imaging device 120 can be reduced to about half. As a result, the accumulation time can be doubled, and the control limit on the high luminance side is raised.

The screen size of each of the imaging areas 120a, 120b and 120c is 2.24 mm × 1.68 mm from the pixel pitch of 2.8 μm and 800 × 600 pixels as described above, and the diagonal size of the screen is 2.80 mm.
Becomes Generally, the angle of view θ of a small camera is set diagonally.
It is easiest to use about 70 °. If the shooting angle of view is 70 °, the focal length is determined from the diagonal size of the screen, and in this case, it is 2.0 mm.

When a person or the like is to be photographed, the virtual object distance D [m] is determined based on the fact that the height of a human is around 170 cm and that one to three persons are often photographed together. Equation (1) can be defined as a function of the angle θ [°].

[0048]

[Outside 2] Substituting 70 ° for θ in equation (1) gives D = 2.0 m. Therefore, if the imaging system 10 is configured to achieve the best focus when the subject distance is 2 m, the lens extension from the infinity position is 0.002 mm, and the lens extension mechanism is determined from the relationship with the allowable confusion circle diameter described later. There is no practical problem at all even with a fixed-focus imaging optical system having no lens.

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

[0050]

[Outside 3] Can be represented by Therefore, if the taking lens 10
Assuming that the refractive index n of 0 is 1.5, r that gives a focal length of 2.0 mm is
1.0mm.

If the sizes of the red, green, and blue object images are made uniform, it is not necessary to perform image magnification correction in the subsequent signal processing, so that the processing time is not extended, which is convenient. Therefore, for the peak wavelengths of transmitted light of the RGB optical filters 530 nm, 620 nm, and 450 nm, the lens units 100a, 100
Optimize b and 100c and set each image magnification constant. This can be realized paraxially by making the distance from the principal point position of each lens unit to the solid-state imaging device 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, wavelengths of 530 nm, 620 nm and 450 nm
Are about 1.503, 1.499, and 1.509, respectively. Suppose the radius of the spherical surface of the lens parts 100a, 100b, 100c
Assuming that r is uniformly -1.0 mm, the focal lengths at these wavelengths are as follows from equation (2).

Lens unit 100a Representative wavelength 530 nm: 1.988 mm Lens unit 100b Representative wavelength 620 nm: 2.004 mm Lens unit 100c Representative wavelength 450 nm: 1.965 mm From the pixel pitch, the allowable confusion circle diameter is set to 3.0 μm, and the F-number of the photographing lens is set to Assuming F5.6, the focal depth expressed by the product of these is 16.8 μm, and it can be seen that the difference between the focal lengths of 620 nm and 450 nm of 0.039 mm has already exceeded this. That is, although only the paraxial image magnification is uniform, it is not focused depending on the color of the subject. Usually, the spectral reflectance of an object spans a wide wavelength range,
Generally, it is extremely rare that a sharp focus is obtained.

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

R = (1-n) f (3) In equation (3), f = 2.0 and n = 1.503, n = 1.499, n = 1.509 in order.
Is calculated and each radius is calculated as follows.

Lens unit 100a Representative wavelength 530 nm: r = 1.006 mm Lens unit 100b Representative wavelength 620 nm: r = −0.998 mm Lens unit 100c Representative wavelength 450 nm: r = −1.018 mm Difference in image magnification at a high image height position In order to balance
If the vertex heights of the lens units 100a, 100b, 100c are slightly adjusted, an ideal form can be obtained with respect to both sharpness and image magnification. Furthermore, an aspherical surface is used for each lens unit to satisfactorily correct field curvature. The image distortion may be corrected in the subsequent signal processing.

As described above, the green color having the highest visibility 555 nm
The reference G image signal by the object light including the wavelength and the image signal by the red and blue object light are respectively obtained, and the imaging system has different focal lengths for a single wavelength and for the representative wavelength of each spectral distribution. If approximately the same focal length is set, by combining these image signals, a color image in which chromatic aberration has been well corrected can be obtained. Since each imaging system has a single configuration, there is also an effect of reducing the thickness of the imaging system. In addition, achromatism usually requires a combination of two lenses having different dispersions, but a single lens configuration also has an effect of reducing costs.

