JP3651015B2 - Solid-state imaging device - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a solid-state image pickup device suitable for being provided in, for example, a high-definition camera device, a high-definition video camera device, and the like, and in particular, shifts imaging light obliquely by a predetermined amount to a so-called three-plate type light receiving unit. The present invention relates to a solid-state imaging device that performs imaging while performing re-sub-Nyquist sampling processing on the imaging signal and outputs the imaging signal to increase the resolution of the imaging signal.
[0002]
[Prior art]
Conventionally, a so-called three-plate type solid-state imaging device having a solid-state imaging device (CCD image sensor) for red (R), a CCD image sensor for green (G), and a CCD image sensor for blue (B) is known. Yes.
[0003]
This solid-state imaging device has a configuration as shown in FIG. 11, and imaging light is incident on a dichroic prism 102 via an imaging lens 100 and an optical low-pass filter (OPLPF) 101. The dichroic prism 102 divides the imaging light into three and emits it. The three-divided imaging light is incident on the color filters 103R, 103G, and 103B, respectively. The color filters 103R, 103G, and 103B extract only the R imaging light, only the G imaging light, and only the B imaging light from the incident imaging light, and emit the extracted light. The imaging light of each color is applied to each color CCD image sensor 104R, 104G, 104B.
[0004]
The CCD image sensors 104R, 104G, and 104B for the respective colors, as shown in FIG. 12, form imaging light at the same position so that the R CCD image sensor 104R and the B CCD image sensor 104B form high-resolution imaging signals. The G CCD image sensor 104G is provided so as to receive light, whereas the G CCD image sensor 104G is provided so as to receive intermediate imaging light received by the R and B CCD image sensors 104R and 104B. Yes.
[0005]
The CCD image sensors 104R, 104G, and 104B for each color receive the imaging light of each color and perform photoelectric conversion, thereby forming and outputting an imaging signal for each color. The imaging signals of the respective colors are supplied to the LPFs 105 to 107, respectively. In addition, among the image pickup signals of the respective colors, the R image pickup signal and the G image pickup signal are respectively supplied to the detail forming circuit 108.
[0006]
The image signals of the respective colors have a frequency band of, for example, 14 MHZ as shown by a solid line in FIG. 13A, but are in phase with the R and B image signals as shown by a left oblique line in FIG. The folding component is generated. Further, as described above, the G CCD image sensor 104G is provided so as to receive imaging light intermediate between imaging light received by the R and B CCD image sensors 104R and 104B. The aliasing component of the G imaging signal is generated in the opposite phase to the aliasing component in phase with the R and B imaging signals, as indicated by the right diagonal line in FIG. Despite the occurrence of the aliasing component, the resolution is degraded due to the aliasing component that extracts the 14 MHz frequency band as it is.
[0007]
For this reason, each of the LPFs 105 to 107 is provided with a characteristic for extracting a band that is less affected by the aliasing component as shown in FIG. Each of the LPFs 105 to 107 extracts a band where the influence of the aliasing component is small from the image signals of the respective colors, and supplies this to adders 110 to 111.
[0008]
On the other hand, since the imaging signals extracted by the LPFs 105 to 107 are missing high frequencies, the outline of the image is blurred. Therefore, the detail forming circuit 108 forms a detail signal for emphasizing the contour from the R and G imaging signals, and supplies the detail signal to a band pass filter (BPF) 109. The detail signal is a monochrome signal because it is formed from the R and G imaging signals. As shown in FIG. 13C, the BPF 109 extracts a high-frequency imaging signal of a predetermined amount from the bands cut by the LPFs 105 to 107 from the imaging signals, and this detail signal is extracted from the adders 110. To ~ 112.
[0009]
The adders 110 to 112 add the image signals from the LPFs 105 to 107 and the detail signals to form image signals for each color as shown in FIG. It outputs via the output terminals 113R, 113G, 113B.
[0010]
As described above, the G CCD image sensor 104G is provided so as to receive imaging light at an intermediate position between the R and B CCD image sensors 104R and 104B. For this reason, it is possible to form RGB image signals in the horizontal (H) direction, and it is possible to form and output an image signal with a higher resolution.
[0011]
Here, when the R imaging signal and the G imaging signal are at the same level (monochrome or yellow), a high-resolution imaging signal can be formed and output. A folding component is generated in the entire band (from DC to the maximum band = 10 MHZ, etc.). The effect of this aliasing component is that the MTF (Modulation Transfer Function) of the optical system has a downward-sloping characteristic, so the vicinity of the 7 MHZ band is particularly prominent. Deteriorate greatly. For this reason, in the conventional solid-state imaging device, the OLPPF 101 is provided between the imaging lens 100 and the dichroic prism 102 so as to reduce the aliasing component to the low range, thereby reducing the adverse effect of the aliasing component. .
[0012]
[Problems to be solved by the invention]
However, the above-described conventional solid-state imaging device is provided with the OPLPF 101 so as to reduce the adverse effect of the aliasing component, and the LPFs 105 to 107 extract an imaging signal in a band with less influence of the aliasing component, Since the monochrome detail signal is added to the image pickup signal, there is a problem in that the resolution is deteriorated as high frequencies are cut. Specifically, only a resolution of about 800 lines can be obtained at the maximum horizontal resolution. For this reason, it was not possible to cope with so-called high-definition television.
[0013]
The G CCD image sensor 104G is provided so as to receive imaging light at an intermediate position between the R and B CCD image sensors 104R and 104B, and RGB imaging signals are aligned in the H direction. However, as shown in the figure, only the image signals of the same color are aligned in the vertical (V) direction as in RB, RB, RB..., G, G, G. There is a problem that the vertical resolution is deteriorated.
