US6677992B1
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Imaging apparatus offering dynamic range that is expandable by weighting two image signals produced during different exposure times with two coefficients whose sum is 1 and adding them up
Assignee: Olympus Corp
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Filing: 1998-10-22
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Granted: 2004-01-13
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Expires: 2018-10-22
Abstract
Abstract An object is imaged continuously during a first exposure time and a second exposure time shorter than the first exposure time. Weights, one of which decreases monotonously and the other of which increases monotonously, are applied to first and second resultant image signals under the condition that the sum of the weights is 1. The first and second image signals that have been weighted are added up, thus producing a synthetic picture signal. When a luminance level is low, the ratio of the first image signal, which has been produced during the longer exposure time, to the second image signal is increased. This results in an image demonstrating a high signal-to-noise ratio. When the luminance level is high, the ratio of the second image signal, which has been produced during the shorter exposure time, to the first image signal is increased. This results in a synthetic image that proves a wide dynamic range, depicts a smoothly varying brightness level, and exhibits a characteristic of being seen as almost natural. Moreover, the first and second image signals are produced to resemble those produced during mutually different exposure times by controlling an amount of light incident on an imaging device or by varying an amount of illumination light.
Inventors
- 👤 Kanichi Matsumoto
- 👤 Katsuyuki Saito
- 👤 Kotaro Ogasawara
- 👤 Kuniaki Kami
- 👤 Shinji Yamashita
- 👤 Noboru Kusamura
- 👤 Akihiko Mochida
- 👤 Wataru Ohno
- 👤 Makoto Tsunakawa
- 👤 Hideki Tashiro
- 👤 Manabu Yajima
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 14:10
CPC Classifications
H; H04; H04N; H04N25/00; H04N25/40; H04N25/42; H04N23/00; H04N23/45; H04N23/70; H04N23/74; H04N25/50; H04N25/57; H04N25/58; H04N25/587; H04N25/589; H04N25/70; H04N25/71; H04N23/50; H04N23/555
Claims Analysis
Total Claims: 42
Claim 1
Independent Claim
215 words
An imaging apparatus comprising: an imaging device for successively outputting a first image signal produced by imaging an object during a first exposure time and a second image signal produced by imaging said object during a time shorted than said first exposure time; an image signal producing circuit composed of: first and second weighting circuits for applying a first weight, which decreases monotonously with an increase in light level from a light level of substantially no luminance up to a light level causing said first and second image signals to have a saturation value, and a second weight, which increases monotonously from said light level of substantially no luminance up to said light level causing said first and second image signals to have said saturation value, to said first and second image signals under the condition that the sum of said first and second weights is 1; and an adding circuit for adding together first and second picture signals produced by applying said first and second weights to said first and second image signals by means of said first and second weighting circuits; and a signal processing circuit for processing a picture signal output from said adding circuit and producing a video signal according to which an image can be displayed on a display device.
Claim 2
Dependent Claim
215 words
An imaging apparatus comprising: an imaging device for successively outputting a first image signal produced by imaging an object during a first exposure time and a second image signal produced by imaging said object during a time shorted than said first exposure time; an image signal producing circuit composed of: first and second weighting circuits for applying a first weight, which decreases monotonously with an increase in light level from a light level of substantially no luminance up to a light level causing said first and second image signals to have a saturation value, and a second weight, which increases monotonously from said light level of substantially no luminance up to said light level causing said first and second image signals to have said saturation value, to said first and second image signals under the condition that the sum of said first and second weights is 1; and an adding circuit for adding together first and second picture signals produced by applying said first and second weights to said first and second image signals by means of said first and second weighting circuits; and a signal processing circuit for processing a picture signal output from said adding circuit and producing a video signal according to which an image can be displayed on a display device.
Claim 3
Dependent Claim
27 words
An imaging apparatus according to claim 1 , further comprising an exposure time setting facility for varying at least one of said first and second exposure times.
Claim 4
Dependent Claim
30 words
An imaging apparatus according to claim 2 , wherein said exposure time setting facility uses a waveform-detected signal produced by detecting the waveform of said first or second image signal.
