JP2006203011A - Solid-state imaging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a color solid-state imaging device having a good condensing rate and sensitivity and a simple structure. <P>SOLUTION: In the solid-state imaging device 10, a liquid microlens device 20 and a CMOS image sensor 40 are formed for each of many pixels. The inside of the translucent cell 26 of the liquid microlens device 20 is filled up with an insulating liquid 28 and a conductive liquid 30, which have a translucency and are separated from each other. By applying voltage between an electrode 34 and the conductive liquid 30, many insulating liquids including the insulating liquid 28 which are colored either red, green, or blue are let to form drops to make the liquid microlens device work as a colored microlens. Regardless of the color of the insulating liquid 28, the shape of the drops of the insulating liquid 28 is so determined that the focus distance of the light transmitted may be constant. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a solid-state image sensor, and more particularly to a solid-state image sensor provided with a large number of liquid microlens devices.

  A solid-state imaging device for obtaining color information usually includes a microlens and a color filter. However, a solid-state imaging device that does not use a color filter by using a colored microlens as a microlens for the solid-state imaging device is also disclosed (see, for example, Patent Document 1).

On the other hand, in order to adjust the focal length, a liquid lens that changes the shape of a droplet by applying a voltage is known (see, for example, Patent Document 2).
Japanese Patent No. 2566087 (FIGS. 5 and 6) JP 2001-13306 (paragraphs [0035] to [0039], FIG. 1)

  In general, a solid-state imaging device having a microlens and a color filter is provided with a color filter in a layered manner, so that the distance from the microlens to the photoelectric conversion member becomes long, reducing the light collection rate, sensitivity of the imaging device, and smear. May be generated to reduce the image quality.

  Further, in a solid-state imaging device using a colored microlens without using a color filter, a plurality of light whose focal lengths are not constant is condensed on a photoelectric conversion member on the same plane because the color of the transmitted microlens is different. It is necessary to let For this reason, it is necessary to adjust the position where the microlens is disposed and the shape of the microlens according to the color, which leads to a complicated structure and an increase in manufacturing cost.

  SUMMARY OF THE INVENTION An object of the present invention is to realize a color solid-state imaging device that has a good light collection rate and sensitivity and has a simple structure.

  The liquid microlens device of the present invention includes a transparent cell, an insulating colored first liquid that forms a droplet for condensing transmitted light in the cell, and a first liquid. In order to change the shape of the liquid droplets, the conductive second transparent liquid filled in the cell in a separated state, the electrode provided along the outer wall surface of the cell, and the like. Voltage applying means for applying a voltage between the liquid and the electrode. In the liquid microlens device, the voltage application unit is configured to change the shape of the droplet so that the focal length of the light transmitted through the droplet becomes a predetermined size regardless of the color of the first liquid. A voltage can be applied.

  For example, the first liquid is colored in any one of the three primary colors of light, red, green, and blue. In addition, the first liquid is colored, for example, in one of complementary colors magenta, green, cyan, and yellow. The first liquid is, for example, an organic solvent.

  The solid-state imaging device of the present invention includes a liquid microlens device for each of a plurality of pixels. In the solid-state imaging device, it is preferable that the focal length of the light transmitted through the droplet is constant regardless of the color of the first liquid.

  The voltage application unit includes, for example, a capacitor. In this case, the capacitor is disposed, for example, in the vicinity of the cell for each pixel. Further, for example, the plurality of capacitors are arranged so as to be close to each other. The solid-state image sensor has a CMOS image sensor, for example.

  According to the present invention, it is possible to realize a color solid-state imaging device having a simple structure and good condensing rate and sensitivity.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a first embodiment of the invention will be described with reference to the drawings. FIG. 1 is a side sectional view schematically showing the structure of a pixel of a solid-state imaging device in the present embodiment. FIG. 2 is a diagram showing circuit diagrams of CMOS image sensors included in the solid-state imaging device.

  The solid-state imaging device 10 includes a liquid microlens device 20 and a CMOS image sensor 40. The liquid microlens device 20 and the CMOS image sensor 40 are provided for each of a large number of pixels of the solid-state imaging device 10. FIG. 1 shows a liquid microlens device 20 and a CMOS image sensor 40 for one pixel included in the solid-state imaging device 10.

  The liquid microlens device 20 is provided with a light transmissive cell 26 including a conductive upper surface member 22 and a lower surface member 24. The cell 26 is filled with an insulating liquid 28 (first liquid) and a conductive liquid 30 (second liquid), both of which are light transmissive. Since the insulating liquid 28 is hydrophobic, the conductive liquid 30 is hydrophilic and the polarities of the two are greatly different. Therefore, the insulating liquid 28 and the conductive liquid 30 are not mixed. Are separated from each other.