[0014]
In addition, since the G CCD image sensor 104G is provided so as to receive imaging light at an intermediate position between the R and B CCD image sensors 104R and 104B, it requires a mounting accuracy of 1 μm or less. It was very difficult to maintain accuracy.
[0015]
The present invention has been made in view of the above-described problems, and reduces the adverse effects of aliasing components and outputs a full-band imaging signal without cutting high frequencies, and improves horizontal resolution and vertical resolution. It is an object of the present invention to provide a solid-state imaging device that can be adapted to high-definition television and can reduce the mounting accuracy of each light receiving portion of a three-plate CCD image sensor.
[0016]
[Means for Solving the Problems]
A solid-state imaging device according to the present invention receives a red imaging light among irradiated imaging light, forms a red imaging signal corresponding to the imaging light, and outputs the red imaging light, of the imaging light A blue light receiving element that receives blue imaging light and generates and outputs a blue imaging signal corresponding to the imaging light, and receives green imaging light among the imaging light, and receives green imaging light corresponding to the imaging light. A light receiving means including a green light receiving element that forms and outputs an image pickup signal, and an optical path of the image pickup light applied to the light receiving element at a predetermined time by one pixel pitch in the horizontal direction and 1/2 pixel pitch in the vertical direction And an optical path shifting means for shifting by a minute.
[0017]
In addition, a low-pass filter that extracts and outputs a frequency component equal to or lower than a predetermined frequency out of all frequencies of each imaging signal from the light receiving unit, and each imaging signal extracted by the low-pass filter, Each imaging signal from the light receiving means And a sub-Nyquist sampling means for removing and outputting a frequency component more than twice the Nyquist frequency from each imaging signal formed by this sampling.
[0018]
Further, in the solid-state imaging device according to the present invention, as the light receiving means, the red light receiving element and the blue light receiving element spatially sample imaging light at the same position, and the green light receiving element is the red light receiving element and There is one that spatially samples imaging light at a position shifted by a ½ pixel pitch in the horizontal direction from the spatial sampling position of the blue light receiving element.
[0019]
In the solid-state imaging device according to the present invention, the light-receiving means includes one in which the light-receiving elements for the respective colors spatially sample imaging light at the same position.
[0020]
Further, the solid-state imaging device according to the present invention, as the optical path shift means, according to a polarizing plate that transmits only the imaging light in the first polarization direction of the imaging light, and a voltage that is turned on and off every predetermined time, Imaging light in the first polarization direction from the polarizing plate is emitted as it is, and imaging light in the first polarization direction from the polarizing plate is imaged in the second polarization direction orthogonal to the first polarization direction. When the voltage-driven liquid crystal plate that converts the light and emits it, and when the imaging light in the first polarization direction is incident from the liquid crystal plate, the above-mentioned is performed without changing the optical path of the imaging light in the first polarization direction. When the image pickup device for each color is irradiated and the image pickup light in the second polarization direction is incident from the liquid crystal plate, the optical path of the image pickup light in the second polarization direction is shifted by a predetermined amount and is applied to the image pickup device for each color. And a crystal plate.
[0021]
The polarizing plate, the liquid crystal plate, and the crystal plate are adjusted in position so as to shift the optical path of the imaging light in the second polarization direction obliquely.
[0022]
Moreover, the solid-state imaging device according to the present invention includes the low-pass filter. Each imaging signal from the light receiving means An ideal low-pass filter that extracts and outputs each imaging signal having a frequency equal to or lower than the Nyquist frequency.
[0023]
Alternatively, as the low-pass filter, each imaging signal is Each imaging signal from the light receiving means A symmetric low-pass filter that gradually cuts off before and after the Nyquist frequency.
[0024]
Alternatively, the low pass filter is Each imaging signal from the light receiving means A Nyquist over low-pass filter that extracts and outputs each imaging signal that is equal to or higher than the Nyquist frequency and equal to or lower than a predetermined frequency.
[0025]
[Action]
The solid-state imaging device according to the present invention irradiates the light receiving means with the imaging light by the optical path shifting means while shifting it obliquely every predetermined time.
[0026]
Specifically, the optical path shifting means is formed by sequentially providing a polarizing plate, a voltage-driven liquid crystal plate, and a quartz plate on the optical axis of the imaging light, and the imaging light is horizontal as a whole. It is shifted by one pixel pitch in the direction and ½ pixel pitch in the vertical direction (diagonal shift).
[0027]
That is, the polarizing plate transmits only the imaging light in the first polarization direction (for example, imaging light whose polarization direction is the horizontal direction = H polarization component) out of the imaging light. This H polarization component is irradiated onto the liquid crystal plate.
[0028]
Note that a polarizing plate that transmits only a vertical polarization component (V polarization component) orthogonal to the H polarization component may be provided.
[0029]
For example, when the voltage is off, the liquid crystal plate emits the H-polarized component imaging light as it is, but when the voltage is turned on, the H-polarized component imaging is performed. The light is converted into V-polarized component imaging light and emitted.
[0030]
On the other hand, the liquid crystal plate emits the H-polarized component imaging light as it is when the voltage is on, and the H-polarized component imaging light when the voltage is off. You may provide what converts into and emits.
[0031]
The imaging light of the H polarization component and the imaging light of the V polarization component from the liquid crystal plate are respectively irradiated on the quartz plate.
[0032]
When the imaging light of the H-polarized component is incident, the quartz plate emits it as normal light without shifting its optical path, and when the imaging light of the V-polarized component is incident, The optical path is shifted by one pixel pitch in the horizontal direction and shifted by ½ pixel pitch in the vertical direction (that is, shifted obliquely) and emitted. Imaging light from the quartz plate is irradiated to the light receiving means.
