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Portable compact imaging and displaying apparatus with rotatable camera    

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United States Patent5612732   
Link to this pagehttp://www.wikipatents.com/5612732.html
Inventor(s)Yuyama; Masami (Oome, JP); Tsukamoto; Akihiro (Hamura, JP); Morikawa; Shigenori (Kokubunji, JP)
AbstractA pocketable imaging apparatus which can be carried by a user. A body case has a liquid crystal display section therein and a rotatable camera section. A memory device built into the body case can store several sheets of images taken by the camera section. The liquid crystal display section displays thereon either an image stored in the memory device or an image taken by the camera section. The liquid crystal display section is provided on the back of the body case. The camera section is provided rotatably on the left side of the body case so as to form the same flat surfaces as the front and back surfaces of the body case even if the camera section is rotated through an angle of 180.degree. forward and backward. A telephone line jack is also provided on the body case to enable the user to transmit the image on a telephone via telephone lines at any place where a telephone can be installed.
   














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Drawing from US Patent 5612732
Portable compact imaging and displaying apparatus with rotatable camera - US Patent 5612732 Drawing
Portable compact imaging and displaying apparatus with rotatable camera
Inventor     Yuyama; Masami (Oome, JP); Tsukamoto; Akihiro (Hamura, JP); Morikawa; Shigenori (Kokubunji, JP)
Owner/Assignee     Casio Computer Co., Ltd. (Tokyo, JP)
Patent assignment
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Company News
Publication Date     March 18, 1997
Application Number     08/210,562
PAIR File History     Application Data   Transaction History
Image File Wrapper   Patent Term   Fees
Litigation
Filing Date     March 18, 1994
US Classification     348/14.01 348/14.04 348/373 348/725 348/838
Int'l Classification     H04N 007/14
Examiner     Kostak; Victor R.
Assistant Examiner     Acosta; Juan G.
Attorney/Law Firm     Frishauf, Holtz, Goodman, Langer & Chick
Address
Parent Case    
Priority Data     Mar 31, 1993[JP]5-098967 Apr 28, 1993[JP]5-124935 Apr 28, 1993[JP]5-124937
USPTO Field of Search     348/13 348/14 348/706 348/725 348/790 348/838 348/373 348/376 348/36 379/55 379/54 379/53
Patent Tags     portable compact imaging displaying rotatable camera
   
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5189691
Dunlap
379/70
Feb,1993

[0 after 0 votes]
5077784
Fujita

Dec,1991

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4978888
Anandan
315/58
Dec,1990

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4639225
Washizuka
434/308
Jan,1987

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4560833
Weber
348/14.01
Dec,1985

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4387271
Artom
370/214
Jun,1983

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4336524
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Jun,1982

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What is claimed is:

1. A pocketable television receiver with a rotatable camera comprising:

a case containing:

a television tuner;

a display section for displaying an image received by the television tuner;

a camera section installed to be rotated on the case;

means for causing an image taken by the camera section to be displayed on the display section;

means for compressing the image taken by the camera section; and

means for modulating the image compressed by the compressing means; and

a telephone line jack provided on the case and connected to a telephone line in order to output the image data modulated by the modulating means to the telephone line.

2. A pocketable television receiver with a rotatable camera according to claim 1, wherein the display section comprises a liquid-crystal display device with a backlight, the backlight comprising a flat fluorescent tube.

3. A pocketable television receiver with a rotatable camera according to claim 1, wherein said camera section is attached to the case such that it can be rotated around a rotating shaft like a semicircle between a front surface and a back surface of the case.

4. A pocketable videophone comprising:

a case containing:

a television tuner;

means for displaying an image received by the television tuner;

a camera section;

means for compressing an image taken by the camera section;

means for modulating the image compressed by the compressing means;

means for demodulating the image modulated by the modulating means;

means for expanding the image demodulated by the demodulating means; and

means for displaying selectively one of the image taken by the camera section and the image expanded by the expanding means;

a telephone line jack connected to a telephone line; and

wherein outputting the image modulated by the modulating means through the telephone line jack to a telephone line and demodulating by the demodulating means a modulated image inputted from the telephone line through the telephone line jack enables the receiver to function as a videophone.

