JP2010243765A - Display device, and display device for optical equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display device capable of reducing luminous display invisibility resulting from response delay of polymer network liquid crystal (PN liquid crystal) in a low-temperature environment. <P>SOLUTION: The display device includes: a display means 112 composed of the polymer network liquid crystal capable of varying the dispersion state of transmitted light; a light-emitting means 123 for irradiating the display means 112 with light at an angle different from the luminous flux angle of the transmitted light; and a temperature detecting means 130 for detecting the temperature of the display device in the environment. In accordance with the detection result obtained by the temperature detecting means, at least one of light emission start timing by the light-emitting means with respect to control timing of an applied signal to the display means 112, luminous intensity of the light-emitting means and light emission duration by the light-emitting means, is adjusted. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a display device having improved display performance in a low temperature environment. More specifically, in a device such as a still camera, binoculars, or telescope that allows the user to observe the scene, when the observer looks into the device, the status display of the device is displayed simultaneously with the optical field image. The present invention relates to a so-called superimpose display capable of being visually recognized and a display device for an optical apparatus.

Conventionally, display devices for superimposing and displaying a large amount of information have been proposed (see Patent Document 1 and Patent Document 2). Here, a display panel in which a display pattern is formed with transmissive electrodes and liquid crystal is enclosed is placed near the focus plate (focus detection plate) of a camera or the like, and the voltage applied to the liquid crystal is controlled to transmit the liquid crystal state in the display pattern area. Switch between state and non-transparent state. In addition, it is difficult to visually recognize the display unit in a low-brightness environment only with a display method that uses a general TN (twisted nematic) liquid crystal to switch the non-transmission and transmission states of the display region. Therefore, a liquid crystal display panel is constructed using polymer dispersed liquid crystal (PN (Polymer Network) liquid crystal) as the liquid crystal material, and the panel is irradiated with light from a light source such as an LED to improve visibility in a dark place. is doing. That is, by utilizing the light diffusibility of the PN liquid crystal, only the PN liquid crystal region (display pattern) in a non-transmissive state is reflected and emitted, thereby improving visibility.

JP-A-6-202202 JP-A-8-166634

However, in the method of emitting light by irradiating the liquid crystal display panel composed of the PN liquid crystal with a light, the display becomes difficult to see at a temperature lower than the freezing point, for example, about −10 ° C. In the TN liquid crystal, when the drive voltage of the drive control unit is OFF, the liquid crystal molecules are aligned horizontally and the panel is in a transmissive state, and when the drive voltage is ON, the liquid crystal molecules are vertically raised and the panel is in a non-transmissive state. Change. On the other hand, a liquid crystal display panel using PN liquid crystal is in a transmissive state when the driving voltage is ON, and changes to a non-transmissive state when the driving voltage is turned OFF. Also, the response speed of TN liquid crystal is generally fast falling (transmission → non-transmission) and slow rising (non-transmission → transmission), but PN liquid crystal has a slow falling (transmission → non-transmission) and rises. There is an opposite feature that (non-transmission → transmission) is fast. Further, it has been found that the liquid crystal material itself used for the PN liquid crystal is slower by several times the response at low temperatures than the TN liquid crystal material. Although these response delays are not a problem at room temperature, the display delay response delays are noticeable in a low temperature environment. In particular, in a display device mounted on an apparatus used outdoors such as a camera, a response delay in an environment exceeding the freezing point such as −10 ° C. impairs comfortable operability. In particular, in a display device using a PN liquid crystal, since the display is switched from power ON to OFF (transmission → non-transmission), the display delay is conspicuous. Furthermore, in order to improve the above-mentioned visibility in the dark place, a display device that irradiates light to the PN liquid crystal display panel with a light source and reflects and emits light in a non-transmissive liquid crystal region (display pattern) of the PN liquid crystal. Had the following problems. In other words, when used in a low temperature environment, the light emission display may become dark or the display may become extremely invisible due to the response delay of the PN liquid crystal.

In view of the above problems, the display device of the present invention used in an optical apparatus such as an imaging device such as a camera has the following characteristics. The display device includes a display unit made of a polymer dispersed liquid crystal capable of changing a diffusion state of the transmitted light, and a light emitting unit that irradiates the display unit with light at an angle different from the angle of the light flux of the transmitted light. And temperature detecting means for detecting the temperature of the display device in the environment. And according to the detection result of the temperature detection means, at least one of the light emission start timing of the light emission means with respect to the control timing of the applied signal to the display means, the light emission intensity of the light emission means, and the light emission duration of the light emission means. Configured to adjust.