The imaging 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 having the same number of pixels with a mosaic optical filter such as a Bayer array, the focus of about 1 / √3 is obtained as described above. The same angle of view is obtained at different distances. Therefore, high-contrast resolution of higher spatial frequency components must be realized. The wavelength-specific optimization of each lens unit described above is a chromatic aberration suppressing technique for this purpose.

In general, methods of improving the aberration characteristics of the photographing optical system to prevent false resolution from occurring and reducing the problem include increasing the number of constituent lenses, making the lens aspherical, using anomalous dispersion glass, diffraction, There are two ways: increasing the degree of freedom in design by using several techniques, such as using an optical element in combination, and reducing the imaging light flux.

The above-described directionality of increasing the degree of design freedom complicates the configuration of the photographing optical system even though the focal length is reduced to 1 / √3, and goes against the thinning of the photographing apparatus. That is not appropriate. On the other hand, the directionality using the above-mentioned thin luminous flux has good compatibility with a thin imaging device.

When the imaging light beam is stopped down, the response function called OTF gradually decreases monotonously in the low frequency component as shown by the solid line (b) in FIG. 10, then takes a slightly negative value and then slightly again. The characteristic has a positive value. On the other hand, in the case where a thick light beam is used without narrowing the imaging light beam, as shown by a dashed line (a) in FIG. Becomes

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

However, when the light beam is narrowed down extremely, the contrast of the high-frequency range is reduced by the influence of light diffraction. In such a situation, the point image is composed of a central bright spot and diffraction fringes surrounding the central bright spot several times. The reason for this is, as is well known, that the intensity of diffraction fringes due to peripheral waves emitted from the edge of the aperture opening relatively increases.

In order to reduce the diffraction fringes, a filter may be added to the photographing lens such that the central portion is transparent and the density increases toward the periphery. This technique is called apodization and is an augmented version of the Optical Technology Handbook (1975,
(Asakura Shoten) on pages 172 to 174.

FIG. 9 is a view showing the transmittance distribution of a transmittance distribution type filter provided on the light incident surface 100e of the photographing lens 100 and opposed to 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 aperture openings 110a, 110b,
The position corresponding to the center of 110c and having the transmittance of zero is matched to the edges of the aperture openings 110a, 110b, 110c. That is,
The transmittance distribution is highest at the center of the stop, and monotonically decreases as the distance from the center increases.

The transmittance distribution type filter is used for the photographing lens 100.
Is formed by vapor deposition or sputtering of a thin film of Inconel, chromel, chrome, or the like on the light incident side of. The characteristics shown in FIG. 9 can be obtained by making the thickness of the thin film the thinnest in the central part and the thickest in the peripheral part. In the formation of such a thin film, the position of the shield in the vapor deposition or sputtering process is continuously controlled.

Here, the transmittance distribution type filters 54a, 54a
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 light emitting side of the taking lens 100.

FIG. 11 is a diagram showing a luminance distribution of a point image.
In the figure, the dashed line (a) shows the case where the transmittance of the aperture opening is constant, and the solid line (b) shows the case where the transmittance of the aperture opening decreases from the center to the periphery. In contrast to the characteristic of (a), the characteristic of (b) has no rebound at the foot of the point image, indicating that the image is clearly good. This is a manifestation of the effect of reducing diffraction fringes by reducing peripheral light beams by apodization.

