JP2005175234A - Imaging device and optical apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging device in which the utilization efficiency of incident light is raised even when the pupil position of a photographing lens is changed large, and to provide an optical apparatus. <P>SOLUTION: The imaging device includes a high refractive index part (5) covering at least part of a plurality of photoelectric converters 3 arranged in one-dimensional or two-dimensional manner, and a low refractive index part (7) provided on the periphery of the high refractive index part (5). The interface between the high refractive index part (5) and the low refractive index pard (7) has a surface substantially parallel to the optical axis of the photographing lens and an oblique surface having an angle different from the parallel surface. The oblique surface is provided at the side near the optical axis of the photographing lens at the incident side when the light beam from the photographing lens is transmitted. The optical apparatus with the photographing lens and the imaging device is provided in which the pupil distance from the imaging device is 10 mm or less, and a micro optical apparatus can incorporate the light beam without waste even if the pupil position of the photographing lens is changed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an internal structure of an image sensor for capturing a subject image and an optical apparatus including the image sensor.

  In order to improve the efficiency of capturing light rays incident on the image sensor, there has been proposed one employing a structure as described in Patent Document 1. As shown in FIG. 7, the structure described in Patent Document 1 includes a first microlens 21 and a second microlens 2 on the surface of an image sensor, and includes a pixel in the vicinity of the optical axis of a photographing lens. A pixel (peripheral part of the chip) existing at a distant place is described. The first microlens 21 is an in-layer lens in which the first lens molding film 12 provided on the color filter film 11 is processed to form a convex lens in the upper part, and the second microlens 2 is the first microlens 2. The two-lens molding film 13 is processed into a lens shape. The incident light L collected by the second microlens 2 enters the first microlens 21 (intralayer lens), and further receives a condensing action and is guided to the photoelectric conversion unit 3. At that time, the first and second microlenses are shifted in the center direction by t1 and t2 as the pixels face the peripheral portion 1a of the chip, respectively, so that the efficiency of capturing light rays is not lowered at the periphery.

Patent Document 2 describes a structure for efficiently guiding light incident on an image sensor to a photoelectric conversion unit. The structure based on the form described in Patent Document 2 is shown in FIG. Reference numeral 15 denotes a cap layer made of resin, which is formed of a material having a refractive index of about 1.6. Reference numeral 14 denotes a low refractive index layer, which is formed in a hollow filled with a resin having a lower refractive index than the cap layer 15 and an inert gas such as air or nitrogen. The microlens 2 is formed after the surface is flattened by providing the flattening layer 16 thereon. The light beam traveling from the cap layer 15 toward the low refractive index layer 14 is totally reflected at the interface when exceeding the critical angle, so that the oblique incident light 42 is totally reflected and led to the photoelectric conversion unit 3.
JP-A-10-229180 Japanese Patent Laid-Open No. 06-224398

  However, the conventional example has the following problems as shown in FIGS. FIG. 9 shows a state where a photographing lens group 202 with a variable focal length is attached to the image sensor 201, where (a) shows a wide-angle state and (b) shows a telephoto state. Here, it is assumed that the image sensor 201 is provided with a microlens on the surface of an image sensor that is often used in the past, and that there is no in-layer lens. When the photographic lens group 202 changes from the wide-angle position to the telephoto position, the pupil position of the photographic lens group 202 changes from T1 to T2. When viewed from the image sensor 201, all light rays that enter the image sensor 201 through the lens can be regarded as being emitted from the pupil position. FIG. 10 schematically shows a relationship in which the light beam emitted from the pupil of the lens reaches the image sensor. When a light beam incident from the wide-angle pupil position reaches a photoelectric conversion unit 3 in a pixel located below the imaging region 101 that captures the subject image through the photographing lens group 202, an image 17 as shown in FIG. FIG. 11 is a view of one pixel as viewed from above, and the center of the optical axis of the photographing lens is located obliquely upward to the right of the drawing. At this time, the microlens provided on the imaging element is arranged slightly shifted in the optical axis direction of the photographing lens so that an image of a pupil is generated on the photoelectric conversion unit 3 provided on the silicon wafer 1. . The Poly-Si wiring layer 8 for switching the electric charge generated in the photoelectric conversion unit 3 transmits a certain amount of light but absorbs many rays. Therefore, the pupil is basically avoided where the Poly-Si wiring layer 8 is avoided. The image 17 is formed.

  Therefore, when zooming to the telephoto side, the image 17 moves in the diagonal direction of the pixel as shown in FIG. In the pixel located in the lower part of FIG. 10, assuming that the angle formed by the light beam (chief ray) emitted from the center of the pupil and passing near the central axis of the microlens is the lens optical axis is the wide angle side θ1 and the telephoto side θ2, the incident angle difference θ = Θ1-θ2 generally tends to increase as the zoom ratio of the taking lens increases. The pupil diameter of the taking lens is determined by the brightness (F number) of the lens, and increases as the lens becomes brighter. For these reasons, when the zoom ratio is increased, the position of the pupil image generated in the photoelectric conversion unit 3 is greatly separated from the wide angle side and the telephoto side (incident angle difference is increased), and it protrudes from the photoelectric conversion unit during zooming. The AL wiring layer 9 may cause vignetting. In addition, when the lens becomes bright, a large image is generated in the photoelectric conversion unit, so that the light rays that hit the photoelectric conversion unit 3 may be further reduced. If it does so, it has the problem that the efficiency which takes in the light ray which entered in the pixel to a photoelectric conversion part falls extremely.

  If the pupil position does not change, that is, in the case of an optical device in which the focal length of the lens is fixed (single focal length lens) and the lens cannot be replaced, the pupil is shifted by a micro lens amount that is specific to the lens. The center of the image may be approximately the center of the photoelectric conversion unit. However, in the case of an optical apparatus in which the pupil position changes, such as a zoom lens or an interchangeable lens system, only the micro lens 2 is shifted for the reasons described above. Is not enough. This occurs similarly even in a structure having an intralayer lens (first microlens 21) as shown in FIG. In this case, there is a problem that the light beam collected by the microlens 2 does not enter the in-layer lens or is not guided to the photoelectric conversion unit even if it is incident, resulting in a loss.

  In the case of the structure as shown in FIG. 8, the incident side of the cap layer 15 having a high refractive index has a small R-arc shape. Therefore, when the angle of oblique incidence is increased, the light beam hitting the arc portion is not totally reflected and escapes. This causes problems such as entering another pixel.

  The present invention has been made in view of such conventional problems, and an object of the present invention is to provide an imaging device and an optical apparatus that improve the use efficiency of incident light even when the pupil position of the photographing lens varies greatly. The challenge is to provide

  In order to solve the above-described problem, the imaging device according to claim 1 includes a high refractive index portion that covers at least a part of a plurality of photoelectric conversion units arranged one-dimensionally or two-dimensionally, and the high refractive index portion. And an interface between the high refractive index portion and the low refractive index portion at an angle different from a plane substantially parallel to the optical axis of the photographing lens and the substantially parallel surface. The tilted surface is provided on the incident side when light rays from the photographic lens are transmitted and on the surface close to the optical axis of the photographic lens, so that the pupil position of the photographic lens varies. However, it is possible to capture light rays without waste.

  According to a second aspect of the present invention, in the image pickup device according to the first aspect, a desired structure can be easily formed by configuring the pixels so that the angle of the inclined surface is substantially the same regardless of the distance from the optical axis of the photographing lens. That's it.

  According to a third aspect of the present invention, in the imaging device according to the first or second aspect, the microlens includes a plurality of microlenses corresponding to a photoelectric conversion unit for condensing light rays from the outside, and the central axis of the microlens is a photographing lens. The structure of the high-refractive-index part can be easily manufactured without changing depending on the location by disposing it by different amounts on the optical axis side of the photographic lens with respect to the central axis of the photoelectric conversion part as it moves away from the optical axis It can be done.

  The optical device according to claim 4 is a low refractive index portion provided around a high refractive index portion that covers at least a part of a plurality of photoelectric conversion portions arranged one-dimensionally or two-dimensionally, and a low refractive index portion provided around the high refractive index portion. A refractive index portion, and an interface between the high refractive index portion and the low refractive index portion includes a surface substantially parallel to the optical axis of the photographing lens and an inclined surface having an angle different from the substantially parallel surface. An imaging element provided on the incident side when a light beam from the photographic lens is transmitted and near the optical axis of the photographic lens, and a photographic lens having a pupil distance from the imaging element of 10 mm or less. It is possible to realize an ultra-compact optical device.

  Furthermore, the optical apparatus according to claim 5 is provided in a periphery of the high refractive index portion and a high refractive index portion that covers at least a part of the plurality of photoelectric conversion units arranged one-dimensionally or two-dimensionally. A low-refractive-index part, and an interface between the high-refractive-index part and the low-refractive-index part is a plane substantially parallel to the optical axis of the photographic lens, and an inclined surface having an angle different from the substantially parallel plane. The inclined surface has an imaging element provided on the incident side when light rays from the photographic lens are transmitted and on the surface close to the optical axis of the photographic lens, and a pupil distance and a shortest focal distance at the longest focal length. By providing a photographic lens with a variable focal length that is 2 or more in terms of the pupil distance, an ultra-compact optical device with a variable focal length can be realized.

  According to the present invention, the imaging device according to claim 1 includes a high refractive index portion covering at least a part of a plurality of photoelectric conversion units arranged one-dimensionally or two-dimensionally, and a periphery of the high refractive index portion. The interface between the high refractive index portion and the low refractive index portion has an angle different from the plane substantially parallel to the optical axis of the photographing lens and the plane parallel to the optical axis of the photographing lens. An inclined surface, and the inclined surface is provided on the incident side when the light beam from the photographing lens is transmitted and close to the optical axis of the photographing lens, so that it is highly resistant to fluctuations in the pupil position of the photographing lens. It has become possible to capture light efficiently even with a zoom lens or interchangeable lens with a magnification.

  Further, in the image pickup device according to claim 1, by configuring the angle of the inclined surface to be substantially the same regardless of the distance from the optical axis of the photographing lens, the structure of the high refractive index portion can be simplified and the structure can be easily created. It was.

  The image pickup device according to claim 1 or 2, further comprising a plurality of microlenses corresponding to a photoelectric conversion unit for condensing light rays from the outside, wherein the center axis of the microlens is separated from the optical axis of the photographing lens. By disposing different amounts on the optical axis side of the photographic lens with respect to the central axis of the photoelectric conversion part, it has become possible to easily manufacture the structure of the high refractive index part without changing depending on the location. .

  In the optical device according to claim 4, a high refractive index portion that covers at least a part of a plurality of photoelectric conversion portions arranged one-dimensionally or two-dimensionally, and a low refractive index portion provided around the high refractive index portion. A refractive index portion, and an interface between the high refractive index portion and the low refractive index portion includes a surface substantially parallel to the optical axis of the photographing lens and an inclined surface having an angle different from the substantially parallel surface. An imaging element provided on the incident side when a light beam from the photographic lens is transmitted and near the optical axis of the photographic lens, and a photographic lens having a pupil distance from the imaging element of 10 mm or less. It became possible to realize an ultra-compact optical instrument.

  Furthermore, in the optical device according to claim 5, the high refractive index portion covering at least a part of the plurality of photoelectric conversion portions arranged one-dimensionally or two-dimensionally, and provided around the high refractive index portion. A low-refractive-index part, and an interface between the high-refractive-index part and the low-refractive-index part is a plane substantially parallel to the optical axis of the photographic lens, and an inclined surface having an angle different from the substantially parallel plane. The inclined surface has an imaging element provided on the incident side when light rays from the photographic lens are transmitted and on the surface close to the optical axis of the photographic lens, and a pupil distance and a shortest focal distance at the longest focal length. It is possible to realize an ultra-compact optical apparatus having a variable focal length by including a photographing lens having a variable focal length that is 2 or more in terms of the pupil distance.

  Examples of the present invention will be described below.

  FIG. 1 is a cross-sectional view of an image pickup device. 1 is a silicon wafer, 2 is a microlens, 3 is a photoelectric conversion unit having a function of converting received photons into electric charges, and 4 is a wavelength selection unit for wavelength-separating light rays. These are color filters, 5 is a high refractive index portion, 6 is a passivation film provided to protect the photoelectric conversion portion, 7 is a low refractive index portion, and 8 is a gate that controls the charge of the photoelectric conversion portion. Poly wiring layer 9 is a wiring layer made of metal such as aluminum.

  In FIG. 1, the microlens 2 has an upward convex spherical shape and has positive lens power. Therefore, the light beam that has reached the microlens 2 has a function of focusing on the photoelectric conversion unit 3. Thereby, since a wider range of light rays can be taken into the photoelectric conversion unit 3, the sensitivity of the imaging element can be increased. The high refractive index portion 5 is formed of a high refractive index material such as titanium dioxide (TiO2) having a refractive index of 2.5 or silicon nitride (SiN) having a refractive index of 2.0, and the low refractive index portion 7 is formed of a refractive index of 1. Molded using a low refractive index material such as .46 silicon dioxide (SiO2). The passivation film 6 is often made of silicon oxynitride (SiON) having a refractive index of about 1.6. As a result, the light incident on the high refractive index portion 5 is totally reflected at the interface between the passivation film 6 and the low refractive index portion 7, so that the light rays exceeding the critical angle are totally reflected from the color filter 4 to the photoelectric conversion portion 3. To act as a light guide. FIG. 2 shows only the high refractive index portion 5 taken out for easy understanding of the shape. The high refractive index portion 5 is a portion near the photoelectric conversion portion 3 and has a prism portion 51 having a surface substantially parallel to the optical axis, and a tapered portion that exists on the incident side of the light beam and is an inclined surface having an angle different from that of the prism portion 51. 52. When viewed from the upper surface (microlens side), the prism portion 51 has a substantially square shape, and there are four surfaces parallel to the optical axis. Similarly, when viewed from above, the tapered portion 52 has a substantially square shape, but the size of the tapered portion 52 differs depending on the cut height. In FIG. 1, the optical axis of the photographing lens is present on the right side of the high refractive index portion 5, and the shape of the tapered portion 52 is tapered only on the surface close to the optical axis of the photographing lens, and the surface on the far side is a prism portion. The surface has the same angle as 51 (parallel to the optical axis). That is, the two surfaces close to the optical axis of the photographic lens are tapered, but the two distant surfaces have a surface parallel to the optical axis continuing from the prism portion 51. FIG. 3 shows how the taper is attached when the high refractive index portion 5 is viewed from the upper part (microlens side) of the imaging region 101. For the sake of simplicity, this figure shows only the pixels near the center of the optical axis of the photographing lens and the pixels at the four corners (diagonal portions). Since the taper is formed only on the surface close to the optical axis of the photographing lens, the direction of the taper is different in four quadrants with the center of the imaging element (the optical axis center of the photographing lens) as the origin. The first quadrant pixel 100amn has a lower left corner, the second quadrant pixel 100bmn has a lower right corner, the third quadrant pixel 100cmn has an upper right corner, and the fourth quadrant pixel 100amn has an upper left taper. Is the same for every quadrant. As a method for forming the high refractive index portion 5, the low refractive index portion 7 and the passivation film 6 are formed flat, a resist is applied thereon, etching is performed, and a hole is formed to the vicinity of the photoelectric conversion portion 3. Thereafter, a material (SiN) for the high refractive index portion 5 is deposited. Further, the tapered portion can be formed in a desired shape by controlling the etching conditions when forming the hole. If the etching conditions change, the taper angle may change or the desired shape may not be obtained, so it is not necessary to change the conditions depending on the location as long as the structure has the same taper angle as in this configuration. be able to.

  Next, the behavior of light rays in the image sensor in this structure will be described with reference to FIGS. FIG. 4 shows light rays incident on a pixel existing in the vicinity of the optical axis of the photographing lens. As can be seen from this figure, it can be seen that the microlens 2 is displaced from the central axis of the photoelectric conversion unit 3 toward the optical axis side of the photographing lens even though it is near the center. Usually, the center axis of the microlens of the pixel existing in the vicinity of the optical axis of the photographing lens is arranged so as to substantially coincide with the center axis of the photoelectric conversion unit. In the case of this configuration, a structure is adopted in which a taper is provided only on a surface where the incident side of the high refractive index portion 5 is close to the optical axis of the photographing lens, and the structure is the same for pixels near the optical axis of the photographing lens. Therefore, since the opening center on the incident side of the high refractive index portion 5 is shifted from the central axis of the photoelectric conversion portion 3 in the optical axis direction of the photographic lens, the high refractive index portion 5 is symmetrical by shifting the microlens 2. Even if it is not, light can enter without vignetting at the entrance, and efficiency is not reduced. Further, since the incident light can be narrowed by providing the microlens 2 as in this configuration, the light can be sufficiently captured even if the incident-side opening of the high refractive index portion 5 is smaller than the pixel opening. When the microlens 2 is not provided, it is desirable that the opening on the incident side of the high refractive index portion 5 is substantially the same as the pixel opening.

  Next, FIGS. 5 and 6 show light rays incident on a pixel located at a position away from the optical axis of the photographing lens. FIG. 5 shows a short distance (for example, a pupil distance on the wide-angle side where the focal length of the photographing lens is short). FIG. 9A shows a case where the photographing lens has a long focal length and a pupil distance is long (for example, T2 = 20 mm in FIG. 9B). Since the distance from the optical axis of the photographing lens is large, the shift amount of the microlens 2 is large, and the color filter 4 is also slightly shifted so that the light beam can be captured well. When the focal length of the photographic lens is short and the pupil distance is short, the incident light beam 41 is totally reflected by a surface (a surface parallel to the optical axis) far from the optical axis of the photographic lens in the high refractive index portion 5 and a photoelectric conversion unit. It can be seen that it uses a fairly high surface.

  FIG. 6 shows a light beam when the focal length of the taking lens is increased and the pupil distance becomes long. When the pupil distance is long, the total reflection at the interface is not used much, unlike when the pupil distance is close. In this regard, it is similar to a pixel in the vicinity of the optical axis of the photographic lens, but the position incident on the high refractive index portion 5 is different. What is important at this time is a portion on the incident side of the high refractive index portion 5. As described above, the incident light beam is shifted in the optical axis direction of the photographing lens, but since the taper is provided on the optical axis side of the photographing lens, the light beam emitted from the color filter 4 is directly incident on the high refractive index portion 5. Yes. If there is no taper, it first enters the low refractive index portion 6 and then moves toward the high refractive index portion 5. As a result, the opposite surface (the surface far from the optical axis of the photographic lens) cannot be totally reflected and transmitted, and cannot enter the photoelectric conversion unit 3, resulting in a loss.

  As described above, the shape of the high refractive index portion 5 is tapered only on the light incident side and the surface closer to the optical axis of the photographing lens. It is possible to obtain an image sensor that does not drop the image.

  Therefore, since the imaging device of the first embodiment has a large redundancy of the angle of view of the incident light to the imaging device, a photographing lens with a short focal length and a short pupil distance or a variable focal length photographing lens with a large zoom ratio is used. For example, a photographing lens with the shortest pupil distance T1 ≦ 10 mm, or a ratio T2 / T1 of the pupil distance T2 when the focal distance of the photographing lens is long and the pupil distance T1 when the focal distance is short. However, even with two or more lens configurations, it is possible to provide an optical device with high light receiving efficiency, so that an ultra-compact optical device can be realized.

It is a figure showing Example 1 which concerns on this invention. It is a perspective view which shows the high refractive index part of Example 1 which concerns on this invention. It is the figure which looked at the high refractive index part of Example 1 which concerns on this invention from the upper direction. It is a light ray trace figure of the photographic lens optical axis vicinity pixel. Ray tracing diagram of pixels away from the optical axis of the taking lens (when pupil distance is short) Ray tracing diagram of pixels away from the optical axis of the taking lens (when pupil distance is far) A diagram showing a conventional configuration The figure showing another conventional form Figure when the zoom lens is applied to the image sensor Schematic diagram showing the relationship between pupil position and image sensor The figure which shows the image of the pupil when a pupil is a short distance The figure which shows the image of the pupil when a pupil is a long distance

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Silicon wafer 2 ... Micro lens 3 ... Photoelectric conversion part 4 ... Color filter 5 ... High refractive index part 51 ... Square column part 52 ... Taper part 6 ... Passivation film 7 ... Low refractive index part 8 ... Poly wiring layer 9 ... wiring layer 10 ... flattening film 11 ... color filter film 12 ... first lens molding film 13 ... second lens molding film 14 ... cap layer 15 ... micro lens support Layer 15... Low refractive index layer 17... Color filter 21... First microlens 22... Second microlenses 40, 41, 42.
100 ... Pixel 100 amn ... First quadrant pixel 100 bmn ... Second quadrant pixel 100 cmn ... Third quadrant pixel 100 dmn ... Fourth quadrant pixel 101 ... Imaging area 201 ... Imaging element 202 ... Shooting lens group

Claims (5)

A high refractive index portion that covers at least a part of a plurality of photoelectric conversion portions arranged one-dimensionally or two-dimensionally, and a low refractive index portion provided around the high refractive index portion,
The interface between the high refractive index portion and the low refractive index portion has a surface substantially parallel to the optical axis of the photographic lens and an inclined surface having an angle different from the substantially parallel surface;
The imaging device according to claim 1, wherein the inclined surface is provided on an incident side when a light beam from the photographing lens is transmitted and on a surface near the optical axis of the photographing lens.   2. The imaging device according to claim 1, wherein the angle of the inclined surface is substantially the same for all pixels regardless of the distance from the optical axis of the photographing lens. In the imaging device according to claim 1 or 2, comprising a plurality of microlenses corresponding to the photoelectric conversion unit for condensing light from the outside,
The image pickup device, wherein the center axis of the microlens is arranged so as to be shifted by a different amount toward the optical axis side of the photographing lens with respect to the central axis of the photoelectric conversion unit as the distance from the optical axis of the photographing lens increases.   4. An optical apparatus comprising the imaging device according to claim 1, wherein an imaging lens having a pupil distance from the imaging element of 10 mm or less is provided.   5. The optical apparatus according to claim 4, wherein the photographing lens has a variable focal length, and a ratio of a pupil distance at the longest focal length to a pupil distance at the shortest focal length is 2 or more. Optical equipment.

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