5. A pocketable imaging and displaying apparatus with a rotatable camera, comprising:

a display section;

a camera section having an imaging means for providing image data, said camera section being smaller in size than said display section and being installed rotatably on said display section; and

said display section including:

means for compressing image data taken by said imaging means;

means for modulating said image data compressed by said compressing means;

means for transmitting said image data modulated by said modulating means, said transmitting means having a telephone line jack connected to a telephone line;

means for receiving said image data transmitted from said telephone line via said telephone line jack;

means for demodulating said image data received by said receiving means;

means for expanding said image data demodulated by said demodulating means; and

means for displaying selectively said image data expanded by said expanding means and said image data taken by said imaging means in said camera section, said displaying means comprising a liquid-crystal display device with a backlight.

6. An apparatus according to claim 5, wherein said backlight comprises a flat fluorescent tube.

7. A pocketable imaging and displaying apparatus comprising:

a display section; and

a camera section having an imaging means for providing image data, said camera section being smaller in size than said display section and being installed rotatably on said display section; and

said display section including;

means for compressing image data taken by said imaging means;

means for storing plural sets of said image data compressed by said compressing means;

means for playing back said image data stored in said storing means; and

means for displaying selectively said image data played back by said playing back means and said image data taken by said imaging means, said displaying means comprising a liquid-crystal display device with a backlight formed of a flat fluorescent tube.

8. A pocketable imaging and displaying apparatus with a rotatable camera, comprising:

a body case;

a liquid-crystal displaying section provided on the back of said body case;

a camera section for taking a picture of a subject, said camera section including a lens and a lens selecting switch for switching a standard lens and a macro lens, respectively, on the front and the side thereof;

a storing section provided in said body case, for storing a plurality of images taken by said camera section;

a display section for displaying one of said image taken by said camera section and said image stored in said storing section;

a key input section provided on the top of said body case; and

a shutter button provided on the top and on an opposite side to said camera section;

wherein said camera section is provided rotatably on a side of the body case so as to form the same flat surfaces as front surface and back surface of the body case even if the camera section is rotated through an angle of 180.degree. forward and backward.
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BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a television receiver, and more particularly to a portable television receiver capable of transmitting image data through a communication channel.

2. Description of the Related Art

Recently, liquid-crystal television sets using a liquid-crystal display unit in the display section in place of a cathode ray tube (CRT), one of typical display devices, have been popularized because of lightness and thinness. For example, they are widely used in the fields of car use and sports watching. Particularly, such miniaturized liquid-crystal television sets as to fit in a breast pocket of the shirt are now on the market. People may go to work or on a business trip, carrying those TV sets with them to watch a TV program whenever they want to.

With such conventional liquid-crystal TV sets, however, since TV waves are received and only the received image data is displayed on the liquid-crystal display unit, the images that people can see on the liquid-crystal TV set are limited to those televised.

In these days, people often use the telephone at a going-out place and can of course transmit only sound to the other party on the phone.

It is unreasonable and inconvenient that people carrying liquid-crystal TV sets with them can transmit only sound to the other party on the telephone without transmitting image data.

SUMMARY OF THE INVENTION

Accordingly, the object of the present invention is to provide a portable television receiver capable of transmitting specific image data together with sound by means of a communication channel.

According to an aspect of the present invention, there is provided a portable television receiver comprising: a television tuner; a display section for displaying the image received by the television tuner; camera means; means for causing the image taken by the camera means to be displayed on the display section; means for compressing the image taken by the camera means; means for modulating the image compressed by the compressing means into an audio signal; and speaker means for outputting the image modulated by the modulating means into an audio signal, wherein the speaker means is pressed against the mouthpiece of a telephone to transmit the image.

According to another aspect of the present invention, there is provided a portable television receiver comprising: a case body; a television tuner; a display section for displaying the image received by the television tuner; a camera section; means for causing the image taken by the camera section to be displayed on the display section; means for binarizing the image taken by the camera section; and a facsimile transmission block containing a facsimile modem for transmitting the image binarized by the binarizing means to a facsimile.

According to still another aspect of the present invention, there is provided a portable television receiver comprising: a case containing: a television tuner; a display section for displaying the image received by the television tuner; camera means; means for causing the image taken by the camera means to be displayed on the display section; means for compressing the image taken by the camera means; and means for modulating the image compressed by the compressing means; and a telephone line jack provided on the case and connected to a telephone line in order to output the image data modulated by the modulating means.