Next, the positional relationship between the photographing lens and the image pickup area will be described. Since the imaging system has three lens units, the positions of the three object images relatively change according to the subject distance. As described above, each imaging area has a size of 2.24 mm × 1.68 mm, and they are arranged adjacent to each other such that their long sides are in contact. Therefore, the center distance between adjacent imaging regions is 1.
68 mm. The YC processing circuit 230 described later performs signal processing on the assumption that the center of the object image matches the center of the imaging region. Assuming that an object image at a virtual object distance of 2 m is formed on the image pickup unit at the same interval as this, the distance between the lens units 100a, 100b, and 100c of the photographing lens 100 is set to 1.6 as shown in FIG.
It will be set to 783mm. In the figure, arrows 55a, 55
b, 55c are three lens parts 100a, 100b,
Symbol representing an imaging system with positive power by 100c, rectangle
Reference numerals 56a, 56b, and 56c denote symbols representing ranges of the imaging regions 120a, 120b, and 120c, and L1, L2, and L3 are optical axes of the imaging 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, and 100c, which are light exit surfaces, are spherical, 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 units 100a, 100b, and 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 object image and the object B is 1.6783 mm. Therefore, the center interval of the imaging region is slightly narrower than 1.68 mm, and the difference ΔY is 0.0
017 mm or 1.7 μm. Also, the highest visibility
Considering the movement of the B object image with reference to the G object image, the difference ΔY
Is twice as large as 3.4 μm. Near objects such as people are often located in the center of the shooting screen, and distant objects are often located around the screen.Furthermore, near the screen, the aberration of the shooting lens increases and image performance deteriorates. From doing
If the maximum image interval change is smaller than twice the pixel pitch,
It can be said that there is no practical problem. As described above, since the pixel pitch P of the solid-state imaging device 120 is 2.8 μm, ΔY <2 × P, and this degree of color shift of the infinite image is at an acceptable level.

Further, the image interval also fluctuates due to a temperature change of the image pickup system 10. The linear expansion coefficient of the solid-state imaging device 120 is α _S ,
Assuming that the linear expansion coefficient of the taking lens 100 is α _L and the temperature change is ΔT, since the imaging system 10 has an extremely small imaging magnification, the image interval change amount ΔZ is the difference between the elongation of the taking lens and the elongation of the solid-state image sensor. , Equation (4).

ΔZ = 1.68 × (α _L −α _S ) × ΔT (4) where α _S = 0.26 × 10 ⁻⁵ , ΔT = 20 [°], and the photographic lens 100 has a low melting point. Assuming that it is made of glass, α _L = 1.2
Assuming × 10 ⁻⁵ , ΔZ is calculated to be 0.00032 [mm]. This is the amount of change in the distance between the G object image and the R object image, and the amount of change in the distance between the R object image and the B object image.

When the B object image is considered as a change with respect to the G object image which is the reference image signal, since the image interval is 1.68 × 2, the image interval change amount is 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. In general, the linear expansion coefficient α _S of the solid-state imaging device 120 takes a small value of about 0.26 × 10 ^−5, so that it is necessary to select the linear expansion coefficient α _L of the imaging lens 100 so as to satisfy Expression (5).

[0074]

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

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

Further, apart from the fluctuation of the image interval due to the change of the object distance and the temperature, the imaging regions 120a, 120b, 12
A method is used in which the resolution is increased by a small number of pixels by shifting 0c mutually by half a pixel. The 1/2 pixel shift amount is set for a virtual subject distance of 2 m.

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

This pixel shift can be realized by slightly decentering the lens portions 100b and 100c of the photographing lens 100 with respect to the lens portion 100a.
And 120c may be realized by slightly decentering the imaging region 120a.

In an optical filter array such as a Bayer array, for example, a pixel having a red optical filter or a pixel having a blue optical filter enters between pixels having a green optical filter, thereby causing aliasing distortion. An optical low-pass filter to suppress is needed. However, if such a configuration is adopted in which images having different spectral distributions are captured for each imaging region, pixels having respective optical filters can be densely arranged, and as a result, the influence of aliasing is small and an optical low-pass filter can be used. A high-definition image can be obtained without the need. Therefore, it is possible to reduce the size of the imaging system and to significantly reduce the cost.

Next, the signal processing will be described.

As described above, the solid-state imaging device 120 is effectively applied to an imaging device having 1800 pixels in the long-side direction and 800 pixels in the short-side direction, each having a total of 1.440,000 pixels. Optical filters of three primary colors of (R), green (G) and blue (B) are arranged for each predetermined area.

