JPS6349009Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to a window circuit that linearly changes the level of an analog output signal corresponding to a digital input signal in a predetermined range. It is something to do.

Conventionally, image output devices used in computer tomography, for example, compress original data for image formation of several tens of bits for each pixel, that is, original data that controls the shading of each pixel, into several bits through software processing. The gradation level based on the original data is compressed into the desired gradation level, and the analog conversion process of the compressed data forms an analog signal that changes linearly according to the gradation of the compressed data. By the signal
An image formed at a desired density level is displayed on a black-and-white monitor television.

By the way, if you want to display the desired gradation range of the image formed as described above in more detailed gradation levels, you can redo the software processing and change the original data so that the gradation levels of the desired gradation range are expanded. In addition to forming new compressed data, it is necessary to perform analog conversion processing on the compressed data so that the change slope of the analog signal corresponding to the desired grayscale range is different from the change slope of the original analog signal, which takes a long processing time. At the same time, it is necessary to perform complicated operations.

That is, when a digital input signal consisting of the aforementioned original data is subjected to analog conversion processing to form an analog output signal and an image is displayed using the analog output signal, the gradient of change in the desired range of the analog output signal is When you want to variably adjust the gradation of the desired gradation range and display more details, it is necessary to redo the software processing as described above, which increases the processing time and complicates the processing. It is necessary to do this.

This invention was made with the above points in mind, and includes a digital/analog converter that converts digital input signals such as digital image signals into analog input signals, and two or three types of converters whose setting levels can be varied by adjustment. a reference signal generator that outputs a reference signal of various kinds; a comparator that outputs a minimum setting signal of a predetermined setting level when the analog input signal is equal to or higher than the reference signal of a minimum setting level; and the analog input signal and each of the standards. an input-side adder that adds the signals with a polarity inverted signal and outputs an added signal; an amplifier that amplifies the added signal with an amplification factor inversely proportional to one of the reference signals and outputs an amplified signal; The amplified signal is passed through and output when the level is between a predetermined negative level and a predetermined positive level symmetrical to the predetermined negative level, and when the amplified signal becomes lower than the predetermined negative level and higher than the predetermined positive level, respectively. a limiter that maintains the output level at the predetermined negative level and the predetermined positive level, and an output side adder that adds the minimum setting signal, the output signal of the limiter, and the calibration signal of the predetermined positive level and outputs an analog output signal. This is a window circuit equipped with the following.

Therefore, the analog output signal output from the output side adder is an amplified signal formed by amplifying the sum signal of the analog input signal obtained by converting the digital input signal and the polarity inverted signal of each reference signal. If the level is between the level and a predetermined negative level, the amplification factor changes at a constant slope based on the predetermined amplification factor of the amplifier, that is, the amplification factor that is inversely proportional to one of the reference signals, and the amplification factor is changed by adjusting the reference signal. In addition, the range of the analog input signal that corresponds to the range that changes with a constant slope of the analog output signal is variably set by each reference signal, so, for example, when forming an image using the analog output signal. , the gradation levels of the desired gradation range set in a predetermined range of the digital input signal are enlarged without any software processing, and the desired gradation range is easily displayed in more detailed gradation levels in a short time. It is something that can be done.

Next, one embodiment of the window circuit of this invention will be described with reference to the drawings.

In FIG. 1, reference numeral 1 denotes a digital/analog converter (hereinafter referred to as a D/A converter) into which a digital input signal D consisting of original data for image formation, etc. is input, and changes in response to the digital input signal D. Outputs analog input signal Aa of analog voltage Va. 2 is the positive power supply terminal +Vx and the negative power supply terminal -Vx
the first to third variable resistors 2 provided between
A reference signal generator consisting of a, 2b, 2c,
Through adjustment, the first reference signal Xa of the minimum setting level, that is, the first reference signal Xa of voltage Ea, is output from the first variable resistor 2a.
is output, the second reference signal Xb with a voltage Eb higher than the voltage Ea is output from the second variable resistor 2b, and the second reference signal Xb with a voltage Eb higher than the voltage Ea is output from the third variable resistor 2c.
A third reference signal Xc of Ec is output.