According to the display device of the present invention, the light emission mode of the light emitting unit is appropriately adjusted with respect to the display by the display unit according to the detection result of the temperature detecting unit, so that the response delay in the low temperature environment of the PN liquid crystal is reduced. Therefore, it is possible to reduce the difficulty in viewing the light-emitting display. In other words, in order to improve visibility in dark places, the light emitting means such as LEDs are irradiated to the PN liquid crystal display means, and only the liquid crystal region (display pattern) that is non-transmissive to the PN liquid crystal is reflected. In the display function of emitting light, the difficulty in viewing as described above can be reduced.

The figure which shows the outline of a camera, and the electrical circuit schematic block of a camera. Optical finder view of the camera. The figure which shows the imaging | photography operation flowchart of a camera, and the operation | movement flowchart of PN liquid crystal and LED. The figure explaining two operation | movement forms of PN liquid crystal and LED. The figure explaining operation | movement of TN liquid crystal and operation | movement of PN liquid crystal. The figure explaining the subject in operation | movement of PN liquid crystal and LED. The figure explaining the display of PN liquid crystal and LED.

Hereinafter, embodiments of the present invention will be described. What is important in the display device of the present invention is the following point. According to the temperature of the display device in the environment, the function is to adjust at least one of the light emission start timing, the light emission intensity, and the light emission duration of the light emission means for the display by the display means having temperature dependency. . Such a display device includes a display unit whose function is temperature-dependent and a light-emitting unit that emits light to the display unit, and the display unit and the light-emitting unit cooperate to display at an appropriate timing with reduced temperature dependency. It can be used with any optical instrument that needs to perform.

Based on the above concept, a basic embodiment of a display device of the present invention used in an optical apparatus such as an imaging device such as a camera has the following configuration. The display device includes a display unit made of a polymer dispersed liquid crystal (PN liquid crystal) capable of changing a diffusion state of transmitted light, and a light emitting unit such as an LED that irradiates the display unit with light at an angle different from the luminous flux of the transmitted light. And temperature detecting means for detecting the temperature of the display device in the environment. And according to the detection result of the temperature detection means, the light emission start timing of the light emission means relative to the control timing of the applied signal such as the voltage signal to the display means, the light emission intensity of the light emission means, and the light emission duration of the light emission means Adjust at least one. “According to the detection result of the temperature detection means” means, for example, when the temperature detected by the temperature detection means is equal to or lower than a predetermined value (for example, 0 ° C. or lower or −10 ° C. or lower, which is considerably lower than normal temperature). It is. The applied signal such as the voltage signal is a signal applied to a transparent electrode such as ITO having a pattern corresponding to display. In such a case, the light emission start timing of the light emitting means with respect to the control timing of the applied signal is such that the temperature is the predetermined value. Delayed when higher than value. Alternatively, the light emission intensity of the light emitting means is increased. Alternatively, the light emission duration of the light emitting means is increased. You may perform combining these adjustments of the light emission means. In the case of the PN liquid crystal, when the voltage is applied to the transparent electrode, the portion of the liquid crystal is transmissive and non-displayed, and when the voltage is not applied to the transparent electrode, the portion of the liquid crystal is non-transmissive and display is performed.

A more specific embodiment includes a focus detection unit capable of detecting a focus in a plurality of focus detection areas in a screen of a subject image of a camera (see examples described later). Here, the first focus detection area display mode and the second focus detection area display mode can be taken. In the first focus detection area display mode, at least one focus detection area is automatically selected from a plurality of focus detection areas, and an area corresponding to the selected focus detection area is displayed on the display means. . In the second focus detection area display mode, when at least one focus detection area is manually selected from the plurality of focus detection areas, an area corresponding to the manually selected focus detection area is displayed on the display unit. Displayed. In the first focus detection area display mode, the above-described adjustment is performed to display the in-focus state after the focus detection operation is performed. In the second focus detection area display mode, the light emission means continuously emits light to display the focus detection area.

Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. In FIG. 1 to FIG. 7, the same numbers are assigned to the same component parts.
In FIG. 1A showing a schematic configuration of a digital camera to which the present invention is applied, 101 is a CPU (Central Processing Unit), and the operation of this camera is controlled by this CPU 101. Reference numeral 105 denotes a photographic lens, which forms an image of photographic field light on the CCD 106 which is an image sensor. The photographic lens 105 depicted in the figure is expressed by a single lens 105a for convenience, but actually includes a plurality of lenses. Reference numeral 128 denotes a focus detection plate (hereinafter referred to as a focus plate) placed on an image formation surface equivalent to the image formation surface of the CCD 106 of the photographing lens 105, and the object scene image is reflected by the main mirror 126, and the focus plate 128. Primary imaging. The photographer can view the object scene image through the pentaprism 127 and the eyepiece 121. Thus, this camera has a so-called TTL optical finder configuration. On the other hand, the main mirror 126 is a semi-transmissive mirror, and a part of the transmitted light beam is guided to the focus detection unit 119 which is a focus detection unit through the sub mirror 122, and a focus detection operation of a known phase difference detection method is performed. Based on the result of the focus detection operation and the like, the CPU 101 controls the position of the photographing lens 105 via the lens driving unit 131 including a lens driving motor. .