  The inner wall surface 24S of the lower surface member 24 is covered with an insulating film (not shown). For this reason, the insulating liquid 28 has a higher affinity with the lower surface member 24 than the conductive liquid 30. On the other hand, the affinity between the insulating liquid 28 and the conductive surface layer 32 covering a part of the lower member inner wall surface 24 </ b> S is lower than the affinity between the conductive liquid 30 and the surface layer 32. From the above, the insulating liquid 28 forms droplets along the lower surface member 24. And since the area | region which is not covered with the surface layer 32 among the lower surface member inner wall surfaces 24S is circular, the droplet of the insulating liquid 28 is a dome shape with a circular bottom face. The insulating liquid 28 is colored in any one of red, green, and blue, and the liquid microlens device 20 collects the transmitted light on the photodiode 42 of the CMOS image sensor 40. Function as.

  An electrode 34 is provided along the outer wall surface 24R of the lower surface member 24, and the upper surface member 22 itself functions as an electrode. Further, a capacitor 36 for accumulating charges from an external power source (not shown) is connected between the electrode 34 and the upper surface member 22, and a voltage is applied between the electrode 34 and the conductive liquid 30. It is possible to apply. When a voltage is applied between the electrode 34 and the conductive liquid 30 via the upper surface member 22 and the lower surface member 24, the shape of the insulating liquid 28 is flat in a state where the voltage indicated by the solid line is not applied. As shown by the broken line, the shape changes to a mountain shape with a raised center. An aluminum light shielding layer 38 for preventing smear is provided under the electrode 34.

  The shape of the insulating liquid 28 changes between a flat shape indicated by a solid line and a mountain shape indicated by a broken line according to the amount of voltage applied. In the liquid microlens device 20, the focal length of light transmitted through the droplet can be adjusted to a predetermined size by changing the shape of the droplet in this way. This is because the focal length of the light transmitted through the flat droplet of the insulating liquid 28 is longer than the focal length of the light transmitted through the mountain-shaped droplet of the same insulating liquid 28.

  Here, the shape of the insulating liquid included in each of a large number of pixels provided in the solid-state imaging device 10 including the insulating liquid 28 is determined so that the focal length of the transmitted light is constant. In other words, the insulating liquid is colored in any of red, green, and blue, and the focal length of the light that has passed through the same droplet in the order of red, green, and blue is increased. The applied voltage amount is set so that the droplets of the insulating liquid are flattened in the order of green and blue, and the radius of curvature is reduced. Furthermore, since the refractive index of light that is transmitted also varies depending on the material of the insulating liquid, the amount of applied voltage depends on the color of the insulating liquid, that is, the wavelength of the light that passes through the insulating liquid, and for each attached color. The focal length is adjusted to be constant by changing the shape (curvature radius) of the insulating liquid according to different materials of the insulating liquid.

  In this way, the amount of voltage to be applied is adjusted according to the color and material of the insulating liquid, and the shape of the liquid droplets is determined, so that all the pixels included in the solid-state imaging device 10 transmit the insulating liquid 28. The focal length of the light is constant. For this reason, it is not necessary to adjust the distance between the liquid microlens device 20 and the CMOS image sensor 40 according to the color of the insulating liquid, and the liquid microlens device 20 and the CMOS image sensor 40 in all the pixels. The structure can be the same. Therefore, the structure of the solid-state image sensor 10 is simplified.

  The CMOS image sensor 40 is general-purpose, and an electric signal generated by the photodiode 42 is amplified by the amplifying unit 44 and transmitted through the vertical signal line 50 or the first and second horizontal signal lines 52 and 54. (See FIG. 2). The electric signal is transmitted while being reset by the reset unit 46 at a predetermined timing, and the signal line to be transmitted is switched between the vertical signal line 50 and the horizontal signal lines 52 and 54 by the changeover switch 48. The capacitor 36 is disposed in the vicinity of the cell 26 for each pixel of the solid-state imaging device 10 as shown in FIGS. 1 and 2.

  FIG. 3 is a top view schematically showing the solid-state imaging device 10 including the insulating liquid 28 colored in red, green, or blue. FIG. 4 is a top view schematically showing the solid-state imaging device 10 including the insulating liquid 28 colored in any one of magenta, green, cyan, and yellow.

  When the liquid microlens device 20 is used as a colored microlens having a primary color filter function, the insulating liquid 28 is colored in any one of red, green, and blue. For example, as shown in FIG. A color array is defined. On the other hand, when the function as a complementary color filter is provided, the insulating liquid 28 is colored in any one of magenta, green, cyan, and yellow, and the color arrangement of each pixel is determined as shown in FIG. 4, for example.

  Even when the insulating liquid 28 is colored in one of the complementary colors magenta, green, cyan, or yellow, as in the case where it is colored in any of the three primary colors red, green, or blue, In consideration of the focal length characteristics that are different among the microlenses of the respective colors, the electrodes 34 are set so that the focal length of the light transmitted through the insulating liquid is constant in all the liquid microlens devices 20 included in the solid-state imaging device 10. And the amount of voltage applied between the conductive liquid 30 and the conductive liquid 30 are determined.