As shown in FIG. 14, the image signals read from the solid-state image pickup device 120 are supplied to the A / A of the image processing system 20 respectively.
It is supplied to the D converter 500. The A / D converter 500 has, for example, a 10-bit signal corresponding to the amplitude of the signal of each exposed pixel.
This is a signal conversion circuit that converts the signal into a digital signal of bits and outputs the converted signal. The 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 the R, G, B digital signals.
G and B color signals are converted to luminance signal Y and color difference signals (RY) and (BY)
To a YC signal represented by

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 imaging device 120 via the A / D converter 500, and includes a white balance circuit, a gamma correction circuit, It has an interpolation operation circuit that performs high resolution by interpolation operation.

The YC processing circuit 230 is a signal processing circuit for generating a luminance signal Y and 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.

The details of the RGB image processing circuit 210 will be described.

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

The interpolation operation circuit in the RGB image processing circuit 210 generates an image signal having a resolution four times as high as 600 × 800 pixels by interpolation processing, and converts the image signal from the solid-state imaging device 120 into a high-definition image quality signal. Then, the signal is supplied to the subsequent high-frequency luminance signal generation circuit, low-frequency luminance signal generation circuit, and color difference signal generation circuit.

Since the size of each of the RGB object images is already the same depending on the setting of the photographing lens 100, first, a calculation process for correcting distortion of the photographing optical system is performed on each image signal by a known method. Subsequent interpolation processing, luminance signal processing, and color difference signal processing conform to 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 FIG.
The G image signal of 0 × 800 pixels is converted into 1200 × 1600 pixels.

Next, the R signal from the image pickup area 120b corresponding to each position of the G image signal obtained by the above equations (6) to (9) is obtained.
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 described above, the imaging area of the R object image and the B object The imaging area of the image is
Since the arrangement is shifted by 1/2 pixel with respect to the imaging area of the G object image, the original output of the address ij is changed to (2
i + 1) (2j + 1).

Similarly, similarly to the R pixels, the B pixels from the image pickup area 120c correspond to the respective positions of the G image signal obtained by the above equations (6) to (9) and correspond to the following equations (14) to (14). Perform the interpolation calculation in step 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) By the above processing, the image is captured from the imaging areas 120a, 120b, and 120c. Each of
RGB signals of 600 × 800 pixels are converted to 1200 × 1600 pixel RGB signals of high definition image quality.

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

The recording / reproducing system 30 is a processing system for outputting an image signal to the memory and outputting an image signal to the liquid crystal monitor 4, and is a recording processing circuit for performing a process of writing and reading the image signal to and from the memory. 300 and a reproduction processing circuit that reproduces the image signal read from the memory and outputs it to the monitor output
310. More specifically, the recording processing circuit 300 includes a compression / expansion circuit that compresses a YC signal representing a still image and a moving image in a predetermined compression format, and expands the compressed data when it is read. The compression / expansion circuit includes a frame memory or the like for signal processing. The YC signal from the image processing system 20 is stored in the frame memory for each frame, and read out for each of a plurality of blocks and compression-encoded. The compression encoding is performed, for example, by performing two-dimensional orthogonal transformation, normalization, and Huffman encoding on an 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 control circuits of respective units for controlling the imaging system 10, the image processing system 20, and the recording / reproducing system 30, respectively, in response to an external operation. Driving the solid-state imaging device 120, RGB image processing circuit 210
, The compression processing of the recording processing circuit 300, and the like.
Specifically, an operation detection circuit 410 that detects the operation of the release button 6, and controls each unit in response to the detection signal,
A system control unit 400 that generates and outputs a timing signal and the like at the time of imaging, and a drive circuit 420 of the solid-state imaging device that generates a drive signal for driving the solid-state imaging device 120 under the control of the system control unit 400. Including.

Next, the operation of the imaging apparatus according to the present embodiment will be described with reference to FIGS. First, when the main switch 5 is turned on, a power supply voltage is supplied to each unit, and the respective units enter an operable state. Next, it is determined whether or not an image signal can be recorded in the memory. At this time, the number of recordable images that can be taken is displayed on the remaining number display 13 of the liquid crystal monitor 4 according to the remaining capacity. When the operator sees the display,
Point the camera at the object scene and press the release button 6.