Reference numeral 130 denotes a photometric sensor made of a silicon photodiode. The photometric sensor 130, which is a photometric means, forms a secondary image on the chip of the photometric sensor 130 with the photometric lens 129, and detects the luminance distribution of the scene. Here, the chip portion of the photometric sensor 130 is divided into an appropriate number of photometric areas, and the luminance of the object scene corresponding to each area can be detected. Further, in the present embodiment, the circuit unit of the photometric sensor 130 is mounted with a thermometer, and serves as temperature detection means that can detect the internal temperature of the camera under the environment.

Reference numeral 112 denotes display means composed of a polymer-dispersed liquid crystal panel (hereinafter referred to as a PN liquid crystal panel) disposed in the vicinity of the focusing screen 128. The display unit 112 performs the above-described focus detection operation on the photographer of the camera looking through the optical viewfinder. Inform the status display. The PN liquid crystal panel 112 is normally placed in a transmissive (transparent) state. As a result of focus detection by the focus detection unit 119, only the focus detection area display portion on the PN liquid crystal panel 112 corresponding to the focus detection area determined to have been brought into focus is made non-transparent (non-transparent), and shooting is performed. It is possible to inform the person of the object position in focus. In addition, when the field luminance is detected from the output of the photometric sensor 130 and it is determined that the luminance is equal to or lower than a predetermined value, the LED 123 which is a light emitting unit emits light. This light is irradiated to the PN liquid crystal panel 112 through the light guide prism 124 as LED irradiation light. Then, only the focus detection area display portion that is non-transmissive on the PN liquid crystal display panel 112 appears to shine to the finder observer.

Here, the PN liquid crystal panel 112 will be described with reference to FIG.
As shown in FIG. 7A, the PN liquid crystal panel 112 includes two upper and lower plate glasses 112a and 112b and a liquid crystal layer 112c sealed therebetween. Moreover, as shown in FIG.7 (b), the electrode pattern is formed in the surface facing the liquid crystal of two plate glass with ITO (transparent electrode). On the liquid crystal side surface of the lower glass plate 112b, an electrode pattern L2 is patterned in a region serving as a focus detection region display unit, and an electrode pattern L1 is patterned in other regions. On the other hand, a COM electrode (common electrode) is patterned over the entire surface of the upper glass plate 112a on the liquid crystal side. By controlling the voltage applied between the COM electrode and the L1 and L2 electrodes, the state of the focus detection area display unit can be switched between the transmissive state and the non-transmissive state.

When no voltage is applied to the PN liquid crystal, the refractive indexes of the liquid crystal internal materials are different from each other, so that light is scattered and is externally non-transmissive. When a voltage is applied to this, the internal refractive index matches and the liquid crystal layer becomes a transmission state. Therefore, in the electrode pattern of FIG. 7B, normally, a voltage is applied between the COM electrode and the L1 and L2 electrodes so as to be transparent. Thereby, the photographer who normally looks into the finder can see a clear field of view in which the focus detection area display unit is not visible. Next, when the focus of the photographic lens 105 is focused on the subject by the focus detection operation of the camera, only the focus detection area display unit is made opaque by turning off the L2 electrode. This notifies the photographer that the camera is in focus at the object position corresponding to the focus detection area display unit. However, when the shooting environment is low in luminance and the object scene image of the finder is dark, it is difficult to distinguish between the transmission state and the non-transmission state of the focus detection area display unit. Therefore, as shown in FIG. 7A, illumination light from the LED 123 or the like is irradiated from the side surface of the PN liquid crystal panel 112 toward the panel. Then, the liquid crystal part of the focus detection area display part in the non-transmissive diffusion state receives the LED light and diffuses and reflects the light to the surroundings. When the observer sees the reflected light, the focus detection area display unit appears to shine.