  FIG. 5 is a diagram illustrating a manufacturing process of the liquid microlens device 20.

  The liquid microlens device 20 is manufactured as follows. First, among the members constituting the cell 26, the upper surface member 22 and the side surface member 23 are fixed with an adhesive so as to form a cell intermediate 27 that is a part of the outer frame of the cell 26. Then, the conductive liquid 30 is injected into the concave portion of the cell intermediate body 27. Thereafter, a predetermined amount of insulating liquid 28 for forming droplets of appropriate size is injected into the recesses of the cell intermediate 27 so that the lower surface member 24 seals the insulating liquid 28 and the conductive liquid 30. And attached to the cell intermediate 27 (see FIG. 5). When the cell 26 is thus completed, the electrode 34, the capacitor 36, the light shielding layer 38, and the like are arranged at predetermined positions, and the liquid microlens device 20 is completed.

  A gelling agent is added to the conductive liquid 30 so as to have a predetermined viscosity. Further, as the insulating liquid 28, for example, an organic solvent such as diethyl phthalate, methyl benzoate, or isobutane is used. An organic azo pigment or the like is used as a colorant for coloring the insulating liquid 28, and a pH adjusting agent is further added to the insulating liquid 28 in order to stabilize the color.

  As described above, according to the present embodiment, since a color filter is not required and the distance from the liquid microlens device 20 to the photodiode 42 is short, the light collection rate and the sensitivity are excellent, and the color according to the attached color. Since the shape of the droplet of the insulating liquid 28 can be adjusted, the solid-state imaging device 10 having a simple structure can be realized.

  FIG. 6 is a diagram schematically showing the arrangement of the capacitors 36 of the solid-state imaging device 10 according to the second embodiment.

  This embodiment is different from the first embodiment in that a large number of capacitors 36 provided for supplying a voltage to the liquid microlens device 20 are arranged so as to be close to each other. In this way, by arranging a large number of capacitors 36 at the end of the solid-state imaging device 10 or the like, the structure of the solid-state imaging device 10 can be further simplified.

  In any of the embodiments, the image sensor provided in the solid-state imaging device 10 is preferably the CMOS image sensor 40 that can be easily applied when a voltage is applied using the capacitor 36, but is not limited thereto. For example, the image sensor may be a CCD image sensor.

  In any embodiment, the conductive liquid 30 may be colored in a predetermined color instead of the insulating liquid 28. Furthermore, both the insulating liquid 28 and the conductive liquid 30 may be colored in a predetermined color.

It is a sectional side view which shows roughly the structure of the pixel of the solid-state image sensor in 1st Embodiment. It is a figure which shows the CMOS image sensor contained in a solid-state image sensor with a circuit symbol. It is a top view which shows roughly the solid-state image sensor containing the insulating liquid colored in red, green, and blue. It is a top view which shows roughly the solid-state image sensor containing the insulating liquid colored magenta, green, cyan, and yellow. It is a figure which shows the manufacturing process of a liquid microlens apparatus. It is a figure which shows roughly arrangement | positioning of the capacitor | condenser of the solid-state image sensor in 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Solid-state image sensor 20 Liquid microlens apparatus 26 Cell 28 Insulating liquid (1st liquid)
30 Conductive liquid (second liquid)
34 electrodes 36 capacitors (voltage application means)
40 CMOS image sensor

Claims (10)

A transparent cell;
An insulative colored first liquid forming a droplet for condensing the transmitted light in the cell;
A conductive and permeable second liquid filled inside the cell in a state separated from the first liquid;
Electrodes provided along the outer wall surface of the cell;
Voltage applying means for applying a voltage between the second liquid and the electrode to change the shape of the droplet;
The voltage applying means can apply a voltage for changing the shape of the droplet so that the focal length of the light transmitted through the droplet becomes a predetermined size regardless of the color of the first liquid. A liquid microlens device characterized by the above.   The liquid microlens device according to claim 1, wherein the first liquid is colored in any one of red, green, and blue.   2. The liquid microlens device according to claim 1, wherein the first liquid is colored in any one of magenta, green, cyan, and yellow.   The liquid microlens device according to claim 1, wherein the first liquid is an organic solvent.   A solid-state imaging device comprising the liquid microlens device according to claim 1 for each of a plurality of pixels.   The solid-state imaging device according to claim 5, wherein a focal length of light transmitted through the droplet is constant regardless of a color of the first liquid.   The solid-state imaging device according to claim 5, wherein the voltage applying unit includes a capacitor.   The solid-state imaging device according to claim 7, wherein the capacitor is disposed in the vicinity of the cell for each pixel.   The solid-state imaging device according to claim 7, wherein the plurality of capacitors are arranged so as to be close to each other. The solid-state imaging device according to claim 5, further comprising a CMOS image sensor.

Images