The present invention relates to an image printer system having a printer equipped with color 5 correcting means capable of printing color corrected image and graphics data. Background Art

Fig. 1 shows one example of a conventional thermal printer system including the color correcting 10 means. In the figure, image signals transmitted from an imaging device (not shown) such as a video camera or the like are A/D—converted by an image input device 1 and are then stored as digital signals or data in an image memory 2 incorporated in a thermal IB printer TP. Graphics signals output from a graphics creating device (not shown) such as a video camera or the like are A/D-converted by a graphics input unit 3 and are stored in a graphics memory 4 of the thermal printer TP. 0 The outputs of the image memory 2 and the graphics memory 4 are connected to a selector circuit 5. The selector 5 selects the print data from the image memory 2 or the other print data from the graphics memory 4 under control of the control 5 circuit 6 (for instance, a microcomputer). The selected data are supplied to a look—up table memory 7. The look-up table memory 7 performs a color corrections on the print digital data supplied thereto in correspondence to a variety of the 0 properties of color donors of ink donor films.

Generally, a memory (for example, ROM or RAM) is used to store the data indicating what color correction is to be effected on the supplied print digital data. The digital data on which the color 5 correction has been effected by the look—up table memory 7 are supplied through a thermal head driver 8 to the thermal head 9. The thermal head driver 8

feeds signals (for example, pulse width modulated signals) to a shift register (not illustrated) provided in the thermal head 9 ₌ These signals serve to determine an ON—time of the respective heating elements ^" (not illustrated) of the thermal head 9 on the basis of the color corrected digital data. The heating elements of the thermal head 9 are selectively driven in accordance with the signals which have thus been stored in the shift register, thereby heating the ink donor films (not illustrated). The printing is executed on a recording medium paper.

In the foregoing conventional thermal printer, the look—up table stored in the memory 7 is used, in common for the color corrections of different kinds of data. For this reason, if the print data are input from two sets of cameras having different characteristics to the image printer system, there can arises defects in the color of the print. Also, since only one look—up table is provided, when concurrently printing different kinds of data, such as image data and graphics data, the same color correction is effected on both two sets of data, and a less than optimum quality print or picture is achieved.

Disclosure of the Invention

It is an object of the present invention to obviate the above—described defects and to provide an improved image printer system capable of effecting desired color corrections on either different types of data or provided from different sources.

To achieve the above—described object, a thermal printer system according to the present invention comprises a thermal printer; storage devices for storing a plurality of digital image signals obtained by effecting digital conversion on a plurality of analog image signals, means for storing

a plurality of look-up tables with each table corresponding to a particular one of storage devices for performing a transformation on digital image signals to effect desired color corrections on such digital image signals supplied from the corresponding storage device; and a control circuit for selecting one of the look—up table memories and for causing the selected look-up table memory to provide its color—corrected digital image signals to the thermal printer.

The look-up table memories provided for each set of digital image signals supplied from the corresponding storage devices perform desired color corrections on each set of image signals thereby providing high image print quality for different types of data. Brief Description of the Drawings

Fig. 1 is a block diagram of the prior art thermal image printer system; Fig. 2 is a block diagram showing one embodiment of thermal printer system according to the present invention; and

Fig. 3 is a diagram showing a developed example of the thermal printer system according to the present invention.

Modes of Carrying Out the Invention

Fig. 2 shows a block diagram of one embodiment of a thermal printing system according to the present invention. In this figure, like components are designated by the same reference numerals as used in Fig. 1.

In this embodiment, analog image signals are A/D-converted by an image input device 1 and are then stored as digital image signals or data in an image memory 2 incorporated in a thermal printer TP. Analog graphics signals are A/D—converted by a

graphics digital signals of input unit 3 and are likewise stored as graphics data in a graphics memory 4 of the thermal printer TP.