[0033]
As described above, the optical path shifting means is adjusted so as to shift the optical path of the imaging light as a whole by one pixel pitch in the horizontal direction and 1/2 pixel pitch in the vertical direction. For this reason, the light receiving means is irradiated with normal light and extraordinary light, for example, every 1/2 field, the first 1/2 field is formed by imaging light using the ordinary light, and the next 1/2 field is generated by abnormal light. Therefore, it is formed by imaging light that interpolates between pixels of the image formed by the ordinary light.
[0034]
Next, the light receiving means is a so-called three-plate type CCD image sensor, and the red light receiving element receives red imaging light of the imaging light, and the blue light receiving element receives blue imaging light of the imaging light. Is received, and the green light-receiving element is received by the green light-receiving element.
[0035]
Further, in each color light receiving element, the red light receiving element and the blue light receiving element are in the same spatial sampling position, and the green light receiving element is horizontal from the spatial sampling position of the red light receiving element and the blue light receiving element. The registration of the light receiving elements for each color is adjusted so that the spatial sampling position is shifted by 1/2 pixel pitch in the direction.
[0036]
For this reason, when the light receiving means is irradiated with imaging light whose optical path is obliquely shifted every 1/2 field as described above, an image in one field is viewed in the horizontal direction as RB, G, RB, G. And formed with image signals of RB, G, RB, G... When viewed in the vertical direction. In other words, the RGB image pickup signals can be arranged in the horizontal direction and the vertical direction.
[0037]
Therefore, by the optical path shift, the horizontal resolution can be improved by doubling the number of horizontal lines, and the vertical resolution can be improved by aligning RGB image pickup signals for each vertical line in the vertical direction. it can.
[0038]
Next, the image signals for the respective colors are respectively supplied to low-pass filters. This low-pass filter is, for example, an ideal low-pass filter, and extracts signal components having a Nyquist frequency equal to or less than ½ of the total frequency of each image-captured signal from the image-captured signals. Supply. Specifically, if each of the imaging signals has a band of 14 MHZ, Each imaging signal above Since the Nyquist frequency is 7 MHZ, the low-pass filter extracts signal components up to 7 MHZ and supplies them to the re-sub Nyquist sampling means.
[0039]
The re-sub-Nyquist sampling unit is configured to capture each imaging signal from the low-pass filter. Each imaging signal above Are sampled with a sampling pulse twice the Nyquist frequency, and a frequency component more than twice the Nyquist frequency is removed from each imaging signal formed by this sampling and output.
[0040]
Specifically, if the optical system bandwidth is 14 MHZ Each imaging signal obtained via the optical system Since the Nyquist frequency is 7 MHZ, the re-sub-Nyquist sampling means samples each imaging signal having a frequency band of 7 MHZ from the low-pass filter using the 14 MHZ sampling pulse (re-sub-Nyquist sampling).
[0041]
When the frequency band up to 7 MHZ is extracted by the low-pass filter, the frequency component of 7 MHZ includes a folding component that occurs at 14 MHZ, which is the entire frequency band of each imaging signal. When the 7 MHZ imaging signal including the aliasing component is sampled with the 14 MHZ sampling pulse by the re-sub Nyquist sampling means, the aliasing component is folded back at the 7 MHZ boundary, and all 14 MHZ imaging signals are reproduced. It becomes.
[0042]
This re-sub-Nyquist sampling generates a aliasing component of frequency components up to 14 MHZ with the 14 MHZ as a boundary. For this reason, by removing the frequency components of 14 MHZ or more, it is possible to extract and output only the frequency components of all 14 MHZ in which no aliasing component is generated.
[0043]
As described above, an imaging signal with high resolution can be formed by the optical path shift by the optical path shifting means, and this imaging signal can be generated by the re-sub Nyquist sampling means at all frequencies without cutting the high frequency range. Since it is possible to reproduce and output the band, it is possible to output an image signal with a higher resolution and to be compatible with a high-definition television receiver.
[0044]
In addition, since the imaging signal can be supplied to the re-sub Nyquist sampling means by the low-pass filter as a half frequency band of the entire frequency band, the transmission band from the low-pass filter to the re-sub Nyquist sampling means is, for example, half. It can be reduced to 7 MHZ. Therefore, for example, when the means before the low-pass filter is the imaging side, and this imaging side is connected to, for example, a video tape recorder apparatus or the like provided with the means after the low-pass filter described below, this cable The cable transmission band can be reduced.
[0045]
Next, in the solid-state imaging device according to the present invention, each imaging signal is Each imaging signal above A signal component of each imaging signal in the vicinity of the 7 MHZ is extracted by a symmetric low-pass filter that is cut off and output gradually before and after the Nyquist frequency.
[0046]
Such a low-pass filter does not need to be designed precisely so as to accurately cut off the frequency band of 7 MHZ or higher like the ideal low-pass filter, for example, and can be easily and inexpensively manufactured. This can contribute to the cost reduction of the solid-state imaging device.
[0047]
Next, a solid-state imaging device according to the present invention is Each imaging signal The Nyquist over-low-pass filter that extracts and outputs each imaging signal that is greater than or equal to the Nyquist frequency and less than or equal to a predetermined frequency extracts the signal components of the imaging signals that are greater than or equal to 7 MHZ and less than or equal to 14 MHZ (for example, up to 10 MHZ).
[0048]
As a result, the frequency component from 7 MHz to 10 MHz can be superimposed on the 14 MHz image signal reproduced by the re-sub Nyquist sampling means as a high frequency emphasis signal, and a higher resolution image signal can be output. it can.
[0049]
As the light receiving means, light receiving elements for the respective colors having the same spatial sampling position may be used.
[0050]
In this case, an image of one field can be formed by RGB, RGB, RGB... Image signals when viewed in the horizontal direction, and can be formed by image signals of RGB, RGB, RGB. it can. In other words, the RGB image pickup signals can be arranged in the horizontal direction and the vertical direction.