The display in the optical finder field will be described with reference to FIG.
A focus detection area display unit (F11 to F35) including 15 areas of the object scene is arranged on the PN liquid crystal panel 112 as a character display. Each focus detection area display unit (F11 to F35) represents an area in which focus detection is possible by the focus detection unit 119 of the phase difference detection method. Here, when the focus detection operation is performed and the camera determines that the photographing lens 105 is focused in a specific area of the object scene, the focus detection of the PN liquid crystal panel 112 corresponding to the focus detection area at the focus position is performed. The area display portion becomes non-transmissive (that is, black). As a result, the photographer is informed that the focus of the taking lens 105 is suitable for the subject area. That is, in FIG. 2, only F22 is displayed in black. At this time, when the object scene is dark, the LED 123 emits light as described above, and only the focus detection area display portion F22 appears to shine red. Furthermore, the other focus detection areas that fall within the depth of field (that is, can be considered to be in focus) according to the aperture of the photographing lens 105 are simultaneously blackened with respect to the focus detection area F22. In-focus display may be performed.

In FIG. 2, the 15 focus detection areas are associated with the same 15 photometry areas (S11 to S35) whose luminance can be detected by the photometry sensor 130 in the object field area. However, the optical viewfinder visual field diagram of FIG. 2 is schematically written for the sake of explanation, and in reality, 15 photometric areas cannot be seen in the viewfinder visual field. Also, as shown in FIG. 2, an internal display unit 115 for displaying camera shooting information is arranged below the viewfinder field, and the shutter time, lens aperture value, and shooting are the camera shooting conditions. A display such as the possible number is displayed.

Here, returning to FIG. When the photographer presses the release switch 114 (see FIG. 1B), the main mirror 126 is retracted out of the optical path of the photographing lens 105. On the other hand, the amount of field light condensed by the photographing lens 105 is controlled by a focal plane shutter 133 and subjected to photoelectric conversion processing as a field image by a CCD (imaging device) 106. Thereafter, the captured image is recorded on the recording medium, and the captured image is displayed on the TFT external display unit 113.

In FIG. 1B, which is an electrical block diagram showing a schematic configuration of a digital camera including the first embodiment of the display device of the present invention, reference numeral 101 denotes the CPU (central processing unit) described above, and a non-volatile circuit therein. EEPROM 101a which is a volatile memory. Connected to the CPU 101 are a ROM 102, a RAM 103, a data storage means 104, an image processing unit 108, a display control unit 111, a release switch 114, and a DC / DC converter 117 for supplying power. . A CCD control unit 107 and a CCD 106 are connected to the image processing unit 108.

An external display unit 113 is connected to the display control unit 111. The external display unit 113 is a TFT color liquid crystal capable of displaying an image obtained by thinning the image captured by the CCD 106 in the vertical and horizontal directions. Furthermore, the display control unit 111 also drives the internal display unit 115 that displays camera information in the finder and the PN liquid crystal panel 112. The LED control unit 125 controls the brightness of the LED 123 for illuminating the PN liquid crystal panel 112 in response to an instruction from the CPU 101. Power is supplied from the battery 116 to the DC / DC converter 117.

The CPU 101 performs various controls based on a control program in the ROM 102. In these controls, processing for reading a captured image signal from the image processing unit 108 and transferring it to the RAM 103, processing for transferring data from the RAM 103 to the LCD display control unit 111, processing for storing the image data in the data storage unit 104, and the like are performed. Further, the CPU 101 instructs the CCD 106, the CCD control unit 107, the image processing unit 108, the LCD control unit 111, and the like to change the number of data fetching pixels and digital image processing.

A focus detection control unit 119 includes the pair of line CCD sensors for focus detection described above. The focus detection control unit 119 performs A / D conversion on the voltage obtained from the line sensor and sends the converted voltage to the CPU 101. Under the instruction of the CPU 101, the focus detection control unit 119 also controls the accumulation time and AGC (auto gain control) of the line sensor. In addition, an instruction of a photographing operation associated with the operation of the release switch 114 and a process of outputting a control signal for controlling power supply to each element to the DC / DC converter 117 are performed based on the control of the CPU 101. .

The RAM 103 includes an image development area 103a, a work area 103b, a VRAM 103c, and a temporary save area 103d. The data storage means 104 is a flash memory for storing captured image data or various attached data referred to by an application. The CCD 106 that converts a captured image projected by the photographing lens 105 into an analog electrical signal can output thinned pixel data in the horizontal and vertical directions in accordance with a resolution conversion instruction from the CPU 101. The CCD control unit 107 includes a timing generator that supplies a transfer clock signal and a shutter signal to the CCD 106, a circuit for performing noise removal and gain processing of the CCD output signal, an A / D conversion circuit that converts an analog signal into a digital signal, and the like. Contains. The image processing unit 108 performs image processing such as gamma conversion, color space conversion, white balance, AE, flash correction, and the like on the 10-bit digital signal output from the CCD control unit 107, and YUV (4: 2: 2). Outputs 8-bit digital signal in format. These photographing lens 105, CCD 106, CCD control unit 107, and image processing unit 108 constitute imaging means. The display control unit 111 receives the image data transferred from the image processing unit 108 or the YUV digital image data from the data storage unit 104, converts it into an RGB digital signal, and outputs it to the external display unit 113.