According to further aspect of the present invention, there is provided a portable television receiver comprising: a case containing: a television tuner; means for displaying the image received by the television tuner; camera means; means for compressing the image taken by the camera means; means for modulating the image compressed by the compressing means; and means for demodulating the image modulated by the modulating means; means for expanding the image demodulated by the demodulating means; and means for displaying selectively one of the image taken by the camera means and the image expanded by the expanding means; and a telephone line jack connected to a telephone line wherein outputting the image modulated by the modulating means through the telephone line jack to a telephone line and demodulating by the demodulating means the modulated image inputted from the telephone line through the telephone line jack enables the receiver to function as a videophone.

In the present invention, the above-mentioned configuration enables even a portable television receiver to transmit image data using a communication channel.

Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate presently preferred embodiments of the invention, and together with the general description given above and the detailed description of the preferred embodiments given below, serve to explain the principles of the invention.

FIG. 1 is a perspective view of a portable television receiver according to a first embodiment of the present invention, viewed from the front;

FIG. 2 is a perspective view of the portable television receiver of the first embodiment, viewed from the back;

FIG. 3 is a block diagram of the primary portion of the portable television receiver of the first embodiment;

FIG. 4 is a perspective view for explaining how to operate the portable television receiver of the first embodiment;

FIG. 5 is a perspective view of a portable television receiver according to a second embodiment of the present invention, taken from the back;

FIG. 6 is a perspective view of a portable television receiver according to a second embodiment of the present invention, taken from the front;

FIG. 7 is a perspective view of a portable television receiver according to a third embodiment of the present invention, viewed from the front;

FIG. 8 is a perspective view of the portable television receiver of the third embodiment with the camera section removed;

FIG. 9 is a perspective view of the portable television receiver according to the third embodiment, viewed from the back;

FIG. 10 is a block diagram of the primary portion of the portable television receiver of the third embodiment;

FIG. 11 is an exploded perspective view of an LCD;

FIG. 12 is an exploded perspective view of a flat fluorescent tube;

FIG. 13 is a flowchart for a binarization process;

FIG. 14 is a diagram for explaining an error diffusion process at a filter in the binarization process;

FIG. 15 is a perspective view of a portable television receiver according to a fourth embodiment of the present invention, viewed from the front;

FIG. 16 is a perspective view of the portable television receiver according to the fourth embodiment, viewed from the back;

FIG. 17 is a drawing to help explain the connection between the portable television receiver of the fourth embodiment and a telephone line;

FIG. 18 is a block diagram of the primary portion of the portable television receiver of the fourth embodiment;

FIG. 19 is a diagram of the format for image and sound in the time division multiplex system;

FIG. 20 is a flowchart for the operation of the control section in the portable television receiver of the fourth embodiment;

FIG. 21 is a flowchart of the operation of the control section continued from FIG. 20;

FIG. 22 is a transition diagram of the communication state during transmission in the fourth embodiment;

FIG. 23 is a transition diagram of the communication state during reception in the fourth embodiment;

FIG. 24 is a perspective view of an application where a card memory is applied to the portable television receiver of the fourth embodiment; and

FIG. 25 is a perspective view of an embodiment of a video printer used to print the image data stored in the card memory applied in FIG. 24.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will be explained hereinafter referring to the accompanying drawings.

With reference to FIGS. 1 to 4, a portable television receiver according to the first embodiment of the present invention will be explained hereinafter.

First, an arrangement of the first embodiment of the present invention will be described hereinbelow.

FIGS. 1 and 2 show an outward appearance of the portable television receiver of the first embodiment, viewed from the front and the back, respectively. Hereinafter, a case where an analog-telephone ordinary subscriber's line is used as a communication channel will be described. In FIG. 1, the portable television receiver 1 is basically composed of a receiver body 2 and a power supply section 3. The receiver body 2 is made up of a reinforced plastic enclosure measuring 65 mm in height, 60 mm in width and 24 mm in thickness. On the front of the body 2, a liquid-crystal display section 5 and a camera section 6 are integrally provided, as shown in FIG. 1. On the back of the body 2, a speaker section 8 is integrally provided, as shown in FIG. 2. A power supply section 3, when attached to the bottom of the receiver body 2, supplies a specific current to the body 2. Specifically, the power supply section 3 is made up of a battery pack incorporating dedicated nickel-cadmium (Ni--Cd) batteries. While in the first embodiment, explanation is given using a battery pack with built-in dedicated nickel-cadmium batteries as the power-supply section 3 attached to the bottom of the body 2, the invention is not limited to this example. For instance, the power-supply section 3 may be composed of a dry-battery pack containing five size AAA alkaline batteries, an AC adapter using an AC (alternating current) power supply, or a car adapter using a DC (direct current) battery in the cigarette lighter of a car. The liquid-crystal display section 5 is a TFT active matrix liquid-crystal display unit having a 1.4-inch screen. This display section is provided with a high-resolution color liquid-crystal display panel having 220.times.279=61380 pixels where each set of pixels corresponding to R (Red), G (Green), and B (Blue) known as primary colors is arranged in a delta. The camera section 6, as shown in FIG. 1, is a compact CCD (Charge Coupled Device) camera installed detachably on the same plane as the screen of the liquid-crystal display section 5. The camera section 6 is connected to the receiver body 2 with a video cable. The speaker section 8 is composed of, e.g., a dynamic cone-type loudspeaker, and outputs sound data from speaker holes 8b made inside a ringed noise-insulating wall 8a provided on the back of the body 2 as shown in FIG. 2. While in the first embodiment, explanation is given using a dynamic cone-type loudspeaker as the speaker section 8, the invention is not restricted to this example. For instance, a speaker used for the speaker section 8 may be an entire surface-driven-type electrostatic or flat loudspeaker or a dome loudspeaker.

As shown in FIG. 1, the receiver body 2 is further provided with various switches: they include a power switch 11, a power indicator 12, a tuning button 13, a volume control dial 14, an earphone terminal 15, a video switch 16, a video-mode select switch 17, and an image taking-in switch 18. The power switch 11 is used to determine whether or not the voltage supplied from the power-supply section 3 is applied to the portable television receiver 1. The power indicator 12 is made up of LEDs (Light Emitting Diodes) and lights up when the power switch 11 is on. The tuning button 13 is used to increase or decrease the tuning frequency. The volume control dial 14 is used to control the earphone volume. The earphone terminal 15 is a terminal for connecting to an earphone also serving as a wire antenna, and acts as an antenna terminal. The video switch 16 is a toggle switch for instructing the liquid-crystal display section 5 whether to display an image on the LCD screen or not. The video-mode select switch 17 is a switch for choosing one, as the image to be displayed on the liquid-crystal display section 5, among the televised image (the television mode), the image data taken in by the camera section 6 (the camera mode), and the image data already stored in a memory (the transmission mode). The switch changes from the television mode to the camera mode, and to the transmission mode each time the switch is pressed. The image taking-in switch 18 is a switch for indicating whether the image on the liquid-crystal display section 5 is to be stored as the image data in a particular memory or the image data is to be transmitted in the transmission mode.

FIG. 3 is a schematic block diagram of the portable television receiver shown in FIGS. 1 and 2. In FIG. 3, the portable television receiver 1 comprises the power supply section 3, a TV tuner section 4, the liquid-crystal display section 5, the camera section 6, a modulating section 7, the speaker section 8, an image compressing section 9, a control section 10, and a key operation section 10a. The modulating section 7, the speaker section 8, and the image compressing section 9, the control section 10, and the key operation section 10a are each connected to a bus B.

The power supply section 3 is composed of a battery pack containing nickel-cadmium (Ni--Cd) batteries, as mentioned earlier. The power supply section 3, when the power switch 11 is turned on, supplies a specific voltage to each section of the receiver body 2.

The TV tuner section 4 is made up of a tuner 21 and an ADC 22. The tuner 21 selectively receives a particular TV wave and outputs the received signal to a DD23 (explained later) of the liquid-crystal display section 5. The tuner also outputs the video signal to a video memory 32 in the image compressing section 9 via the ADC 22. The ADC 22 converts the analog video signal supplied from the tuner 21 into a digital signal. In FIG. 3, the audio signal (AUDIO OUT) demodulated at the tuner 21 is supplied to the earphone via the earphone terminal 15.

The liquid-crystal display section 5 is composed of a DD (Display Driver) 23 and an LCD (Liquid Crystal Display) 24, as shown in FIG. 3. The DD23 is a display driving section for driving the LCD 24 to display the image on the basis of the image signal taken in by the camera section 6 or the video signal received by the TV tuner section 4. More specifically, the DD23 converts the supplied video signal into an analog video signal (analog RGB signal) of a specific number of bits for 220.times.279 pixels and outputs the converted signal to the LCD 24. The LCD 24 is made up of a color liquid-crystal display unit having a liquid-crystal panel (not shown). In the LCD 24 of this embodiment, a compact flat fluorescent tube (not shown) is used as a backlight (back illumination).

The camera section 6 is composed of a lens 25, a CCD 26, and an ADC 27. The lens 25 is an optical lens formed of glass or plastic, provided on the body 2 of the portable television receiver 1. The CCD 26 generates an electric signal on the basis of the intensity of light focused by the lens 25, and supplies the generated electric signal (analog signal) to the ADC 27. The ADC 27 converts the video signal (analog signal) from the CCD 26 into a signal (digital signal) that can be processed in the image compressing section 9.

The modulating section 7 is composed of a buffer memory 28 and a data modulating circuit 29. The buffer memory 28 temporarily stores the compressed image data to be modulated at the data modulating circuit 29. The data modulating circuit 29 acts as a modulator which converts the digital signal held in the buffer memory 28 into a transmission signal (analog signal) that can be transmitted through a communication channel (in this case, an analog telephone ordinary subscriber's line). The data transfer speed of the data modulating circuit 29 in the first embodiment is set at 1200 bps because the image data is transmitted in sound using an analog-telephone ordinary subscriber's line.

The speaker section 8 is such that, for example, as shown in FIG. 4, sound data is supplied to the mouthpiece through the speaker holes 8b (see FIG. 2) made inside the noise-isolating wall 8a by pressing the noise-isolating wall 8a provided on the receiver body 2 against the mouthpiece of the handset 101 of a telephone. The noise-isolating wall 8a is formed of an elastic material such as synthetic rubber.

The image compressing section 9 comprises a buffer memory 30, a data compressing circuit 31, a video memory (VRAM) 32, and a DAC (Digital to Analog Converter: D/A converter) 33. The buffer memory 30 temporarily stores the image data that has undergone data compression at the data compressing circuit 31. The image data stored in compressed form in the buffer memory 30 is supplied to the modulating section 7 under the control of a CPU 35. The data compressing circuit 31 performs a compressing (encoding) process on the image data stored in the video memory 32 by a particular encoding method. Specifically, each 8.times.8 pixel block is compressed by the DCT (Discrete Cosine Transform), quantization, and Huffman coding techniques, using, e.g., a JPEG (Joint Photographic (Coding) Experts Group) algorithm, depending on the type of images to be handled (in this case, still images). This circuit then supplies the compressed image data to the buffer memory 30, which stores it. In this case, the data compressing circuit 31 has the capability of converting the image data to be transmitted in the form of a color video signal for 110.times.160 pixels in up to 4096 colors (12 bits) into a YC signal consisting of a luminance signal (hereinafter, referred to as signal Y) corresponding to 220.times.279 pixels and a color signal (hereinafter, referred to as signal C) corresponding to 4096 colors. The above-mentioned 12 bits of digital image data for 220.times.279 pixels is converted into 12 bits of image data for 110.times.160 pixels. The compression factor of the compressed image data to be transferred is determined to be nearly 7/100 (nearly 68/1000) in consideration of the picture quality after compression and expansion. The video memory 32 is composed of a VRAM (Video RAM), which is a semiconductor image memory for storing the original image data (digital data) to be compressed at the data compressing circuit 31. The DAC 33 converts the video signal (digital signal) of the image data stored in the video memory 32 into a signal (analog signal) that can be displayed on the liquid-crystal display section 5, and outputs the converted signal. In the first embodiment, because an analog data driver is used for the driver for the aforementioned LCD 24 to provide multi-gradation representation, the DAC (D/A converter) is required. However, when a digital data driver is used as the data driver for the liquid-crystal display section 5, the DAC 33 is not required.

The control section 10 comprises a CPU (Central Processing Unit) 34, a RAM (Random Access Memory) 35, and a ROM (Read Only Memory) 36. The CPU 34 supplies various control signals via the bus B to the individual circuits in the portable television receiver 1. The CPU 34 also outputs the compressed image data supplied via bus B from the image compressing section 9 to the modulating section 7 via bus B. The RAM 35 is a semiconductor memory for storing the program data used in a programmed process executed at the CPU 34, the compressed image and sound data, etc. The ROM 36 is a semiconductor memory for storing programs and data used in the portable television receiver 1. The key operation section 10a is composed of various operation switches including the video switch 16, the video-mode select switch 17, and the image taking-in switch 18. When a key switch is pressed, the process corresponding to the key switch is executed by the CPU 34. The bus B is a common signal path to which the modulating section 7, the image compressing section 9, the control section 10, and the key operation section 10a are connected separately, and is made up of an address bus for specifying an address and a data bus for transferring data.

