Television – Camera – system and detail – Combined image signal generator and general image signal...
Reexamination Certificate
1998-12-01
2003-09-23
Garber, Wendy R. (Department: 2712)
Television
Camera, system and detail
Combined image signal generator and general image signal...
C348S169000, C348S155000, C348S302000
Reexamination Certificate
active
06624849
ABSTRACT:
This application claims priority under 35 USC 119 from Japanese patent application no. 09-336955, filed Dec. 8, 1997 and Japanese patent application no. 10-226101, filed Aug. 10, 1998.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention pertains to a solid-state imaging apparatus for motion detection which detects differences between frames. Specifically, the present invention pertains to a solid-state imaging apparatus for motion detection that reduces external processing circuits and reduces erroneous detection of motion due to small background motions and noise when detecting motion.
2. Description of the Related Art
Prior art processing apparatuses for motion detection sequentially take images of image data from a solid-state imaging apparatus and detect motion based on differences between frames of this image data.
FIG. 9
is representative of a prior art image processing apparatus for motion detection
100
. The image processing apparatus for motion detection
100
consists of a solid-state imaging apparatus
101
, A/D conversion circuit
102
that converts the image signal (an analog signal) from the solid-state imaging apparatus
101
into a digital signal, image memory
103
(first image memory) and image memory
104
(second image memory) that save the digital signal from A/D conversion circuit
102
, and an image processing circuit
105
that compares the digital image data saved in the image memories
103
and
104
against one another and detects motion.
In this image processing apparatus for motion detection
100
, a first frame's image signal (analog signal) obtained by solid-state imaging apparatus
101
is converted into a digital signal by the A/D conversion circuit
102
, and then is saved in first image memory
103
.
Next a second frame's image signal (analog signal) obtained by solid-state imaging apparatus
101
is converted into a digital signal by the A/D conversion circuit
102
, and then is saved in second image memory
104
.
The image processing circuit
105
then compares pixels of the digital signal saved in the first image memory
103
with pixels of the digital signal saved in the second image memory
104
. The processing circuit detects pixels that differ by more than a specified threshold value and generates a signal indicating detection of a moving object (hereafter the “moving object signal”).
In this manner, inter-frame comparison makes it possible to detect motion of a subject.
Nevertheless, the aforesaid conventional image processing apparatus for motion detection
100
has defects in that the motion detection circuitry for the solid-state imaging apparatus
101
is complicated making the image processing apparatus for motion detection
100
overly large and costly.
Another defect is that the image signal output from solid-state imaging apparatus
101
is an analog signal, which is supplied to A/D conversion circuit
102
as an analog signal. Therefore, the analog signal is conducted along a path presenting an opportunity to be easily affected by noise (interference).
Furthermore, in the aforesaid conventional image processing apparatus for motion detection
100
the dynamic range of the analog image signal is limited by A/D conversion circuit
102
. The input dynamic range of A/D conversion circuit
102
is usually narrower than the dynamic range of the solid-state imaging apparatus
101
. Therefore, there is a defect in that the wide dynamic range of solid-state imaging apparatus
101
cannot be effectively used in the course of detecting and processing a moving object.
Also, the sampling timing in the A/D conversion circuit
102
may become slightly out-of-phase between the successive frames. This type of phase shifting in inter-frame sampling timing creates a slight phase shift in the pixel position to be compared at the image processing circuit
105
. If this type of phase shift occurs, a stationary body may have inter-frame differences at its edge portions. Therefore, there is a defect in prior art solid-state imaging apparatuses that the precision and reliability of moving object detection are lowered.
One proposal for avoiding the aforesaid defects is to provide a memory to store the image signal for the immediately previous frame and the current frame in each pixel of solid-state imaging apparatus
101
, and to additionally provide each pixel with a comparison circuit to compare the image signal stored in this memory, and to generate a moving object signal for each pixel.
However, this sort of countermeasure has the defects of making the structure of the unit pixel complicated, and reducing the numerical aperture and resolution of solid-state imaging apparatus
101
. In addition, the aforesaid countermeasure can output only the moving object signal from each pixel. Thus, this design has the defect that the solid-state imaging apparatus would not be able to simultaneously provide an image signal, which is an undesirable result.
Incidentally, it is generally known that a solid-state imaging apparatus consisting of a semiconductor device experiences charge fluctuations, which create shot noise.
The magnitude of shot noise is proportional to the square root of the signal magnitude. Therefore, the brighter the subject and the higher the signal level, the greater the shot noise that is created. As a result, in bright locations shot noise looms large in inter-frame differences. If shot noise occurs in inter-frame differences and exceeds the threshold value for a moving-object decision, erroneous motion detection may occur.
One proposal for avoiding erroneous detection due to shot noise is to set the comparison threshold value for differences between frames uniformly high. Nevertheless, this sort of countermeasure has the problem that sufficient motion detection cannot be performed for a low-contrast subject.
Also, in addition to the case described above, differences between frames also occur in situations, such as when tree leaves wave in a wind. This sort of motion is small motion in the background, and should be distinguished from motion of the detection subject which is being monitored.
SUMMARY OF THE INVENTION
The present invention provides a solid-state imaging apparatus for motion detection which reduces external image comparison processing circuits and does not detect shot noise or small background motions when detecting motion. In addition, the present invention provides a solid-state imaging apparatus for motion detection which can simultaneously output a moving object signal and an image signal. Also, the present invention provides a solid-state imaging apparatus for motion detection which can selectively reduce erroneous detection of motion due to shot noise.
Furthermore, the present invention provides a solid-state imaging apparatus for motion detection which can reduce erroneous detection of motion in the screen's horizontal direction and in the screen's vertical direction. In addition, the present invention provides a solid-state imaging apparatus for motion detection which can reduce erroneous detection of motion in the time axis direction.
In a preferred embodiment of the present invention a solid-state imaging apparatus for motion detection includes a plurality of photoreceptive units arranged in a matrix and creating pixel output corresponding to incident light and a plurality of vertical read lines disposed on each column of the plurality of photoreceptive units. A vertical transfer circuit sequentially selects a specified row of the plurality of photoreceptive units and successively outputs to the vertical read line the previous frame's pixel output saved in the past from the specified row of photoreceptive units, then the current frame's pixel output newly saved from the specified row of photoreceptive units. A comparison circuit, disposed on each of the vertical read lines, compares the previous frame's pixel output and the current frame's pixel output transferred by time division via the vertical read lines. A horizontal transfer circuit horizontally
Garber Wendy R.
Ipsolon LLP
Nikon Corporation
Villecco John M
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