Patent Application
20110074775
The present invention relates to an image display device displaying an object three-dimensionally, particularly to an image signal processing device using a left-eye image signal and a right-eye image signal for an object.
To display an image three-dimensionally on an image display device, various methods are examined. Among them, the following method is well known. That is, a right-eye image and a left-eye image of an object are prepared; a mechanism is provided that allows a viewer to view these images with the right and left eyes separately to present a stereoscopic image of the object. Viewing something with the human eye produces parallax between images by the right and left eyes for a same object. The parallax allows the human to perceive an object three-dimensionally and to sense the depth of the object. Accordingly, to prepare right- and left-eye image signals including such parallax allows implementing an image display device enabling an object to be viewed three-dimensionally.
Next, a description is made of parallax between right- and left-eye images. For instance, as the object in the right-eye image shifts to the left; and as the object in the left-eye image shifts to the right, the object appears to project forward. Reversely, as the object in the right-eye image shifts to the right; and as the object in the left-eye image shifts to the left, the object appears to be withdrawn backward. Without parallax (the right-eye image is identical to the left-eye image), the object appears to be positioned at the display surface of the image display device.
A stereoscopic image including parallax is easily obtained through shooting an object with two cameras of the same type. Usually, the right-eye camera is positioned on the right; and the left-eye camera, on the left.
Next, each image signal obtained from the right- and left-eye cameras is transmitted to an image display device. Then, the image display device has only to provide a mechanism that allows each image signal from the cameras to be viewed with the right and left eyes. Various methods have been devised according to such a mechanism. To transmit image signals for stereo vision, both right- and left-eye image signals need to be sent. Hence, to transmit these signals directly, the transmission rate increases to twice that of a regular case.
In field sequential method shown in
To reduce the transmission rate, several types of methods are disclosed as shown in
Meanwhile, an image display device employs various methods. In active shutter method, for instance, right-eye image R and left-eye image L are arranged in time series and displayed sequentially. By using shutter glasses that open and close shutters for the right- and left-eye lenses in accordance with right-eye image R and left-eye image L, respectively, right-eye image R and left-eye image L result in being viewed by the right and left eyes, respectively. This provides a stereoscopic image of an object. (Refer to patent literature 1.)
Thus using right-eye image R and left-eye image R including parallax therebetween provides stereo vision. Right-eye image R and left-eye image L are usually obtained through shooting an object with two cameras positioned separately from each other at a certain distance so as to obtain parallax. This causes unevenness (e.g. contrast, black level, and depth of a color in images) in a signal state of right-eye image R and left-eye image L.
In the conventional technology, displaying right-eye image R and left-eye image R on a display device causes unevenness (e.g. contrast, black level, and depth of a color in images) in an image state due to two cameras being used, thereby sometimes giving unnatural visual feeling.
[Patent literature]
[Patent literature 1] Japanese Patent Unexamined Publication No. 2002-262310
An image signal processing device of the present invention is a stereoscopic image display device that displays a stereoscopic image by means of right- and left-eye image signals including parallax therebetween. The device includes a parallax detecting unit; a non-parallax signal generating unit; a right-left level difference detecting unit; and a level difference correcting unit. The parallax detecting unit detects parallax information on the basis of parallax from right- and left-eye image signals. The non-parallax signal generating unit generates non-parallax, right- and left-eye image signals free from parallax therebetween. The right-left level difference detecting unit detects a level difference between non-parallax, right- and left-eye image signals to produce level difference information. The level difference correcting unit corrects right- and left-eye image signals according to level difference information for each given level.
With such a configuration, right- and left-eye image signals are corrected for each given level according to level difference information obtained by the right-left level difference detecting unit, thereby reducing unnatural visual feeling produced from different signal levels between right- and left-eye image signals including parallax therebetween.
An image signal processing method of the present invention includes a parallax detecting step; a non-parallax signal generating step; a right-left level difference detecting step; and level difference correcting step, in a stereoscopic image display device that displays a stereoscopic image by means of right- and left-eye image signals including parallax therebetween. The parallax detecting step detects parallax information on the basis of parallax from right- and left-eye image signals, in the parallax detecting unit. The non-parallax signal generating step generates non-parallax, right- and left-eye image signals free from parallax therebetween, in the non-parallax signal generating unit. The right-left level difference detecting step detects a level difference between non-parallax, right- and left-eye image signals to produce level difference information, in the right-left level difference detecting unit. The level difference correcting step corrects right- and left-eye image signals according to level difference information for each given level, in the level difference correcting unit.
Hereinafter, a description is made of an embodiment of the present invention with reference to the related drawings.
Parallax detecting unit 202 detects parallax information on the basis of parallax between right-eye image signal 201R and left-eye image signal 201L. Parallax detecting unit 202 outputs parallax information detected as parallax degree signal 210. Non-parallax signal generating unit 203 receives right-eye image signal 201R and left-eye image signal 201L. Then, non-parallax signal generating unit 203 shifts the phase of at least one of right-eye image signal 201R and left-eye image signal 201L, according to parallax information output from parallax detecting unit 202. Next, parallax detecting unit 202 generates non-parallax right- and left-eye image signals 212R and 212L free from parallax therebetween, and then outputs them.
Right-left level difference detecting unit 204 receives non-parallax right- and left-eye image signals 212R and 212L output from non-parallax signal generating unit 203. Then, right-left level difference detecting unit 204 detects a level difference between right-eye image signal 201R and left-eye image signal 201L to produce level difference information. Next, right-left level difference detecting unit 204 outputs the level difference information detected as level difference signal 214.
Level difference correcting unit 205 receives right-eye image signal 201R and left-eye image signal 201L. Then, level difference correcting unit 205 corrects a level difference between right-eye image signal 201R and left-eye image signal 201L according to level difference signal 214 (i.e. level difference information) output from right-left level difference detecting unit 204. As a result, level difference correcting unit 205 sets right-eye image signal 206R and left-eye image signal 206L for each given level. Here, the given level has only to be set to a level such that a user cannot perceive the differences. Further, level difference correcting unit 205 may correct right-eye image signal 206R and left-eye image signal 206L so that they are substantially at the same level. Doing so reduces unnatural visual feeling produced from different signal levels between right-eye image signal 201R and left-eye image signal 201L.
Next, a description is made of operation in each configuration described above, taking concrete examples. As described using
In field sequential method for instance, as shown in
Parallax detecting unit 202 operates in the following way in order to detect parallax degree dW as parallax information based on the parallax. That is, parallax detecting unit 202 shifts the phase of left-eye image 220L stepwise by pixel sampling unit on a certain image line Vn, for instance. Then, parallax detecting unit 202 detects a difference between left-eye image 220L and right-eye image 220R each time shifting the phase. Next, parallax detecting unit 202 presumes the amount of phase shift at a minimum difference as parallax degree dW.
In this case, image line Vn is desirably set so as to include an object. Attention-focused pixel 230 including a singular part is desirably set to such as the boundary of an object. This is because the brightness and color tone of a pixel are assumed to change largely around the boundary of an object. Image line Vn may be set so as to include attention-focused pixel 230. Image line Vn, however, does not necessarily need to be set so as to include attention-focused pixel 230 if the amount of phase shift is easily detected at a part other than attention-focused pixel 230.
As shown in
Parallax detecting unit 202 inputs parallax degree dW thus obtained to non-parallax signal generating unit 203 as parallax information. Non-parallax signal generating unit 203 shifts the phase of at least one of right-eye image signal 201R and left-eye image signal 201L according to parallax information for a parallax degree dW of zero. Non-parallax signal generating unit 203 thus obtains non-parallax right- and left-eye image signals 212R and 212L (not including a phase difference in an image signal) and outputs them.
Right-left level difference detecting unit 204 receives non-parallax right- and left-eye image signals 212R and 212L to detect a level difference between them. To correct a brightness difference, for instance, right-left level difference detecting unit 204 detects a difference between the brightness components of non-parallax right- and left-eye image signals 212R and 212L having been input. The detection is made simply by determining the difference between the brightness components of non-parallax right- and left-eye image signals 212R and 212L.
Concretely, the difference between the brightness components can be obtained as follows. That is, a delay circuit is used to superimpose non-parallax left-eye image signal 212L on non-parallax right-eye image signal 212R; and then a difference circuit is used to subtract the level of non-parallax right-eye image signal 212R from that of non-parallax left-eye image signal 212L.
To increase the accuracy of detecting the difference between the brightness components, right-left level difference detecting unit 204 receives non-parallax right- and left-eye image signals 212R and 212L through LPF 208, as shown in
Next, level difference correcting unit 205 corrects brightness components of right-eye image signal 201R and left-eye image signal 201L according to level difference signal 214 obtained by right-left level difference detecting unit 204. At this moment, determination is needed that either one of right-eye image signal 201R and left-eye image signal 201L is a reference image signal and that the other is an image signal requiring correction. The system needs to uniquely determine which one is to be corrected. The image signal processing device according to the embodiment is assumed to always correct left-eye image signal 201L, for instance, to reduce fluctuation in the signal level. Hence, level difference correcting unit 205 is assumed to subtract brightness components from left-eye image signal 201L to obtain left eye image signal 206L corrected.
Alternatively, not left-eye image signal 201L but right-eye image signal 201R may be always corrected. Instead, to reduce the degree to which the screen darkens, an image signal to be corrected may be selected so as to always keep the higher brightness. Doing so allows reducing the circuit size. Otherwise, right-eye image signal 201R and left-eye image signal 201L may be corrected to the average value of the level of each image signal. Doing so decreases the difference in signal level in between a region corrected and that not corrected, thereby further reducing user's unnatural feeling. In other words, level difference correcting unit 205 may always select one of the following ways. First, correction is made so that one of non-parallax right- and left-eye image signals 212R and 212L becomes substantially same as the other in level. Second, correction is made so as to keep the higher brightness. Third, correction is made to the average value of non-parallax right- and left-eye image signals 212R and 212L.
In this way, level difference correcting unit 205 can obtain right-eye image signal 206R and left-eye image signal 206L with the difference in brightness level corrected.
To correct a color signal level, what is needed is the following. That is, right-left level difference detecting unit 204 detects a difference in color signal level, and level difference correcting unit 205 corrects color signals. Hence, the present invention does not limit a property of a signal to be corrected to the difference in brightness level. In other words, both brightness level and color signal level may be corrected simultaneously, or only one of them may be corrected.
In an image including parallax as shown in
In the image signal processing device according to the embodiment, level difference correcting unit 205 makes setting so that left-eye image signal 201L and right-eye image signal 201R are output at a substantially same level, but not limited to this setting.
Next, a description is made of a method of processing image signals performed by an image signal processing device according to the embodiment, using the flowchart shown in
Parallax detecting step S100 detects parallax information on the basis of parallax from right-eye image signal 201R and left-eye image signal 201L, and then outputs parallax information detected as parallax degree signal 210, in parallax detecting unit 202.
Non-parallax signal generating step S102 shifts the phase of either one of right-eye image signal 201R and left-eye image signal 201L according to parallax information, and then generates non-parallax right- and left-eye image signals 212R and 212L free from parallax therebetween, from right-eye image signal 201R and left-eye image signal 201L according to parallax information, in non-parallax signal generating unit 203. These non-parallax right- and left-eye image signals 212R and 212L are output from non-parallax signal generating unit 203.
Right-left level difference detecting step S104 detects a level difference between non-parallax right- and left-eye image signals 212R and 212L to generate level difference information, in right-left level difference detecting unit 204. Then, level difference signal 214 is output according to the level difference information.
Level difference correcting step S106 corrects right-eye image signal 201R and left-eye image signal 201L for each given level according to level difference information, in level difference correcting unit 205. As the result, right-eye image signal 206R and left-eye image signal 206L are set for each given level, in level difference correcting unit 205. Level difference correcting step S106 may correct right-eye image signal 206R and left-eye image signal 206L for a substantially same level, in level difference correcting unit 205. Doing so reduces unnatural visual feeling produced from different signal levels between right-eye image signal 206R and left-eye image signal 201L including parallax therebetween.
Right-left level difference detecting step S104 may receive non-parallax right- and left-eye image signals 212R and 212L through LPF 208, for instance, in right-left level difference detecting unit 204. By doing so, the step may detect only a level difference between low-frequency components of non-parallax right- and left-eye image signals 212R and 212L, in right-left level difference detecting unit 204. Here, the cutoff frequency of LPF 208 being set to approximately 2 to 3 MHz, for instance, enhances the effect of preventing malfunction caused by noise (high-frequency components) in detecting a level difference.
In an image including parallax as shown in
Further, as shown in
Level difference correcting step S106 may always select one of the following ways, in level difference correcting unit 205. First, correction is made so that one of non-parallax right- and left-eye image signals 212R and 212L becomes substantially same as the other in level. Second, correction is made so as to keep the higher brightness. Third, correction is made to the average value of non-parallax right- and left-eye image signals 212R and 212L. In this way, the circuit size can be reduced; the degree to which the screen darkens can be reduced; and user's unnatural feeling can be further reduced because the difference in signal level decreases in between a region corrected and that not corrected.
The present invention relates to an image signal processing device that adjusts the difference in signal level of between a left-eye image signal and a right-eye image signal in stereo vision to reduce visual uncomfortable feeling.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2008-247871 | Sep 2008 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2009/004707 | 9/18/2009 | WO | 00 | 11/22/2010 |
