JPS58211133A - Data copying device of camera - Google Patents

Abstract

PURPOSE:To facilitate a check on a power supply voltage and to prevent a failure of data copying, by driving a liquid-crystal display for inside copying and a liquid-crystal display for outside monitoring with the same power supply battery, and setting the threshold voltages of both displays to different values. CONSTITUTION:Different LCDs having different characteristics are used for displaying and copying; the threshold voltage of the LCD2 for outside display is set higher than that of the LCD8 for inside copying, and the threshold voltage of the LCD2 is set to a power supply voltage which is inconvenient to a data copying function. When a switch SW1 is closed by releasing a shutter, a lamp L turns on and data is recorded on a film by light transmitted through an LCD8 for copying. If the driving voltage of a power source E2 drops below the threshold voltage of an LCD2 for outside display, the quantity of transmitted light of the LCD8 decreases abruptly and the current display of the display LCD2 become thin, so the drop of the power battery voltage is known easily.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a data imprinting device for a camera using a liquid crystal display device.

2. Description of the Related Art In recent years, data imprinting devices have been put into practical use that automatically record photographic data such as the date and time on film at the same time as photographing, using an electronic clock having a liquid crystal display device.

The power source for this type of data imprinting device is generally provided separately from the power source for the camera body. Button-type steel batteries or button-type lithium batteries are used as the power source for electronic watches that use liquid crystal display devices, and although the lifespan of special KIJ lithium batteries is quite long, lasting several years or more, the battery voltage will drop at the end of its life. When the amount of light transmitted decreases, the amount of light transmitted through the liquid crystal decreases.
If you continue to use the battery without realizing it, the data image recorded on the film will become unclear and difficult to read.

Conventionally, the lifespan of a battery has generally been detected using an electrical detection method, such as using the threshold voltage of a semiconductor element (e.g., a MOS transistor). In order to set the voltage, it is necessary to use a multiplication table adjustment element, and a notification means is also required to display the results detected in this way. Figure 1 is a block diagram showing an example of a conventional power supply voltage detection method.
E is a power supply battery, R1 and R2 constitute a resistor voltage divider circuit, the midpoint of which is connected to the gate of a MOS transistor inverter M, and when the midpoint potential of R1 and R2 becomes below the gate threshold voltage of the MOS transistor, the LCD (Liquid crystal display device) It is configured to display a warning on the LCD via the driver.

In such electrical detection means, (1) increase in circuit scale for electrical detection, fit) i! It is essential to install means for notifying the results of internal detection.

The present invention is a liquid crystal display device (hereinafter referred to as LCD) for external display.
In a camera data imprinting device that uses two LCDs, an internal imprinting LCD and an internal imprinting LCD, the photographer can easily check the power supply using the external display LCD without using a power supply voltage detection device with a complicated configuration as described above. The purpose is to check the voltage and prevent failures in data imprinting due to drops in power supply voltage.

Therefore, in the present invention, LCDs with different characteristics are used for display and imprinting, and the threshold voltage of the external display LCD is set higher than that of the internal imprint LCI, and the threshold voltage of the external display LCD is set higher than that of the internal imprint LCI. The voltage was set to a power supply voltage that is inconvenient in terms of data imprinting function. Due to this pressure, the person using the camera can know that there is a problem with data imprinting, as the characters displayed on the external display LCD become faint or difficult to see.

Embodiments of the present invention will be described below with reference to the drawings.

2 and 6 are rear views of a camera equipped with a data imprinting device to which the present invention is applied, with FIG. 2 showing the back cover in a closed state and FIG. 3 showing the back cover in an open state.

In the figure, 1 is the back cover of the camera, 2 is a reflective LCD that monitors and displays the imprint data set by the electronic clock circuit, 7 is the film pressure plate, and 8 is the transmissive type for imprinting that displays the imprint data. The LCD is illuminated by a light source as shown in the subfigure, and the transmitted light passes through an opening 7a provided in the pressure plate 7 to imprint data from the back side of the film. 6°4.5 is a switch for setting data calibration, and 6 is an AHA changeover switch for setting the lighting time of the light source lamp according to the sensitivity of the film used (or the color of the subject).

