JP2658517B2 - Video printer - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video printer that prints image information input by a video signal or the like, and more particularly to a video printer that can automatically adjust contrast.

(Prior Art) Japanese Patent Application Laid-Open No. 63-179677 discloses a video printer provided with image quality adjusting means for manually adjusting the image quality of an input video signal.

Japanese Patent Application Laid-Open No. 1-2229572 discloses a method for determining the contrast of an original image, a means for storing a plurality of energization data, and a means for selecting energization data in accordance with the result of the contrast determination. 2. Description of the Related Art A video printer has been disclosed in which a power supply time of a heating element in a heating head portion is controlled in accordance with data to obtain a print image having a predetermined contrast.

(Problems to be Solved by the Invention) However, a video printer provided with a manual image quality adjusting means must adjust the image quality every time an image is different.
The operation is troublesome.

On the other hand, a device that selects energization data must have a large number of energization data in order to improve the accuracy of correction of contrast.

The present invention has been made to solve such a problem, and an object of the present invention is to automatically adjust the level of an image signal to be supplied to a printing unit so as to print a predetermined contrast regardless of the density of an original image. It is to provide a video printer which can obtain a video printer.

(Means for Solving the Problems) In order to solve the above problems, a video printer according to the present invention includes a horizontal weighting circuit for weighting a specific range in luminance information of an original image for one frame, and a vertical weighting circuit. A direction weighting circuit, weighted averaging means for weighing the weighted luminance information of the original image for one frame, and averaging the weighted value with the area of the original image for one frame or the total number of pixels; And a level adjusting circuit for controlling the amplification of the original image for one frame based on the output from the converting means.

(Operation) Since the level of the image signal supplied to the printing unit is adjusted based on the information related to the luminance of the original image signal, even if the contrast of the original image is insufficient or too bright, it is corrected in a state where it is corrected. Can print automatically.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a block diagram of a video printer according to the present invention.

The video printer 1 receives a composite video signal VC from a television, a VTR or the like and a still image signal VA supplied in an analog RGB system as input and performs color printing of the original image information. A processing unit 3 and a printing unit 4 are provided.

The image memory unit 2 includes a Y / C separation circuit 21 for separating a luminance signal Y and a chrominance signal C from the composite video signal VC applied to the composite video signal input terminal 5, and demodulates the separated color signal to generate two color difference signals. Signal and combine it with the luminance signal Y to obtain R,
A color signal reproduction circuit (decoder) for reproducing G and B primary color signals 2
2 and A / D converters 23R, 2 which sample and quantize each primary color signal R, G, B at a predetermined cycle and convert them into digital primary color signals RD, GD, BD.
RA for temporarily storing 3G, 23B and digital primary color signals RD, GD, BD
Storage circuits 24R, 24G, and 24B composed of M, etc .;
D / A converters 25R, 25G, and 25B that convert digital primary color signals read from 24G and 24B into analog primary color signals RA, GA, and BA, and various horizontal and vertical synchronization signals Hd and Vd from the luminance signal Y Synchronization separation circuit 26 that extracts and outputs
The control circuit 27 controls writing and reading of the storage circuits 24R, 24G and 24B based on Hd and Vd.

In the standby state, the image memory unit 2 converts the primary color signals R, G, and B reproduced from the input composite video signal VC through the A / D converters 23R, 23G, and 23B into the digital primary color signals R at a predetermined cycle.
D, GD, BD, and write to each of the storage circuits 24R, 24G, 24B in a predetermined order, and the written digital primary color signals RD, GD,
The BD is read out in a predetermined order, converted into analog primary color signals RA, GA, and BA via the respective D / A converters 25R, 25G, and 25B, and output. Each storage circuit 24R, 24G, 24B has at least one
It has a capacity to store digital primary color signals RD, GD, BD for frames.

When a printing command is applied to the printing command input terminal 27a, the control circuit 27 outputs a digital primary color signal for one frame of the video signal.
New writing is stopped when RD, GD, and BD are written to each of the storage circuits 24R, 24G, and 24B. Then, the control circuit 27 outputs the digital primary color signals RD, GD, B fixed to the storage circuits 24R, 24G, 24B.
By repeatedly reading D at a predetermined frame period, the original image signals to be printed are continuously output as analog primary color signals RA, GA, and BA via the D / A converters 25R, 25G, and 25B.