Claim 5
Dependent Claim
216 words
An imaging apparatus comprising: an imaging device for successively outputting a first image signal produced by imaging an object during a first exposure time, and a second image signal that has a saturation value relative to a higher light level than said first image signal; a picture signal producing device composed of: first and second weighting circuits for applying a first weight, which decreases monotonously with an increase in light level from a light level of substantially no luminance up to a light level causing said first and second image signals to have the saturation value, and a second weight, which increases monotonously from said light level of substantially no luminance up to said light level causing said first and second image signals to have said saturation value, to said first and second image signals under the condition that the sum of said first and second weights is 1; and an adding circuit for adding together first and second picture signals produced by applying said first and second weights to said first and second image signals by means of said first and second weighting circuits; and a signal processing circuit for processing a picture signal output from said adding circuit and producing a video signal according to which an image can be displayed on a display.
Claim 6
Dependent Claim
216 words
An imaging apparatus comprising: an imaging device for successively outputting a first image signal produced by imaging an object during a first exposure time, and a second image signal that has a saturation value relative to a higher light level than said first image signal; a picture signal producing device composed of: first and second weighting circuits for applying a first weight, which decreases monotonously with an increase in light level from a light level of substantially no luminance up to a light level causing said first and second image signals to have the saturation value, and a second weight, which increases monotonously from said light level of substantially no luminance up to said light level causing said first and second image signals to have said saturation value, to said first and second image signals under the condition that the sum of said first and second weights is 1; and an adding circuit for adding together first and second picture signals produced by applying said first and second weights to said first and second image signals by means of said first and second weighting circuits; and a signal processing circuit for processing a picture signal output from said adding circuit and producing a video signal according to which an image can be displayed on a display.
Claim 7
Dependent Claim
51 words
An imaging apparatus according to claim 4 , wherein said imaging device images an object during a second exposure time that is shorter than said first exposure time, and thus outputs said second image signal that has the saturation value relative to a higher light level than said first image signal.
Claim 8
Dependent Claim
72 words
An imaging apparatus according to claim 4 , wherein during a second exposure time during which said second image signal is produced, an amount of light coming from said object and falling on said imaging device through an imaging window is restricted by an amount-of-light restricting device, and said imaging device outputs said second image signal that has the saturation value relative to a higher light level than said first image signal.
Claim 9
Dependent Claim
81 words
An imaging apparatus according to claim 4 , wherein said weights applied by said picture signal producing device are such that: when a light level is much lower than the light level causing said first image signal to have the saturation value, said first weight is larger than said second weight; and when the light level is higher than the light level causing said first image signal to have the saturation value, said second weight is larger than said first weight.
Claim 10
Dependent Claim
219 words
An imaging apparatus comprising: an imaging device for successively outputting a first image signal produced by imaging an object during a first exposure time, and a second image signal that has a saturation value relative to a higher light level than said first image signal; a picture signal producing device composed of: first and second weighting circuits for applying a first weight, which decreases monotonously with an increase in light level up to a light level causing said first and second image signals to have a saturation value, and a second weight, which increases monotonously therewith, to said first and second image signals under the condition that the sum of said first and second weights is 1; and an adding circuit for adding together first and second picture signals produced by applying said first and second weights to said first and second image signals by means of said first and second weighting circuits; and a signal processing circuit for processing a picture signal output from said adding circuit and producing a video signal according to which an image can be displayed on a display; wherein said first weight function F 1 (x) is cos 2 (px) where x is a light level and p is a coefficient, and said second weight function F 2 (x) is sin 2 (px).
Claim 11
Dependent Claim
219 words
An imaging apparatus comprising: an imaging device for successively outputting a first image signal produced by imaging an object during a first exposure time, and a second image signal that has a saturation value relative to a higher light level than said first image signal; a picture signal producing device composed of: first and second weighting circuits for applying a first weight, which decreases monotonously with an increase in light level up to a light level causing said first and second image signals to have a saturation value, and a second weight, which increases monotonously therewith, to said first and second image signals under the condition that the sum of said first and second weights is 1; and an adding circuit for adding together first and second picture signals produced by applying said first and second weights to said first and second image signals by means of said first and second weighting circuits; and a signal processing circuit for processing a picture signal output from said adding circuit and producing a video signal according to which an image can be displayed on a display; wherein said first weight function F 1 (x) is cos 2 (px) where x is a light level and p is a coefficient, and said second weight function F 2 (x) is sin 2 (px).
Claim 12
Dependent Claim
27 words
An imaging apparatus according to claim 8 , wherein said coefficient p satisfies p≈π/(2s) where s is a light level of light incident on said imaging device.