[0051]
Therefore, it is possible to form an image obtained by interpolating between pixels by the optical path shift, and to improve the horizontal resolution and the vertical resolution by aligning RGB imaging signals in the horizontal direction and the vertical direction.
[0052]
In addition, the light receiving means in which the registration of the light receiving elements for each color is adjusted so that the light receiving elements for each color are at the same spatial sampling position, the horizontal light receiving element for only the green light receiving elements is ½ pixel pitch in the horizontal direction. Unlike the light receiving means in which the registration is adjusted so that the spatial sampling position is shifted, the precise adjustment accuracy of the registration is not necessary. For this reason, the registration accuracy of the registration is improved by using the light receiving means in which the registration of the light receiving elements for each color is adjusted so that the light receiving elements for each color are at the same spatial sampling position. Can be reduced.
[0053]
【Example】
Hereinafter, preferred embodiments of a solid-state imaging device according to the present invention will be described in detail with reference to the drawings.
[0054]
As shown in FIG. 1, the solid-state imaging device according to the first embodiment of the present invention receives an optical path shift unit 1 that shifts an optical path of imaging light every predetermined time, and receives imaging light from the optical path shift unit 1. Then, an imaging signal forming unit 2 that forms imaging signals of three primary colors of red (R), green (G), and blue (B), and a predetermined signal component is extracted from each imaging signal from the imaging signal forming unit 2 A low-pass filter (LPF) 3 that performs re-sub-Nyquist sampling processing to be described later on each imaging signal based on the control of the re-sub-Nyquist sampling timing circuit 7, and A A synthesis memory 5 that synthesizes and outputs the imaging signals from the / D converter 4 and a D / A converter 6 that converts the imaging signals from the synthesis memory 5 into an analog output and outputs them.
[0055]
The optical path shift unit 1 includes a polarizing plate 10 that transmits horizontal (H) imaging light among the incident imaging light, and a liquid crystal plate that emits by rotating the polarization direction of the imaging light that is incident upon voltage on / off. 11 and the imaging lens 12 and the imaging light in the H direction are emitted as normal light without shifting the optical path, and only the imaging light in the vertical (V) direction is abnormal light, and the optical path is vertical by, for example, one pixel pitch in the horizontal direction. A quartz crystal plate 13 that emits a ½ pixel pitch shifted (obliquely shifted) in the direction and a phase difference plate 14 that circularly polarizes incident imaging light and emits it are provided in order on the optical axis of the imaging light. It is constituted by.
[0056]
In the optical path shift unit 1, the positions of the units 10, 11, and 13 are adjusted so that the imaging light in the V direction is shifted obliquely by the polarizing plate 10, the liquid crystal plate 11, and the crystal plate 13.
[0057]
The imaging signal forming unit 2 extracts only the R component, the G component, and the B component from the dichroic prism 15 that divides and outputs the imaging light from the optical path shift unit 1 and the three-divided imaging light, respectively. An R filter 16R, a G filter 16G, and a B filter 16B, an R solid-state image pickup device (CCD image sensor) 17R that receives the imaging light extracted by the filters 16R, 16G, and 16B, and a CCD image sensor 17G for G It is composed of a B CCD image sensor 17B.
[0058]
The CCD image sensors 17R, 17G, and 17B are provided so that the R CCD image sensor 17R and the B CCD image sensor 17B receive imaging light at the same position, as shown in FIG. On the other hand, the G CCD image sensor 17G is provided so as to receive intermediate imaging light of the imaging light received by the R and B CCD image sensors 17R and 17B.
[0059]
The LPF 3 has a frequency band of image pickup signals obtained from the CCD image sensors 17R, 17G, and 17B of, for example, 14 MHZ. The imaging signal transmitted through the transmission system This is an ideal LPF having a characteristic of extracting an imaging signal up to 7 MHz, which is the Nyquist frequency.
[0060]
Next, the operation of the solid-state imaging device according to the first embodiment will be described.
First, when imaging is started, imaging light is irradiated to the polarizing plate 10 through an iris (not shown). The polarizing plate 10 transmits only the imaging light of which the polarization direction is the H direction after the imaging light. The imaging light in the H direction is incident on the liquid crystal plate 11.
[0061]
For example, when the voltage is turned on, the liquid crystal plate 11 transmits the imaging light in the H direction as it is. When the voltage is turned off, the polarization direction of the imaging light in the H direction is converted into the V direction and emitted.
[0062]
Specifically, the voltage to the liquid crystal plate 11 is turned on / off according to the on / off of the switch 11a. The switch 11a is connected to an unshown timing control circuit via an input terminal 11b. The control pulse is supplied only for an odd field, for example. For this reason, from the liquid crystal plate 11, imaging light in the H direction is emitted in the odd field, and imaging light in the V direction is emitted in the even field.
[0063]
The imaging light in the H direction and the imaging light in the V direction emitted for each field enter the quartz plate 13 through the imaging lens 12.
[0064]
When the imaging light in the H direction is incident, the quartz plate 13 emits it as ordinary light without shifting its optical path, and when the imaging light in the V direction is incident, The light path is shifted, for example, by 1/2 pixel pitch and emitted.
[0065]
As described above, the polarizing plate 10, the liquid crystal plate 11, and the crystal plate 13 shift the abnormal light (imaging light in the V direction incident on the crystal plate 13) obliquely by a ½ pixel pitch. Is provided. Therefore, imaging light (ordinary light) that is not shifted in the crystal plate 13 is emitted from the crystal plate 13 to the odd field, and the optical path of the crystal plate 13 in the horizontal direction is one pixel pitch horizontally in the even field. In addition, imaging light (abnormal light) that is shifted (obliquely shifted) by 1/2 pixel pitch in the vertical direction is emitted.