When the release button 6 is pressed halfway down,
Exposure time is calculated. When all shooting preparation processing is completed, shooting becomes possible, and the display is reported to the photographer. As a result, when the release button 6 is pressed down to the end, the operation detection circuit 410 sends a detection signal to the system control circuit 400. At this time, the elapsed time of the exposure time calculated in advance is counted, and when the predetermined exposure time has elapsed, a 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 out 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 an interpolation process to quadruple the pixel resolution in a state where these have been subjected to white balance and gamma correction, respectively.
To supply.

In the YC processing circuit 230, the high-frequency luminance signal generation circuit generates a high-frequency luminance signal YH for each of the RGB pixels, and the low-frequency luminance signal generation circuit similarly generates the low-frequency luminance signal YH.
Calculate YL respectively. High-frequency luminance signal YH resulting from the calculation
Is output to the adder via the low-pass filter.
Similarly, the low-frequency luminance signal YL is output to the adder through a low-pass filter after the high-frequency luminance signal YH is subtracted. As a result, the difference YL between the high-frequency luminance signal YH and its low-frequency luminance signal
The luminance signal Y is obtained by adding -YH. Similarly, the color difference signal generation circuit obtains and outputs the color difference signals RY and BY. The output color difference signals RY and BY are each passed through a low-pass filter and supplied to the recording processing circuit 300.

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

When each image is reproduced from an image signal representing a still image or a moving image recorded in the memory, when the reproduction button 9 is pressed, the operation is detected by the operation detecting circuit 410, and the system control unit Supply the detection signal to 400. Thus, the recording processing circuit 300 is driven. The driven recording processing circuit 300 reads the recorded content 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.

(Second Embodiment) FIG. 18 shows a photographing lens.
FIG. 11 is a diagram illustrating another embodiment of the transmittance distribution of the transmittance distribution type filter provided at a position facing 100 stop apertures 110a, 110b, 110c. The transmittance changes stepwise, and the position where the transmittance of the transmittance distribution type filter is the highest is the aperture 110a,
At the center of 110b, 110c, the position where the transmittance becomes zero coincides with the edges of the aperture openings 110a, 110b, 110c. FIG. 19 is a front view of the transmittance distribution type filter. Aperture circular aperture
A region 600, a region 601, a region 602, and a region 603 are formed concentrically with 110a, and the transmittance is the region 600, the region 601, the region 602, and the region 603.
In order.

As in the first embodiment, the transmittance distribution type filter is formed by depositing or sputtering a thin film of Inconel, chromel, chrome, or the like on the light incident side of the taking lens 100. Adjust the thickness of the thin film in the central area
The characteristic shown in FIG. 18 can be obtained by making the region 600 thinnest and becoming thicker toward the region 601, the region 602, and the region 603. To form such a thin film, the position of the shield is controlled during the vapor deposition or sputtering process. May be controlled in a stepwise manner. As a result, the position of the shield becomes easy, and the production equipment can be simplified.

When such apodization is performed, the intensity of the diffraction fringes is strictly higher than in the first embodiment, but has little effect on the image and is sufficiently practical.

When the pixel pitch of the image pickup device is coarsened to reduce the size of the memory and reduce the amount of image processing,
Since the necessity of increasing the high-frequency contrast is reduced, the number of transmittance steps may be reduced as shown in FIG.

(Third Embodiment) FIG. 21 is a diagram showing a third embodiment of the imaging apparatus according to the present invention. As in the first embodiment, the diaphragm 110 of the imaging system 190 has three circular openings 110a, 110b, and 110c as shown in FIG. Of 3
The light is emitted from the three lens units 100a, 100b, and 100c to form three object images on the imaging surface of the solid-state imaging device 120.

The hatched portions 52a, 52b, 52c of the area between the diaphragm 110 and the taking lens 100 are optical filters. The optical filters 52a, 52b, 52c are the taking lens 1
4, as viewed from the light incident side, as shown in FIG.
a, 110b, and 110c are completely formed.

