JPS643111B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a projection situation correction device for a projection television receiver using three cathode ray tubes corresponding to three primary colors.

Generally, such a receiver uses three cathode ray tubes corresponding to three primary colors consisting of a reference color and two other colors, and projects rasters of each color onto the same screen, thereby producing a color image. However, it is necessary for the horizontal and vertical center positions and amplitudes of the raster of each color to match each other. Manual adjustments are made to ensure that the rasters match, which is time-consuming and causes drawbacks such as fluctuations in the adjustment status due to changes over time, resulting in mismatched rasters of each color and deterioration of video quality. Was.

The purpose of the present invention is to fundamentally eliminate such drawbacks of the conventional technology, by providing small-diameter through holes in each of the four corners of the screen, and detecting raster pulse signals for each color on the back side of these holes. Top of,
Based on this signal, the projection condition of a projection television receiver is extremely effective in controlling the horizontal and vertical center positions and amplitudes of the reference color raster and the other two color rasters to match. A correction device is provided.

Hereinafter, details of the present invention will be explained with reference to figures showing examples.

Figure 1 is a front view of the screen. Near the four mutually symmetrical corners of the screen S, there are small diameter through holes H ₁ to _{H 4} through which about 2 to 3 rasters pass. On the back side of these, an optical system shown in FIG. 2 is provided for each of the through holes H ₁ to _{H 4} .

FIG. 2 is a diagram showing the configuration of the optical system. Half mirrors HM ₁ and HM ₂ are arranged on the optical axis passing through the through hole H, and are designed to split the incident light L into three directions. The divided light uses the edge color (hereinafter referred to as
G) Color filter FG that transmits light, and color filter FR that transmits red (hereinafter referred to as R) light and blue (hereinafter referred to as B) light as the other two colors.
Each light enters the FB and passes through each one to become R light, G light, and B light, respectively, and a light receiving element such as a light receiving transistor provided in each corresponding to the color filters FR, FG, and FB. It is designed to be incident on PR, PG, and PB.

Therefore, when R, G, and B rasters are projected onto the portion of the through hole H, the R raster is received by the light receiving element PR, and the G raster is received by the light receiving element PR.
The raster of B is received by the photodetector PB, and each photodetector PR, PG,
From the PB, a pulse-like signal having a mutual relationship depending on the timing at which the R, G, and B rasters are projected is obtained for each color.

That is, the time when each output of each light receiving element PR, PG, PB is generated corresponds to the time when the raster of each color is projected onto the part of the through hole H, and if the time when each output is generated coincides, The rasters of each color are projected in agreement with each other, but if the rasters of each color are projected in an inconsistent state, the times at which each output occurs will be inconsistent, so it is necessary to calculate the time difference between each output. Accordingly, it is possible to detect a mismatch situation between the color rasters.

However, since the raster projection situation on the screen S causes deviations in the center position and amplitude in each horizontal and vertical direction, as shown in Fig. 1,
The mutual relationship of each color raster is detected individually at the four corners of the screen S, and the outputs obtained from the light receiving elements PR, PG, PB are combined for each through hole _H1 to _H4 , and then
Each deviation component of horizontal position, horizontal amplitude, and vertical position and vertical amplitude must be obtained.

In addition, in order to obtain each deviation component and control the projection status of each color raster in the direction of matching, it is necessary to use the G output as a reference, find each deviation component of the R output and B output with respect to this, and calculate the R , B to each deflection circuit in the cathode ray tube.

FIG. 3 is a block diagram showing the circuit configuration.
Light receiving elements PR ₁ - provided corresponding to through holes H ₁ - H ₄
The output of PR ₄ is given to each of the time difference detection circuits TDR ₁ to _{TDR 4} , and similarly arranged light receiving elements PB ₁ to _{PB 4.}
The output of is given to each time difference detection circuit TDB ₁ to TDB ₄ , and the light receiving element similarly provided.
The output of PG ₁ ~ _{PG 4} is the time difference detection circuit TDR ₁ ~
It is given as a reference input to TDR ₄ , TDB ₁ to TDB ₄ , and each circuit TDR ₁ to TDR ₄ , TDB ₁ to _{TDB 4}
, horizontal time difference signals HR ₁ to _{HR 4} , HB ₁ to HB ₄ indicating horizontal deviations for each R and B, and vertical time difference signals VR ₁ to VR ₄ , VB ₁ to indicating vertical deviations.
VB ₄ is supposed to be sent.

