JP2008016481A - Single-plate solid-state imaging element and digital camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a single-plate solid-state imaging element in which deterioration of a resolution never occurs and a false color is not generated. <P>SOLUTION: The single-plate solid-state imaging element is provided with a semiconductor substrate 11 having a plurality of photoelectric conversion elements formed in a two-dimensional array on a light-receiving surface; and signal reading means for each reading a signal detected by each of the photoelectric conversion elements, in response to a light receiving quantity. The imaging element is configured by laminating the following on an upper layer of the light-receiving surface: a first liquid crystal layer 23R to be switched into a first state where a first color light of three primary colors is transmitted and second and third color lights are interrupted, and a second state where the first, second and third color lights are transmitted; a second liquid crystal layer 23G to be switched into a first state where the second color light is transmitted and the first and third color lights are interrupted, and a second state where the first, second and third color lights are transmitted; and a third liquid crystal layer 23B to be switched into a first state where the third color light is transmitted and first and second color lights are interrupted, and a second state where the first, second and third color lights are transmitted. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a single-plate solid-state image pickup device and a digital camera that pick up a color image, and more particularly, to a single-plate solid-state image pickup device and a digital camera that do not generate false colors and do not cause a resolution reduction.

  For example, in a conventional single-plate solid-state imaging device using a primary color filter, red (R), green (G), and blue (B) on each photodiode (photoelectric conversion device) arrayed on a semiconductor substrate. Among them, a color filter of one color is laminated, a photodiode (R pixel) in which a red filter is laminated, a photodiode (G pixel) in which a green filter is laminated, and a photodiode (B pixel) in which a blue filter is laminated. Are arranged in a mosaic and periodically on the surface of the semiconductor substrate.

  In addition, there exists a thing of the following patent document 1 as a thing relevant to a prior art.

JP 2006-163316 A

  When capturing a color image of a subject, three components of a red signal component, a green signal component, and a blue signal component at each pixel position of the solid-state image sensor are required. However, for example, the R pixel detects a signal corresponding to the amount of received red light, but blue light and green light are not received because they are cut by a red filter stacked on the R pixel.

  For this reason, the blue signal component at the R pixel position is obtained by interpolating the signal component detected by the B pixel provided around the R pixel, and similarly, the green signal component is provided around the R pixel. It is obtained by interpolation calculation of the signal component detected by the G pixel.

  As described above, in a single-plate solid-state image pickup device, color signals of three colors R, G, and B cannot be obtained with one pixel, and therefore, it is not possible to obtain a resolution equivalent to the number of pixels provided on the semiconductor substrate. And a problem that a color (false color) different from that of the subject occurs.

  An object of the present invention is to provide a single-plate solid-state imaging device and a digital camera that can eliminate a reduction in resolution and generation of false colors.

  The single-plate solid-state imaging device of the present invention reads a semiconductor substrate having a plurality of photoelectric conversion elements arranged in a two-dimensional array on a light receiving surface, and a signal detected by each of the photoelectric conversion elements according to the amount of received light. In a single-plate solid-state imaging device including a signal reading unit, the first state, the first color light, and the second color light that transmit the first color light of the three primary colors and block the second color light and the third color light are formed above the light receiving surface. A first liquid crystal layer that is switched between a second state that transmits color light and third color light; a first state that transmits second color light and blocks first color light and third color light; first color light; second color light; A second liquid crystal layer that is switched between a second state that transmits three-color light, a first state that transmits third color light and blocks the first color light and the second color light, and the first color light, the second color light, and the third color light. Layered with a third liquid crystal layer that can be switched between the second state of transmission Characterized in that was.