The image data dealt with in the first embodiment is the color image data one screen of which has 110.times.160 pixels in 4096 colors (12 bits). The amount of image data for one screen comes to 110.times.279.times.12=211200 bits (approximately 25.8 kilobytes). This is simultaneously compressed at a ratio of approximately 68/1000 by the image compressing process into 14400 bits of image data. These 14400 bits are transferred in units of 1200 bits per second, and consequently still images are transferred intermittently at a rate of one frame in 12 seconds (=14400+1200). Therefore, the amount of data actually transferred in a second is 17600 bits (approximately 2.15 kilobytes) of image data obtained by dividing 211200 by 12. These 17600 bits of image data is compressed at a ratio of approximately 68/1000 into an video code including 1200 bits of image data.

Generally, liquid-crystal display units are much thinner than such image display means as CRTs and are easy to make more compact and lighter. Because active matrix LCDs provide minute half-tone control, assure a high contrast ratio, and achieve a high response speed, as compared with simple matrix LCDs, the former are effective devices in the fields requiring multi-gradation color of high picture quality. Particularly, TFT active matrix LCDs with three terminals provide as high a picture quality as that of CRTs.

In the first embodiment, to make more use of the features of the liquid-crystal display unit, a flat fluorescent tube is used as a backlight, thereby making the unit more compact.

Next, an operation of the first embodiment of the present invention will be described hereinbelow.

An operation of the control section 10 in FIG. 3 will be explained first. The program corresponding to the processing effected by the CPU 34 in the control section 10 is stored in the ROM 36 in the same control section 10. The portable television receiver 1 of the first embodiment has a mode (the television mode) in which the TV tuner section 4 receives a television broadcast and the received broadcast is displayed on the liquid-crystal display section 5 (i.e., in this mode, the portable television receiver 1 acts as a television set) and a mode (the camera mode) in which the image data is taken in from the camera section 6.

In the television mode, by turning on the power switch 11 and operating the tuning button 13, the wave from the desired television station is tuned in and the televised image is displayed on the liquid-crystal display section 5, as well as the sound is provided through an earphone connected to the earphone terminal 15. The volume of the earphone is adjusted to the optimum level with the volume control dial 14. When the user wants to listen to only the sound in receiving a TV broadcast, he or she can turn off the televised image on the liquid-crystal display section 5 by pressing the video switch 16. The image data corresponding to the televised image is supplied to the video memory 32 via the ADC 22.

To specify the camera mode, the video-mode select switch 17 is pressed. By doing this, the image data from the camera section 6 is displayed on the LCD 24 of the liquid-crystal display section 5 (the video through image). With either mode specified, to record the image appearing on the LCD 24, the image taking-in switch 18 is pressed. By doing this, the video signal received at the TV tuner section 4 in the television mode or the image data taken in from the camera section 6 in the camera mode is converted into digital data and then stored in the video memory 32. The image data stored in the video memory 32 is compressed at the data compressing circuit 31 and then stored in the buffer memory 30.

To specify the transmission mode, the video-mode select switch 17 is pressed again. Then, the image data already stored in the memory is selected. As shown in FIG. 4, by pressing the noise-isolating wall 8a formed on the back of the receiver body 2 against the mouthpiece of the handset 101 of the telephone now in a busy state, the speaker section 8 is made ready to output the sound data. In this state, when the image taking-in switch 18 is pressed, the compressed image data stored in the buffer memory 30 is outputted to bus B under the control of the CPU 34. A header (identifier) in a specified format is added to the compressed image data and then temporarily stored in the buffer memory 28 in the modulating section 7 via bus B. Next, the data modulating circuit 29 reads the compressed image data from the buffer memory 28 sequentially, and modulates the read-out compressed image data. The modulated compressed image data is outputted in the form of sound data, which is transmitted through a communication channel (in this case, an analog ordinary subscriber's line) to the other party.

