JPH0452668B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an electronic still camera with a liquid crystal viewfinder.

BACKGROUND ART AND PROBLEMS There has been proposed an electronic still camera in which an image sensor is provided at the film position of a photographic camera, and one frame of a video signal is taken out and recorded on a recording medium when desired.

That is, in FIG. 1, 11 is a lens, 12
is an image sensor, and a video signal from this image sensor 12 is supplied to an amplifier and signal processing circuit 13. A signal from this circuit 13 is supplied to an amplifier and signal processing circuit 15 through a gate circuit 14,
The signal from this circuit 15 is transmitted to a memory device 1 having a recording medium such as a disk, sheet, or tape.
6. And when desired, shutter 17
When is pressed, a control signal is supplied to the gate circuit 14, and only one frame of the video signal is sent to the gate circuit 1.
4 is made conductive, and the extracted video signal for one frame is recorded in the memory device 16. Furthermore, a signal from the circuit 13 is supplied to a viewfinder device 18, and the image captured by the image sensor 12 is displayed.

In this device, the viewfinder 18 is normally continuously supplied with a video signal from the image sensor 12, and the image captured by the image sensor 12 is displayed as a moving image.

On the other hand, there is a demand for displaying the image recorded after pressing the shutter 17 as a still image on the viewfinder 18 and confirming the recorded content. In that case, it is conceivable to reproduce and display the signal recorded in the memory device 16, for example.

However, for this purpose, it is necessary to newly provide a reproducing circuit or the like corresponding to the circuit 15. However, since this type of device is used only for recording and reproduction is performed by a separate device, a completely redundant reproduction circuit is required. And for this reason, the number of circuits increases,
This may become complicated and may impede efforts to make the device smaller and lighter.

Further, providing a frame or field memory separately from the memory device 16 also becomes an obstacle to reducing size and weight.

Incidentally, in such an apparatus, an image display device using liquid crystal, for example, is used as the viewfinder 18.

In FIG. 2, reference numeral 1 denotes an input terminal to which a video signal from an image sensor (not shown) is supplied, and the signal from this input terminal 1 is divided into, for example, N channels.
Switching elements M ₁ , M ₂ ……Mm consisting of FETs
Lines L ₁ , L ₂ in the vertical (Y-axis) direction through...
Supplied to Lm. Note that m is a number corresponding to the number of pixels in the horizontal (X-axis) direction. Furthermore, an m-stage shift register 2 is provided, and clock signals Ф _1H and Φ 2H with m times the horizontal frequency are supplied to this shift register 2, and clock signals Ф _1H and Φ _2H from each output terminal of this shift register _{2 are} supplied. Drive pulse signals φ _{H1 ,} φ _{H2 ,} . Note that the shift register 2 is supplied with a low potential (V _SS ) and a high potential V ( _DD ), and drive pulses of these two potentials are formed.

Furthermore, switching elements M ₁₁ , M ₂₁ , M _o1 , M ₁₂ , M ₂₂ , which are each made of, for example, N-channel FETs and arranged in a matrix are arranged in each line L ₁ to Lm.
...M _o2 , ...M _1n , M _2n ...M _on are connected to one end of the elements constituting each column line. Note that n is a number corresponding to the number of horizontal scanning lines. This switching element
The other ends of M ₁₁ ~ Mnm are liquid crystal cells C ₁₁ and C ₂₁ respectively
...Connected to target terminal 3 through C _on .

Furthermore, an n-stage shift register 4 is provided,
Horizontal frequency clock signals Ф _1V and Ф _2V are supplied to this shift register 4.
Drive pulse signals φ _{v1 ,} φ _v2 , which are sequentially scanned by clock signals Ф _1V , Ф _2V from each output terminal of .
φ _vo is each row line in the X-axis direction of switching elements M ₁₁ to M _on (M ₁₁ to M _1n ), (M ₂₁ to _{M 2n} )...
(M _o1 to M _on ) are respectively supplied to control terminals. Note that, like the shift register 2, the shift register 4 is also supplied with V _SS and V _DD .

That is, in this circuit, shift registers 2 and 4 are supplied with clock signals Τ _1H , Τ _2H , Τ _1V , and Τ _2V as shown in FIGS. 3A and 3B. The shift register 2 outputs φ _H1 to φ _Hn for each pixel period as shown in FIG. 3C, and the shift register 4 outputs φ _V1 to φ for each horizontal period as shown in FIG. 3D. _Vo is output. Furthermore, the input terminal 1 is supplied with a signal as shown in FIG. 3E.

