JPH0253040A - Lcd iluminator for camera - Google Patents

Abstract

PURPOSE:To realize pertinent illumination by deciding the brightness of light made incident on a liquid crystal display (LCD) and controlling the illumination. CONSTITUTION:A LED (light emitting diode) 20, i.e., a illuminating means is provided on the one edge surface of the light guid plate 13; a phototransister 21, i.e., the light receiving means of a photometry means is provided on a position which faces the surface provided with the LED 20 and which does not directly face the LED 20. When the environment of the LCD 10 become darker than a designated value, the LED 20 turns on, and changes in brightness in response to the ennvironmental darkness; the LED 20 is thus controlled so that the environmental brightness of the LCD 10 becomes constant. Besides, when the environment is in a range brighter than the designated value, the LED 20 never turns on: When the environment is in a range darker than the designated value, the LED 20 turns on at a largest current. Therefore, preferable and economical illumination is possible without troublesome operation of an operational switch.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a lighting device for a liquid crystal display (hereinafter referred to as 'rLCDJ') that displays various information using a liquid crystal element.

"Prior art and its problems" In recent years, cameras have been equipped with LCD panels that display various information such as exposure mode, shirt speed, and number of film shots.
Displayed by CD. In this type of LCD, the liquid crystal itself does not emit light due to the nature of the liquid crystal, so it is difficult to see in a dark place. Therefore, an illumination device (backlight) has been developed in which a liquid crystal panel is formed into a transmissive type, a light source is provided on the back side, and the light source illuminates the liquid crystal panel from behind.

This conventional lighting device has a switch to turn on the light source, and when this switch is pressed (turned ON), it lights up for a certain period of time (5 to 10 seconds) or the open light source that is being pressed is generally turned on. be. In such a conventional lighting device, the above-mentioned switch had to be operated in order to turn on the light, and the operability was poor.

Furthermore, there have been some that turn on the lighting device if the brightness of the object is below a certain level based on the object brightness signal from the photometric light receiving element of the camera. However, in this lighting device, the positions of the photometric light receiving element of the camera and the LCD are different.

Therefore, even if the LCD environment is dark and lighting is necessary, if the subject is bright, the lighting device will not turn on and the LCD will be difficult to see. When it is dark, the lighting device turns on, which wastes electricity.

``Object of the Invention'' The present invention has been made based on the above-mentioned problems of the prior art. The purpose of the present invention is to provide an LCD lighting device that enables the following.

"Summary of the Invention" The present invention provides an LCD illumination device having a transflective liquid crystal panel and provided outside a camera, comprising: illumination means for illuminating the liquid crystal panel from the rear side; It is characterized in that it has a photometric means for measuring the brightness at the side, and an illumination control means for turning on the illumination means when the brightness detected by the photometric means is lower than a predetermined value.

According to this configuration, since the illumination means is controlled to ON10FF by measuring the brightness of the environment of the LCD, the illumination means is turned ON.
There is no need for a switch to turn on and off, allowing for appropriate and efficient lighting.

Further, by adjusting the brightness of the illumination means so that the photometric value of the photometry means is constant, more appropriate illumination becomes possible.

“Embodiments of the invention” The invention will now be described with reference to illustrated embodiments.

FIG. 1 is a vertical cross-sectional view taken at the center of an embodiment in which the illumination device according to the present invention is applied to an LCD mounted on the outside of a camera, and FIG. It is an enlarged longitudinal cross-sectional view.

This LCD 10 has a box-shaped (U-shaped cross section) holder 11.
The holder 11 has a printed circuit board 12, a light guide plate 13, an anti-transmissive reflector 14, a polarizing plate 15, a liquid crystal panel 16, and a polarizing plate 17 arranged in this order from the bottom. , there is a fastener 18 for fixing each of the above members.
is fitted.

The liquid crystal panel 16 has liquid crystal elements forming predetermined character and graphic information arranged between two transparent plates, and the electrodes of each liquid crystal element extend to the lower surface of the flange of the liquid crystal panel 16. There is. The printed circuit board 12 is provided with electrodes at positions corresponding to the electrodes of the liquid crystal panel 16.