Figure 4 shows the electric circuit for data imprinting.
is a power battery on the camera body side, and SWl is a switch that is linked to the shooting operation of the camera. R2 is a power battery for a data imprinting circuit provided on the back cover of the camera, 10 is an LSI for data imprinting, and L is a light source lamp.

When the switch sw1 is closed by the shutter release, the potential V1 changes from low level to high level due to the resistor R, and the trigger input terminal TR of the LSI 10
The signal for imprinting is taken in by I (IN),
It remains at a high level for a certain period of time determined by the selection of A and SA changeover switches B, transistor Q is turned on, and lamp L is lit. As a result, data is recorded on the film using the light transmitted through the imprinting LCD s.

FIG. 5 is a diagram showing the relationship between the LCD driving voltage and the amount of light reflection (or amount of light transmission) in the present invention, where curve A shows the characteristic curve of the amount of light reflection versus the driving voltage of the LCD 2 for external monitor display; Curve B shows a light transmission amount characteristic curve with respect to the driving voltage of the data imprinting LCD 8.

In the figure, 10
The drive voltage level at the point where the amount of reflected light is low, that is, the point where the amount of reflected light is small and the display becomes thin and difficult to see, or the point where it is almost invisible, is defined as the threshold voltage (Vthi), and
The drive voltage level at the point where the amount of transmitted light is 10% of the saturated reflected light amount trap is shown as the threshold voltage (Vth2).

As can be seen from the figure, when the driving voltage drops below the threshold voltage (vth+) of the external display LCD, the amount of light transmission of the imprinting LCD begins to decrease rapidly, and at this time, the display of the external display LCD becomes thinner. Since it is almost invisible, the camera user can tell when the battery voltage is low.

Figure 6 is a diagram showing the discharge characteristics of the power supply battery for data imprinting, and the battery voltage gradually decreases over time.
It shows a rapid decline from nearby locations.

The threshold voltage shown in FIG. 5 may be set around y, that is, Vth1, taking into account the decrease in the amount of lamp light due to voltage drop.

Ve indicates that the battery is discharging and the external monitor display L
This indicates a battery potential at which not only the CD but also the LCD for imprinting cannot be displayed.

As described above, the present invention sets the threshold voltage of the LCD for external monitor display to be higher than the threshold voltage of the LCD for internal imprinting, and the threshold voltage of the LCD for external monitor display is set in consideration of the discharge characteristics of the battery used, etc. By setting the external display LCD without the need for special battery voltage detection means, etc.
The user can judge whether or not data can be imprinted based on the visibility of the data, and can replace the battery at an appropriate time, thereby providing an inexpensive and reliable data imprinting device.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a conventional example of a power supply voltage detection device.
2 to 6 show embodiments of the present invention. FIG. 2 is a rear view of a camera equipped with the device of the present invention, FIG. 6 is a rear view showing the camera back in its open state, and FIG. The figure is an electric circuit diagram of the data imprinting device, Figure 5 is a line diagram showing the relationship between the drive voltage of the liquid crystal display device and the amount of light transmission or light reflection, and Figure 6 is a line diagram showing the discharge characteristics of the battery. be. 1: Camera body 2; Liquid crystal display device for external display 8; Liquid crystal display device for imprinting 10; LSI E for data display
2; Power supply battery for imprinting device L; Including for imprinting, light source applicant: Canon Co., Ltd. ζ14Δ

Claims (3)

[Claims] (1) The imprinting liquid crystal display device installed inside the camera and displaying shooting data and the external display liquid crystal display device displaying shooting data outside the camera are driven by the same power battery. A data imprinting device for a camera, characterized in that threshold voltages of liquid crystal display devices are set to different values. (2) The data imprinting device for a camera according to claim (1), wherein the threshold voltage of the external display liquid crystal display device is higher than the threshold voltage of the imprinting liquid crystal display device. (3) The threshold voltage of the external display liquid crystal display device is set to a voltage that interferes with the data imprinting function of the camera. Included device.