Radiant energy – Photocells; circuits and apparatus – Photocell controlled circuit
Reexamination Certificate
1999-04-12
2001-06-26
Lee, John R. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Photocell controlled circuit
C250S214100, C257S432000
Reexamination Certificate
active
06252219
ABSTRACT:
BACKGROUND OF THE INVENTION
RELATED APPLICATION DATA
The present application claims priority to Japanese Application No. P10-104949 filed Apr. 15, 1998 which application is incorporated herein by reference to the extent permitted by law.
1. Field of the Invention
The present invention relates to a solid-state imaging element having a concave lens structure (interlayer lens) formed therein.
2. Description of the Related Art
In accordance with an increasing demand of miniaturizing an element, recent color solid-state imaging elements come to have a so-called on-chip lens structure in which a microlens is formed on the upper portion of the element and are able to improve sensitivity in a sensor (light-receiving portion) by focusing an incident light with this microlens.
Some solid-state imaging element having the above-mentioned on-chip lens structure further includes a second lens structure having a light condenser characteristic, i.e. interlayer lens formed between the microlens on the surface and the light-receiving portion.
As this interlayer lens structure, there are enumerated a concave lens structure in which a boundary surface between two layers having different refractive indexes is formed as a concave surface on which a concave lens is formed.
In a CCD (charge-coupled device) solid-state imaging element in which the interlayer lens mentioned above is formed, although the interlayer lens should preferably be shaped such that sensitivity may become maximum, lights having various incident angles become incident on the CCD solid-state imaging element depending upon a value of stop (F number) of a camera lens system.
When the F number is large, for example, the incident light is narrowed so that it becomes approximately a vertical light. At that time, a quantity of the incident light decreases.
When on the other hand the F number is small, the incident light is widened so that an oblique light component increases. At that time, a quantity of incident light increases.
However, when a light becomes incident on the curved surface of the interlayer lens from the oblique direction, depending upon its incident angle, the light is totally reflected on the concave surface of the interlayer lens and cannot reach the light-receiving portion. There is then the risk that an improvement of sensitivity becomes insufficient.
Also, with respect to the on-chip lens of the same shape, when the F number of the camera changes, a quantity of oblique light component changes so that sensitivity becomes different.
Therefore, in order to obtain the standards for determining a shape in which sensitivity may become maximum, trial products of interlayer lens have heretofore been manufactured and trial and error have been made.
Then, the optimum shape of interlayer lens capable of avoiding the aforementioned problems and which can sufficiently improve sensitivity has not been yet clarified up to now.
SUMMARY OF THE INVENTION
In view of the aforesaid aspect, it is an object of the present invention to provide a solid-state imaging element which can maximize sensitivity relative to a variety of light sources having different incident angles.
According to an aspect of the present invention, there is provided a solid-state imaging element in which a maximum inclination angle of a curved surface of an interlayer lens relative to a surface parallel to a substrate surface is set to an angle near a critical angle of a total reflection.
According to another aspect of the present invention, there is provided a solid-state imaging element which is comprised of a substrate, a light-receiving portion formed within the substrate, an interlayer insulator formed so as to have a concave portion above the light-receiving portion, and a high refractive index layer having a refractive index larger than that of the interlayer insulator formed so as to fill the concave portion, wherein a maximum inclination angle of a curved surface of the concave portion relative to a surface parallel to a surface of a substrate is an angle near a critical angle of a total reflection.
According to the arrangement of the present invention, since the maximum inclination angle of the curved surface of the interlayer lens is set to the angle near the critical angle of the total reflection, the inclination angle of the curved surface of the interlayer lens cannot exceed the critical angle of the total reflection at any portion so that an incident light can be prevented from being totally reflected on the curved surface of the interlayer lens and much more light can travel through this curved surface. Also, since the maximum inclination angle is in the proximity of the critical angle of the total reflection, focusing property of interlayer lens can be improved and much more light can be focused on the light-receiving portion.
According to other aspect of the present invention, in the solid-state imaging element, the angle near the critical angle of the total reflection is an angle which falls within a critical angle ±10° of the total reflection.
According to a further aspect of the present invention, in the solid-state imaging element, the maximum inclination angle of the curved surface of the interlayer lens is an angle near the critical angle of the total reflection in a cross-section of a short side direction of a sensor opening of a pixel.
REFERENCES:
patent: 5321297 (1994-06-01), Enomotto
patent: 5371397 (1994-12-01), Maegawa et al.
patent: 5633527 (1997-05-01), Lear
patent: 5691548 (1997-11-01), Akio
patent: 5711890 (1998-01-01), Hawkins et al.
patent: 5734190 (1998-03-01), Hawkins et al.
patent: 5796154 (1998-08-01), Sano et al.
patent: 6069350 (2000-05-01), Ohtsuka et al.
patent: 6104021 (2000-08-01), Ogawa
Lee John R.
Sonnenschein Nath & Rosenthal
Sony Corporation
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