On the other hand, adders AD ₁ a to AD ₁ c, AD ₂ a to AD ₂ c,
AD _{3 a} ~ AD ₃ c, AD ₄ a ~ AD ₄ c and subtractor SU ₁ ~
A synthesis circuit STS consisting of ₄ SUs is provided, which adds the signals located diagonally to each other in Fig. 1 for each signal of the same color, horizontal and vertical. Addition is made for each addition output to obtain horizontal position correction signals PHR, PHB and vertical position correction signals PVR, PVB for each R and B, and these are sent to the horizontal position correction circuits HPR and HPB attached to each deflection circuit of the R and B cathode ray tubes. and the vertical position correction circuits VPR and VPB, and the output obtained by adding the diagonally related signals for each horizontal and vertical signal of the same color is subtracted for each horizontal and vertical addition output of the same color. , horizontal amplitude correction signal for each R, B
WHR, WHB and vertical amplitude correction signal WVR,
WVB is obtained, and each position correction circuit HPR,
Horizontal amplitude correction circuit similar to HPB, VPR, VPB
HWR, HWB and vertical amplitude correction circuit VWR,
VWB is controlled so that the horizontal and vertical center positions and amplitudes of the R and B rasters match those of the G raster.

Figure 4 shows the time difference detection circuit in Figure 3.
Horizontal time difference signal of TDR ₁ to TDR ₄ , TDB ₁ to _{TDB 4}
It is a block diagram showing an example of a part for obtaining HR,
The waveforms of each part are as shown in the waveform diagram of FIG. 5, and the case where the outputs of the light receiving elements PR and PG are given is illustrated.

Here, when the horizontal synchronizing pulse S _H (a) is applied, the counters CT ₁ and CT ₂ are reset, while when the vertical synchronizing pulse S _V is applied, the flip-flop circuits (hereinafter referred to as FFC) FF ₁ and FF _{2 are} reset. is set, and AND gates G ₁ and G ₂ are set by the set output.
turns on, and the output P _R (b) of the photodetector PR and the output P _G (c) of the photodetector PG are connected to the AND gates G ₁ , G ₂
It will be in a state where it passes through.

Then, when the outputs P _R (b) and P _G (c) are given, the counters CT ₁ and CT ₂ become operational,
The count outputs of counters _{CT 1} and CT _{2 are} , the outputs P _R (b) and P _G (c) shown in FIG.
The time from t _R to horizontal synchronization pulse S _H (a) and
t represents _G.

Therefore, each count output of counters CT ₁ and CT ₂ is converted to a digital-to-analog converter (hereinafter referred to as
DAC) D/A ₁ and D/A ₂ to generate analog signals, and by calculating the difference between the two using differential amplifier DA ₁ , a time difference signal HR between times t _R and t _G can be obtained.

On the other hand, the outputs of DAC・D/A ₁ and D/A ₂ are also given to comparators CP ₁ and CP ₂ , and the reference voltages E _S1 and
_A comparison output is generated by the coincidence of both inputs, and in order to reset FFC・FF ₁ and FF ₂ , AND gates G ₁ and G ₂ are turned off, and if the output P _R ( b) and P _G (c), even if
The counters CT ₁ and CT ₂ do not respond to these.

Note that the reference voltages E _S1 and E _S2 are set at the expected time t _R
and correspondingly defined as slightly less time than t _G.

Furthermore, if _the holes are provided corresponding to _the through holes T _{3 and H 4 in} FIG. Therefore, as vertical synchronization pulse S _V ,
It is preferable to use one delayed by about 1/2 V (V is the period of the vertical synchronizing pulse).