Note that the control circuit 27 includes a circuit that generates synchronization signals HD and VD corresponding to the synchronization signals Hd and Vd even when various synchronization signals Hd and Vd from the period separation circuit 26 are not provided. When the composite video signal VC is applied to the composite video signal input terminal 5, the synchronization signals HD and VD synchronized with the various synchronization signals Hd and Vd output from the synchronization separation circuit 26 are supplied to the signal processing unit 3. At the same time, based on these signals HD, VD, the writing / reading to the storage circuits 24R, 24G, 24B is controlled, and when the composite video signal VC is no longer applied, various synchronization signals HD, It is configured to output VD to the signal processing unit 3 and to read stored image information based on these various synchronization signals.

The analog primary color signals RA and G output from the image memory unit 2
A, BA and various synchronization signals HD, VD
Is supplied to the signal processing unit 3 via the. The print input selection circuit 6 switches between a signal input to the signal processing unit 3 and an output signal of the image memory unit 2 or a still image signal VA supplied from another device (not shown). .
In this embodiment, an analog RGB signal capable of arbitrarily designating the intensity of each color is used as the still image signal VA, and is supplied to the signal processing unit 3 including various synchronization signals and a signal relating to a printing command by an interlocking switch. The configuration is such that the original image signal is switched.

The signal processing unit 3 receives the original image signals RI, GI, and BI selected by the print input selection circuit 6 as inputs, and adjusts the levels of the print primary color signals RP, GP, and BP to be supplied to the print unit 4; , Each output signal RP, GP, BP of the level adjustment circuit 31
Circuit 32 which combines the luminance signal YP and the color signal CP with the input as the input, generates a composite video signal VP based on each output YP, CP of the encoder circuit 32 and various synchronization signals HD, VD, and outputs it to the monitor terminal 33a. Y / C mixing circuit 33 and weighted averaging means for weighting at least information relating to luminance in the original image signals RI, GI, and BI inputted to the signal processing unit 3 by weighting a specific range of the image. 34, each output signal of the level adjustment circuit 31 based on the output of the weighted average means 34.
RP, GP, BP are controlled.

The level adjustment circuit 31 includes voltage-controlled variable gain wideband amplifiers (hereinafter, referred to as video amplifiers) 31R, 31G, and 31B provided corresponding to the respective original image signals RI, GI, and BI. 31R, 31G, and 31B are configured so that the gain can be increased or decreased within a predetermined range based on the DC voltage VDC applied to the gain control terminal 31a. The video amplifiers 31R, 31G, and 31B are configured so that their gains decrease as the DC voltage VDC increases.

The weighted averaging means 34 includes an area generator 40 for generating a signal related to a range to be weighted and a weighting coefficient.
And a clamp pulse generation circuit 41 that receives the horizontal synchronization signal HD as an input and generates a clamp pulse CLUP synchronized with the horizontal synchronization signal HD,
It comprises a clamp circuit 42 that receives a luminance signal YP and outputs a luminance signal YA that has been subjected to DC component correction so as to make the pedestal level uniform, a gate circuit 43, an integral averaging circuit 44, and a voltage holding circuit 45.

The area generator 40 includes a horizontal weighting circuit 40a that generates a horizontal weighting voltage signal HW based on the horizontal synchronization signal HD, and a vertical weighting circuit that generates a vertical weighting voltage signal VW based on the vertical synchronization signal VD. 40
b, and an arithmetic circuit 40C that receives the output voltages HW and VW of the weighting circuits 40a and 40b as inputs and outputs a weighting voltage signal W corresponding to the product.

 FIG. 2 is an explanatory diagram showing an example of weighting.

In this embodiment, even if the upper part of the screen is bright (for example, in the case of a landscape image and the upper part is bright sky), the mountain-shaped weighted voltage signal HW is applied in the horizontal direction so that the contrast in the central part of the screen is appropriate. , A trapezoidal weighting voltage VW is generated by each of the weighting circuits 40a and 40b, and the weighting of the luminance signal in the portion indicated by hatching on the screen is increased.

The vertical weighting voltage waveform VW shown in FIG.
Indicates a case of non-interlaced scanning, and in the case of interlaced scanning, a voltage waveform different from that shown in FIG.