On the other hand, the image data (digital data) written in the video memory 32 is D/A converted by the DAC 33, and the converted data is supplied to the DD 23. The DD 23 displays the image data on the LCD 24. Each time the video-mode select switch 17 is pressed, the televised image, the image of the subject from the camera section 6, and the image stored in the memory are displayed one after another in that order. When the operator wants to record the image on the calling party side (the image to be transmitted) appearing on the LCD 24 during telephone conversation, he or she presses the image taking-in switch 18. This causes the image data stored in the buffer memory 30 to be stored in the RAM 35. In this case, as explained in the aforementioned transmission process, the amount of image data for a compressed single screen is approximately 25.8 kilobytes. Therefore, if the image data storage area of the RAM 35 has a capacity of 256 kilobytes, it can store nearly 10 screens of image data. When during communication, the state of the communication channel deteriorates and the picture quality transmitted worsens seriously, the transmission of the image data may be stopped automatically.

As has been described above, with the first embodiment, high-quality images are transmitted through an analog ordinary subscriber's line by transferring a screen of image data (211200 bits) displayed on the LCD 24 at a rate of one screen in 12 seconds, conforming to the data transfer speed (1200 bps) of the compressed image data transmitted through the communication channel. Specifically, because the screen size of the LCD 24 is 1.4 inches and its single screen has 110.times.160 pixels.times.12 bits (4096 colors)=211200 bits of data, the image data is transferred at a rate of one frame in 12 seconds. However, as the number of pixels and the number of colors (the number of gradations) in one screen increase or decrease as a result of the change of the screen size, the time required to transfer a single screen of image data is changed. Specifically, for example, it is assumed that a mode in which the image data is transferred in 4096 colors is determined to be a normal mode, and a mode in which representation is made in 65536 colors (16 bits) using the same number of pixels (110.times.160 pixels) is determined to be a high-quality mode. When the image data is transferred in the high-quality mode, the amount of image data for one screen is 110.times.160.times.16=281600 bits (approximately 34.4 kilobytes), which is compressed by the image compressing process at a ratio of approximately 68/1000 into 19200 bits of image data. Still images are transferred at a rate of one frame during the time obtained by dividing these 19200 bits by the number of bits (1200 bits) transmittable in a second (that is, 19200+1200=16 seconds).

Conventional television receivers are generally manufactured on the assumption that they are installed in a room. Therefore, once they are installed in a place, it is not easy to move them to another place where the user wants to watch a TV program. With the first embodiment, since the picture quality of recent liquid-crystal display units has improved much, a color TFT liquid-crystal display unit is used for the display section in place of a conventional CRT, thereby reducing the power consumption and making the receiver more compact and lighter. In this case, using a small flat fluorescent tube for a backlight in the liquid-crystal unit enables the LCD 24 to be much thinner, thereby making the unit compact and light remarkably. By providing a composite video input/output terminal or an analog/digital RGB input/output terminal as a video input terminal for the ADC 22 that outputs the input signal from the tuner 21 to the video memory 32, the receiver can be connected to video equipment including a video cassette recorder (VCR) and a laser disc player (LDP) or to a computer. For instance, connecting a video cassette recorder with a video output terminal to the receiver enables video images to be displayed on the liquid-crystal display section 5.

The compression method of image data is not limited to the JPEG algorithm in this embodiment. For instance, a block coding method, a predictive coding method, and an orthogonal transform coding method may be used to compress the image data.

With reference to FIGS. 5 and 6, a portable television receiver according to a second embodiment of the present invention will be explained hereinafter.

FIGS. 5 and 6 are perspective views of a portable television receiver of the second embodiment, taken from the back and the front, respectively. While in the first embodiment, the camera section 6 is fixed, it may be mounted movably, thereby making it possible to transmit a wider subject image. Specifically, a portable television receiver 100 in FIGS. 5 and 6 is provided with a lightweight electronic camera. Its enclosure 100a is formed into a laterally long, narrow, thin rectangular parallelepiped. The enclosure 100a contains a tuner section and a liquid-crystal display section 105 that displays the video signal demodulated at the tuner section, both sections constituting the television receiver. It also contains an earphone terminal 115 for outputting the audio signal demodulated at the tuner section. Inserting an earphone serving as a wire antenna into the earphone terminal 115 enables the user to listen to the sound as well as to receive the televised signal. On the front of the enclosure 100a, there is provided a speaker section 108 which compresses the image during image transmission, modulates the compressed image into an audio signal, and outputs the audio signal. The speaker section 108 is composed of a noise-isolating wall 108a formed on the front of the enclosure 100a and speaker holes 108b made inside the noise-isolating wall 108a. The speaker section is pressed against the mouthpiece of a telephone 101 to output the sound data.

On the right of the enclosure 100a, a camera section 1