US5572074A
Expired / Lapsed
US
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Compact photosensor circuit having automatic intensity range control
Assignee: Re Secured Networks LLC
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Filing: 1995-06-06
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Granted: 1996-11-05
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Expires: 2015-06-06
Abstract
Abstract A compact photosensor circuit provides automatic intensity range control for machine vision systems. The circuit may be implemented with standard CMOS integrated circuit technology to provide high sensitivity, fully static operation, and automatic exposure control with no moving parts. For each pixel of an imaging array, a photodetector provides an input photocurrent to a corresponding photosensor circuit. The photodetector is connected to provide an output voltage and an input to the gates of a pair of series-connected FETs that act as an attenuator. The attenuator is connected to a biasing source that provides a floor bias voltage. An output of the attenuator is connected to the gate of a third FET connected to the input photocurrent. The output voltage responds as a function of the light intensity at the photodetector while the bias voltage determines the range of light intensity for normal operation of the photosensor circuit. In a photosensor array with an appropriate bias current, the image scene contrast is amplified while the photosensor circuits automatically adapt to the overall light intensity.
Inventors
- 👤 David L. Standley
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 09:02
CPC Classifications
H; H03; H03F; H03F3/00; H03F3/04; H03F3/08; H03F3/082; H03G; H03G3/00; H03G3/20; H03G3/30; H03G3/3084
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
75 words
A photosensor circuit, comprising: a photodetector providing a current input and a voltage output in response to light intensity; an attenuator comprising first and second FETs connected in series with a bias source and providing an attenuator output, said first and second FETs having gates connected to said current input; a transconductance means connected to receive said current input and said attenuator output; and said voltage output responding as a function of said light intensity.
Claim 2
Dependent Claim
75 words
A photosensor circuit, comprising: a photodetector providing a current input and a voltage output in response to light intensity; an attenuator comprising first and second FETs connected in series with a bias source and providing an attenuator output, said first and second FETs having gates connected to said current input; a transconductance means connected to receive said current input and said attenuator output; and said voltage output responding as a function of said light intensity.
Claim 3
Dependent Claim
35 words
The photosensor circuit of claim 1, wherein said transconductance means comprises a third FET connected to said current input, said third FET having a gate connected to a node between said first and second FETs.
Claim 4
Dependent Claim
26 words
The photosensor circuit of claim 1, wherein said bias source comprises a bias node connected to at least one neighboring photosensor circuit in a photodetector array.
Claim 5
Dependent Claim
19 words
The photosensor circuit of claim 3, wherein said bias node comprises a global bus connected to a current source.
Claim 6
Dependent Claim
23 words
The photosensor circuit of claim 3, wherein said bias node comprises a global bus having a switching means for selectively switching bias modes.
Claim 7
Dependent Claim
27 words
The photosensor circuit of claim 3, wherein said bias node is connected by resistive means to said at least one neighboring photosensor circuit in said photodetector array.
Claim 8
Dependent Claim
32 words
The photosensor circuit of claim 3, wherein said bias node is connected to said at least one neighboring photosensor circuit by a fourth FET having a gate connected to said current input.
Claim 9
Dependent Claim
86 words
A photosensor circuit for a pixel in a photodetector array, comprising: a photodetector providing a current input and a voltage output in response to light intensity; an attenuator comprising first and second FETs connected in series to a bias node and having gates connected to said current input; a transconductance means connected to said current input and to an attenuator node between said first and second FETs to receive an output of said attenuator; and said voltage output responding as a function of said light intensity.
Claim 10
Dependent Claim
86 words
A photosensor circuit for a pixel in a photodetector array, comprising: a photodetector providing a current input and a voltage output in response to light intensity; an attenuator comprising first and second FETs connected in series to a bias node and having gates connected to said current input; a transconductance means connected to said current input and to an attenuator node between said first and second FETs to receive an output of said attenuator; and said voltage output responding as a function of said light intensity.
Claim 11
Dependent Claim
38 words
The photosensor circuit of claim 8, wherein said transconductance means comprises a third FET connected between said current input and ground, said third FET having a gate connected to said attenuator node between said first and second FETs.
Claim 12
Dependent Claim
28 words
The photosensor circuit of claim 9, wherein said bias node is connected to a corresponding bias node of at least one neighboring photosensor circuit in said photodetector array.
Claim 13
Dependent Claim
22 words
The photosensor circuit of claim 10, wherein said bias node comprises a global bus connecting said photodetector array to a current source.
Claim 14
Dependent Claim
32 words
The photosensor circuit of claim 10, wherein said bias node is connected by resistive means to said corresponding bias node of said at least one neighboring photosensor circuit in said photodetector array.
Claim 15
Dependent Claim
37 words
The photosensor circuit of claim 10, wherein said bias node is connected to said corresponding bias node of said at least one neighboring photosensor circuit by a fourth FET having a gate connected to said current input.
Claim 16
Dependent Claim
46 words
The photosensor circuit of claim 8, wherein said first FET comprises a first NFET having a source connected to said bias node and a drain connected to said attenuator node, and said second FET comprises a second NFET having a source connected to said attenuator node.
Claim 17
Dependent Claim
122 words
A photosensor circuit for a pixel in a photodetector array, comprising: a photodetector providing a current input and a voltage output in response to light intensity; a bias node connected to a bias source and to a corresponding bias node of at least one neighboring photosensor circuit in said photodetector array; an attenuator comprising first and second FETs connected in series to said bias node and having gates connected to said current input; a transconductance means comprising a third FET connected between said current input and ground and having a gate connected to an attenuator node between said first and second FETs to receive an output of said attenuator; and said voltage output responding as a logarithmic function of said light intensity.
Claim 18
Dependent Claim
122 words
A photosensor circuit for a pixel in a photodetector array, comprising: a photodetector providing a current input and a voltage output in response to light intensity; a bias node connected to a bias source and to a corresponding bias node of at least one neighboring photosensor circuit in said photodetector array; an attenuator comprising first and second FETs connected in series to said bias node and having gates connected to said current input; a transconductance means comprising a third FET connected between said current input and ground and having a gate connected to an attenuator node between said first and second FETs to receive an output of said attenuator; and said voltage output responding as a logarithmic function of said light intensity.
Claim 19
Dependent Claim
23 words
The photosensor circuit of claim 15, wherein said connected bias nodes comprise a global bus connecting a current source to said photodetector array.
Claim 20
Dependent Claim
29 words
The photosensor circuit of claim 15, wherein said bias node is connected by resistive means to said corresponding bias node of said at least one neighboring photo sensor circuit.
Claim 21
Dependent Claim
40 words
The photosensor circuit of claim 15, wherein said bias node is connected to said corresponding bias node of said at least one neighboring photosensor circuit by a fourth FET, said fourth FET having a gate connected to said current input.
Claim 22
Dependent Claim
24 words
The photosensor circuit of claim 15, further comprising an auxiliary current source connected to said attenuator node and said gate of said third FET.
Claim 23
Dependent Claim
67 words
The photosensor circuit of claim 15, wherein said first FET comprises a first NFET having a source connected to said bias node and a drain connected to said attenuator node, said second FET comprises a second NFET having a source connected to said attenuator node, and said third FET comprises a third NFET having a drain connected to said current input and a source connected to ground.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1999-11-05 | 2000-05-06 | 2000-11-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2003-11-05 | 2004-05-06 | 2004-11-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2007-11-05 | 2008-05-06 | 2008-11-05 | $7700.00 | Window Closed / Lapsed |