Between the printed circuit board 12 and the liquid crystal panel 16,
Conductive rubber 19 is disposed along the electrodes to conduct the corresponding electrodes. A large number of conductive bottles (not shown) which are insulated from each other are buried in the conductive rubber 19, and both ends of each conductive bottle are in contact with the electrodes of the printed circuit board 12 and the liquid crystal panel 16, respectively. The electrode and the corresponding electrode of the liquid crystal panel 16 are electrically connected. Therefore, when a predetermined combination of voltages is applied to the electrodes of the printed circuit board 12, predetermined liquid crystal elements of the liquid crystal panel 16 become opaque so that character and graphic information can be visualized.

The fastener 18 fitted to the upper end of the holder 11 directly contacts the outer peripheral edge of the uppermost polarizing plate 17, and
The polarizing plate 15, anti-transmissive reflector 14, light guide plate 13, and printed circuit board 12 are pressed against the holder 11 to fix them, and the conductive rubber 19 is pinched between the liquid crystal panel 16 and the printed circuit board 12 to form a conductive bottle. Ensures continuity with the electrodes.

On one end surface of the light guide plate 13, an LED (
A phototransistor 21 (light emitting diode) 20 as a light receiving means of the photometric means is provided on an end face opposite to the end face on which the LED 20 is provided, and at a position not directly facing the LED 20 (second light emitting diode). (see figure),
The light guide plate 13 uniformly diffuses the light from the LEDs 20 and guides it toward the liquid crystal panel 16 to uniformly illuminate the liquid crystal panel 16, and has a reflective surface 22 formed on the bottom surface. Therefore, the light beam emitted from the LED 20 is repeatedly reflected by the upper surface of the light guide plate 13 and the reflective surface 22, and then travels through the light guide plate 13, passes through the upper surface of the light guide plate 13 little by little, and passes through the anti-transmission type reflector 14, The light passes through the polarizing plate 15, the liquid crystal panel 16, and the polarizing plate 17, and functions as illumination for the liquid crystal panel 16.

On the other hand, external light from the environment is transmitted through the polarizing plate 17, the liquid crystal panel 16,
It passes through the polarizing plate 15 and is reflected by the anti-transmissive plate 14 to illuminate the liquid crystal panel 16. A part of the light passes through the semi-transmissive plate 14 and is guided into the light guide plate 13, and a part of it enters the phototransistor 21. However, the rest is reflected by the reflective surface 22 and illuminates the liquid crystal panel 16.

As described above, the phototransistor 21 receives outside light that has passed through the polarizing plate 17, the liquid crystal panel 16, the polarizing plate 15, and the anti-transmissive reflector 14 and entered the light guide plate 13, and the above-mentioned LED.
Light is emitted from 20 and enters.

The above is the configuration of the LED 20 and its lighting device,
A light emitting element other than the LED 20 may be used as a light source, and a photoelectric conversion element other than the phototransistor 21 may be used as a light receiving element, and their number and arrangement position are arbitrary.

In addition, the structure of the lighting device is as shown in Fig. 3.
0. A phototransistor 21 is provided on the printed circuit board 12, the outer periphery of the liquid crystal panel 16 is surrounded by a reflection plate 23 instead of the light guide plate 13, and a diffusion sheet 2 is placed on the lower surface of the anti-transmission type reflection plate 14.
4 may be provided.

Although the configuration of the LCD 10 is as described above, the above LED
The lighting control circuit No. 20 will be explained with reference to FIG. In this figure, for convenience of explanation, the LCD 10 to LED 20
Although the phototransistors 21 and 21 are shown separated from each other, they are actually constructed as shown in FIGS. 1 to 3.

The overall camera system to which the present invention is applied is an LCDl0
It is controlled by a control unit 30 which also functions as an illumination control means and a photometry means. This camera is
In addition to the LCD 10 provided outside the camera, the camera has an in-finder LCD 31 provided inside the finder. The finder LCD 31 is provided outside the finder field of view (focusing screen), and an LED 41 is provided as illumination means on the back surface thereof. This LED4
Needless to say, 1 is provided so that the light does not enter the TTL light receiving element 32 and the film.
The LCD 10 and the finder LCD 31 are each connected to the port PC of the control unit 3o by a pass line, and predetermined display drive control is performed via this pass line.