[0066]
The imaging light from the crystal plate 13 is circularly polarized by the phase difference plate 14 and is incident on the dichroic prism 15.
[0067]
The dichroic prism 15 divides the imaging light from the retardation plate 14 into three parts and emits them. The three-divided imaging light enters the R filter 16R, the G filter 16G, and the B filter 16B, respectively.
The filters 16R, 16G, and 16B extract R imaging light, G imaging light, and B imaging light, respectively, from the incident imaging light, and irradiate the CCD image sensors 17R, 17G, and 17B for the respective colors. .
[0068]
The color CCD image sensors 17R, 17G, and 17B receive the color imaging light, respectively, and form and output an R imaging signal, a G imaging signal, and a B imaging signal.
[0069]
As described above, the crystal plate 13 emits imaging light whose optical path is obliquely shifted every other field. The CCD image sensors 17R, 17G, and 17B are provided so that the R CCD image sensor 17R and the B CCD image sensor 17B receive imaging light at the same position, whereas the G CCD image is provided. The sensor 17G is provided so as to receive imaging light intermediate between the imaging light received by the R and B CCD image sensors 17R and 17B.
[0070]
For this reason, the image of one frame is the same as the image of the odd field in which the pixels of each line are formed by RB, G, RB, G... As viewed in the H direction as shown in FIG. b) Interpolate between the lines of the odd-numbered field image, and obliquely so that the G pixel is located below the RB pixel and the RB pixel is located below the G pixel. It is formed with the shifted even field image.
[0071]
Therefore, the image of one frame can be interpolated between horizontal lines as shown in FIG. 2C, and the RGB pixels can be aligned in the vertical direction (see the right diagonal line in the figure). Therefore, it is possible to obtain a high-resolution image in which the horizontal resolution and the vertical resolution are improved.
The imaging signals for each color are supplied to the LPF 3 respectively.
[0072]
Here, assuming that the imaging signals output from the CCD image sensors 17R, 17G, and 17B have a frequency band of 14 MHZ, the optical path among the imaging signals output from the CCD image sensors 17R, 17G, and 17B. The imaging signal formed without shifting becomes a spectrum (N) having a frequency band of 0 to 14 MHZ and a frequency band of a folded component of 14 MHZ to 28 MHZ as shown by a solid line in FIG.
[0073]
Further, since the imaging signal formed by performing the optical path shift has been subjected to the optical path shifting process described above, the phase thereof is shifted by a half period from the phase of the imaging signal formed without performing the optical path shift. As shown by a dotted line in FIG. 4A, the spectrum (N) of the imaging signal formed without performing the optical path shift is a spectrum (S) that is symmetric.
[0074]
Therefore, the spectrum (N) of the imaging signal not subjected to the optical path shift and the combined spectrum (NS) of the spectrum (S) of the imaging signal subjected to the optical path shift are as shown by the one-dot chain line in FIG. The spectrum is in the form of a half-cycle phase shift from the spectrum (N).
[0075]
As shown in FIG. 3, the LPF 3 is obtained from the imaging signals having a frequency band of all 14 MHZ. Each imaging signal above The frequency band up to 7 MHz, which is the Nyquist frequency, is extracted. Therefore, the LPF 3 outputs imaging signals of spectrum (N), spectrum (S) and composite spectrum (NS) up to the frequency band of 7 MHZ as shown in FIG. 4B. . This imaging signal is supplied to the A / D converter 4.
[0076]
The A / D converter 4 samples the imaging signal in the frequency band up to 7 MHZ (re-sub Nyquist sampling) with the 14 MHZ sampling pulse from the re-sub Nyquist sampling timing circuit 7, thereby digitally converting the imaging signal. To form imaging data, which is supplied to the synthesis memory 5.
[0077]
By this re-sub-Nyquist sampling, as shown in FIG. 4C, aliasing components of the spectrum (N), spectrum (S), and composite spectrum (NS) of the imaging data having the frequency band of 7 MHZ are generated, Imaging data having the same spectrum as the imaging signal shown in FIG. At this time, the imaging data of the spectrum (N) is canceled by the imaging data of the spectrum (S) that appears as an opposite phase to the imaging data of the spectrum (N).
[0078]
For this reason, at the time when the re-sub-Nyquist sampling process is performed, the imaging data of the composite spectrum (NS) having a frequency band of 0 MHZ to 14 MHZ, the imaging data having a frequency band of 14 MHZ to 28 MHZ, and the above 0 MHZ to 14 MHZ Only the imaging data of the aliasing component of the imaging data having the frequency band remains.
[0079]
By performing the optical path shift, a negative characteristic component due to a π shift is generated in the signal phase. Therefore, by combining with the original imaging signal, it is possible to fold and return the spectrum.
[0080]
The synthesizing memory 5 performs interpolation processing and the like on the image data from the A / D converter 4, and an LPF for extracting a frequency band from 0 MHZ to 14 MHZ is provided at the output stage. 4 (d), the imaging data of the aliasing component having the frequency band of 14 MHZ to 28 MHZ is cut as shown in FIG. 4D, and only the imaging data of the composite spectrum having the frequency band of 0 MHZ to 14 MHZ is extracted. The A converter 6 is supplied.
[0081]
The D / A converter 6 analogizes the image data of each color having the frequency band of 0 MHz to 14 MHZ to form an image signal of each color, and outputs these signals via output terminals 18R, 18G, and 18B, respectively. To do.
[0082]
As described above, the imaging signals output from the CCD image sensors 17R, 17G, and 17B are imaging signals that have been increased in resolution by oblique shift of the optical path of the imaging light, and are limited to a frequency band of 7 MHZ by the LPF 3. Even so, an imaging signal in the frequency band of 14 MHZ can be reproduced by the re-sub Nyquist sampling process. For this reason, it is possible to output the complete frequency band without cutting the high frequency of the imaging signal to be finally output. Therefore, it is possible to output an imaging signal that can be used for a so-called HD television receiver.