The release switch 114 is for instructing the start of the photographing operation. The switch 114 takes a two-stage switch position by pressing the release button (not shown). When the first position (SW1 is ON) is detected, camera settings such as white balance and photometry are locked. When the second position (SW2 is ON) is detected, the object scene image signal is captured. Operation is performed.

The photometric control unit 132 drives and controls the photometric sensor 130 in accordance with an instruction from the CPU 101, captures the object field luminance signal, and sends data to the CPU 101. As a basic photometric operation, luminance signals respectively generated in the divided photometric areas of the photometric sensor 130 are A / D converted by the CPU 101 to become digital signals. Several corrections are made to this, and finally information on the field luminance signal value can be obtained. Based on this information, the optimum exposure calculation of the camera is performed, and the shutter speed and the aperture of the photographing lens are adjusted. The optimal exposure of the object scene image can be obtained by optimal control. As described above, the photometric sensor 130 has a built-in temperature sensor, and monitors the temperature in the camera and sends it to the CPU 101. The battery 116 is a rechargeable secondary battery or a dry battery. Further, the DC / DC converter 117 receives a power supply from the battery 116, generates a plurality of power supplies by performing boosting and regulation, and supplies a power supply of a necessary voltage to each element including the CPU 101. The DC / DC converter 117 can control the start and stop of each voltage supply by a control signal from the CPU 101.

Next, the operation of the digital camera according to the present embodiment will be described using the flowchart of FIG.
First, in step S200, when a power switch (not shown) is turned on from a non-operating state of the digital camera, a photographing operation is started. In step S201, the process waits until the release SW 114 is pushed in and SW1 is turned on. If it is detected in step S201 that SW1 is turned on, the process proceeds to step S202. In step S202, the CPU 101 obtains the field luminance information obtained by dividing the photographic field into 3 × 5 from the photometric sensor 130, and then stores the information in the memory. Also, based on the field luminance information obtained by the photometry in step S202, the aperture value of the photographic lens and the shutter time, which are exposure values of the camera, are determined by a program built in the camera according to a predetermined photometric algorithm calculation. The algorithm for calculating the optimum exposure value from the 3 × 5 luminance information obtained from the photometric sensor 130 may be a simple addition average, or the maximum in the photometric area corresponding to the focus detection area determined in step S206 below. An operation with weighting may be used.

In step S203, the CPU 101 determines whether or not the focus detection area selection mode is set to the manual mode. If the manual mode is set, the process proceeds to step S204. In step S204, at least one of the plurality of focus detection areas is sequentially displayed in accordance with a switch dial operation (not shown) of the photographer, and the focus detection area can be arbitrarily selected (second selection). Focus detection area display mode). On the other hand, if the automatic mode is set, the process proceeds to step S205. In step S205, based on the defocus amount in the focus detection area corresponding to the 15 focus detection area display units of the known phase difference type focus detection unit, one of the plurality of focus detection areas is selected by the focus detection area automatic selection subroutine. Select. Although several methods are conceivable as an automatic selection algorithm, a near-point priority algorithm in which a weight is assigned to a central focus detection area, which is well-known in a multipoint AF camera, is effective. As described above, regardless of whether the focus detection area selection mode is set to the manual mode or the automatic mode, one focus detection area is determined as a result in step S206. Then, from the focus detection deviation amount (defocus amount) obtained in the focus detection region determined in step S206 and the lens drive sensitivity of the photographing lens 105 mounted on the camera, the lens extension amount to be finally obtained is It is determined.