When φ _V1 and φ _H1 are being output, switching elements M ₁ and M ₁₁ to _{M 1n} are turned on, and input terminal 1 → M ₁ → L ₁ → M ₁₁ → C ₁₁ → target terminal 3
A current path is formed to input terminal 1 to liquid crystal cell _C11.
The potential difference between the signal supplied to the target terminal 3 and the target terminal 3 is supplied. Therefore, the capacity of this cell _C11 is supplied. Therefore, for the capacity of this cell C ₁₁ ,
A charge corresponding to the potential difference due to the signal of the first pixel is sampled and held. The light transmittance of the liquid crystal changes depending on the amount of charge. The same thing is done sequentially for cells C ₁₂ to _{C on} , and when the signal of the next field is supplied, each cell
The amount of charge of C ₁₁ to _{C on} is rewritten.

In this way, the light transmittance of the liquid crystal cells C ₁₁ to Cnm is changed corresponding to each pixel of the video signal, and this is sequentially repeated to display an image.

When displaying with a liquid crystal, alternating current driving is generally used to improve its reliability and longevity. In this case, the applicant has previously proposed the following circuit. In FIG. 4, a matrix circuit (indicated by a dot in the symbol) equivalent to the switching elements M ₁ to Mm, M ₁₁ to _{M on} and liquid crystal cells C ₁₁ to C _on is provided, and each row line is connected as shown in the figure. They are arranged in alternating combinations in the vertical direction. The control terminals of the switching elements M ₁ ′ to Mm′ and M ₁₁ ′ to _{M on} ′ are commonly connected to the shift registers 2 and 4 of the same suffix. Furthermore, the signal input terminals of the switching elements M ₁ to Mm and M ₁ ′ to M _n ′ are connected in common.

Further, the input terminal 1 is connected to one fixed contact of the switch 5 and the other fixed contact of the switch 6. A DC voltage source 7 having a predetermined voltage V _DC is connected to the other fixed contact of the switch 5 and one of the fixed contacts of the switch 5 . The switches 5 and 6 are simultaneously switched to one and the other fixed contact by the field pulse Pf. Signals from switches 5 and 6 are supplied to signal input terminals of switching elements M ₁ -Mm and M ₁ ' -M _n ', respectively.

In this device, the equivalent circuit of the circuit constituting one pixel is as shown in FIG. In the figure,
R _LC and C _LC are the equivalent resistance and capacitance of the liquid crystal, and the DC blocking capacitance existing at the interface between the C _DC switching element M and the liquid crystal. On the other hand, the video signal S _V is directly supplied to the input terminal 1 as shown in No. 6A. Then, by switching switches 5 and 6,
Switching elements M ₁ to Mm and M ₁ ′ to M _n ′ are supplied with signals in which a video signal and a DC potential alternately appear in opposite timing every field, as shown in FIG. 6B and C, respectively. . By sampling and holding this signal at, for example, time Tji, the output side of the switching element M in the equivalent circuit of FIG. 5 has a signal voltage as shown in FIG. 6D.
A voltage V _LC ′ appears that is an alternation of Vs and the DC voltage V _DC .
Then, this voltage V _LC ' is DC-blocked by the capacitor C _DC , so that an AC voltage V _LC that changes around the target potential V _T of terminal 3 is applied to the opposite end of the liquid crystal, as shown in FIG. 6E. be done.

Furthermore, the effective voltage applied to the opposite end of the liquid crystal
V _{LC rns} becomes V _LC rms = 1/2 (Vs - V _DC ), and even if the input video signal is applied as signal -> DC -> signal -> DC for each field, the information is converted into image information.

The image is displayed in this way.

FIG. 7 is another example of the circuit proposed earlier by the applicant, and in this example, the switching element
M ₁ ′ ~ M _n ′, M ₁₁ ′ ~ _{M on} ′ and liquid crystal cell C ₁₁ ′ ~
C _on ′ are arranged in combination in the horizontal direction for each column line. In addition, a delay circuit 8 for one pixel is provided at the input terminal 1, and a video signal is supplied to the liquid crystal cells C ₁₁ ′ to _{C on} ′ provided on the left side by a switch 9 controlled by a field pulse Pf. Causes the signal to be delayed only for a period of time. Note that 10 is a video signal amplifier that performs normal amplification. The rest is the same as in FIG.

In this circuit as well, liquid crystal cells C ₁₁ to C _on and
An amplified signal and a DC potential are applied to C ₁₁ ′ to C _on ′ alternately for each field at opposite timings. Further, the video signals applied to the left liquid crystal cells C ₁₁ ′ to _{C on} ′ are delayed by one pixel to adjust the horizontal position of the displayed image.

Even if you do this, the image will be displayed.

OBJECTS OF THE INVENTION In view of the above points, the present invention enables a recorded image to be displayed as a still image on the view under with a simple configuration.