[0083]
Further, even if the frequency band extracted by the LPF 3 is 7 MHZ, an imaging signal of 14 MHZ (original frequency) can be reproduced by the re-sub-Nyquist sampling process. Therefore, the transmission band of the imaging signal output from the LPF 3 can be reduced. Can be reduced. For this reason, for example, when the image pickup signal from the LPF 3 is directly recorded by a video tape recorder device or transmitted to another signal processing device, the transmission band of the transmission line can be reduced, which is effective. it can.
[0084]
Of the imaging signals output via the output terminals 18R, 18G, and 18B, the R imaging signal is supplied to the adder 21 and the detail forming circuit 20 shown in FIG. And the B image pickup signal is supplied to the adder 23.
[0085]
The detail forming circuit 20 forms a detail signal for contour enhancement having a frequency band of 14 MHZ from the R imaging signal and the G imaging signal, and supplies the detail signal to a band pass filter (BPF) 25.
[0086]
The BPF 25 has a characteristic of extracting a predetermined frequency band before and after the center of, for example, 7 MHZ. For this reason, the BPF 25 extracts, for example, a frequency band of a predetermined frequency around 7 MHZ from the detail signal having the frequency band of 14 MHZ, and supplies this to the adders 21 to 23.
[0087]
The adder 21 adds the detail signal to the R imaging signal, the adder 22 adds the detail signal to the G imaging signal, and the adder 23 adds the B imaging signal. The detail signal is added to the signal.
[0088]
As described above, since each imaging signal is reproduced and output in the entire frequency band of 14 MHZ, by adding the detail signal to each imaging signal, the above 7 MHZ is obtained as shown in FIG. Each imaging signal to which the detail signal for contour enhancement is added is formed in the vicinity, and an imaging signal with higher resolution can be formed.
[0089]
Each imaging signal is supplied to, for example, a process processing circuit (not shown) via the output terminals 24R, 24G, and 24B.
[0090]
Next, a solid-state imaging device according to the second embodiment of the present invention will be described.
The solid-state imaging device according to the second embodiment is provided with a Nyquist over LPF (high frequency type ideal LPF) for extracting a predetermined frequency band from 7 MHZ to 14 MHZ as the LPF 3 as shown in FIG. It is.
[0091]
In the description of the second embodiment, since the configuration other than the Nyquist over LPF is the same as that of the solid-state imaging device according to the first embodiment described above, only the operation of the Nyquist over LPF will be described. Detailed description is omitted.
[0092]
That is, in the solid-state imaging device according to the second embodiment, when the imaging signals from the CCD image sensors 17R, 17G, and 17B are supplied to the Nyquist over LPF, the Nyquist over LPF is shown in FIG. As shown in a), a predetermined frequency band from 7 MHZ to 14 MHZ is extracted and supplied to the A / D converter 4.
[0093]
The A / D converter 4 is supplied with a 14 MHZ sampling pulse from the re-sub Nyquist sampling timing circuit 7, and the sub-Nyquist sampling process is performed on the imaging signal from the Nyquist over LPF by this sampling pulse. To the synthesis memory 5.
[0094]
By this re-sub Nyquist sampling process, as shown in FIG. 7B, the spectrum (N), spectrum (S), synthesized spectrum (NS), and their aliasing components of the imaging data from the Nyquist over LPF are generated. The imaging data having the same spectrum as the original imaging signal output from the CCD image sensors 17R, 17G, and 17B is reproduced. At this time, the imaging data of the spectrum (N) is canceled by the imaging data of the spectrum (S) that appears as an opposite phase to the imaging data of the spectrum (N).
[0095]
For this reason, at the time when the re-sub-Nyquist sampling processing is performed, the imaging data of the composite spectrum (NS) having a frequency band of 0 MHZ to 14 MHZ, and the frequency of 0 MHZ to 14 MHZ having a frequency band of 14 MHZ to 28 MHZ. Only the imaging data of the aliasing component of the imaging data having a band remains.
[0096]
The synthesis memory 5 performs interpolation processing and the like on the imaging data from the A / D converter 4, and an LPF for extracting imaging data in a frequency band up to 14 MHZ is provided at the output stage. Then, the imaging data of the aliasing component having the frequency band of 14 MHZ to 28 MHZ is cut, and only the imaging data of the synthetic spectrum having the frequency band of 0 MHZ to 14 MHZ is extracted and supplied to the D / A converter 6.
[0097]
Here, in the solid-state imaging device according to the second embodiment, the imaging data is extracted slightly larger than 7 MHZ by the Nyquist over LPF as described above. Therefore, the imaging data output from the LPF of the synthesis memory 5 is in a form in which the imaging signal of the synthetic spectrum (NS) in the frequency band of 7 MHZ or higher is superimposed as shown in FIG. 7C.
[0098]
The imaging data from the synthesis memory 5 is converted to analog by the D / A converter 6 and output as imaging signals via the output terminals 18R, 18G, and 18B.
[0099]
In the solid-state imaging device according to the second embodiment, the transmission band of the imaging signal from the Nyquist over LPF is 7 MHZ or more, and the transmission bandwidth is somewhat wider than that of the solid-state imaging device according to the first embodiment. Except for the above, the same effects as those of the solid-state imaging device according to the first embodiment can be obtained.
[0100]
When the detail signal is added to each imaging signal, the detail signal is superimposed on a band in the vicinity of the superimposed composite spectrum (NS) as shown in FIG. If this detail signal is added, higher resolution can be achieved.
[0101]
Next, a solid-state imaging device according to a third embodiment of the present invention is described.