The respective outputs of these memories 2 and 4 are supplied to the corresponding image and graphics look—up table memories 10 and 11. A control circuit 12 selects only one of the look—up table memories 10 and 11 at a time. Various kinds of structures may be adopted for the control circuit 12. For instance, it is possible to employ a microcomputer which restores a format on the recording medium indicating where the image and the graphics are to be printed. In accordance with this format, the microcomputer makes a selection by enabling the image look—up table memory 11 when printing graphics data. The print digital data output from one of the look—up table memories 10 and 11 are supplied to the thermal head driver 8. The subsequent processes have already been explained in accordance with Fig. 1 and the description thereof will be omitted.

The ^' operation of the embodiment of Fig. 2 will be described in connection with an example where a color picture of somebody's face and logograms (graphic data) are printed one after another. The face is imaged by a video camera, and the video signals thereof are input to the image input device 1. Then the image input device 1 divides the video signals into the color signals which exhibit the individual color components such as red (R) , green

(G), and blue (B); the color signals are subsequently A/D—converted into digital image signals corresponding to the respective color components of R, G, and B. The digital image signals are further converted into other digital image signals indicating the color components such as cyan, magenta, and yellow. The digital image signals produced by the

image input device 1 are stored in the image memory 2. On the other hand, the logograms are input from another camera, the properties of which differ from those of the video camera that images the picture. As in the case of the former image signal processing, these video signals are converted into the digital graphics signals by means of the graphics input unit 3 and are then stored in the graphics memory 4. Alternatively, the digital signals indicating logograms may be obtained by graphics—processing from a computer, and hence the digital signals from a computer can be stored in the graphics memory 4.

In the case of printing the image or picture, the control circuit 12 selects the image look-up table memory 10, and this memory 10 performs the color correction on digital image signals in accordance with the properties of the ink donor film and the difference in characteristics of the video camera. When printing graphics data, the control circuit 12 selects the graphics look—up table memory 11. This memory 11 performs the color correction on the graphics -data in accordance with the properties of the ink donor film. It will be understood that the color correction based on the in characteristics of the video camera has already been done by the image look-up table memory 10, so that the look-up table memory 11 does not generally carry out such color correction. If necessary, the graphics look-up table memory 11 may be a device which effects an artificial color correction (for example, a color correction in which specified colors are emphasized) on the graphics data.

The thermal head driver produces the data for controlling the ON-period of the heating elements of the thermal head 9 and sends the data to the thermal head 9 in accordance with image or graphics

data. Image data has been color—corrected by the look— p table memory 10. Graphics data has been color—corrected by the look—up table memory 11. Since the look—up table memories are provided for each kind of data, it is possible to make the color correction for the difference characteristics of the respective video cameras. Owing to this color correction, the images having the best quality can be acquired. In addition, look—up table memories having different color correction properties from each other can be employed as desired, and it is therefore possible to obtain different kinds of outputs appropriate to the printing process. When a thermal printer system is used, for example, in printing of an identification card, the best quality of the image can be acquired by providing three look—up table memories corresponding to the image data in the form of a picture, the logograms of a company mark or a school mark and the text such as an address or a name.

In the embodiment of Fig. 2, two types of data—the image data and the graphics data—are input, and the color corrections are made by the look—up table memories having different color correction properties from each other. It is apparent that this invention can be applied to a process of concurrently printing the image data and the text data. Two different types of video signals are not necessarily input, but both of the two input video signals may be the image signals or the graphic signals.

In Fig. 3, a plurality of, input units

13a. 13,D, .... 13.N. and memories 14a, 14,b,

..., 14 are provided. The number N of such devices is equal to 2 or more, and the same or different types of input video signals such as image signals and graphics signals, are input Look-up table

memories 15 , 15. , ..., 15.. are provided, a b corresponding to the respective memories 14 — c _*

14 , to perform desired color corrections on the digital print data. Consequently, on the basis of the digital data input to the thermal printer TP an output print with a desired image quality can be obtained. Industrial Applicability and Advantages

The present invention has been described as improving prints in thermal printer systems.

However, the present invention can be applied to all types of image printer systems such as a laser printer system, an LED printer system, an ink jet printer system and the like.