In step S207, the CPU 101 sends a signal to the lens driving unit 131 in accordance with a signal from the focus detection control unit 119 to drive the photographing lens 105 by a predetermined amount before the lens is driven. On the other hand, a focus detection area display unit (for example, F22 in FIG. 2) corresponding to the focus detection area determined in step S206 is turned on, and an indication of where in the object field area the photographing lens 105 is focused is displayed. This is performed in step S208. This display is performed on the PN liquid crystal panel 112 described above, and details will be described later. In step S209, it is determined whether SW1 is turned on. When the in-focus display is performed, the photographer continues to turn on SW1 while looking at the viewfinder field in the focused display state. If SW1 is ON, it is determined in step S210 whether or not the release button has been further pressed and SW2 has been turned ON. When SW2 is turned on in step S210, in step S211, the CPU 101 transmits signals to a shutter control unit, a diaphragm driving unit, and a CCD control unit 107 (not shown) to perform a known photographing operation. If it is determined in step S209 that SW1 is OFF, the process returns to step S202 to enter a standby state waiting for SW1 to turn ON. If SW2 is not ON in step S210, the process returns to step S209 to enter a standby state waiting for SW2 to be turned ON.

In the photographing operation in step S210, first, the motor is energized via a motor control unit (not shown) to raise the semitransparent main mirror 126, and the aperture of the photographing lens 105 is narrowed down. Thereafter, one magnet of the shutter 133 is energized, and the front curtain of the shutter 133 is opened to start accumulation of field light in the image sensor 106. After a predetermined shutter time elapses, the other magnets are energized, and the rear curtain of the shutter 133 is closed to complete the accumulation of the field light in the image sensor 106. Next, the motor is energized again to perform mirror down and shutter charging, and the series of shutter release sequence operations (photographing operations) is completed. With such an operation, the image sensor 106 accumulates the light amount from the object scene image. The object scene image exposed to the image sensor 106 in the photographing operation in step S211 is photoelectrically converted, converted into digital data in the image processing unit 108, and temporarily stored in the RAMa 103.

Next, in step S212, the stored whole image digital data of an appropriate number of pixels is converted into whole image data that has been thinned out appropriately in the vertical and horizontal directions for display on the display unit 113. Then, the image is re-stored in the display VRAM 103c, and the entire image data is displayed on the display unit 113, so that the photographer can check the entire image of the photographed image. On the other hand, the entire image digital data stored in the RAM 103a is compressed and then recorded as image data on a recording medium such as a compact flash (registered trademark) by the data storage means 104. Next, in step S213, the state again waits for the input of SW1, and during that time, the entire image is continuously displayed. When an input is made, the captured image display on the display unit 113 is turned off, and the process returns to step S210 to wait for input of SW2, and if there is no input of SW1, the process returns to step S201 and waits in a state of waiting for input of SW1.

Here, in the finder display using the PN liquid crystal panel 112 which is the main part of the present invention, the light emission control at the low temperature of the LED 123 that emits light toward the PN liquid crystal panel 112 at the time of low luminance and the drive control of the PN liquid crystal panel 112 itself. The relationship will be described. FIG. 5A schematically shows a timing chart when a TN (twisted nematic) liquid crystal panel generally used for a display panel is operated by static drive. Here, the horizontal direction in the figure represents the time axis, and the vertical axis direction of the liquid crystal represents the transmittance. In the TN liquid crystal, when the driving voltage of the LCD control unit is OFF, the liquid crystal molecules are aligned horizontally, and the character part to be displayed on the panel is in a transmissive state (for convenience, the transmittance is 100%). When the drive voltage is ON, the liquid crystal molecules rise vertically and the panel changes to non-transmissive (for convenience, the transmittance is 0%). On the other hand, in the timing chart of the liquid crystal panel using the PN liquid crystal shown in FIG. 5B, the character display portion is in the transmissive state when the drive voltage is on, and changes to non-transmissive when the power is turned off. As can be seen from FIG. 5A, the response speed of the TN liquid crystal generally has a fast fall (transmission → non-transmission) time Td and a slow rise (non-transmission → transmission) time Tr. On the other hand, the PN liquid crystal shown in FIG. 5B has a reverse feature that the fall (transmission → non-transmission) time Td is slow and the rise (non-transmission → transmission) time Tr is fast. Furthermore, there is a fact that the PN liquid crystal material itself has a lower low temperature response than the TN liquid crystal material. Due to these characteristics, the problem described in the explanation of the problem occurs. This phenomenon will be described with reference to FIG.

In FIG. 6, when the LCD (display) control unit turns off the voltage to the PN liquid crystal, the PN liquid crystal falls in a short time (transmission → non-transmission) when the photographing environment is at room temperature. At this time, the LED control unit 125 also causes the LED 123 to emit light simultaneously, and the light energy in the hatched area in FIG. 6 reaches the observer's eyes and the liquid crystal character display unit is visually recognized. However, at a low temperature of about −10 ° C., a falling response delay occurs in the PN liquid crystal as shown in FIG. Thereby, even if the LED 123 emits light, the PN liquid crystal still does not have sufficient diffusibility to be reflected, and the energy of the hatched area reaching the observer's eyes is greatly reduced. In other words, it looks dark.