In the solid-state imaging device according to the third embodiment, a symmetrical LPF that gradually cuts the frequency band before and after the 7 MHZ as shown in FIG. 8 is provided as the LPF 3.
[0102]
In the description of the third embodiment, since the configuration other than the symmetric LPF is the same as that of the solid-state imaging device according to the first embodiment described above, only the operation of the symmetric LPF will be described and details of other portions will be described. Description is omitted.
[0103]
That is, in the solid-state imaging device according to the third embodiment, the imaging signals from the CCD image sensors 17R, 17G, and 17B are supplied to the symmetric LPF.
[0104]
The symmetric LPF gradually cuts the frequency component of each imaging signal before and after the 7 MHZ, thereby extracting an imaging signal in a frequency band that slightly exceeds the 7 MHZ as shown in FIG. Is supplied to the A / D converter 4.
[0105]
The A / D converter 4 is supplied with a 14 MHZ sampling pulse from the re-sub-Nyquist sampling timing circuit 7, and the sub-Nyquist sampling process is performed on the imaging signal from the symmetric LPF by this sampling pulse. This is supplied to the synthesis memory 5.
[0106]
By this re-sub Nyquist sampling process, as shown in FIG. 9B, the spectrum (N), the spectrum (S), the synthesized spectrum (NS), and their aliasing components of the imaging data from the symmetric LPF are generated, Imaging data having the same spectrum as the original imaging signal is reproduced. At this time, the imaging data of the spectrum (N) is canceled by the imaging data of the spectrum (S) that appears as an opposite phase to the imaging data of the spectrum (N).
[0107]
For this reason, at the time when the re-sub-Nyquist sampling processing is performed, the imaging data of the composite spectrum (NS) having a frequency band of 0 MHZ to 14 MHZ, and the frequency of 0 MHZ to 14 MHZ having a frequency band of 14 MHZ to 28 MHZ. Only the imaging data of the aliasing component of the imaging data having a band remains.
[0108]
The synthesis memory 5 performs interpolation processing and the like on the imaging data from the A / D converter 4, and an LPF for extracting imaging data up to a frequency band of 14 MHZ is provided at the output stage. To cut the imaging data of the aliasing component having the frequency band of 14 MHZ to 28 MHZ, and extract only the imaging data of the composite spectrum having the frequency band of 0 MHZ to 14 MHZ as shown in FIG. The A converter 6 is supplied.
[0109]
The D / A converter 6 converts the imaging data having the frequency band of 14 MHZ into an analog signal to form an imaging signal, and outputs the imaging signal via the output terminals 18R, 18G, and 18B.
[0110]
In the solid-state imaging device according to the third embodiment, the transmission band of the imaging signal from the symmetric LPF is 7 MHZ or more, and the transmission band is somewhat wider than that of the solid-state imaging device according to the first embodiment. Can obtain the same effect as the solid-state imaging device according to the first embodiment.
[0111]
In addition, an LPF that cuts a signal component gradually before and after a target frequency can be manufactured more inexpensively and easily than a filter that cuts a band above the target frequency. Therefore, the LPF can be manufactured inexpensively and easily by providing the symmetric LPF instead of the ideal LPF (first embodiment) or the Nyquist over LPF (second embodiment). The cost of the solid-state imaging device can be reduced.
[0112]
It should be noted that higher resolution can be achieved by adding the detail signal to each image pickup signal.
[0113]
Finally, in each of the above-described embodiments, the light receiving means is provided with the spatial sampling position of the G CCD image sensor 17G shifted by a ½ pixel pitch in the horizontal direction. As shown in FIG. 10A, the CCD image sensors 17R, 17G, and 17B may have the same spatial sampling position. In this case, if the optical path oblique shift described above is performed, the lines can be interpolated as shown in FIG. 10B, and the RGB can be aligned in the vertical direction. The resolution of the imaging signal can be increased. In addition, there is no need for precise registration adjustment accuracy as in the case of the light receiving means in which the spatial sampling position is shifted in the horizontal direction by 1/2 pixel pitch only for the green light receiving element. Therefore, the adjustment accuracy of registration can be reduced.
[0114]
In the description of each of the above-described embodiments, the frequency band of the imaging signal output from each of the CCD image sensors 17R, 17G, and 17B is 14 MHZ, and the LPF is an imaging signal that is 7 MHZ or less or a predetermined signal that is 7 MHZ or more and 14 MHZ or less. The frequency imaging signal is extracted, but this is only an example, and it goes without saying that other numerical values may be changed according to the design.
[0115]
【The invention's effect】
The solid-state imaging device according to the present invention can irradiate the light receiving means by obliquely shifting the optical path of the imaging light every predetermined time by the optical path shifting means. In addition, even if the frequency band of each imaging signal from the light receiving means is reduced to about half of the frequency band using a low-pass filter, the entire frequency band before passing through the low-pass filter is cut off by the re-sub Nyquist sampling means. You can play and output without having to. For this reason, it is possible to output a high-resolution imaging signal, and it is possible to cope with so-called high-definition television.
[0116]
In addition, since the imaging signal can be supplied to the re-sub Nyquist sampling unit as a half frequency band using a low-pass filter, the transmission band from the low-pass filter to the re-sub Nyquist sampling unit can be reduced. it can.
[0117]
Further, by using light receiving elements for the respective colors having the same spatial sampling position as the light receiving means, the same effect as described above can be obtained, and only the green light receiving element can be horizontally spaced by a ½ pixel pitch. Since there is no need for precise registration adjustment accuracy as in the case of the light receiving means in which the registration is adjusted so that the sampling position is shifted, the registration adjustment accuracy can be reduced.
[Brief description of the drawings]
FIG. 1 is a block diagram of a first embodiment of a solid-state imaging device according to the present invention.
