The present disclosure relates to an image display apparatus and an image display method.
A digital image display apparatus in which display states of an image are basically allowed to take only two states of on and off (light emission (bright)/no-light emission (dark)) has been in practical use. In the digital image display apparatus, a DMD (Digital Micromirror Device) or a PDP (Plasma Display Panel), for example, is used as a light modulator. Basically, unlike an analog-type display apparatus, the digital image display apparatus is not able to perform continuous grayscale expression and thus performs the grayscale expression in multiple steps. A method thereof includes a PWM (Pulse Width Modulation; pulse width modulation) system, for example. This system is a system that performs the grayscale expression by maintaining luminance of a light source at a fixed magnitude and varying a width of a light emission time in accordance with the luminance.
PTL 1: Japanese Unexamined Patent Application Publication No. 2001-343950
PTL 2: Japanese Unexamined Patent Application Publication (Published Japanese Translation of PCT Application) No. JP2000-510252
In a digital image display apparatus, a band necessary for data transfer of image data to a light modulator increases with higher resolution and higher grayscale, and an algorithm for the data transfer may be complicated to cope with this.
It is desirable to provide an image display apparatus and an image display method that make it possible to suppress the band necessary for the data transfer and to make the algorithm for the data transfer relatively simple.
An image display apparatus according to an embodiment of the present disclosure includes: a light modulator that performs light modulation on the basis of data of a bit plane for each grayscale bit; and a transfer controller that divides the data of the bit plane into data of a plurality of groups and transfers the data of the respective groups to the light modulator at shifted transfer timings, the shifted transfer timings being sequentially shifted only by a predetermined shift amount corresponding to a subframe period of a least significant grayscale bit multiplied by a predetermined integral.
An image display method according to an embodiment of the present disclosure includes: performing light modulation by a light modulator on a basis of data of a bit plane for each grayscale bit; and dividing the data of the bit plane into data of a plurality of groups and transferring the data of the respective groups to the light modulator at shifted transfer timings, the shifted transfer timings being sequentially shifted only by a predetermined shift amount corresponding to a subframe period of a least significant grayscale bit multiplied by a predetermined integral.
In the image display apparatus or the image display method according to the embodiment of the present disclosure, the data of the bit plane is divided into the data of the plurality of groups, and the data of the respective groups is transferred to the light modulator at the shifted transfer timings that are sequentially shifted only by the predetermined shift amount corresponding to the subframe period of the least significant grayscale bit multiplied by the predetermined integral.
According to the image display apparatus or the image display method of the embodiment of the present disclosure, the data of the bit plane is divided into the data of the plurality of groups, and the data of the respective groups is transferred to the light modulator at the shifted transfer timings that are sequentially shifted only by the predetermined shift amount corresponding to the subframe period of the least significant grayscale bit multiplied by the predetermined integral, which thus makes it possible to suppress the band necessary for data transfer and to make the algorithm for data transfer relatively simple.
It is to be noted that effects described here are not necessarily limited and may include any of effects described in the present disclosure.
In the following, some embodiments of the present disclosure are described in detail with reference to the drawings. It is to be noted that the description is given in the following order.
1.5 Method of Calculating Shift Amount between Transfer Timings (
The light source drive circuit 5 drives the light source 4 in accordance with control of the controller 1.
The data formatter 2 generates data of a bit plane for each grayscale bit to be described later from inputted image data Din in accordance with the control of the controller 1. As illustrated in
In the image display apparatus that performs grayscale expression with the PWM system, the light modulator 3 is continuously irradiated with light having fixed luminance from the light source 4. The light modulator 3 controls modulation of the light into two states, that is, bright and dark states for each pixel, in accordance with luminance of an image to be displayed. At this time, as light modulation control, the light modulator 3 performs pulsed on (light emission)/off (non-light emission) control on light reaching an image display surface. Then, the light modulator 3 varies a pulse width of the light by varying a timing of switching on/off for each pixel to perform the grayscale expression. The image is displayed in multistep grayscale by irradiating the image display surface with the thus-modulated light.