The output of the light receiving element 32 is logarithmically compressed by a photometric circuit 33, converted into a digital signal by a photometric A/D conversion circuit 34, and sent to port PB of the control unit 30 via a path line.
is input. The control unit 30 receives this signal and I
Photometric calculations are performed based on the SO sensitivity data and other data, and the shutter and diaphragm mechanisms are driven via the n-ratio control circuit 35 to perform exposure.

36 is a battery, and the negative terminal is the control unit 30
The positive terminal is connected to the GND terminal of the control unit 30, and the positive terminal is connected to the vOO terminal of the control unit 30.
"Gives level voltage VDD. Photometering circuit 33, photometry A
Power for operation and driving is supplied to the /D conversion circuit 34 and the exposure control circuit 35 via a transistor 37. The base of the transistor 37 is connected to the boat P6 of the control unit 30 via the resistor R1, so when the potential of the boat P6 becomes low (“L” level), the transistor 37 is turned ON. Power is supplied to the A/D conversion circuit 34 and the exposure control circuit 35.

A photometric switch 38 is provided between the boat PL and GND of the control unit 30, and a release switch 39 is provided between the boat P2 and GND. As is well known, these photometering switch 38 and release switch 39 are linked to a release button (not shown), and when the release button is pressed halfway (the first step), the photometry switch 38 turns ON, and when the release button is pressed fully (the second step), the photometry switch 38 is turned ON. Switch 39 is turned on.

When the photometry switch 38 is turned on, the boat P1 goes to the "L" level and automatic focus adjustment processing and photometry calculation processing are executed, and when the release switch 39 is turned on, the boat P1 is turned on.
2 becomes L'' level and the exposure process is executed.

The LED 20 has a cathode connected to the port P5 of the control unit 30 via a resistor R2, and an anode connected to the collector of the transistor 37. The collector of the phototransistor 21 is connected to the transistor 37 via a resistor R3.
is connected to the collector of resistor R3 and phototransistor 2.
The connection point with the collector No. 1 is connected to the boat P3 of the control unit 30 via the inverter 40. The emitter of the phototransistor 21 is connected to GND.

Further, an LED 41 is provided in parallel with the LED 20, and its cathode is connected to Baud 1-P4 of the control unit 30 via a resistor R4, and its anode is connected to the collector of the transistor 37.

Next, the operations of the LED 20, phototransistor 21, and LED 41 in the lighting control circuit will be described. When the photometry switch 38 is turned on, the port P6 goes to the °L'' level and the transistor 37 is turned on. Therefore, power is supplied to the photometry circuit 33, the photometry A/D conversion circuit 34, and the exposure control circuit 35. .LED20.4
The positive voltage of the battery 36 (■1) is applied to the anode of 1.
is applied.

When light enters the phototransistor 21 (base), a current flows between the collector and the cathode depending on the intensity of the light. Therefore, one end of the resistor R3, that is, the collector voltage of the phototransistor 21 changes depending on the intensity of the light. The stronger the light, the lower the collector voltage, and the weaker the light, the higher the collector voltage. This collector voltage is then input to the inverter 40. When the collector voltage is higher than the threshold voltage, the inverter 40 outputs the °°L" level, and when the collector voltage is lower than the threshold voltage, the °°H"°H" level is input to the boat P3. Therefore, the input level of the boat P3 is is LCD I
When the environment of O is brighter than the specified value, it is at the °H" level, and when it is darker than the specified value, it is at the °L" level. Note that the above specified value (specified brightness) is determined by the resistance R3.
It can be changed (adjusted) by changing the resistance value.

When the photometry switch 38 is turned on, the control unit 30 measures the brightness of the environment by measuring the level of the boat P3. If the measured value is "L" level, current is passed through the boat P5 to the °゛L゛L°゛ level ED20 to light it up (light emit light), and it is turned on while the photometry switch 38 is on and off. and then maintain it for a specified period of time.

If the above measured value is at the “H°° level,” then boat P5 is “
If the boat P5 is at the "H" level, maintain that state (the LED 20 is off), and if the boat P5 is at the "L" level and the LED 20 is lit, change the lighting state to the photometry switch 3 in the same way as above.
It is maintained for a predetermined time while 8 is ON and after 0FFL.