Weighted voltage signal W generated by area generator 40
Is applied to the control input terminal 43a of the gate circuit 43. This gate circuit 43 has a signal input terminal 43b and a signal output terminal 43c.
The transfer coefficient between the input and output terminals is varied based on the voltage applied to the control input terminal 43a. For example, a voltage-controlled amplifier or attenuator, or an FET (field effect transistor)
And a circuit that applies a weighted voltage signal W to the gate and uses the drain and source as input / output terminals.

A luminance signal YA output from the clamp circuit 42 is applied to an input terminal 43b of the gate circuit 43, and the weighted luminance signal YB output from the output terminal 43c is integrated with an integral averaging circuit having a predetermined integration time constant. 44, where the luminance components for one frame are averaged with the integrated weighting amount according to the area for one frame, and the averaged voltage signal YC is held by the voltage holding circuit 45, and the held. The voltage is output as a DC voltage VDC for gain control of each video amplifier 31R, 31G, 31B. The voltage holding circuit 45 is configured to sample the average output voltage YC for one frame based on the vertical synchronization signal VD and hold the sampled voltage, and the output voltage of the integration circuit 44 is set in advance. When the voltage is out of the range (when no video signal is input, etc.), a predetermined specific DC voltage VDC is output to keep the gain of each video amplifier 31R, 31G, 31B in the initial state. doing.

With the above configuration, the weighted averaging means 34 outputs the signal YB obtained by weighting the signal YA having the same pedestal level of the luminance signal YP output from the encoding circuit 32 to the range specified by the area generator 40. An operation of obtaining a voltage signal YC obtained by integrating and averaging the luminance information by the integration and averaging circuit 44 is performed for each frame, and the voltage signal YC obtained by weighting and averaging the luminance information is held by the voltage holding circuit 45 and DC voltage V that controls the gain of video amplifiers 31R, 31G, 31B
Output as DC. Therefore, when the contrast of the print primary color signals RI, GI, and BI input to the signal processing unit 3 is insufficient, the weighted average output YC is a low voltage, and the DC voltage VDC of the gain control is a low voltage. Video amplifier 31R, 31G, 3
Increase 1B gain. Conversely, the printing primary color signals RI, GI,
If the contrast of BI is excessive, each video amplifier 31R,
Decrease the gain of 31G and 31B. Therefore, the print primary color signals RP, GP, BP, which are the outputs of the video amplifiers 31R, 31G, 31B, are automatically adjusted to an appropriate contrast state.

The monitor terminal 33a is an output terminal for monitoring an image related to the printing primary color signals RP, GP, BP, the level of which has been adjusted by the level adjusting circuit 31, on a monitor television or the like (not shown).
In this embodiment, a composite video signal input type monitor TV is assumed, and the configuration is such that a composite video signal is output via the Y / C mixing circuit 33.However, when a monitor having a Y / C separation input is used, The configuration may be such that the output signals YP and CP of the encoding circuit 32 are directly supplied. When a monitor having an analog RGP input or the like is used, the configuration may be such that each output signal RP, GP, BP of the level adjustment circuit 31 is directly supplied.

Further, the area generator 40 is configured to generate a signal for weighting a predetermined range which is set in advance, but a means for designating an area to be weighted by operating a cursor or a pointing device is provided on the monitor TV side. The designated area information is supplied to the area generator 40 in the signal processing unit 3 to perform weighting based on the luminance information of the designated area on the screen of the monitor television, and the video amplifiers 31R, 31G, 31B A configuration for controlling the gain may be adopted.

The printing unit 4 includes a selector circuit 4a for selecting the print primary color signals RP, GP, BP, an A / D converter 4b, a print signal processing circuit 4c, and a thermal head 4d.
The thermal head 4d is driven for each of RP, GP, and BP to perform multi-tone color printing.

When the printing operation control signal PS output from the control circuit 27 in the image memory unit 2 is input, the printing unit 4 waits until the level adjustment operation based on the luminance information in the signal processing unit 3 is completed. The printing operation is performed after a lapse of time. Also, the weighted averaging means of the signal processing unit 3
For example, a level adjustment operation completion detection circuit that detects that the previously held voltage and the currently held voltage are the same or within a predetermined voltage difference is provided in 34, and the printing operation can be started based on the detection output. The time until the start of printing may be shortened.

With the above configuration, the original image signals RI, GI, and BI input to the signal processing unit 3 are supplied to the printing unit 3 and the monitor terminal 33a based on information on the luminance of the original image signals RI, GI, and BI. Since the level to be adjusted is adjusted, the original image signals RI, GI, BI
If the contrast of the image is insufficient or the image is too bright, printing can be performed automatically in a corrected state, and the contrast is automatically corrected by connecting a monitor TV or the like to the monitor terminal 33a. Image can be confirmed.