In the following, a principle of the grayscale expression of the PWM system is described more specifically with reference to
It is possible to express an image of the 16 grayscales by combining at least four kinds of images that are different in luminance, within a predetermined period of time (normally, one frame). That is, in a case where the 16 grayscales are expressed, first, for each pixel, the luminance is quantized to four grayscale bits, for example. Then, image data of the one frame, for example, is expressed by a combination of four kinds of image data that are weighted with each grayscale bit. At this time, a collection of the image data for each grayscale bit is typically referred to as a “bit plane”. The bit plane is an information plane of the luminance for each grayscale bit.
In
The image display apparatus causes each pixel to emit light in a predetermined subframe period, and thus the data of each bit plane is transferred from the data formatter 2 to the light modulator 3 in a predetermined period that is provided in advance of each subframe period. That is, all the data of the bit plane BP0 of the grayscale bit B0, for example, is fed from the data formatter 2 to the light modulator 3 in the predetermined period that is provided earlier than a period of the subframe SF0. Simultaneously with start of the subframe SF0, the light modulator 3 performs switching of the on/off state concurrently for all the pixels on the basis of the data of the bit plane BP0 and holds this state during the period of the subframe SF0. Moreover, all the data of the bit plane BP1 of the grayscale bit B1, for example, is fed from the data formatter 2 to the light modulator 3 within the predetermined period that is provided earlier than a period of the subframe SF1. Simultaneously with start of the period of the subframe SF1, the light modulator 3 performs the switching of the on/off state concurrently for all the pixels on the basis of the data of the bit plane BP1 and holds this state during the period of the subframe SF1. Subsequently, the data of the bit plane BP2 of the grayscale bit B2 and the data of BP3 of the grayscale bit B3 are similarly transferred sequentially from the data formatter 2 to the light modulator 3 in predetermined periods provided earlier than periods of the subframes SF2 and SF3. The image display apparatus repeats such control for each frame.
Therefore, it is necessary that a transfer period during which the data of the bit planes is transferred be at least within the period of the subframe SF0 of the grayscale bit B0. The grayscale bit B is a least significant grayscale bit (LSB). In
Then, it is necessary to transfer all the data of the bit plane BP1 at least within this subframe period SF0 of the LSB; therefore, the transfer rate of the data to be transferred from the data formatter 2 to the light modulator 3 reaches (1920×1080)/21.79=95.2 Gbps, for example, in a case of a full HD image having a resolution of 1920×1080. As described above, there is an issue that in particular, in image display of high resolution and high grayscale, a necessary data transfer band becomes high.
To solve the foregoing issue, as illustrated in
In this data transfer technique, however, the data arrangement sequence (transfer sequence) or a transfer start timing differs among the divided groups. Thus, an algorithm for finding out a format that avoids overlapping of the transfer start timings, and transferring the data of the bit planes in a sequence in accordance with the format may be complicated.
In the present embodiment, in the image display apparatus that performs grayscale expression with the PWM system, similarly to the comparative example described above, there is provided a data transfer system that reduces a transfer band of image data to be transferred from the data formatter 2 to the light modulator 3 and makes an algorithm for transferring the image data relatively simple.
It is to be noted that a configuration of the image display apparatus and a principle of grayscale expression according to the present embodiment may be substantially similar to those of the image display apparatus in
In the image display apparatus according to the present embodiment, however, a display region of the light modulator 3 is spatially divided into a plurality of divided display regions, and the light modulator 3 performs light modulation on each divided display region. The data formatter 2 generates data of a bit plane for each grayscale bit from inputted image data Din in accordance with control of the controller 1. The data formatter 2 divides the data of the bit plane for each grayscale bit into data of a plurality of groups corresponding to the plurality of divided display regions and transfers the data of the respective groups to the light modulator 3 at shifted transfer timings with a data transfer system to be described later. The shifted transfer timings are sequentially shifted only by a predetermined shift amount. The controller 1 may be a transfer controller that controls a transfer timing of the data from the data formatter 2 to the light modulator 3. In the following, a specific example of the data transfer system of the present embodiment and a specific example of a method of calculating the shift amount between the transfer timings are described.