The reason why the LED 20 is not turned off even if the boat P3 reaches the °L" level after the LED 20 is lit is because once the LED 20 is lit, the light beam of the LED 20 enters the phototransistor 21, making it impossible to measure the brightness of the environment. It is.

On the other hand, when the photometry switch 38 is turned on, the control unit 30 inputs photometry data from the light receiving element 32 and starts photometry calculation. If this photometric calculation result is lower than a certain value (for example, Ev value is 6 or less), the boat P4 is set to the °゛L" level and a current is passed through the LED 41.
Turn this on. This lighting is caused by the photometry switch 38 being turned on.
This is maintained for a predetermined period of time and after turning OFF.

The above is an outline of the lighting operation of the LED 20.41.Next, the operation of this embodiment will be explained in more detail based on the flowchart shown in FIG.

When power is applied, boats P4, P5 and P6 are
The software will be reset to “H” level and this software will proceed to step 5.
Start running from 1. First, in step 51, it is checked whether the photometry switch 38 is turned on. If the photometry switch 38 is OFF, this check is repeated until it is turned ON.

When the photometry switch 38 is turned on, the process proceeds to step 52.
Set the port P6 to the °L" level, turn on the transistor 37, activate the photometry circuit 33, the photometric A/D conversion circuit 34, and the exposure control circuit 35, and apply the °H" level voltage to the collector of the phototransistor 21. and step 53
Proceed to.

In step 53, it is checked whether the level of boat P3 is higher than a certain value, that is, whether it is necessary to light up LED 20.

If the level of the boat P3 is L", it is necessary to light up the LED 20, so proceed to step 54, set the boat P5 to the °°L" level, energize the LED 20, turn it on, and proceed to step 55. , if the level of boat P3 is °゛H°゛, which does not require lighting the LED 20, 1. Skip step 54 and proceed to step 55.
In short, in steps 53 and 54, it is determined whether or not it is necessary to turn on the illumination (LED 20) of the LCD 10, and the lighting is controlled.

In step 55, the photometric A/D conversion circuit 34
The D-converted subject brightness data is input and a predetermined photometric calculation is performed, and in step 56 it is determined whether the calculation result (brightness) is lower than a certain value, that is, whether it is necessary to light up the LED 41. .

If the brightness is low, proceed to step 57 and move boat P4 to
The LED 41 is turned on to turn it on, and the process proceeds to step 58. If the brightness does not require lighting, step 57 is skipped and the process proceeds to step 58.

In step 58, LCD10 and the LCD in the finder
The photometry result is displayed at 31, and the process proceeds to step 59.

In step 59, it is checked whether the photometry switch 38 is turned on.

If the photometry switch 38 is OFF, the LED 20.41
Although it is not necessary to keep the LED on for a predetermined period of time (5 to 10 seconds), the photographer may want to check the shooting information and it is preferable to leave the LED on for a predetermined period of time (5 to 10 seconds). A timer to turn off the light later is started, and the process proceeds to step 62. If the timer has already started, the process proceeds to step 62.

When the photometry switch 38 is ON, the LED 20.
41 must be lit, proceed to step 61, reset the above timer to 0, and then proceed to step 62.
Proceed to.

Step 62 checks to see if the timer has timed out. If the time has elapsed, that is, if a predetermined time has elapsed since the photometry switch 38 was turned off, the process proceeds to step 63, where the boats P6, P5, and P4 are set to the ``°H°°'' level, and the process returns to step 51. When the port P6 becomes 'H°' level, the transistor 3
7 is turned off, power is cut off, and LED 20.41 goes out. Even if the ports P5 and P4 are at the °H°°H°° level and the transistor 37 is turned on, the LEDs 20 and 41 do not light up until the ports P5 and P4 are set to the L'' level in step 54 or step 57.

If the time has not exceeded, the process proceeds to step 64 and checks whether the release switch 39 is ONL. If it is ON, the process proceeds to step 65, where the exposure control circuit 35 is activated and exposure processing is performed, and then the process returns to step 55. If it is OFF, the process immediately returns to step 55.
Repeat the above process.