Claim 13
Dependent Claim
25 words
An imaging apparatus according to claim 4 , wherein said imaging device includes a progressive imaging device having two systems of horizontal transfer output circuits.
Claim 14
Dependent Claim
21 words
An imaging apparatus according to claim 10 , wherein said signal processing means produces a video signal conformable to the interlacing.
Claim 15
Dependent Claim
48 words
An imaging apparatus according to claim 4 , wherein said image signal producing circuit includes a weight data storage that stores data of said first weight to be applied to said first image signal and data of said second weight to be applied to said second image signal.
Claim 16
Dependent Claim
45 words
An imaging apparatus according to claim 12 , wherein said weight data storage stores data of a weight to be applied to said first image signal and data of a weight to be applied to said second image signal, and the weights exhibit different characteristics.
Claim 17
Dependent Claim
68 words
An imaging apparatus according to claim 13 , further comprising a brightness detector for detecting brightness information of an object in an output signal of said imaging device, wherein a weight to be applied to said first image signal and a weight to be applied to said second image signal are selected based on the brightness information of an object, and thus read from said weight data storage.
Claim 18
Dependent Claim
30 words
An imaging apparatus according to claim 5 , wherein said imaging device images said object during said first exposure time, and produces said first image signal and second image signal.
Claim 19
Dependent Claim
56 words
An imaging apparatus according to claim 4 , wherein said picture signal producing device produces a synthetic picture signal exhibiting such a characteristic that a differential coefficient thereof relative to a light level varies continuously with an increase in light level up to a light level causing said second image signal to have the saturation value.
Claim 20
Dependent Claim
19 words
An imaging apparatus according to claim 16 , wherein the differential coefficient decreases monotonously relative to the light level.
Claim 21
Dependent Claim
260 words
An endoscopic imaging apparatus, comprising: an endoscope having an elongated insertion unit, irradiating illumination light to an object through an illumination window located at the distal end of said insertion unit, and including an imaging device for successively outputting a first image signal produced by imaging said object illuminated with said illumination light during a first exposure time, and a second image signal that has a saturation value relative to a higher light level than said first image signal; an image signal producing circuit composed of: first and second weighting circuits for applying a first weight, which decreases monotonously with an increase in light level from a light level of substantially no luminance up to a light level causing said first and second image signals to have the saturation value, and a second weight, which increases monotonously from said light level of substantially no luminance up to said light level causing said first and second image signals to have said saturation value, to said first and second image signals under the condition that the sum of said first and second weights is 1; and an adding circuit for adding together first and second picture signals produced by applying said first and second weights to said first and second image signals by means of said first and second weighting circuits; a signal processing circuit for processing a picture signal output from said adding circuit and producing a video signal which can be displayed; and a display for displaying a synthetic image represented by said picture signal when inputting said video signal.
Claim 22
Dependent Claim
260 words
An endoscopic imaging apparatus, comprising: an endoscope having an elongated insertion unit, irradiating illumination light to an object through an illumination window located at the distal end of said insertion unit, and including an imaging device for successively outputting a first image signal produced by imaging said object illuminated with said illumination light during a first exposure time, and a second image signal that has a saturation value relative to a higher light level than said first image signal; an image signal producing circuit composed of: first and second weighting circuits for applying a first weight, which decreases monotonously with an increase in light level from a light level of substantially no luminance up to a light level causing said first and second image signals to have the saturation value, and a second weight, which increases monotonously from said light level of substantially no luminance up to said light level causing said first and second image signals to have said saturation value, to said first and second image signals under the condition that the sum of said first and second weights is 1; and an adding circuit for adding together first and second picture signals produced by applying said first and second weights to said first and second image signals by means of said first and second weighting circuits; a signal processing circuit for processing a picture signal output from said adding circuit and producing a video signal which can be displayed; and a display for displaying a synthetic image represented by said picture signal when inputting said video signal.
Claim 23
Dependent Claim
52 words
An endoscopic imaging apparatus according to claim 18 , wherein said imaging device images said object during a second exposure time that is shorter than said first exposure time, and thus outputs said second image signal that has the saturation level relative to a higher light value than said first image signal.
Claim 24
Dependent Claim
72 words
An endoscopic apparatus according to claim 18 , wherein during a second exposure time during which said second image signal is produced, an amount of light coming from said object and falling on said imaging device through an imaging window is restricted by a light restricting device, and said imaging device outputs said second image signal that has the saturation value relative to a higher light level than said first image signal.
Claim 25
Dependent Claim
44 words
An endoscopic imaging apparatus according to claim 18 , further comprising a light source unit for supplying illumination light to a light guide that runs through said insertion unit of said endoscope, propagates illumination light, and emits the illumination light through said illumination window.
Claim 26
Dependent Claim
70 words
An endoscopic imaging apparatus according to claim 21 , wherein during a second exposure time during which said imaging device produces a second image signal, said light source unit allows a light restricting device to restrict illumination light to be supplied to said light guide, and said imaging device outputs said second image signal that has the saturation value relative to a higher light level than said first image signal.
Claim 27
Dependent Claim
35 words
An endoscopic imaging apparatus according to claim 22 , wherein said light restricting device is a light restriction filter for restricting illumination light generated by a lamp and supplying resultant light to said light guide.
Claim 28
Dependent Claim
24 words
An endoscopic imaging apparatus according to claim 22 , wherein said light restricting device restricts an amount of illumination light generated by a lamp.
Claim 29
Dependent Claim
50 words
An endoscopic imaging apparatus according to claim 18 , wherein said endoscope is an electronic endoscope and said imaging device being provided with the ability to photoelectrically convert a signal, placed on the image plane of an objective optical system located at the distal end of said elongated insertion unit.
Claim 30
Dependent Claim
90 words
An endoscopic imaging apparatus according to claim 18 , wherein said endoscope is a TV camera-mounted endoscope composed of an optical endoscope having an image propagating device for propagating an object image formed by an objective optical system located at the distal end of said elongated insertion unit to an optical system, and a TV camera that is mounted on an eyepiece of said optical endoscope and has an imaging device, which is included in said imaging device and provided with the ability to photoelectrically convert a signal, incorporated therein.
Claim 31
Dependent Claim
54 words
An endoscopic imaging apparatus according to claim 18 , wherein said endoscope includes a common image formation optical system, and said imaging device is composed of a plurality of imaging devices located at positions respectively at which a plurality of images are formed through a plurality of apertures by said image formation optical system.
Claim 32
Dependent Claim
33 words
An endoscopic imaging apparatus according to claim 19 , wherein said imaging device images said object during said first exposure time so as to produce said first image signal and second image signal.
Claim 33
Dependent Claim
27 words
An endoscopic imaging apparatus according to claim 18 , wherein said imaging device has a color separation filter used to achieve color imaging under white illuminating light.
Claim 34
Dependent Claim
45 words
An endoscopic imaging apparatus according to claim 18 , wherein said imaging device is a field-sequential imaging device that includes a monochrome imager not having a color separation filter, and that carries out color imaging under illumination of field-sequential light having a plurality of wavelengths.
Claim 35
Dependent Claim
235 words
An imaging apparatus, comprising: an imaging device for successively outputting a first image signal produced by imaging an object during a first exposure time, and a second image signal that is produced by imaging said object during a second exposure time shorter than said first exposure time and that has a saturation value relative to a higher light level than said first image signal; a picture signal producing circuit composed of: first and second weighting circuits for applying a first weight, which decreases monotonously with an increase in light level from a light level of substantially no luminance up to a light level causing said first and second image signals to have the saturation value, and a second weight, which increases monotonously from said light level of substantially no luminance up to said light level causing said first and second image signals to have said saturation value, to said first and second image signals under the condition that the sum of said first and second weights is 1; and an adding circuit for adding together first and second picture signals produced by applying said first and second weights to said first and second image signals by means of said first and second weighting circuits; and a signal processing circuit for processing a picture signal output from said adding circuit and producing a video signal according to which an image can be displayed on a display.
Claim 36
Dependent Claim
235 words
An imaging apparatus, comprising: an imaging device for successively outputting a first image signal produced by imaging an object during a first exposure time, and a second image signal that is produced by imaging said object during a second exposure time shorter than said first exposure time and that has a saturation value relative to a higher light level than said first image signal; a picture signal producing circuit composed of: first and second weighting circuits for applying a first weight, which decreases monotonously with an increase in light level from a light level of substantially no luminance up to a light level causing said first and second image signals to have the saturation value, and a second weight, which increases monotonously from said light level of substantially no luminance up to said light level causing said first and second image signals to have said saturation value, to said first and second image signals under the condition that the sum of said first and second weights is 1; and an adding circuit for adding together first and second picture signals produced by applying said first and second weights to said first and second image signals by means of said first and second weighting circuits; and a signal processing circuit for processing a picture signal output from said adding circuit and producing a video signal according to which an image can be displayed on a display.
Claim 37
Dependent Claim
216 words
An imaging apparatus, comprising: an imaging device for successively outputting a first image signal produced by imaging an object during a first exposure time, and a second image signal that has a saturation value relative to a higher light level than said first image signal; a picture signal producing circuit composed of: first and second weighting circuits for applying a first weight, which decreases monotonously with an increase in light level from a light level of substantially no luminance up to a light level causing said first and second image signals to have the saturation value, and a second weight, which increases monotonously from said light level of substantially no luminance up to said light level causing said first and second image signals to have said saturation value, to said first and second image signals under the condition that the sum of said first and second weights is 1; and an adding circuit for adding together first and second picture signals produced by applying said first and second weights to said first and second image signals by means of said first and second weighting circuits; and a signal processing circuit for processing a picture signal output from said adding circuit and producing a video signal according to which an image can be displayed on a display.
Claim 38
Dependent Claim
216 words
An imaging apparatus, comprising: an imaging device for successively outputting a first image signal produced by imaging an object during a first exposure time, and a second image signal that has a saturation value relative to a higher light level than said first image signal; a picture signal producing circuit composed of: first and second weighting circuits for applying a first weight, which decreases monotonously with an increase in light level from a light level of substantially no luminance up to a light level causing said first and second image signals to have the saturation value, and a second weight, which increases monotonously from said light level of substantially no luminance up to said light level causing said first and second image signals to have said saturation value, to said first and second image signals under the condition that the sum of said first and second weights is 1; and an adding circuit for adding together first and second picture signals produced by applying said first and second weights to said first and second image signals by means of said first and second weighting circuits; and a signal processing circuit for processing a picture signal output from said adding circuit and producing a video signal according to which an image can be displayed on a display.
Claim 39
Dependent Claim
213 words
An imaging apparatus, comprising: an imaging device for successively outputting a first image signal produced by imaging an object during a first exposure time, and a second image signal that has a saturation value relative to a higher light level than said first image signal; a picture signal producing circuit composed of: first and second weighting circuits for applying a first weight, which decreases monotonously with an increase in light level from a light level of substantially no luminance up to a light level causing said first and second image signals to have the saturation value, and a second weight, which increases monotonously from said light level of substantially no luminance up to said light level causing said first and second image signals to have said saturation value, to said first and second image signals under the condition that the sum of said first and second weights is 1; and an adding circuit for adding together picture signals produced by applying said first and second weights to said first and second image signals by means of said first and second weighting circuits; and a signal processing circuit for processing a picture signal output from said adding circuit and producing a video signal according to which an image can be displayed on a display.
Claim 40
Dependent Claim
213 words
An imaging apparatus, comprising: an imaging device for successively outputting a first image signal produced by imaging an object during a first exposure time, and a second image signal that has a saturation value relative to a higher light level than said first image signal; a picture signal producing circuit composed of: first and second weighting circuits for applying a first weight, which decreases monotonously with an increase in light level from a light level of substantially no luminance up to a light level causing said first and second image signals to have the saturation value, and a second weight, which increases monotonously from said light level of substantially no luminance up to said light level causing said first and second image signals to have said saturation value, to said first and second image signals under the condition that the sum of said first and second weights is 1; and an adding circuit for adding together picture signals produced by applying said first and second weights to said first and second image signals by means of said first and second weighting circuits; and a signal processing circuit for processing a picture signal output from said adding circuit and producing a video signal according to which an image can be displayed on a display.
Claim 41
Dependent Claim
39 words
An imaging apparatus according to claim 33 , wherein when a light level is higher than the light level causing said first image signal to have the saturation value, said first weighting circuit outputs a weight coefficient of 0.
Claim 42
Dependent Claim
52 words
An imaging apparatus according to claim 33 , wherein when a light level is higher than the light level causing said first image signal to have the saturation value, said picture signal is determined substantially with a weight coefficient that is applied to said second image signal by said second weighting circuit.
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