And analog input signal Aa of D/A converter 1
The voltage Va of the first reference signal Xa and the voltage Ea of the first reference signal Xa are compared by the comparator 3, and as shown in FIG. 2a,
Voltage Va of analog input signal Aa is the first reference signal
If the voltage Ea of Xa is greater than or equal to the voltage Ea, the comparator 3 outputs the minimum setting signal S1 of the voltage V1 to the output side adder 4.

On the other hand, each reference signal Xa to Xc is input to each of the first to third inverters 5a, 5b, and 5c, and the voltage polarity of each reference signal Xa to Xc is inverted by each inverter 5a to 5c. 5a outputs a first polarity inverted signal -Xa of a voltage -Ea obtained by inverting the voltage Ea of the first reference signal Xa, and the second inverter 5b outputs a first polarity inverted signal -Xa.
A second polarity inverted signal -Xb of the voltage -Eb obtained by inverting the voltage Eb of the second reference signal Xb is output, and the third inverter 5
A third polarity inversion signal -Xc, which is obtained by inverting the voltage Ec of the third reference signal Xc to a voltage -Ec, is output from the third reference signal Xc.

Furthermore, the analog input signal Aa and each polarity inversion signal -Xa to -Xc are input to the input side adder 5, and from the input side adder 5 to the amplifier 6, Va-(Ea
An addition signal Sa having a voltage of +Eb+Ec) is output.

The amplification factor of the amplifier 6 is the third reference signal Xc
For example, the amplification factor is set to V2/Ec, where V2 is a predetermined constant voltage value.

Therefore, the voltage of the amplified signal Sb output from the amplifier 6 to the limiter 7 is {Va−(Ea+Eb+Ec)}(V
2/Ec), and the voltage Va of the analog input signal Aa becomes a predetermined negative level voltage -V2 when Va=(Ea+Eb), and Va=(Ea+Eb).
+2Ec), the voltage V2 becomes a predetermined positive level symmetrical to the voltage -V2.

Further, a limiter 7 to which the amplified signal Sb is input
While the voltage of the amplified signal Sb is between the voltage -V2 and the voltage V2, that is, the voltage Va of the analog input signal Aa is (Ea +
Eb)≦Va≦(Ea+Eb+2Ec), the second
As shown in Figure b, the voltage of the amplified signal Sb becomes equal to the voltage of the amplified signal Sb, and the voltage of the amplified signal Sb becomes the voltage -V2.
When the voltage Va becomes lower than the voltage V2 and when the voltage Va becomes higher than the voltage V2, respectively, the voltage Va of the analog input signal Aa is Va<(Ea+Eb), (Ea+Eb+2Ec)<Va
When the voltages are respectively set to -V2 and V2, the voltages are held at -V2 and V2, respectively.

Then, the output side adder 4 receives the minimum setting signal S
1 and the output signal S2, and the calibration signal S3 of the calibration input terminal 8 having the voltage V2 are input, and the voltage Vb of the analog output signal Ab output from the output side adder 4 is as shown in FIG. 2c. , voltage Va of analog input signal Aa is held at zero when Va<Ea, becomes V1 when Ea≦Va<(Ea+Eb), and changes from voltage V1 when (Ea+Eb)≦Va≦(Ea+Eb+2Ec). The voltage changes linearly with a slope of V2/Ec up to the voltage V1+V2, and is held at the voltage V1+V2 when (Ea+Eb+2Ec)<Va.

