Image sensor

• US 9,257,475 B2
• Filed: 07/11/2014
• Issued: 02/09/2016
• Est. Priority Date: 04/06/2009
• Status: Active Grant

• Current Assignee: Nokia Technologies Oy (Nokia Corporation)
• Original Assignee: Nokia Technologies Oy (Nokia Corporation)
• Inventors: Kalevo, Ossi M., Koskinen, Samu T., Rissa, Tero
• Primary Examiner(s): Pert, Evan
• Assistant Examiner(s): Cruz, Leslie Pilar
• Application Number:
  US14/328,851
• Publication Number:
  US 20140319324A1
• Time in Patent Office: 578 Days
• US Class Current: 1/1
• CPC Class Codes: G01J 1/46 using a capacitor
• CPC Class Codes: G01J 3/02 Details
• CPC Class Codes: G01J 3/0264 Electrical interface; User interface
• CPC Class Codes: G01J 3/0291 Housings; Spectrometer accessories; Spatial arrangement of elements, e.g. folded path arrangements
• CPC Class Codes: G01J 3/2823 Imaging spectrometer
• CPC Class Codes: G01J 3/50 using electric radiation detectors
• CPC Class Codes: H01L 27/14607 Geometry of the photosensitive area
• CPC Class Codes: H01L 27/14634 Assemblies, i.e. Hybrid structures
• CPC Class Codes: H01L 27/14645 Colour imagers
• CPC Class Codes: H01L 27/14647 Multicolour imagers having a stacked pixel-element structure, e.g. npn, npnpn or MQW elements
• CPC Class Codes: H04N 2209/047 using multispectral pick-up elements
• CPC Class Codes: H04N 25/00 Circuitry of solid-state image sensors [SSIS]; Control thereof
• CPC Class Codes: H04N 25/772 comprising A/D, V/T, V/F, I/T or I/F converters

Abstract

An apparatus includes a three dimensional array of light receptors disposed within a substrate having a light receiving surface, where light receptors disposed closer to the light receiving surface are responsive to light having shorter wavelengths than light receptors disposed further from the light receiving surface, and where each light receptor is configured to output a binary value and to change state between an off-state and an on-state by the absorption of at least one photon.

Claims

1. A method comprising:

illuminating a light-receiving surface of a substrate for an exposure period, said light-receiving surface including a three-dimensional array of light receptors, wherein the light receptors in the three-dimensional array are disposed in layers, and wherein at least some light receptors in a first layer are disposed so as to be laterally shifted with respect to at least some light receptors in an adjacent layer,

wherein light receptors disposed in an x-y plane closer to the light-receiving surface are responsive to light having shorter wavelengths than are light receptors disposed in an x-y plane farther from the light-receiving surface,

wherein each light receptor is constructed to change state between an off-state and an on-state by the absorption of at least one photon and includes a photodiode and a circuit configured to perform one-bit quantification,

wherein a circuit for each single one of the light receptors outputs a one-bit binary value indicative of whether or not only the photodiode for the single light receptor absorbed enough optical energy to cause the single light receptor to change state between the off-state and the on-state,

wherein the circuit configured to perform one-bit quantification comprises a comparator,

wherein each light receptor further comprises a current source producing a threshold current (I_t) as input to the photodiode, and

wherein each light receptor is triggered to the on-state in response to signal current (I_s) caused by absorption of optical energy plus background current (I_b) for the photodiode exceeding the threshold current, and in response to the voltage produced by the photodiode due to discharging current of I_s+I_b−

I_t falling below a threshold voltage of the comparator; and

reading out binary values from light receptors disposed in at least two different x-y planes of the three-dimensional array at the end of the exposure period.

2. The method of claim 1, further comprising a preliminary step of resetting the light receptors to the off-state.

3. The method as in claim 1, further comprising:

grouping together the binary outputs of some number of adjacent light receptors.

4. The method as in claim 3, where grouping together is at least one of grouping together the binary outputs of some number of light receptors adjacent to one another in the same x-y plane of the three-dimensional array;

grouping together the binary outputs of some number of light receptors adjacent along a z-axis of the three-dimensional array; and

grouping together the binary outputs of some number of light receptors adjacent to one another in the same x-y plane and along the z-axis of the three-dimensional array.

5. The method as in claim 3, further comprising:

changing the grouping of light receptors from one exposure to the next.

6. The method as in claim 1, further comprising:

compressing the binary values that are read out from the three-dimensional array.

7. The method as in claim 1, executed during operation of an image sensor within a wireless communication device.