Figure 6 shows the time difference detection circuit in Figure 3.
Vertical time difference signal of TDR ₁ to TDR ₄ , TDB ₁ to TDB ₄
It is a block diagram showing an example of a part to obtain VR,
The waveforms of each part are as shown in the waveform diagram in Figure 7, and as in Figures 4 and 5, the light receiving element
An example is shown in which the outputs of PR and PG are given. Here, the configuration and operation in Fig. 6 are almost the same as in Fig. ₄ , but a retrigger type monostable _{multivibrator} (hereinafter referred to as
Monomulti) RM ₁ and RM ₂ are inserted, and the vertical synchronizing pulse (a) is used to reset the counters CT ₃ and CT ₄ , and the through holes H ₁ to _{H 4} are
Even if about three rasters pass through and outputs P _R (b) and P _G (d) consisting of multiple pulses are given,
Retrigger multi slightly larger than these synchronous tp
By setting the pulse width tr generated by MR ₁ and MR ₂ , a series of pulses (c) and (e) can be obtained, while the vertical synchronization pulse S _V (a)
CT ₃ and CT ₄ are designed to stop the counting operation.

Therefore, the count outputs of counters CT ₃ and CT ₄ represent the times T _R and _TG shown in FIG. 7, and the count outputs of counters CT ₃ and CT ₄ are
The time difference signal VR can be obtained by converting the analog signals from the DAC/D/A ₃ and D/A ₄ into analog signals and applying them to the differential amplifier DA ₂ and finding the difference between them.

In addition, AND gates G ₃ , G ₄ , FFC, FF ₃ , FF ₄ ,
The circuits such as comparators CP ₃ and CP ₄ and reference voltages E _S3 and E _S4 operate in the same manner as in FIG.

Further, when providing corresponding to the through holes H ₃ and H ₄ , it is preferable to use a vertical synchronizing pulse S _V delayed by 1/2 V, as described above.

However, in Fig. 2, half mirror HM ₁ ,
Instead of HM ₂ and the color filters FR, FG, and FB, a dichroic mirror with a color filter may be used, and the configurations shown in Figures 4 and 6 can be selected arbitrarily depending on the conditions, and or B
The present invention can be modified in various ways, such as using the reference color as the reference color.

As is clear from the above description, according to the present invention, since the rasters of each color are automatically controlled in the direction of matching, the effort of manual adjustment is omitted, and mismatching of the rasters of each color due to changes over time is prevented. Therefore, images of good image quality can always be obtained, and a remarkable effect can be obtained in a projection type television receiver.

[Brief explanation of the drawing]

The figures show an embodiment of the present invention, in which Fig. 1 is a front view of the screen, Fig. 2 is a configuration diagram of the optical system, Fig. 3 is a block diagram of the circuit configuration, and Fig. 4 is a horizontal time difference signal in the time difference detection circuit. 5 is a waveform diagram showing the waveforms of each part in FIG. 4, FIG. 6 is a block diagram of the part that obtains the vertical time difference signal in the time difference detection circuit, and FIG. 7 is a block diagram of each part in FIG. 6. FIG. S...Screen, _H1 ~ _H4 ...Through hole, FR,
FG, FB...Color filter, PR, PG, PB,
PR ₁ ~ PR ₄ , PG ₁ ~ PG ₄ , PB ₁ ~ _{PB 4} ... Light receiving element, TDR ₁ ~ TDR ₄ , TDB _{1 ~} TDB ₄ ... Time difference detection circuit, STS ... Synthesis circuit, AD ₁ a - AD ₁ c,
AD ₂ a ~ AD ₂ c, AD ₃ a ~ AD ₃ c, AD ₄ a ~ AD ₄ c...
Adder, SU ₁ to _{SU 4} ...Subtractor.

Claims (1)

[Claims] 1. In a projection type television receiver that displays a color image by projecting rasters of the reference color and other two colors onto the same screen using three cathode ray tubes provided corresponding to the reference color and the other two colors. , small-diameter through-holes provided near the four corners of the screen, and three-color color filters that transmit the reference color and the other two colors, each provided on the back side of each of the through-holes; A light-receiving element provided corresponding to each of the color filters that receives the transmitted light of each color filter, and an output of the light-receiving element corresponding to the color filter that transmits the reference color and transmits the other two colors. a time difference detection circuit provided for each of the through holes, which detects the mutual relationship between the raster of the reference color and the raster of the other two colors as a time difference based on the output of the corresponding color filter and the corresponding light receiving element; and a synthesis circuit that synthesizes each detection output of the detection circuit and sends out a correction signal that controls the horizontal and vertical position and amplitude of the other two color rasters in a direction that matches the reference color raster. A projection situation correction device for a projection type television receiver, characterized by: