JP2012028372A - Solid-state image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-sensitive solid-state image pickup device having high utilization efficiency of incident light.SOLUTION: A solid-state image pickup device has at least a condenser lens (A) for condensing incident light, a parallel conversion lens (B) for converting condensed light to parallel light and a prism (C) for spectroscopically dividing the parallel light. A plurality of photoelectric conversion elements are arranged so that the respective spectroscopic light components spectroscopically divided by (C) are incident to a plurality of the photoelectric conversion elements respectively, and (A), (B), (C) and the photoelectric conversion elements are successively constructed in close contact with one another. The surface at the light incident side of (A) has a convex curved surface at the light incident side, the interface between (A) and (B) has a concave curved surface at the light incident side, and the interface between (B) and (C) has a sloped flat plane. The refractive index of (A) is smallest among (A), (B) and (C), and the refractive index of (C) is largest among (A), (B) and (C).

Description

  The present invention relates to a solid-state imaging device. More particularly, the present invention relates to a solid-state imaging device having a color separating optical system in a pixel.

  In recent years, digital cameras that convert a captured image captured using a solid-state imaging device such as a CCD into digital image data and record it on a recording medium such as a built-in memory or a memory card have become widespread. In a solid-state imaging device such as that provided in this digital camera, a color filter that transmits any of red, green, and blue light is provided on the upper surface of a semiconductor substrate in which light receiving elements (photodiodes) are arranged in a matrix. The incident light from the photographic lens optical system is collected by a microlens provided above the color filter, passes through the color filter, and is received by each light receiving element.

Recently, as the solid-state imaging device is miniaturized and the number of pixels is increased, the area of the aperture through which incident light passes to the light receiving device is decreasing. As a result, the light-collecting efficiency to the light-receiving element is insufficient only with the conventional microlens, and therefore a solid-state imaging device having a configuration for increasing the light-collecting efficiency to the light-receiving element has been proposed ( For example, see Patent Document 1).
In the solid-state imaging device described in Patent Document 1, a microlens, a color filter, a waveguide, and a light receiving element are formed in order from the light incident side, and light is guided to the light receiving element through the waveguide and collected. We are trying to improve the light efficiency.

JP 2006-185947 A

However, even if the light condensing effect is enhanced by the waveguide, the method of mounting a color filter in front of the light receiving element can theoretically obtain only 1/3 of the total amount of incident light, and the sensitivity is low. was there.
It is an object of the present invention to provide a high-sensitivity solid-state imaging device with improved incident light utilization efficiency.

 As a result of intensive studies in view of the above problems, the present inventors have reached the present invention. That is, the present invention includes a solid-state imaging device in which a plurality of color separation optical systems and a plurality of photoelectric conversion elements that photoelectrically convert spectral light split by the color separation optical system are arranged in a plane, and the plurality of colors The resolving optical system includes at least a condensing lens (A) that condenses incident light, a parallel conversion lens (B) that converts the condensing light collected by (A) into parallel light, and (B) The plurality of photoelectric conversion elements includes a prism (C) that splits the parallel light converted by the step (C), and the spectral lights separated by the (C) are incident on the plurality of different photoelectric conversion elements. (A), (B), (C), and the photoelectric conversion element are arranged in close contact with each other, and the surface on the incident light side of (A) is a convex curved surface on the incident light side. The interface between (A) and (B) has a concave curved surface on the incident light side. And the interface between (B) and (C) has an inclined plane, and the refractive index of (A) is the smallest among (A), (B), and (C). The solid-state imaging device is characterized in that the refractive index of (C) is the highest among (A), (B) and (C).

  According to the present invention, since a solid-state imaging device having a color separation optical system in a pixel can be configured, it is possible to realize a solid-state imaging device with high incident light utilization efficiency and high sensitivity. In addition, a color separation optical system using a combination of a lens and a prism can be realized, and an electric signal corresponding to the intensity of each spectral color and each spectral color can be generated by a single pixel of the image sensor, so that faithful color reproduction is possible. Become. In addition, since the condenser lens (A), the parallel conversion lens (B), the prism (C), and the photoelectric conversion element are in close contact with each other, a compact solid-state imaging device can be obtained.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of a solid-state imaging device for one pixel for carrying out one embodiment of the present invention.
In FIG. 1, reference numeral 100 denotes one pixel of the solid-state imaging device. Reference numeral 101 denotes a light beam on which light from the subject is imaged on the solid-state imaging device 100.

  Reference numeral 102 denotes a condenser lens (A). The surface on the incident light side of the condenser lens (A) has a convex curved surface on the incident light side. In this embodiment, the condenser lens (A) has a lateral width of 3 μm, a refractive index n1 of 1.3, a focal length F1 of 3 μm, and is made of a fluorine resin. The material of the condensing lens (A) is not limited to fluorine-based resin, but it is preferable that the condensing lens (A) is made of a material having a low refractive index comparable to this.

  Reference numeral 103 denotes a parallel conversion lens (B). The parallel conversion lens (B) has a concave curved surface on the incident light side at the boundary surface with the condenser lens (A). In this embodiment, the parallel conversion lens (B) has a lateral width of 3 μm, a refractive index n2 of 1.5, a focal length F2 of 3 μm, and is made of polymethyl methacrylate. The material of the parallel conversion lens (B) is not limited to polymethyl methacrylate, and is composed of the same material as that of a general optical lens. However, since the condensed light collected by the condenser lens (A) is converted into parallel light by the parallel conversion lens (B), the refractive index of the parallel conversion lens (B) is the refractive index of the condenser lens (A). It needs to be bigger. The optical axis of the parallel conversion lens (B) needs to coincide with the optical axis of the condenser lens (A). In this embodiment, the distance from the concave surface (B) on the optical axis of the parallel conversion lens (B) to the inclined surface 106 of the prism (C) described later is set to 1 μm.