  The digital camera of the present invention is a digital camera equipped with the above-described single-plate solid-state imaging device, wherein the first liquid crystal layer is set to the first state, and the second liquid crystal layer and the third liquid crystal layer are set to the first state. A first imaging process for imaging in a predetermined time in two states, a first readout process for reading a signal from each photoelectric conversion element after the first imaging process, and the second liquid crystal layer in the first state. A second imaging process for performing imaging for a predetermined time with each of the one liquid crystal layer and the third liquid crystal layer being in the second state; and a second reading process for reading a signal from each of the photoelectric conversion elements after the second imaging process; A third imaging process in which the third liquid crystal layer is set to the first state and the first liquid crystal layer and the second liquid crystal layer are respectively set to the second state to perform imaging for a predetermined time; Third reading process for reading a signal from the photoelectric conversion element Characterized in that it comprises a control means for continuously.

  The control means of the digital camera of the present invention is characterized in that the first, second, and third liquid crystal layers are respectively set to the first state during the first, second, and third reading processes. .

  The control means of the digital camera of the present invention combines the first color imaged image data, the second color imaged image data, and the third color imaged image data read out by the first, second and third reading processes, respectively. It is characterized by generating color image data of a subject.

  According to the present invention, although there is a slight time difference, the image data of the first color, the second color, and the third color is picked up by one pixel, so that a color image without a decrease in resolution and without a false color is picked up. It becomes possible.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is an explanatory diagram of a single-plate solid-state image sensor according to an embodiment of the present invention. The single-plate solid-state imaging device 10 includes photodiodes (photoelectric conversion elements: pixels) 13 arranged in a two-dimensional array on a light receiving surface 12 of a semiconductor substrate 11.

  In the present embodiment, the odd-numbered pixel rows are formed by being shifted by 1/2 pitch with respect to the even-numbered pixel rows, and the vertical charge transfer path (between the adjacent pixels 13 in the horizontal direction ( VCCD) 14 is formed to meander in the vertical direction.

  A horizontal charge transfer path (HCCD) 15 connected to the end of each vertical charge transfer path 14 and extending in the horizontal direction is provided at the lower side of the semiconductor substrate 11, and output to the output stage of the horizontal charge transfer path 15. An amplifier 16 is provided.

  In such a single-plate solid-state imaging device, the signal charges detected by the respective photodiodes (pixels) 13 are read out to the vertical charge transfer path 14 and transferred in the vertical direction, and then, in the direction of the output amplifier 16 by the horizontal charge transfer path 15. The output amplifier 16 outputs a voltage value signal corresponding to the transferred charge amount of each signal charge as an image signal.

  The single-plate solid-state image pickup device shown in the figure is a solid-state image pickup device using a CCD (Charge Coupled Device) as a signal read-out means. However, the solid-state image pickup device such as a CMOS type using a transistor circuit as a signal read-out means. Also, this embodiment can be applied. Further, in FIG. 1, a solid-state imaging device having a so-called honeycomb pixel arrangement has been described as an example. However, the present embodiment can also be applied to a solid-state imaging element having a square lattice arrangement.

  FIG. 2 is a schematic cross-sectional view of approximately 3 pixels of the single-plate solid-state imaging device shown in FIG. On the surface portion of the semiconductor substrate 11, a photodiode (not shown), a buried channel of a vertical charge transfer path, and the like are formed. The outermost surface of the semiconductor substrate 11 is covered with a gate insulating film, on which a transfer electrode film 14a constituting the vertical charge transfer path 14 is provided, and a light shielding film 21 having an opening 21a on the photodiode thereon. Is provided.

  A transparent planarizing layer 22 is laminated on the light shielding film 21 to planarize the surface, and three liquid crystal layers 23B, 23G, and 23R are laminated thereon. The liquid crystal layer 23B transmits only blue light when voltage application is on, and becomes transparent (a state where all incident light is transmitted) when voltage application is off. The liquid crystal layer 23G transmits only green light when the voltage application is on, and becomes transparent when the voltage application is off. The liquid crystal layer 23R transmits only red light when the voltage application is on, and becomes transparent when the voltage application is off.