To solve such a problem, as shown in FIG. 4 (a), when the LED 123 starts to emit light after being delayed by δTe time from the timing when the applied signal to the LCD is turned OFF, the transmittance of the PN liquid crystal substantially falls. LED lighting will be received in the state where it is complete. Therefore, light energy in a sufficiently hatched area can be delivered to the observer, and the observer can see a bright character display section. That is, it can be seen that delaying the light emission start timing of the LED 123 according to the temperature of the environment in which the display device using the PN liquid crystal is used is effective in improving the display appearance, particularly at low temperatures.

The operation related to the display of the PN liquid crystal of the digital camera to which the above method is applied will be described with reference to the flowchart of FIG. First, it is assumed that the photographer has determined the focus detection area by manual operation in the focus detection area automatic selection subroutine in step S205 of FIG. 3A or in step S204. At this time, as a result, when the focus detection region is determined in step S206 and the focus detection operation step S207 of the photographing lens 105 is performed, whether or not the focus detection operation is successful in step S300 of FIG. Confirm. Here, in the case of focusing failure, it waits to wait for the result of the next focus detection operation. On the other hand, if the focus detection is successful, in step S301, the PN liquid crystal panel 112 causes the focus detection area display unit corresponding to the focus detection area in focus in the finder field of FIG. The character display unit is switched from the power ON state to the OFF state. In other words, the character display unit changes from the transparent state to the non-transmissive state (black) so that the photographer knows that the photographing lens is focused on the finder field position corresponding to the focus detection area display unit F22. Close.

At the same time as step S301, in step S302, when the photographing field luminance is detected from the output of the photometric sensor 130 and it is determined that the luminance is not more than a predetermined value, for example, BV = 4 or less, in step 303. Check the camera's internal temperature. On the other hand, when the luminance exceeds BV = 4, the process proceeds to step 305. A plurality of temperature sensors used for determining the temperature inside the camera in step 303 are arranged in the camera, and are built in, for example, the photometric sensor 130 or the AF sensor inside the focus detection unit 119. This is a type of thermometer that measures the temperature using the fact that the electrical resistance of a metal oxide or semiconductor changes with temperature. Here, a thermometer in the photometric sensor 130 disposed at a location relatively close to the PN liquid crystal panel 112 is used (temperature detection means). Here, if it is determined that the temperature of the camera is −10 ° C. or lower, a timer for delaying the light emission start timing of the LED 123 in step S304 is activated. In this case, the LED 123 starts irradiation toward the PN liquid crystal panel 112 with a delay time (δTe) of 200 mS.

If it is determined in step S303 that the temperature inside the camera exceeds −10 ° C., the LED 123 starts to emit light in step S305 without any LED light emission delay. Also, if it is determined in step S302 that the shooting field luminance exceeds BV = 4, the LED 123 starts to emit light in step S305 without any LED light emission delay. Next, the LED 123 illuminates the PN liquid crystal panel 112 for a predetermined time, here 300 mS, and then turns off in step S306. In step S307, the display by the PN liquid crystal is turned off (that is, the applied voltage is turned off). Switch from OFF state to ON state). The time until turning off at this time depends on the timing when the SW1 signal is turned off when the photographer presses the release switch 114.

In the above description, the LED light emission delay time δTe is set to 200 mS or zero depending on whether or not the temperature determination condition in step S303 in the flowchart of FIG. 3B is −10 ° C. or less, but is not limited to this setting. . For example, it is effective to set a fine condition such as 100 mS when the LED light emission start delay time is from 0 ° C. to less than −15 ° C., and 300 mS at a low temperature exceeding −15 ° C. Further, the temperature and delay time are also effective. It is also possible to calculate by formulating the relationship.

Next, as a second technique for improving the appearance of the PN liquid crystal at low brightness and low temperature, the one shown in FIG. 4B can be adopted. Here, the LED 123 is turned on at the same timing as the start of driving the PN liquid crystal (power OFF), but the timing at which the LED 123 is turned off is delayed from that at room temperature. Even if it does in this way, the same effect as the above is acquired. That is, the light emission duration of the LED 123 is increased by adding the delay time δTc at a low temperature to the light emission duration until the LED 123 is turned on and off at room temperature. This also makes it possible to make the character display portion appear brighter. In this case as well, the delay time of δTc with respect to the temperature may be made variable, and as a result, the total light emission duration of the LED 123 may be made variable, as in the method of delaying the light emission start of the LED 123.