In this embodiment, the configuration in which the contrast is corrected based on the luminance signal YP output from the encoding circuit 32 has been described, but the green primary color signal containing a large amount of luminance information has been described.
The configuration may be such that the contrast is corrected based on the GP.

The signal processing unit 3 shown in FIG.
Since the configuration is such that the gain of 31 is controlled by a feedback loop based on analog signal processing, high-speed contrast correction processing can be performed with a relatively small circuit scale.

Next, another embodiment of the video printer according to the present invention will be described with reference to the block diagram shown in FIG.

The video printer 51 includes an image memory unit 52, a monitor interface unit 53, and a print unit 54.

The image memory unit 52 reproduces the primary color signals of R, G, and B, and the Y / C separation circuit 21 that separates the luminance signal Y and the color signal C from the composite video signal VC applied to the composite video signal input terminal 55. A color signal reproducing circuit (decoder) 22, A / D converters 23R, 23G, and 23B for converting the primary color signals R, G, and B into digital primary color signals, and storage circuits 24R, 24G, and 24B composed of RAM and the like. And storage circuits 24R, 24
D / A converters 25R, 25G, 25B for re-converting digital primary color signals read from G, 24B into analog primary color signals, sync separation circuit 26, control circuit 56, and area designation for specifying the area for weighted averaging Means 57, weighted average means 58, and weighted average means
A calculating means 59 for performing a predetermined operation on the digital primary color signals stored in each of the storage circuits 24R, 24G, 24B based on the output of 58 to obtain a contrast corrected digital primary color signal.

In the standby state, the image memory unit 52 converts the primary color signals R, G, and B reproduced from the input composite video signal VC into digital primary color signals in predetermined synchronization via the A / D converters 23R, 23G, and 23B. RD, GD, BD and write to each storage circuit 24R, 24G, 24B in a predetermined order, and read out the written signal in a predetermined order to read each D / A converter 25R, 25G, 25B. The analog primary color signals are converted into analog primary color signals RA, GA, and BA and output. Thus, the composite video signal YC can be monitored by a monitor television or the like (not shown) via the monitor interface unit 53. Each storage circuit 24R, 24G, 24B has a capacity capable of storing at least one frame of digital primary color signals RD, GD, BD.

When a print command is applied to the print command input terminal 56a, the control circuit 56 outputs a digital primary color signal for one frame of the video signal.
When RD, GD, BD are written to each memory circuit 24R, 24G, 24B, A
/ D output control signal ADCE to generate each A / D converter 23R, 23G, 2
Control the output of 3B to a high impedance state. And
The control circuit 56 outputs the weighted average processing start signal AVES to activate the weighted average means 58.

The weighted averaging means 58 is for weighing the green digital primary color signal GD read from the storage circuit 24G for all the pixels, and is connected to the input terminal 58a based on the weighting constant WD for each pixel given from the area designating means 57. A multiplying circuit that multiplies (or divides) the applied green digital primary color signal GD, an integrating circuit that integrates the multiplied output of each pixel, and a weighted average output AVEW that divides the integrated result of all pixels by a predetermined number Is composed of a division circuit that outputs the output terminal 58b.

The area designating means 57 stores a preset weighting constant for each pixel or a preset pixel group region.
M, etc., and an address signal A given from the control circuit 56.
It is configured to output a weighting coefficient WD for the primary color signal GD of the pixel currently given to the weighted averaging means 58 based on the DDR.

Note that the area designating means 57 may be configured to generate a predetermined weighting coefficient for a region designated on the screen of the monitor television.

The operation means 59 performs a corresponding multiplication or division operation based on the weighted average output AVEW.
Is at the H level, the result obtained by performing a predetermined operation on the red digital primary color signal RD supplied to the input terminal 59b is output to the output terminal 59c, and the input terminal 59e, similarly designated by the control input terminal 59d or 59g, Digital primary color signals GD and BD given to 59h
And performs a predetermined operation on the corresponding output terminals 59f and 59i.
It is configured to output to.

When the control circuit 56 activates the weighted averaging means 58 and obtains the weighted average output AVEW for all the pixels, the contrast correction signals RC, GC, and BC are sequentially set to the H level for each color, and the respective storage circuits 24R, 24G , 24B, the digital primary color signals RD, GD, B
Print primary color signals RDP, GD read out one pixel at a time from D and subjected to contrast correction corresponding to the weighted average output AVEW
The P and BDP are obtained by the calculating means 59, and these are written to the address of the read pixel.

The control circuit 56 stops the operation of each of the D / A converters 25R, 25G, and 25B by the D / A conversion control signal DACE while performing the weighted average calculation and the contrast correction calculation, and also stores the memory circuits 24R and 24G. , 24B are controlled so as to match the arithmetic processing speed of the weighted averaging means 58 and the arithmetic means 59.

Then, when the contrast correction has been completed for all pixel information of the storage circuits 24R, 24G, and 24B,
The operation of the A converters 25R, 25G, and 25B is restarted, and a print start command is output to the print unit 4 to start the print operation.

Because of the above configuration, the digital primary color signals RD, GD, and BD once stored in the storage circuits 24R, 24G, and 24B have sufficient contrast based on the weighted average result of the green primary color signal GD containing a lot of luminance information. It is determined and rewritten to the print digital primary color signals RDP, GDP and BDP corrected based on the determination result, so that the image signal supplied to the printing unit 4 is automatically adjusted to an appropriate level.

Note that the weighted averaging means 58 may be configured to obtain a signal related to luminance from the three primary color signals read from each of the storage circuits 24R, 24G, 24B, and to perform a weighted average of the signal related to luminance.

Also, the print digital primary color signal RD after contrast correction
A storage circuit for temporarily storing P, GDP, and BDP is provided independently, and signals supplied to a monitor television or the like via the monitor interface unit 53 are switched so as to switch the input of the D / A converters 25R, 25G, and 25B. You may comprise so that it may not be interrupted.

The monitor interface unit 53 includes the encoder circuit 32,
It comprises a Y / C mixing circuit 33. The print unit 54 is different from the print signal processing circuit 4c in that the printing start control conditions are different.
It is the same as that shown in FIG.

(Effects of the Invention) As described above, the video printer according to the present invention includes a horizontal weighting circuit and a vertical weighting circuit for weighting a specific range in luminance information of an original image for one frame; A weighted averaging unit for weighing the weighted luminance information of the original image for one frame, and averaging the weighted value with the area of the original image for one frame or the total number of pixels; A level adjustment circuit for controlling the amplification of the original image for one frame based on the output, so that the conventional print unit can be adjusted without
Even if the contrast of the original image signal is insufficient or too bright, printing can be performed automatically with the contrast corrected.

[Brief description of the drawings]

FIG. 1 is a block diagram of a video printer according to the present invention, FIG. 2 is an explanatory diagram showing an example in which a specific area of an image is weighted, and FIG. 3 is a block diagram of a video printer according to another embodiment. It is. 1,51 ... Video printer, 2,52 ... Image memory unit, 3 ...
... Signal processing unit, 4,54 ... Printing unit, 5,55 ... Composite video signal input terminal, 23R, 23G, 23B ... A / D converter, 24R, 24G, 24
B: Storage circuit, 25R, 25G, 25B ... D / A converter, 27, 56 ...
Control circuit 27a, 56a Print command input terminal 31, Level adjusting circuit 34 Weighted averaging means 40 Area generator 43 Gate circuit 44 Integral averaging circuit 45
... voltage holding circuit, 57 ... area designation means, 58 ... averaging means, 59 ... arithmetic means constituting level adjustment means,
AVEW: Weighted average output, C, CP ... Color signals, Hd, Vd, HD, VD
… Various synchronization signals, HW… vertical weighted voltage signals, R, G, B… primary color signals, RA, GA, BA… analog primary color signals, RD, GD, BD… digital primary color signals, RDP, GDP, BDP, RP, G
P, BP: printing primary color signal, VC: composite video signal, VDC:
Gain control DC voltage, VW: vertical weighting voltage signal, WD: weighting coefficient, Y, YP: luminance signal, YC: integrated output.

Claims (1)

(57) [Claims] 1. A horizontal weighting circuit and a vertical weighting circuit for weighting a specific range among the luminance information of an original image for one frame, and a luminance information of the weighted original image for one frame. Weighted averaging means for averaging the weighted value with the area of the original image for one frame or the total number of pixels, and amplifying the original image for one frame based on the output from the weighted averaging means A video printer comprising a level adjusting circuit for controlling the degree.