That is, the voltage Ea of each reference signal Xa to Xc,
Three threshold voltages Ea and Ea+ are determined by Eb and Ec.
Eb, Ea + Eb + 2Ec are formed, and the voltage Va of the analog input signal Aa converted from the digital input signal D
However, between (Ea+Eb)≦Va≦((Ea+Eb+2Ec), the voltage Vb of the analog output signal Ab changes linearly with a constant slope determined by the amplification factor of the amplifier 6, that is, V2/Ec, and each reference signal Xa~ Since the voltages Ea, Eb, and Ec of Xc are variably set by adjusting each variable resistor 2a to 2c, the slope when the voltage Vb of the analog output signal Ab changes linearly and the range of the voltage Va of the analog input signal Aa are shortened. The time can be easily set variable.

Then, with the analog output signal Ab in Fig. 2C,
When forming an image on a black and white monitor TV,
Voltage of zero analog output signal Ab when Va<Ea
Vb forms the pure black part of the image, and Ea≦Va
Analog output signal of V1 when <(Ea+Eb)
The voltage Vb of Ab forms a gray area close to black to indicate the distinction between the background and outline of the image, and the linearly varying analog output signal Ab when (Ea + Eb) ≦ Va ≦ (Ea + Eb + 2Ec). Voltage Vb
As a result, each part in the shade range from gray close to black to white is formed, and (Ea + Eb +
2Ec) Voltage of analog output signal Ab when <Va
A white part is formed by Vb.

Furthermore, if you want to display a predetermined gray scale range of the displayed image in detail, adjust each variable resistor 2a to 2c while watching a black and white monitor TV to obtain (Ea + Eb).
and (Ea + Eb + 2Ec) should be set so that it becomes the threshold voltage of the voltage Va of the analog input signal Aa corresponding to a predetermined grayscale range. In this case,
There is no need for conventional software processing, and it is possible to easily enlarge and display the shading levels of a desired shading range in detail in a short time.

Note that the second reference signal Xb may be omitted if necessary,
The voltage Va of analog input signal Aa is Ea≦Va≦
(Ea + 2Ec), the voltage Vb of the analog output signal Ab may vary linearly;
The amplification factor of the amplifier 6 is the first and second reference signals Xa, Xb
It may be made to be inversely proportional to the respective voltages Ea and Eb.

Furthermore, it goes without saying that the present invention can be applied not only to displaying images but also to outputting audio using an analog output signal Ab formed by converting a digital input signal D into an analog signal.

[Brief explanation of the drawing]

The drawings show one embodiment of the window circuit of this invention. Fig. 1 is a block diagram, and Figs. 2 a to c each show the voltage of the analog input signal, the output voltage of the comparator, the output voltage of the limiter, and the voltage of the analog output signal. It is a relationship diagram with each voltage. 1...Digital/analog converter, 2...Reference signal generator, 3...Comparator, 4...Output side adder, 5...Input side adder, 6...Amplification factor, 7...
Limiter, Aa...Analog input signal, Ab...Analog output signal, D...Digital input signal, Sa
... Addition signal, Sb ... Amplified signal, S1 ... Minimum setting signal, S2 ... Limiter output signal, S3 ...
...Calibration signal, Xa to Xc...Reference signal, -Xa to -Xc
...Polarity inversion signal.

Claims (1)

[Scope of utility model registration request] A digital/analog converter that converts a digital input signal such as a digital image signal into an analog input signal, a reference signal generator that outputs two or three types of reference signals whose setting levels are variable by adjustment, and the analog input signal a comparator that outputs a minimum setting signal of a predetermined setting level when the signal is equal to or higher than a reference signal of a minimum setting level, and an input side adder that adds the analog input signal and the polarity inverted signal of each of the reference signals and outputs a sum signal. an amplifier for amplifying the added signal with an amplification factor inversely proportional to one of the reference signals and outputting an amplified signal; a limiter that sometimes passes through and outputs the amplified signal, and holds the output level at the predetermined negative level and the predetermined positive level when the amplified signal becomes lower than the predetermined negative level and higher than the predetermined positive level, respectively; and an output-side adder that adds the minimum setting signal, the output signal of the limiter, and the calibration signal of the predetermined positive level and outputs an analog output signal.