FIG. 2 is a diagram for explaining a spatial sampling position of each CCD image sensor provided in the solid-state imaging device according to the first embodiment and an optical path shift operation of an optical path shift unit.
FIG. 3 is a diagram illustrating characteristics of an ideal LPF provided in the solid-state imaging device according to the first embodiment.
FIG. 4 is a diagram illustrating a spectrum of an imaging signal for explaining a re-sub Nyquist sampling process in the solid-state imaging device according to the first embodiment.
FIG. 5 is a block diagram of a circuit for forming a detail signal of the solid-state imaging device according to the first embodiment.
FIG. 6 is a diagram illustrating characteristics of a Nyquist over LPF provided in a solid-state imaging apparatus according to a second embodiment of the present invention.
FIG. 7 is a diagram illustrating a spectrum of an imaging signal for explaining a re-sub Nyquist sampling process in the solid-state imaging device according to the second embodiment.
FIG. 8 is a diagram illustrating characteristics of a symmetric LPF provided in a solid-state imaging apparatus according to a third embodiment of the present invention.
FIG. 9 is a diagram illustrating a spectrum of an imaging signal for explaining a re-sub Nyquist sampling process in the solid-state imaging device according to the third embodiment.
FIG. 10 is a diagram for explaining a high-resolution imaging signal obtained by imaging each CCD image sensor whose mounting position is adjusted so as to be the same spatial sampling position, by obliquely shifting the optical path of imaging light; FIG.
FIG. 11 is a block diagram of a conventional three-plate type solid-state imaging device.
FIG. 12 is a diagram for explaining a spatial sampling position of each CCD image sensor provided in a conventional three-plate solid-state imaging device.
FIG. 13 is a diagram illustrating a state in which an imaging signal output from a conventional solid-state imaging device is formed.
[Explanation of symbols]
1 Optical path shift section
2 Imaging signal forming part
3 Low-pass filter (LPF)
4 A / D converter
5 Synthesis memory
6 D / A converter
7 Sub-Nyquist sampling timing circuit
10 Polarizing plate
11 LCD panel
12 Imaging lens
13 Crystal plate
14 Phase plate
15 Dichroic prism
16R red filter
16G green filter
16B Blue filter
17R CCD image sensor for red
17G CCD image sensor for green
17B Blue CCD image sensor
18R Red image signal output terminal
Output terminal for 18G green image signal
18B Output terminal for blue image signal
20 Detail forming circuit
21-23 Adder

Claims (7)

A red light receiving element that receives red imaging light among the irradiated imaging light, and forms and outputs a red imaging signal corresponding to the imaging light, and receives blue imaging light among the imaging light and receives the imaging light. A blue light-receiving element that forms and outputs a blue imaging signal according to light, and a green light that receives green imaging light among the imaging light and forms and outputs a green imaging signal according to the imaging light A light receiving means comprising a light receiving element for use;
An optical path shift means for shifting the optical path of the imaging light applied to the light receiving element at a predetermined time by one pixel pitch in the horizontal direction and by ½ pixel pitch in the vertical direction;
A low-pass filter that extracts and outputs a frequency component equal to or lower than a predetermined frequency among all the frequencies of each imaging signal from the light receiving means;
Each imaging signal extracted by the low-pass filter is sampled with a sampling pulse twice the Nyquist frequency of each imaging signal from the light receiving means, and twice the Nyquist frequency from each imaging signal formed by this sampling. Re-sub Nyquist sampling means for removing and outputting the above frequency components, and a solid-state imaging device.   The light receiving means spatially samples the imaging light at the same position of the red light receiving element and the blue light receiving element, and the green light receiving element is horizontal from the spatial sampling position of the red light receiving element and the blue light receiving element. The solid-state imaging device according to claim 1, wherein imaging light at a position shifted by a ½ pixel pitch is spatially sampled.   2. The solid-state imaging device according to claim 1, wherein the light receiving means spatially samples the imaging light at the same position of the light receiving elements for the respective colors. The optical path shifting means is
A polarizing plate that transmits only the imaging light in the first polarization direction of the imaging light;
The imaging light in the first polarization direction from the polarizing plate is emitted as it is according to the voltage that is turned on / off every predetermined time, and the imaging light in the first polarization direction from the polarizing plate is output as the first polarization light. A voltage-driven liquid crystal plate that converts and emits imaging light in a second polarization direction orthogonal to the polarization direction;
When imaging light in the first polarization direction is incident from the liquid crystal plate, the image sensor for each color is irradiated as it is without changing the optical path of the imaging light in the first polarization direction, and the second light is emitted from the liquid crystal plate. A crystal plate that shifts the optical path of the image light in the second polarization direction by a predetermined amount and irradiates the image sensor for each color when the image light in the polarization direction is incident;
The position of the polarizing plate, the liquid crystal plate, and the quartz plate is adjusted so as to obliquely shift the optical path of the imaging light in the second polarization direction. 3. The solid-state imaging device according to 3. The said low-pass filter is an ideal low-pass filter which extracts and outputs each imaging signal below the Nyquist frequency of each imaging signal from the said light-receiving means , The claim 1, 2, 3 or claim Item 5. The solid-state imaging device according to Item 4. 3. The symmetric low-pass filter, wherein the low-pass filter is a symmetric low-pass filter that gradually cuts off and outputs the respective imaging signals before and after the Nyquist frequency of each imaging signal from the light receiving means. The solid-state imaging device according to claim 3 or 4. The low-pass filter is a Nyquist over low-pass filter that extracts and outputs each imaging signal that is greater than or equal to a Nyquist frequency and less than or equal to a predetermined frequency of each imaging signal from the light receiving means . The solid-state imaging device according to claim 3 or 4.

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