  Each of the liquid crystal layers 23B, 23G, and 23R includes, for example, a birefringence effect of a birefringence effect type (ECB type) liquid crystal and a polarization of a polarizing plate sandwiching the liquid crystal, as described in JP-A-10-10532, for example. Each can be realized by a combination with characteristics, and each is formed with a thickness of about 1 μm.

  On the surface of the uppermost liquid crystal layer 23R, a microlens 24 having a condensing point on the surface of the photodiode is laminated for each opening 21a of the light shielding film 21.

  In the single-plate solid-state imaging device having such a configuration, for example, as shown in FIG. 3, when the voltage application of the liquid crystal layer 23R is turned on and the voltage application of the liquid crystal layers 23G and 23B is turned off, the liquid crystal layer 23R transmits red light. Since both the liquid crystal layers 23G and 23B are transparent, only the red light of the incident light reaches the photodiode.

  Similarly, when the voltage application of the liquid crystal layer 23G is turned on and the voltage application of the liquid crystal layers 23R and 23B is turned off, the liquid crystal layer 23G transmits green light, and both the liquid crystal layers 23R and 23B become transparent. Only green light of the light reaches the photodiode.

  When the voltage application of the liquid crystal layer 23B is turned on and the voltage application of the liquid crystal layers 23G and 23R is turned off, the liquid crystal layer 23B transmits blue light, and both the liquid crystal layers 23G and 23R become transparent. Of these, only blue light reaches the photodiode.

  When all voltages applied to the liquid crystal layers 23R, 23G, and 23B are turned on, the incident light does not reach the photodiode (or is greatly attenuated) as shown in FIG.

  FIG. 5 is an operation explanatory diagram when a subject image is captured by a digital camera equipped with the single-plate solid-state imaging device according to the present embodiment described above. Similar to a normal CCD solid-state image sensor, exposure time is calculated and automatic focusing is performed when the shutter button is half-pressed, and shooting is performed when the shutter button is fully pressed. At this time, in the digital camera of the present embodiment, a control unit (not shown) continuously performs photographing three times.

  First, the first exposure (imaging) is performed by continuing the state in which the voltage application to the liquid crystal layer 23R is on and the voltage application to the liquid crystal layers 23G and 23B is off for a predetermined time. Thereby, all the photodiodes 13 provided on the light receiving surface of the single-plate solid-state image sensor receive red light, and a red image of the subject is captured.

  When the voltage application to the three liquid crystal layers 23R, 23G, and 23B is turned on after the predetermined time has elapsed, the incident light is shielded by the three liquid crystal layers 23R, 23G, and 23B as described with reference to FIG. . During this shielding, the accumulated charge of each photodiode 13 is transferred to the vertical charge transfer path 14 and the horizontal charge transfer path 15, and the red picked-up image data is read from the output amplifier 16 and stored in a frame memory (not shown).

  After this read transfer operation is completed, the state in which the voltage application to the liquid crystal layer 23G is turned on and the voltage application to the liquid crystal layers 23R and 23B is turned off continues for the same predetermined time as the second time. Perform the second exposure. As a result, all the photodiodes 13 provided on the light receiving surface of the single-plate solid-state image sensor now receive green light, and a green image of the subject is captured.

  After the second exposure, the green captured image data is read from the solid-state image sensor in the same manner as described above, and the green captured image data is stored in the frame memory. After this read transfer operation is completed, the state in which the voltage application to the liquid crystal layer 23B is turned on and the voltage application to the liquid crystal layers 23R and 23G is turned off is continued for the same predetermined time as described above. Perform the second exposure. As a result, all the photodiodes 13 provided on the light receiving surface of the single-plate solid-state image sensor now receive blue light, and a blue image of the subject is captured.

  After the third exposure, blue captured image data is read from the solid-state image sensor and stored in the frame memory in the same manner as described above.

