Radiant energy – Photocells; circuits and apparatus – Photocell controlled circuit
Reexamination Certificate
2002-06-19
2003-06-10
Pyo, Kevin (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Photocell controlled circuit
C348S308000
Reexamination Certificate
active
06576882
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image sensor, and particularly to an MOS image sensor that extends the dynamic range with respect to the amount of incident light.
2. Description of the Related Art
In contrast to a CCD image sensor that requires a dedicated process, MOS image sensors, such as the sensor of the present invention, have received considerable attention in recent years because they can be fabricated by standard MOS processes and therefore enable the advantages of low power consumption by means of a low-voltage and single-power supply and because they allow incorporation of peripheral logic and macros on a single chip.
FIG. 1
shows an example of a prior-art method of extending the dynamic range with respect to the amound of light by O. Yadid-Pecht and E. Fossum as reported in “Wide Intrascene Dynamic Range CMOS APS Using Dual Sampling”, (IEEE Transactions on Electron Devices”, Vol. 44, No. 10, pp. 1721-1723 (October, 1997).
According to this prior-art example for extending the dynamic range with respect to amount of light, the signal charge of pixel
21
for row n and row (n−&Dgr;), which have different exposure times, is read out separately to each of first horizontal transfer register
22
above and second horizontal transfer register
23
below, and these are integrated off-chip.
The above-described method, however, results in an increase in circuit scale because it necessitates both upper and lower horizontal scan circuits. There is the additional drawback that system scale increases because the integration of two screens having different exposure times is realized by off-chip processing.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an image sensor that can realize an image having wider dynamic range with respect to the amount of light in which overexposure and underexposure are mitigated without an accompanying increase in circuit scale.
The first image sensor of the present invention is an image sensor that includes a semiconductor device having a semiconductor region and a diffusion layer formed within the semiconductor region having the opposite conductivity of the semiconductor region; that, after discharging carrier in the diffusion layer of the semiconductor device, causes light to be irradiated into the diffusion layer to generate carrier in the diffusion layer, outputs a signal to an output section based on the surface potential of the generated carrier, and measures the amount of incident light; and that includes:
a timing generation means for creating: a first exposure period for, when irradiating light into the diffusion layer and generating carrier inside the diffusion layer, irradiating the light into the diffusion layer and generating a first carrier inside the diffusion layer; a storage period after the first exposure period for moving the first carrier to a storage section; a second exposure period after the storage period for irradiating the light into the diffusion layer and generating a second carrier inside the diffusion layer; and a readout period after the second exposure period; and
a carrier integration means for, when outputting to an output section a signal based on the surface potential of carrier that is generated by the timing generation means and measuring the amount of incidence of light, integrating the first carrier and the second carrier in the readout period and reading out the integrated carrier.
Furthermore, in a first mode of application of the first image sensor; the operation of irradiating light into the diffusion layer during the first exposure period and generating the first carrier in the diffusion layer is carried out in a state in which the diffusion layer and storage section conduct, and the operation of moving the first carrier to the storage section during the storage period that follows the first exposure period is carried out in a state in which the diffusion layer and storage section are cut off. In addition, carrier in the first image sensor that is contained in the diffusion layer and storage section is discharged before the second exposure period by means of a reset transistor that is connected to the power supply.
In a second mode of application of the first image sensor of the present invention, the operation of irradiating light into the diffusion layer during the first exposure period and generating the first carrier in the diffusion layer is carried out in a state in which the diffusion layer and storage section are cut off, and the operation of moving the first carrier to the storage section during the storage period that follows the first exposure period is carried out in a state in which the diffusion layer and storage section conduct.
The second image sensor of the present invention is an image sensor that includes a semiconductor device having a semiconductor region and a diffusion layer formed inside the semiconductor region having the opposite conductivity of the semiconductor region; that, after discharging carrier in the diffusion layer of the semiconductor device, causes light to be irradiated into the diffusion layer to generate carrier in the diffusion layer, outputs a signal to an output section based on the surface potential of the generated carrier, and measures the amount of incident light; and that includes:
a timing generation means for creating: a first exposure period for, when irradiating light into the diffusion layer and generating a first carrier, irradiating the light into the diffusion layer and generating carrier in the diffusion layer; a storage period after the first exposure period for moving a portion of the first carrier to a storage section and leaving first carrier in the diffusion layer; a second exposure period after the storage period for irradiating light into the diffusion layer and generating the second carrier inside the diffusion layer, and a readout period after the second exposure period; and
a carrier integration means for, when outputting to an output section a signal based on the surface potential of the generated carrier and measuring the amount of incidence of light, reading out carrier that is the sum of the second carrier and the first carrier that is left in the diffusion layer during a readout period.
In the above-described first and second image sensors of the present invention, a modification is possible in which carrier that is contained in the diffusion layer and storage section is discharged before the first exposure period by means of a reset transistor that is connected to the power supply; the period that extends-from the first exposure period to the second exposure period is positioned within the preceding readout period; and the first exposure period is longer than the second exposure period.
The third image sensor, which expands on the first image sensor of the present invention, is an image sensor that includes: a semiconductor device having a semiconductor region and a diffusion layer formed inside the semiconductor region having the opposite conductivity, of the semiconductor region; that, after discharging carrier in the diffusion layer of the semiconductor device, causes light to be irradiated into the diffusion layer to generate carrier in the diffusion layer, outputs a signal to an output section based on the surface potential of the generated carrier, and measures the amount of incidence of light; including:
a timing generation means for creating: when irradiating light into the diffusion layer and generating carrier inside the diffusion layer, a plurality of exposure periods that do not mutually overlap for irradiating light into the diffusion layer and generating carriers that correspond to the plurality of exposure periods inside the diffusion layer; a storage period for moving a preceding carrier that was generated inside the diffusion layer, in the one preceding exposure period of the plurality of exposure periods that relatively preceded to a storage section after the preceding exposure period; a succeeding exposure period after t
Kurosawa Susumu
Muramatsu Yoshinori
Nagata Tsuyoshi
Nakashiba Yasutaka
Ohkubo Hiroaki
NEC Electronics Corporation
Pyo Kevin
LandOfFree
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