The optical filter 52a has a spectral transmittance characteristic of mainly transmitting green 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. Therefore, as the product of the characteristics of the infrared cut filters formed on the lens units 100a, 100b, and 100c, the image circle 51a
The object image formed in the image circle 51b has a green light component, the object image formed in the image circle 51b has a red light component, and the object image formed in the image circle 51c has a blue light component.

On the other hand, three image pickup areas 120a of the image pickup element 120,
Optical filters 53a, 53b and 53c are also formed on 120b and 120c, and their spectral transmittance characteristics are also the same as those shown in FIG. That is, the imaging region 120a is for green light (G), the imaging region 120b is for red light (R),
The imaging region 120c has sensitivity to blue light (B).

Since the light receiving spectrum distribution of each imaging region is given as the product of the pupil and the spectral transmittance of the imaging region, the combination of the pupil and the imaging region is selected according to the wavelength range. That is, the object light that has passed through the aperture 110a of the diaphragm is mainly
The object light photoelectrically converted at 0a and passed through the aperture 110b of the aperture is photoelectrically converted mainly at the imaging region 120b, and
The object light that has passed through 110c is mainly subjected to photoelectric conversion in the imaging region 120c. That is, the imaging area 120a stores the G image and the imaging area 120a.
b outputs an R image, and the imaging area 120c outputs a B image.

Since the peak wavelength of relative luminous efficiency is 555 nm, subsequent signal processing is performed with reference to a G image including this wavelength.

Since the imaging system 190 captures three object images for each wavelength, it is about 1 / √ when compared with an imaging system having the same number of pixels having a mosaic optical filter such as a Bayer array.
The same shooting angle of view is obtained with a focal length of 3. Therefore, it has been described in the first embodiment that higher spatial frequency component resolution must be realized.

It is well known that the contrast of an object image is reduced by the diffraction of light at the aperture. In order to reduce diffraction fringes, apodization is performed in which a filter is added to the photographing lens so that the center is transparent and the density increases toward the periphery. However, in general, CCD and CMO
Since the S sensor has a lower sensitivity on the blue side and a higher sensitivity on the longer wavelength side in the visible wavelength range, the third embodiment selects whether or not to employ apodization with respect to the wavelength range.

As described above, the imaging area 120a stores the G image,
Since the imaging region 120b outputs an R image and the imaging region 120c outputs a B image, the sensitivity increases in the order of the imaging region 120c, the imaging region 120a, and the imaging region 120b. Therefore, the imaging area 120a and the imaging area
Apodization may be applied only to the aperture openings 110a and 110b corresponding to 120b.

Reference numerals 610a and 610b shown in FIG. 21 are transmittance distribution type filters formed on the taking lens. The position where the transmittance is highest coincides with the center of the aperture openings 110a, 110b and 110c, and the position where the transmittance becomes zero is coincident with the edges of the aperture openings 110a, 110b and 110c. That is, the transmittance distribution is highest at the center of the stop, and monotonically decreases as the distance from the center increases.

Furthermore, the simplification may be made in consideration of the relative luminous efficiency characteristics. The relative luminous efficiency has a peak at 555 nm, and the sensitivity decreases on both the shorter wavelength side and the longer wavelength side. Therefore, compared to the G image containing the peak wavelength of relative luminosity,
Even if the definition of the R image and the B image is reduced, it is difficult for a human to find a defect when evaluating a color image obtained by combining the R image and the B image.
Therefore, the apodization is omitted for the aperture opening 110b corresponding to the imaging region 120b where the R image is formed, and the apodization is adopted only for the aperture opening 110a corresponding to the imaging region 120a. FIG. 22 is an explanatory view of the image pickup system.
Reference numeral 611a of 191 denotes a transmittance distribution type filter formed on the taking lens.

By reducing the area in which the transmittance distribution type filter is formed, the production process of the photographic lens 100 is simplified, which is advantageous in cost.

The above is an explanation of the embodiments of the present invention. However, the present invention is not limited to the configurations of the embodiments, and the functions described in the claims or the embodiments are not limited thereto. Any configuration that can achieve the function of the above configuration can be applied.