Summary of the Invention The present invention includes an image sensor, a storage means for storing a video signal from the image sensor, and a display device that sequentially supplies the video signal from the image sensor to a liquid crystal display device arranged in a matrix to display an image. a shutter button, and when the shutter button is pressed, the video signal sequentially read out from the liquid crystal display element is replaced with a video signal from the image pickup device, and the video signal is displayed on the liquid crystal display again. This electronic still camera is characterized in that it displays still images by sequentially supplying them to a display element, and with this, recorded images can be displayed as still images under the view with a simple configuration.

Embodiment In FIG. 8, a signal from a circuit 13 is supplied to one fixed contact of a switch 21, and a signal from a movable contact of this switch 21 is passed through a video amplifier 22 to one fixed contact of a switch 5 and the other fixed contact of a switch 6. Supplied. Further, a load resistor 23 is provided between the other fixed contact of the switch 5 and one of the fixed contacts of the switch 6 and the DC voltage source 7.
The terminal voltage of is applied to the switch 2 through the preamplifier 24.
1 to the other fixed contact. Further, a control signal from the shutter 17 is supplied to a monostable multivibrator 25, and a signal from this end-stable multivibrator 25 is supplied to a control terminal of the switch 21. The rest is the same as in FIGS. 1 and 4.

In this device, when the shutter 17 is pressed, one frame of video signal is taken out and recorded in the memory device 16 in the same way as described above, and a control signal is supplied to the monostable multivibrator 25 to generate a signal for a predetermined period. is formed, and during this time switch 2
1 is switched to the other fixed contact.

On the other hand, the switches 5 and 6 are switched for each field by the field pulse Pf as described above. Here, for example, when the switch 6 is connected to the DC voltage source 7 side, voltage is supplied from the DC voltage source 7 to the matrix on the side where the dowel is not attached in FIG.
A current whose size corresponds to the signal charge accumulated in the capacitor C _DC of each pixel is caused to flow. As a result, a voltage corresponding to the signal charge is generated in the load resistor 23, and is supplied to the matrix on the side marked with a dot in FIG. 4 through the signal voltage amplifier 24, switch 21, amplifier 22, and switch 5.

That is, as shown in FIG. 9, when the shutter 17 is pressed at time T _S , while DC is being supplied to one matrix in one field, the signal of this one matrix is supplied to the other matrix, This is done in reverse for the next field, and the same signal is repeatedly supplied to display the still image when the shutter 17 is pressed.

Still images are displayed in this way, but since this device uses the accumulated charge of each pixel, there is no need to provide a new memory or playback circuit, and the configuration is extremely simple. Still images can be displayed, thereby making it easy to confirm the recorded content after imaging.

Furthermore, although the above example is applied to the fourth circuit, when applied to the circuit of FIG. 7, the following procedure is performed. That is, in FIG. 10, the signal from switch 9 of FIG. 7 is applied to one fixed setting of switch 21. In FIG. In this example as well, a still image is displayed in the same manner as described above. Furthermore, switch 5,
6 is equivalent to that shown in FIG. 4 even if it is connected as shown.

Further, in the above example, the gain of the amplifier 24 is determined so that the loop gain of the amplifier 21, the liquid crystal cell, and the amplifier 24 becomes 1, but if this is not done completely, the gain of the amplifier 24 is determined as shown in FIG. The output of the amplifier 24 is then supplied to the AD conversion circuit 31, and after being quantized, this output is again supplied to the DA conversion circuit 3.
2, the loop gain can be made completely 1.

Effects of the Invention According to the present invention, recorded images can now be displayed as still images on the viewfinder with a simple configuration.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a conventional device, Figs. 2 to 7 are diagrams for explaining a liquid crystal display device, Fig. 8 is a block diagram of an example of the present invention, and Fig. 9 is a diagram for explaining the same. 10 and 11 are configuration diagrams of other examples. 5 and 6 are switches, 7 is a DC voltage source, 12 is an image sensor, 16 is a memory device, 17 is a shutter,
18 is an electronic viewfinder device, 21 is a switch, 22 and 24 are amplifiers, 23 is a load resistor,
25 is a monostable multivibrator, M is a switching element, and C is a liquid crystal cell.

Claims (1)

[Claims] 1. An image sensor, a storage means for storing a video signal from the image sensor, and a liquid crystal view finder that sequentially supplies the video signal from the image sensor to liquid crystal display elements arranged in a matrix to display an image; a shutter button, the liquid crystal display element is arranged by combining two sets of matrices, and by pressing the shutter button, the video signal supplied to one of the matrices is supplied again to the other matrix. An electronic still camera characterized by displaying a still image in a manner as follows.