With this system, a data amount to be transferred during the subframe period of the LSB is just ¼ of the bit plane. Thus, in a case of the color display of the time-division system with an image having full HD resolution, the data transfer band is (1920×1080/4)/21.79=23.8 Gbps. That is, it is possible to reduce the transfer band to ¼ of a data transfer band of 95.2 Gbps of a basic system in which the bit planes are not divided. Moreover, the data transfer sequence or the transfer start timing is the same among the divided groups, which thus makes it possible to make a circuit configuration for generation of a data signal from the image signal in accordance with this transfer format relatively simple.
In this system, the subframe periods of three upper-order bits (bit5 to bit7) are divided into a plurality of short periods in one frame period. Then, the data of bit planes of the respective upper-order bits (bit5 to bit7) is dispersed among the plurality of short periods in the one frame period. Besides, similarly to the foregoing system in
With this system, similarly to the foregoing system in
It is to be noted that although
In this system, the bit planes are divided into eight groups (group0 to group7), and the image data is transferred so as not to cause overlapping of the data transfer periods of the bit planes of the respective groups by shifting the transfer timings of the respective groups only by a period corresponding to 11 times the subframe period of the LSB (bit0).
With this system, the data amount to be transferred during the subframe period of the LSB is just ⅛ of the bit plane. Thus, in the case of the color display of the time-division system with an image having full HD resolution, the data transfer band is (1920×1080/8)/21.79=11.9 Gbps. That is, it is possible to reduce the transfer band to ⅛ of the data transfer band of 95.2 Gbps of the basic system in which the bit planes are not divided. Moreover, the data transfer sequence or the transfer start timing is the same among the divided groups, which thus makes it possible to relatively easily configure the circuit for generation of a data signal from the image signal in accordance with this transfer format.
In this system, the subframe periods of two upper-order bits (bit6 and bit7) are divided into a plurality of short periods in one frame period. Then, the data of bit planes of the respective upper-order bits (bit6 and bit7) is distributed among the plurality of short periods in the one frame period. Besides, similarly to the foregoing system in
With this system, similarly to the foregoing system in
It is to be noted that although
In the following, a method of determining the shift amount between the transfer timings of the groups is described.
To transfer the image data so as not to cause overlapping of all of the data transfer periods of the bit planes of the respective groups, it is only necessary that a transfer start timing of arbitrary data does not overlap a transfer start timing of other data. It is possible to represent a transfer start timing T of the arbitrary data in a case where the data of the bit planes is transferred in sequence from the LSB, by the following expression.
T=jΔ+2k−1 (1)
j=0, 1, 2, . . . , p−1
k=0, 1, 2, . . . , q−1
Here, Δ is a shift amount between the transfer timings of the respective groups (the shift amount is Δ times the subframe period of the LSB), j is a number of the divided group, k is a bit number of the grayscale bit, p is the division number of the bit plane, and q is the number of grayscale bits.
Moreover, it is necessary that a shift between the transfer start timing of a first divided group and the transfer start timing of a last divided group be less than one frame period; therefore, the shift amount Δ is limited as below.
Δ<(2q−1)/(p−1) (2)
That is, an appropriate shift amount Δ in this technology is subject to a condition that the transfer start timings T, which are calculated by an expression (1), of the data of all the bit planes are different from one another and an expression (2) is satisfied.
As a specific example,
This technique allows for determination of the shift amount between the transfer timings of the groups with any number of bits and any division number.
From
Moreover, in a case where the division number of the bit plane is not less than 4 and not more than 7, it is preferable to control the shift amount between the transfer timings to the period that is nine times the subframe period of the LSB.
Further, in a case where the division number of the bit plane is 8 or larger, it is preferable to control the shift amount between the transfer timings to the period that is 11 times the subframe period of the LSB.
As described above, according to the embodiment, the data of the bit planes is divided into the data of the plurality of groups and the data of the respective groups is transferred to the light modulator 3 at shifted transfer timings that are sequentially shifted only by a predetermined shift amount corresponding to the subframe period of the LSB multiplied by a predetermined integral, which thus makes it possible to reduce the transfer band of the image data to be transferred from the data formatter 2 to the light modulator 3 and make the algorithm for transferring the image data relatively simple.
Moreover, according to the embodiment, reducing the data transfer band makes it possible to reduce the number of signals between the data formatter 2 and the light modulator 3 and to reduce the number of pads of a controller chip. As a result, it is possible to reduce power consumption of the data formatter 2. Further, by dividing the subframe periods of the upper-order bits and distributing the data of the bit planes of the upper-order bits in one frame period, it is possible to suppress visual deterioration in image quality, which is referred to as the pseudo contour (or the false contour), specific to the PWM system and thus achieve an image display apparatus with high image quality.
It is to be noted that the effects described herein are merely illustrative and non-limiting, and may further include other effects.
The technology achieved by the present disclosure is not limited to the description of the foregoing respective embodiments, and may be modified in a variety of ways.
For example, the technology may have the following configurations.
(1)
An image display apparatus, including:
a light modulator that performs light modulation on the basis of data of a bit plane for each grayscale bit; and
a transfer controller that divides the data of the bit plane into data of a plurality of groups and transfers the data of the respective groups to the light modulator at shifted transfer timings, the shifted transfer timings being sequentially shifted only by a predetermined shift amount corresponding to a subframe period of a least significant grayscale bit multiplied by a predetermined integral.
(2)
The image display apparatus according to (1), in which the transfer controller divides a subframe period of at least one predetermined grayscale bit in each of the groups into a plurality of periods in one frame period, distributes data of a bit plane of the predetermined grayscale bit among the plurality of periods, and transfers the data of the bit plane of the predetermined grayscale bit to the light modulator.
(3)
The image display apparatus according to (1) or (2), in which the transfer controller controls the predetermined shift amount to a value that causes transfer start timings T calculated by a following expression (1) of data of all bit planes to be different from one another and satisfies a following expression (2),
T=jΔ+2k−1 (1)
Δ<(2q−1)/(p−1) (2)
j=0, 1, 2, . . . , p−1
k=0, 1, 2, . . . , q−1
where Δ is an shift amount between transfer timings of the respective groups (the shift amount is Δ times the subframe period of the least significant grayscale bit), j is a number of the group, k is a bit number of the grayscale bit, p is a division number of the bit plane, and q is a number of grayscale bits.
(4)
The image display apparatus according to any one of (1) to (3), in which the transfer controller causes the division number of the bit plane to be 2 or 3, and controls the predetermined shift amount to a period that is five times the subframe period of the least significant grayscale bit.
(5)
The image display apparatus according to any one of (1) to (3), in which the transfer controller causes the division number of the bit plane to be not less than 4 and not more than 7, and controls the predetermined shift amount to a period that is nine times the subframe period of the least significant grayscale bit.
(6)
The image display apparatus according to any one of (1) to (3), in which the transfer controller causes the division number of the bit plane to be 8 or larger, and controls the predetermined shift amount to a period that is 11 times the subframe period of the least significant grayscale bit.
(7)
The image display apparatus according to any one of (1) to (6), in which the light modulator performs light modulation on each of divided display regions of which a number is equal to the division number of the bit plane.
(8)
An image display method, including:
performing light modulation by a light modulator on the basis of data of a bit plane for each grayscale bit; and
dividing the data of the bit plane into data of a plurality of groups and transferring the data of the respective groups to the light modulator at shifted transfer timings, the shifted transfer timings being sequentially shifted only by a predetermined shift amount corresponding to a subframe period of a least significant grayscale bit multiplied by a predetermined integral.
This application claims the benefit of Japanese Priority Patent Application No. 2016-090213 filed with the Japan Patent Office on Apr. 28, 2016, the entire contents of which are incorporated herein by reference.
It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.
Number | Date | Country | Kind |
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2016-090213 | Apr 2016 | JP | national |
Filing Document | Filing Date | Country | Kind |
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PCT/JP2017/010922 | 3/17/2017 | WO | 00 |