In short, in this embodiment, the brightness of the environment of the LCD 10 when the photometry switch 38 is turned on is judged, and the L E D
2.0 to decide whether to turn it on or off. After that, when the environment of the LCD 10 becomes dark, in steps 53 and 54, the LED 20
is lit. Once the LCD environment is dark and the LED 20 is turned on, the LED 20 continues to be lit even if the environment becomes dark until a predetermined time elapses after the power is turned off or the photometry switch 38 is turned off. That is, LED20
After the phototransistor 21 is turned on, the collector voltage of the phototransistor 21 changes depending on the brightness of the LED 20, but the brightness of the environment of the LCD 10 changes only once under the condition that the LED 20 is off when the photometry switch 38 is turned on. , the influence of the LED 20 need not be considered at all.

The LED 41 is turned on and off in accordance with the photometric A/D conversion value (subject brightness).

According to the above embodiment, regarding the illumination of the LCD 10, the phototransistor 21 directly measures the brightness of the environment of the LCD 10, and the in-finder LCD 31 in the finder
Since the brightness of the subject is measured and controlled using the TTL photometry light-receiving element 32, appropriate and efficient illumination is possible.

Furthermore, in the above embodiment, the input level of the boat P3 can be changed by changing the value of the resistor R3, so it is possible to adjust the boundary value for lighting the LED 20 without changing the software settings. .

Next, adjust the brightness of LCD 10 based on external light and LED 20.
An embodiment having a function of keeping the voltage constant will be described with reference to the circuit diagram shown in FIG. This embodiment is a lighting device having an automatic dimming function that dims the LED 20 using a circuit.

The cathode of the LED 20 is connected via a resistor R5 to the output of an operational amplifier 42 as a photometry and illumination control means, and the anode is connected to the transistor 3 as in the embodiment of FIG.
7 collector. Phototransistor 21
The emitter of is grounded, and the collector is connected to the collector of the transistor 37 via the inverting input terminal of the operational amplifier 42 and the resistor R5.

Furthermore, series dividing resistors R7 and R8 are connected in parallel between the collector of the transistor 37 and GND.
The terminal R8 is connected to the non-inverting input terminal of the operational amplifier 42. This operational amplifier 42 causes current to flow through the LED 20 so that the emitter-collector voltage v2 of the phototransistor 21 and the voltage v3 between the resistors R7 and R8 become equal.The operation thereof will be described below.

First, when the power is turned on and the photometric switch 38 is turned on, the transistor 37 is turned ON, and the LED 20 is connected to GND.
A voltage Vl is applied between the anodes of. In this condition.

V3=VIXR8/ (R7+R8) note, V3<V
It is l.

If no light enters the phototransistor 21 and the phototransistor 21 is OFF, no current flows through the resistor R6, so the voltage is V24V1 (ignoring dark current), that is, L
When the CD l O environment is dark or dark, V1'
=FV2>V3.

When light enters the phototransistor 21, a current flows through the resistor R6. When the amount of incident light increases, the current flowing through the resistor R6 increases and the voltage v2 decreases. When the amount of incident light exceeds a certain value, V2<V3 becomes.

When V2>V3, the amount of light incident on the phototransistor 21 decreases, and the operational amplifier 42 causes a current to flow through the LED 20 according to the difference to turn it on.

Then, the light emitted from the LED 20 enters the phototransistor 21, the current flowing through the phototransistor 21 increases, and the voltage v2 decreases. The operational amplifier 42 has V2=
Increase or decrease the current to LED20 so that it becomes V3, v2=
Maintaining the current at V3, phototransistor 2
The amount of light incident on the LCD 10 is kept constant, that is, the brightness of the LCD 10 is kept constant.

In this way, according to this dimming circuit, when the environment of the LCD I O becomes darker than a predetermined value, the LED 20 lights up, and the brightness of the LED 20 changes according to the darkness of the environment, so that the LCD
The brightness of the D I O is adjusted to be constant. Note that the LED 20 does not light up at all in a range where the environment is brighter than a certain value, and conversely, lights up with the maximum current in a dark range.

