Image processing apparatus and method, and video camera

• US 5,396,288 A
• Filed: 07/19/1993
• Issued: 03/07/1995
• Est. Priority Date: 08/21/1992
• Status: Expired due to Term

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fuji Photo Film Co Limited (Fujifilm Holdings Corporation)
• Inventors: Masukane, Kazuyuki, Tsugita, Makoto
• Primary Examiner(s): Groody, James J.
• Assistant Examiner(s): Murrell, Jeffrey S.
• Application Number:
  US08/092,798
• Time in Patent Office: 596 Days
• Field of Search: 358/160, 358/166, 358/209, 358/228, 358/213.19
• US Class Current: 348/229.1
• CPC Class Codes: H04N 23/76 by influencing the image signals
• CPC Class Codes: H04N 25/57 Control of the dynamic range
• CPC Class Codes: H04N 5/20 Circuitry for controlling amplitude response

Abstract

A suitable image signal is obtained even with regard to a subject exhibiting a very large difference in luminance between bright and dark areas. A video signal obtained from a CCD by imaging the subject is amplified by a first amplifier, converted into digital image data A by a first A/D converter and then stored in a first memory. The video signal from the CCD is also amplified by first and second amplifiers, converted into image data B by a second A/D converter and then stored in a second memory. The amplification factor of the first second amplifier is set such that a comparatively dark area of the image of the subject will assume a level having an appropriate brightness. A multiplexer selects data representing a comparatively bright area of the image of the subject from image data read out of the first memory as well as data representing a comparatively dark area of the image of the subject from image data read out of the second memory. The selected items of data are combined (by inlay synthesis) to obtain image data representing an image exhibiting overall brightness.

Claims

1. An image processing apparatus comprising:

image sensing means for outputting one input image signal;

amplifying means for amplifying said one input image signal so as to provide identical first and second image signals and amplifying at least one of the first and second image signals in conformity with a difference in brightness between a relatively bright area and a relatively dark area of an image represented by the one input image signal;

discriminating means for discriminating a boundary between the relatively bright area and the relatively dark area of the image; and

synthesizing means for producing a composite image signal using the first image signal obtained from said amplifying means with regard to the relatively bright area and the second image signal obtained from said amplifying means with regard to the relatively dark area, said relatively bright and dark areas being demarcated by the boundary discriminated by said discriminating means.

2. The apparatus according to claim 1, wherein said amplifying means outputs the first image signal as is and outputs the second image signal upon amplifying said second image signal.

3. The apparatus according to claim 1, wherein said amplifying means comprises first and second amplifier means having different amplification factors;

said first amplifier means amplifying the one input image signal at a first amplification factor to output the first image signal; and

said second amplifier means amplifying the one input image signal at a second amplification factor larger than the first amplification factor to output the second image signal.

4. The apparatus according to claim 1, further comprising two A/D converters for converting the first and second image signals outputted by said amplifying means into corresponding digital image data.

5. The apparatus according to claim 1, wherein said synthesizing means includes:

first memory means for storing the first image signal;

second memory means for storing the second image signal;

third memory means for storing an area designating signal that designates either of the relatively bright and dark areas defined by the boundary discriminated by said discriminating means; and

changeover means for selectively outputting, in accordance with the area designating signal read out of said third memory means, one of the first and second image signals read synchronously out of said first and second memory means.

6. The apparatus according to claim 1, wherein said discriminating means includes comparison means for comparing the first image signal or the second image signal with a prescribed threshold level.

7. The apparatus according to claim 1, wherein said discriminating means includes:

low-pass filtering means for low-pass filtering the first image signal or the second image signal; and

comparison means for comparing the low-pass-filtered image signal with a prescribed threshold level.

8. The apparatus according to claim 1, wherein said discriminating means extracts an area in which luminance in the image represented by the first image signal is comparatively high and which has an area or length greater than a prescribed value, or an area in which luminance in the image represented by the second image signal is comparatively low and which has an area or length greater than a prescribed value.

9. The apparatus according to claim 1, wherein said synthesizing means weighting includes means for producing a weighted image signal representing a weighted mean of the first and second image signals in the vicinity of the boundary.

10. The apparatus according to claim 1, wherein said synthesizing means includes low-pass filtering means for low-pass filtering the first and second image signals in the vicinity of the boundary.

11. The apparatus according to claim 1, wherein said synthesizing means includes:

a comparator for comparing the first image signal with a prescribed threshold level and generating an output when the level of the first image signal exceeds said prescribed threshold level; and

a multiplexer, to which the first and second image signals are entered, for normally selecting and outputting the second image signal and selecting and outputting the first image signal when an output of said comparator is applied thereto.

12. The apparatus according to claim 11, further comprising a low-pass filter for eliminating high-frequency components of the first image signal, wherein an output from said low-pass filter is applied to said comparator.

13. The apparatus according to claim 11, further comprising:

a duration detecting circuit for applying the output signal of said comparator to said multiplexer if the duration of the output signal of said comparator is greater than a reference duration; and

a delay circuit for applying the first and second image signals to said multiplexer upon delaying the first and second image signals for a period of time corresponding to the reference duration.

14. A still-video camera comprising:

image pick-up means, which includes a solid-state electronic image sensing device, for outputting a video signal, which represents an image obtained by imaging a subject, from said solid-state electronic image sensing device;

first amplifier means for amplifying the video signal, which is outputted by said image pick-up means, at a first amplification factor suited to a comparatively bright area of the image, and outputting a first video signal obtained by said first amplification factor;

second amplifier means for amplifying the video signal, which is outputted by said image pick-up means, at a second amplification factor greater than the first amplification factor and suited to a comparatively dark area of the image, and outputting a second video signal obtained by said second amplification factor;

first A/D converting means for converting the first video signal into first digital image data corresponding to said first video signal;

second A/D converting means for converting the second video signal into second digital image data corresponding to said second video signal;

discriminating means for discriminating a boundary between the comparatively bright area and the comparatively dark area of the image based upon the first digital image data or the second digital image data; and

synthesizing means for producing composite image data using the first digital image data obtained from said first A/D converting means with regard to the comparatively bright area and the second digital image data obtained from said second A/D converting means with regard to the comparatively dark area, said comparatively bright and dark areas being demarcated by the boundary discriminated by said discriminating means.

15. A still video camera comprising:

image pick-up means, which includes a solid-state electronic image sensing device, for outputting a video signal, which represents an image obtained by imaging a subject, from said solid-state electronic image sensing device;

first amplifier means for amplifying the video signal, which is outputted by said image pick-up means, at a first amplification factor suited to a comparatively bright area of the image, and outputting a first video signal obtained by said first amplification factor;

second amplifier means for amplifying the video signal, which is outputted by said image pick-up means, at a second amplification factor greater than the first amplification factor and suited to a comparatively dark area of the image, and outputting a second video signal obtained by said second amplification factor;

comparison means for comparing the first video signal with a prescribed threshold level and generating an output when the level of the first video signal exceeds said prescribed threshold level; and

a multiplexer, to which the first and second video signals are entered, for normally selecting and outputting the second video signal and selecting and outputting the first video signal when an output of said comparator is applied thereto.

16. An image processing apparatus for a still-video camera including image sensing means for outputting one input image signal, comprising:

amplifying means for producing identical first and second image signals from one input image signal and amplifying at least one of said first and second image signals in conformity with a difference in brightness between a relatively bright area and a relatively dark area of an image represented by the one input image signal; and

synthesizing means for combining the first image signal and the second image signal, which are obtained from said amplifying means, by adding said first and second image signals at a prescribed ratio.

17. The apparatus according to claim 16, wherein said amplifying means outputs the first image signal as is and outputs the second image signal upon amplifying said second image signal.

18. The apparatus according to claim 16, wherein said amplifying means comprises first and second amplifier means having different amplification factors;

said first amplifier means amplifying the one input image signal at a first amplification factor to output the first image signal; and

said second amplifier means amplifying the one input image signal at a second amplification factor larger than the first amplification factor to output the second image signal.

19. The apparatus according to claim 16, further comprising two A/D converters for converting the first and second image signals outputted by said amplifying means into corresponding digital image data, said synthesizing means combining the digital image data obtained from said two A/D converters.

20. The apparatus according to claim 16, wherein the prescribed ratio in said synthesizing means is a fixed value.

21. The apparatus according to claim 16, wherein said synthesizing means comprises varying means for varying said prescribed ratio in dependence upon the level of the first image signal in such a manner that the proportion of the first image signal is enlarged for the relatively bright area and the proportion of the second image signal is enlarged for the relatively dark area.

22. A digital still video camera comprising:

image pick-up means, which includes a solid-state electronic image sensing device, for outputting a video signal, which represents an image obtained by imaging a subject, from said solid-state electronic image sensing device;

first amplifier means for amplifying the video signal, which is outputted by said image pick-up means, at a first amplification factor suited to a comparatively bright area of the image, and outputting a first video signal obtained by said first amplification factor;

second amplifier means for amplifying the video signal, which is outputted by said image pick-up means, at a second amplification factor greater than the first amplification factor and suited to a comparatively dark area of the image, and outputting a second video signal obtained by said second amplification factor;

first A/D converting means for converting the first video signal into first digital image data corresponding to said first video signal;

second A/D converting means for converting the second video signal into second digital image data corresponding to said second video signal; and

synthesizing means for combining the first digital image data and the second digital image data by adding the first and second digital image data at a prescribed ratio.

23. An image processing method comprising the steps of:

producing identical first and second image signals from one input image signal;

amplifying at least one of the first and second image signals in conformity with a difference in brightness between a relatively bright area and a relatively dark area of an image represented by the one input image signal;

finding a boundary between the relatively bright area and the relatively dark area of the image; and

producing a composite image signal using the first image signal with regard to the relatively bright area and the second image signal with regard to the relatively dark area, said relatively bright and dark areas being demarcated by the boundary found.

24. An image processing method for a still-video camera comprising the steps of:

producing identical first and second image signals from one input image signal;

amplifying at least one of the first and second image signals in conformity with a difference in brightness between a relatively bright area and a relatively dark area of an image represented by the one input image signal; and

combining the first image signal and the second image signal at a prescribed ratio.