Further, as a third means, there is also an effect that the light emission intensity of the LED 123 is changed in a low temperature environment without changing the timing of the light emission start and light emission end of the LED 123. That is, at a low temperature, the character display can be brightened by increasing the amount of current to be supplied to the LED 123 or the drive duty ratio from that at normal temperature. Also here, by making the amount of current loaded on the LED 123 and the drive duty ratio variable with respect to the temperature, a character display with appropriate and constant brightness can be visually recognized by the observer even at low temperatures.

Until now, in the description of the flowchart of FIG. 3B, the focus display method of the PN liquid crystal panel 112 after the focus detection area in step S206 of the camera photographing operation of FIG. The case of the first focus detection area display mode has been described. Next, the second focus detection area display mode in step S204 in the flowchart of FIG. That is, according to the switch dial operation of the photographer, at least one of the plurality of focus detection areas is sequentially displayed, and the PN liquid crystal in the focus detection area manual selection mode for arbitrarily selecting the focus detection area. A method of displaying the panel 112 will be described.

The focus detection region manual selection mode is entered when the photographer presses a setting button (not shown) provided on the camera body. In addition, the button may be pressed again to complete the setting or exit the mode. When the camera enters the focus detection area manual selection mode, as shown in the viewfinder view of FIG. 2, the focus detection area showing 15 areas on the PN liquid crystal panel 112 capable of detecting the focus of the object scene. Are displayed (F11 to F35). This is the display form of the second focus detection area display mode. In the focus detection area display unit displayed at this time, the currently set specific focus detection area is displayed first. For example, if the central region F23 has been selected in the previous operation, that region is displayed as the character display unit, and if the focus detection region automatic selection mode is set, all 15 regions are displayed at once. Here, when the second focus detection area display mode is entered at the time of low luminance, the LED 123 that illuminates the PN liquid crystal panel 112 emits light, but unless the button is pressed again or the release switch 114 is operated, the LED 123 The light emission continues. That is, when the switch dial is continuously operated in order to designate the focus detection area, the character display portion in the focus detection area is sequentially moved and displayed in the light emitting state. Further, at low brightness and low temperature, as described above, the PN liquid crystal repeats falling (transmission → non-transmission) and rising (non-transmission → transmission) in accordance with the operation of the switch dial according to the switch dial operation. Response delays are noticeable when falling. However, since the LED 123 is always in an illuminated state, the character display portion in the focus detection area is never darkened.

According to the above embodiment, it is possible to reduce the difficulty in viewing the illumination light-emitting display that occurs due to the response delay in the low-temperature environment of the PN liquid crystal.

101 CPU (central processing unit)
105 Shooting lens 106 CCD (imaging device)
112 PN liquid crystal panel (display means)
119 Focus detection unit (focus detection means)
123 LED (light emitting means)
130 Photometric sensor (temperature sensor, temperature detection means)

Claims (3)

Display means comprising a polymer-dispersed liquid crystal capable of changing the diffusion state of transmitted light; and light emitting means for irradiating the display means with light at an angle different from the angle of the transmitted light beam. A display device,
Temperature detecting means for detecting the temperature of the display device in the environment,
According to the detection result of the temperature detecting means, at least one of the light emission start timing of the light emitting means relative to the control timing of the signal applied to the display means, the light emission intensity of the light emitting means, and the light emission duration of the light emitting means. A display device characterized by adjusting one. A focus detection means capable of focus detection in a plurality of focus detection areas in the screen of the subject image of the optical device;
A first focus detection area display mode in which at least one focus detection area is automatically selected from the plurality of focus detection areas, and an area corresponding to the selected focus detection area is displayed on the display means. When at least one focus detection region is manually selected from the plurality of focus detection regions, a region corresponding to the manually selected focus detection region is displayed on the display means. Focus detection area display mode,
In the first focus detection area display mode, according to the detection result of the temperature detection means, the light emission start timing of the light emission means relative to the control timing of the applied signal to the display means, the light emission intensity of the light emission means, At least one of the light emission durations of the light emitting means is adjusted to display the in-focus state after execution of the focus detection operation, and the light emission of the light emitting means is continuously performed in the second focus detection area display mode. The display device according to claim 1, wherein the focus detection area is displayed in a manual manner. When it is detected from the detection result of the temperature detection means that the temperature of the display device under the environment is equal to or lower than a predetermined value, the light emission start timing and the light emission intensity of the light emission means with respect to the control timing of the signal applied to the display means The display device according to claim 1, wherein at least one of the light emission duration is delayed, made larger, or made longer than when the temperature is higher than the predetermined value.

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