For example, in the above embodiment, the optical filters for color separation use the primary color filters of red, green, and blue. However, the present invention replaces these with the complementary colors of cyan, magenta, and yellow. The present invention is applicable even when a filter is used.

In the above embodiment, the change in the distance due to the change in the object distance from the object image having the other visibility (color) will be described with reference to the object image having the highest visibility (green). However, this is applicable to the present invention even when the reference is not based on the most visible (green) object image.

It should be noted that the present invention may be implemented by combining the above embodiments or their technical elements as necessary.

Further, the present invention is directed to a system in which all or a part of the configuration of the claims or the embodiment forms one device and is combined with another device. However, it may be an element constituting the device.

[0127]

As described above, according to the present invention,
It is possible to provide a small-sized imaging device capable of obtaining high image performance.

[Brief description of the drawings]

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

FIG. 2 is a front view of the solid-state imaging device of the imaging system in FIG. 1;

FIG. 3 is a front view of a stop of the imaging system in FIG. 1;

FIG. 4 is a diagram illustrating a formation range of an optical filter of the imaging system in FIG. 1;

FIG. 5 is a diagram of a photographing lens of the imaging system in FIG. 1 as viewed from a light exit side.

FIG. 6 is a diagram illustrating a spectral transmittance characteristic of an optical filter of the imaging system in FIG. 1;

FIG. 7 is a diagram illustrating a spectral transmittance characteristic of a color purity correction filter of the imaging system in FIG. 1;

8 is a diagram illustrating a spectral transmittance characteristic of the photochromic glass of the imaging system in FIG.

FIG. 9 is a diagram illustrating a transmittance distribution of a transmittance distribution type filter of the imaging system of FIG. 1;

10 is a diagram illustrating OTF characteristics of a photographing lens of the imaging system in FIG.

11 is a diagram illustrating a luminance distribution of a point image of the imaging system in FIG. 1;

FIG. 12 is a diagram for explaining setting of an interval between lens units of the imaging system in FIG. 1;

13 is a diagram for explaining a position of an image of an object at infinity of the imaging system in FIG. 1;

FIG. 14 is a block diagram of a signal processing system of the digital color camera of FIG. 1;

15 is a diagram illustrating a positional relationship between an imaging region for R pixels and an imaging region for B pixels with respect to an imaging region for a G image of the imaging system in FIG. 1;

FIG. 16 is an explanatory diagram of an interpolation process of the digital color camera of FIG. 1;

FIG. 17 is a diagram illustrating an entire configuration of the digital color camera in FIG. 1;

FIG. 18 is a diagram illustrating a transmittance distribution of a transmittance distribution type filter according to a second embodiment of the present invention.

FIG. 19 is a front view of the transmittance distribution type filter of FIG. 18.

FIG. 20 is a diagram illustrating a transmittance distribution of another transmittance distribution type filter according to the second embodiment of the present invention.

FIG. 21 is a sectional view of an imaging system according to a third embodiment of the present invention.

FIG. 22 is a cross-sectional view of another imaging system according to the third embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Camera main body 2 Illumination light capturing window 3 Front viewfinder frame 4 Color LCD monitor 5 Main switch 6 Release button 7, 8, 9 switch 10 Imaging system 11 Viewfinder eyepiece window 12 Prism 13 Display of remaining number of images that can be photographed 51b, 51c Image circles 52a, 52b, 52c Optical filters 53a, 53b, 53c formed on photographing lens Optical filters 54a, 54b, 54c formed on solid-state imaging device Transmittance distribution type filter 100 Photographing lenses 100a, 100b , 100c Lens portion of photographing lens 110 Aperture 120 Solid-state image sensor

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G02B 5/20 G02B 5/20 5/22 5/22 G03B 11/00 G03B 11/00 19/07 19 / 07 H04N 5/238 H04N 5/238 Z 9/097 9/097 // H04N 9/64 9/64 R

Claims (23)

[Claims] 1. An image pickup apparatus comprising: a photographing optical system; and an image pickup device having a plurality of image pickup regions, wherein a plurality of images corresponding to the plurality of image pickup regions are projected onto the image pickup device via the photographing optical system. In the apparatus, the photographing optical system includes a plurality of image forming systems, and the image forming system includes an optical filter unit whose transmittance decreases as a distance from the optical axis of the image forming system itself increases. An imaging device, comprising: 2. The imaging apparatus according to claim 1, wherein the optical filter means gradually decreases the transmittance as the distance of the imaging system from the optical axis increases. 3. An image pickup apparatus comprising: a photographing optical system; and an image pickup device having a plurality of image pickup regions, and projecting a plurality of images corresponding to the plurality of image pickup regions onto the image pickup device via the photographing optical system. In the apparatus, the imaging optical system includes an imaging system including an optical filter unit whose transmittance decreases as a distance from the optical axis of the imaging system itself increases, and an imaging system including no optical filter unit. An imaging apparatus comprising an image system. 4. The imaging apparatus according to claim 1, wherein a light incident side of the optical filter means of the imaging system is provided.
An imaging device, wherein color filters are arranged. 5. The imaging device according to claim 4, wherein a color filter of the same color as the color filter is arranged on an imaging region of the imaging device corresponding to the imaging system. 6. The imaging device according to claim 4, wherein the number of the imaging systems is three, and the color filters are a red (R) color filter, a green (G) color filter, and a blue (B) color filter. 2.) An imaging device, which is a color filter. 7. The imaging device according to claim 1, wherein the imaging system is a photochromic glass. 8. A plurality of image pickup units for respectively receiving different wavelength components of subject light, and a plurality of image pickup units for guiding the subject light to the plurality of image pickup units, the light being transmitted as the distance from an optical axis increases. An imaging apparatus comprising: a plurality of optical systems each having a filter function for reducing a rate. 9. A plurality of imaging units for receiving different wavelength components of the subject light, and a plurality of optical systems for guiding the subject light to the plurality of imaging units, respectively.
At least one of the plurality of optical systems has a filter function of decreasing transmittance as the distance from the optical axis increases, and at least one of the other optical systems increases the distance from the optical axis. An imaging device, which does not have a filter function of decreasing transmittance according to the following. 10. The imaging device according to claim 8, wherein the different wavelength components of the subject are representative wavelengths of light having different spectral distributions. 11. The imaging apparatus according to claim 8, wherein one of the different wavelength components of the subject is included in a spectral distribution including a peak wavelength of visibility. 12. The imaging apparatus according to claim 8, wherein said different wavelength components are any two of red, green, and blue color components, respectively. 13. The imaging apparatus according to claim 8, wherein the plurality of optical systems have filters for extracting the different wavelength components, respectively. 14. The imaging apparatus according to claim 8, wherein each of the plurality of optical systems has a single lens. 15. The imaging device according to claim 14, wherein the single lens is integrally formed of a glass material or a resin material. 16. The imaging device according to claim 15, further comprising a light-shielding film between the integrally formed single lenses. 17. The imaging apparatus according to claim 8, wherein each of the plurality of optical systems has a single lens having an infrared cut filter. 18. The imaging device according to claim 8, wherein each of the plurality of optical systems includes photochromic glass. 19. The imaging apparatus according to claim 8, wherein each of the plurality of optical systems has a color purity correction filter. 20. The imaging apparatus according to claim 8, wherein the virtual subject distance D [m] is a function of the imaging angle of view θ [°] of the plurality of optical systems. When the subject is at the virtual subject distance and when the subject is at infinity, a subject image received by one of the plurality of imaging units and a subject image received by the other one of the plurality of imaging units An optical axis interval between the plurality of optical systems, so that a change in the interval between the optical systems is smaller than twice the pixel pitch of the imaging unit. 21. The imaging device according to claim 8, wherein the plurality of imaging units are integrally configured. 22. The imaging device according to claim 8, wherein the plurality of imaging units are configured in a planar shape. 23. The imaging apparatus according to claim 8, wherein said plurality of optical systems have a plurality of openings for taking in external light.