As described above, regarding the present invention, the LCD 20 mounted on the camera.
Although the present invention is applied to all LCDs installed in optical and electrical devices other than cameras,
It can be applied to

"Effects of the Invention" As is clear from the above description, the present invention provides an illumination means for illuminating a liquid crystal panel of an LCD from the back side.

Since it has a photometric means for measuring the brightness on the back side of the liquid crystal panel, and an illumination control means for turning on the illumination means when the brightness detected by the photometric means is lower than a predetermined value, it is possible to control the environment of the LCD. The lighting means lights up according to the brightness, making it possible to provide appropriate lighting and efficient lighting without having to operate cumbersome operation switches.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing an embodiment of an LCD to which the present invention is applied, FIG. 2 is an enlarged longitudinal sectional view of the light source and light receiving element of the same embodiment, and FIG. 3 is an enlarged longitudinal sectional view of the light source of the same embodiment. , FIG. 4 is an enlarged sectional view showing another embodiment of the arrangement structure of the light receiving element, FIG. 4 is a block diagram showing the illumination circuit configuration of the same embodiment, and FIG.
B) is a flowchart showing the sequence related to the operation of the lighting device, and FIG. 6 is a circuit diagram showing an embodiment of another lighting circuit. DESCRIPTION OF SYMBOLS 10... LCD, 11... Holder, 12... Printed circuit board, 13... Light guide plate, 14... Anti-transmissive reflector, 16... Liquid crystal panel, 20... LED (lighting) means), 21... phototransistor (light receiving element), 3
o... Control unit (photometering means, lighting control means), 3
1... LCD in viewfinder, 32... Light receiving element for TTL photometry, 33... Photometry circuit, 34... A/for photometry
D conversion circuit, 38...Photometering switch, 39...Release switch, 42...Operational amplifier (photometering means, lighting control means) Patent applicant Asahi Optical Co., Ltd. Agent Kunio Miura Zen Sasayama Fig. 1 Fig. 2 Fig. 3 Fig. 5 (A) Fig. 5 (B) Procedure Nebo Seisho (spontaneous) Director General of the Patent Office Yoshi 1) Moon Yi 1, Indication of the case 1985 Patent Application No. No. 205224 No. 2, Title of the invention: LCD illumination device for camera 3, Relationship with the case of the person making the amendment Detailed description of the invention in the patent applicant's specification and drawing 6, Contents of the amendment (1) Specifications attached to the application On page 10, line 4 of the book, in line 5 of the same page, the statement "via 30 boat PCs" was changed to "connected to each of 30 LCD control boat PCs, "via the LCDCD control boat". (2) Amend Figure 4 of the drawings attached to the application as shown in the attached sheet. (that's all)

Claims (5)

[Claims] (1) An LCD illumination device that has a transflective liquid crystal panel and is installed outside the camera, including an illumination means that illuminates the liquid crystal panel from the back side, and a photometer that measures the brightness on the back side of the liquid crystal panel. 1. An LCD illumination device for a camera, comprising: a photometering means for detecting a brightness; and a illumination control means for lighting the illumination means when the brightness detected by the photometry means is lower than a predetermined value. (2) In claim 1, the illumination means is an LED, the photometry means has a photoelectric conversion element, a light guide plate is provided on the back surface of the liquid crystal panel, and the LED and the photoelectric conversion element are provided on the side end surface of the light guide plate. LCD lighting device for the installed camera. (3) In claim 1, the illumination means is an LED, the photometry means has a photoelectric conversion element, and the LED and the photoelectric conversion element are arranged on the back side of the liquid crystal panel facing the liquid crystal panel. Camera LCD lighting device. (4) In claim 1, the photometry means receives and measures the light transmitted through the liquid crystal panel and the light emitted from the illumination means, and the illumination control means adjusts the photometry value of the photometry means to a predetermined value. L of the camera dimming the illumination means so that
CD lighting equipment. (5) Claim 1, further comprising: an in-finder LCD provided in the finder; and illumination means for illuminating the in-finder LCD, wherein the illumination control means is configured such that the illumination means for the in-finder LCD is used for photometry of a camera. An LCD illumination device for a camera, wherein the illumination means of the LCD is controlled according to the output of the photometry means in accordance with the output of the light receiving element.