Reference numeral 105 denotes a prism (C). The prism (C) has a flat surface (inclined surface 106) inclined at the boundary with the parallel conversion lens (B). In this embodiment, the refractive index n3 is 1.7 and the material is episulfide resin. The material of the prism (C) is not limited to episulfide resin, and can be made of a material having a high refractive index such as thiourethane resin. However, since the parallel light from the parallel conversion lens (B) is split by the prism (C), the refractive index of the prism (C) needs to be larger than that of the parallel conversion lens (B).
Reference numeral 107 denotes a solid-state image sensor. In the solid-state imaging device, a plurality of photoelectric conversion elements that receive the spectral light split by the prism (C) are arranged on a plane.

In the present invention, an optical system including the condenser lens (A), the parallel conversion lens (B), and the prism (C) is referred to as a color separation optical system.
In the solid-state imaging device of the present invention, the condenser lens (A), the parallel conversion lens (B), the prism (C), and the solid-state imaging device are configured to be in close contact with each other in this order. A compact solid-state imaging device can be obtained by adopting an intimate configuration.

  The operation of the solid-state imaging device will be described. Incident light 101 from the subject enters the condenser lenses (A) and (102). If an image side telecentric lens is used that is far from the solid-state imaging surface, the incident light beam 101 is incident substantially parallel to the optical axis of the condenser lenses (A) and (102). The subject light incident on the condenser lenses (A) (102) is condensed on the focal point of the condenser lenses (A) (102). The condensed light beam is converted into a parallel light beam 104 by the parallel conversion lenses (B) and (103) disposed near the focal points of the condensing lenses (A) and (102), and is incident on the prism (C) (105).

  The parallel light beam 104 incident on the inclined surface 106 of the prism (C) is refracted according to the wavelength of the light and is incident on the solid-state image sensor 107. The parallel light beam 104 incident on the inclined surface 106 of the prism (C) includes red (wavelength: 600 to 700 nm), green (wavelength: 500 to 600 nm), and blue (wavelength: 400 to 500 nm) light. . Then, the parallel light beam 104 is incident on the inclined surface 106 inclined with respect to the optical axis, and refraction occurs here. However, long wavelength light is small in refraction, and short wavelength light is dispersed because refraction is large. . For example, in FIG. 1, red component light having a long wavelength is refracted to become red spectral light 108-1 and enters the red photoelectric conversion element 109-1. The green component light becomes green spectral light 108-2 and enters the green light photoelectric conversion element 109-2. Further, the blue component light becomes blue spectral light 108-3 and is incident on the blue light photoelectric conversion element 109-3. If an optical material having a small Abbe number is used for the prism (C), the spectrum for each wavelength can be efficiently performed.

  Here, the Abbe number indicates the inverse dispersion rate of light, and the Abbe number is larger as the optical material has less chromatic aberration. In the case of the present invention, on the contrary, a smaller Abbe number and a larger chromatic aberration can be efficiently dispersed and a good prism is obtained. Further, by appropriately adjusting the angle θ of the inclined surface 106, the distance from the inclined surface 106 to the solid-state imaging device 107, and the formation positions of the photoelectric conversion elements 109-1 to 109-3, the red spectral light 108-1 and the green spectral light 108. -2 and blue spectral light 108-3 can be incident on the red light photoelectric conversion element 109-1, the green light photoelectric conversion element 109-2 and the blue light photoelectric conversion element 109-3, respectively.

  With the configuration described above, light from a subject incident on one pixel is divided into, for example, red, green, and blue color components, and converted into video signals of each color by the photoelectric conversion elements 109-1 to 109-3. The solid-state image sensor 107 is taken out.

  Since the solid-state imaging device of the present invention does not require the use of a color filter as in the prior art, a solid-state imaging device with high incident light utilization efficiency and high resolution can be realized. The present invention can be applied to both MOS type and CCD type.

  In the above embodiment, the incident position on the prism (C) is set at the focal position of the parallel conversion lens (B), but the light beam from the parallel conversion lens (B) is a parallel light beam. The distance can be set as appropriate.

  As mentioned above, although one Example of this invention was described in detail, this invention is not limited to this.

It is a schematic block diagram of the solid-state imaging device for demonstrating one Example of this invention.

  DESCRIPTION OF SYMBOLS 100: Solid-state image sensor, 101: Incident light, 102: Condensing lens (A), 103: Parallel conversion lens (B), 104: Parallel light beam, 105: Prism (C), 106: Inclined surface of prism (C) 107: solid state imaging device, 108-1: red spectral light, 108-2: green spectral light, 108-3: blue spectral light, 109-1: red light receiving device, 109-2: green light receiving device, 109 -3: Blue light receiving element

Claims (1)

  A plurality of color separation optical systems, and a solid-state imaging device in which a plurality of photoelectric conversion elements that photoelectrically convert spectral light split by the color separation optical system are arranged in a planar shape, and the plurality of color separation optical systems are: A condensing lens (A) for condensing at least incident light, a parallel conversion lens (B) for converting the condensing light collected by (A) into parallel light, and the parallel converted by (B) The plurality of photoelectric conversion elements are arranged so as to have a prism (C) that splits light, and the respective spectral lights separated by (C) are incident on the different photoelectric conversion elements. A), (B), (C), and the photoelectric conversion element are in close contact with each other, the surface on the incident light side of (A) has a convex curved surface on the incident light side, The interface between (A) and (B) has a concave curved surface on the incident light side, and the (B) And the interface of (C) has an inclined plane, and the refractive index of (A) is the smallest among (A), (B) and (C), and A solid-state imaging device having a refractive index that is the highest among (A), (B), and (C).

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