  Thereafter, a control unit (not shown) of the digital camera reads the red captured image data, the green captured image data, and the blue captured image data on the frame memory, and performs white balance correction processing, gamma correction processing, RGB / YC conversion processing, and the like. JPEG image data and the like are generated and stored in an external memory medium.

  At this time, since the single-plate solid-state imaging device of the present embodiment can obtain image data of three colors of R, G, and B with one pixel, the interpolation calculation process as described in [Problems to be solved by the invention] Is not required, and high-resolution captured image data can be obtained. Further, since image data of three colors of R, G, and B can be obtained with one pixel, no false color is generated.

  Further, in the single-plate solid-state image pickup device of the present embodiment, defective pixel correction is easier than in the single-plate solid-state image pickup device in which color filters are arranged in a mosaic pattern, and defective pixel patterns that become defective can be reduced. The yield of the image sensor can be improved.

  The single-plate solid-state imaging device according to the present invention can obtain image data of three colors of R, G, and B with one pixel, and is mounted on a digital camera that captures a high-resolution color image without generating false colors. Then it is useful.

It is a surface schematic diagram of the single plate type solid-state image sensing device concerning one embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of an essential part of approximately 3 pixels of the single-plate solid-state imaging device shown in FIG. It is operation | movement explanatory drawing of the liquid-crystal layer shown in FIG. It is a figure explaining the state which the liquid-crystal layer shown in FIG. 2 shields incident light. It is operation | movement explanatory drawing of the digital camera which concerns on one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Single plate type solid-state image sensor 11 Semiconductor substrate 12 Light-receiving surface 13 Photodiode (pixel)
14 Vertical charge transfer path (VCCD)
14a Vertical charge transfer electrode film 15 Horizontal charge transfer path (HCCD)
16 Output amplifier 21 Light shielding film 21a Light shielding film opening 22 Flattening layers 23R, 23G, 23B Liquid crystal layer 24 Microlens

Claims (4)

  A single-plate solid-state imaging device comprising: a semiconductor substrate having a plurality of photoelectric conversion elements arranged in a two-dimensional array on a light receiving surface; and a signal reading means for reading out signals detected by the photoelectric conversion elements according to the amount of received light. In the element, the first state in which the first color light of the three primary colors is transmitted and the second color light and the third color light are blocked, and the first color light, the second color light, and the third color light are transmitted to the upper layer of the light receiving surface. A first liquid crystal layer that can be switched, a first state that transmits the second color light and blocks the first color light and the third color light, and a second state that transmits the first color light, the second color light, and the third color light. A second liquid crystal layer that is switched, a first state that transmits the third color light and blocks the first color light and the second color light, and a second state that transmits the first color light, the second color light, and the third color light are switched. Single-plate solid characterized by laminating three liquid crystal layers Image element.   2. A digital camera equipped with the single-plate solid-state imaging device according to claim 1, wherein the first liquid crystal layer is set in the first state and the second liquid crystal layer and the third liquid crystal layer are set in the second state, respectively. A first imaging process for performing imaging of time; a first readout process for reading a signal from each of the photoelectric conversion elements after the first imaging process; and setting the second liquid crystal layer to the first state and the first liquid crystal layer and A second imaging process for performing imaging for a predetermined time with each of the third liquid crystal layers in the second state; a second readout process for reading a signal from each photoelectric conversion element after the second imaging process; and the third liquid crystal layer In the first state, the third liquid crystal layer and the second liquid crystal layer in the second state, respectively, a third imaging process for imaging for a predetermined time, and a signal from each photoelectric conversion element after the third imaging process Control unit for continuously performing the third reading process of reading Digital camera comprising: a.   3. The control unit according to claim 2, wherein the control unit sets the first, second, and third liquid crystal layers to the first state during the first, second, and third readout processes. Digital camera.   The control means combines the first color imaged image data, the second color imaged image data, and the third color imaged image data read out by the first, second, and third reading processes, respectively, to obtain color image data of the subject. The digital camera according to claim 2, wherein the digital camera is generated.

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