JPH0147763B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a focus display device for a camera, more specifically, a focus display device for displaying a focus in a camera having a focus detection device that outputs different status signals based on the focus point. This invention relates to a focus display device.

As is well known, in recent years, electrical focus detection devices that utilize the photoelectric effect of photoelectric conversion elements have come into use. Such a focus detection device is
Unlike microprisms and split images, this method does not rely on the photographer's vision, so it has the advantage of being able to accurately adjust the focus without being affected by the brightness of the subject or skill level. However, among conventional focus detection devices of this type, there are devices that output different status signals for near and far distances from the in-focus point, and the output from such devices It was not possible to directly display the focus based on the signal.

In view of the above-mentioned points, an object of the present invention is to provide a delay circuit that delays an output signal from a focus detection device, and to compare the output from this delay circuit with the output from the focus detection device to achieve a To provide a focus display device for a camera, which obtains a focus display signal.

According to the present invention, it is possible to easily extract a focus display signal for driving a display member including a sounding element, a light emitting element, etc., based on the output from the focus detection device whose state is reversed at the in-focus point. can.

Hereinafter, the present invention will be explained based on an illustrated embodiment.

FIG. 1 shows a light receiving section and a focus detection device in a focus display device of the present invention. The light receiving unit 1 is formed of a light receiving element substrate having a large number of photoelectric conversion units such as a photoelectric conversion element array and a charge-coupled device, and the output of each photoelectric conversion unit is inputted to the focus detection device 2. It's summery. The focus detection device 2 receives the output signal from the light receiving section 1, and when it is in the front focus state as shown in FIG. 2A, the focus detection device 2 outputs a low level (hereinafter referred to as When the state signal S ₁ (referred to as "L" level) is output and the in-focus state is achieved as shown in FIG. When the state signal _S1 is inverted to a high level (hereinafter referred to as "H" level) and is in the rear pin state as shown in FIG. ``It is designed to output a level status signal _S1 . In FIGS. 2A to 2C, reference numeral 3 indicates a photographic lens or an imaging lens, and 4 indicates a photographic film surface or a light-receiving surface of the light-receiving section 1, respectively.

Status signal S ₁ output from the focus detection device 2
As shown in FIG. 4, is input to the delay circuit 5 and also to one input terminal of an exclusive OR circuit 6 as a detection circuit. The delayed signal S ₂ output from the delay circuit 5 is input to the other input terminal of the exclusive OR circuit 6, and the focus display signal S ₃ output from the exclusive OR circuit 6 is input to a display member (not shown). When input, the same member is driven to display.

According to the focus display device of the present invention configured as described above, when the focus detection device 2 outputs the state signal _S1 as shown in FIG. 5A, this state signal
S ₁ is delayed to the state of the delayed signal S ₂ in the delay circuit 5 as shown in FIG. 5B, and this delayed signal S ₂
is input to the exclusive OR circuit 6 together with the state signal _S1 , so that the output terminal of the exclusive OR circuit 6 receives the delay of the delay circuit 5 from the inversion of the state signal _S1 , as shown in FIG. A focus display signal _S3 that is at the "H" level only for a certain period of time is obtained. The display member is driven based on this focus display signal _S3 , and a focus display is performed. Note that the status signal _S1 changes from “L” level to “H” level.
Although only the states of the signals S ₁ , S ₂ , and S ₃ are shown when the state signal S ₁ changes from the “H” level to the “L” level, the focus display signal Needless to say, S ₃ can be obtained.

FIG. 6 shows an electric circuit in which the delay circuit 5, the exclusive OR circuit 6, and the display member drive circuit shown in FIG. 4 are further detailed. In this electric circuit, the delay circuit is formed by a CR timer circuit consisting of a resistor 12 and a capacitor 13, and the exclusive OR circuit is formed by an inverter 1
1, an AND circuit 14, a NOR circuit 15, and an OR circuit 16. The state signal S ₁ outputted from the focus detection device 2 is applied to an input end of an inverter 11, one input end of an AND circuit 14, and one input end of a NOR circuit 15, respectively. The output end of the inverter 11 is connected through a resistor 12 to the other end of a capacitor 13 whose one end is grounded, and the other end of the capacitor 13 is further connected to the other input ends of an AND circuit 14 and a NOR circuit 15. has been done. The output terminal of the AND circuit 14 is connected to one input terminal of the OR circuit 16, and the output terminal of the NOR circuit 15 is connected to the other input terminal of the OR circuit 16. AND circuit 17
is connected to one input end of the AND circuit 1
7 has its output end connected to the base of a switching transistor 19 for display member drive control, and serves as a gate for supplying the oscillation output of the oscillation circuit 18 to this transistor 19. The switching transistor 19 is formed of an NPN type transistor, and its emitter is grounded, while the operating voltage Vcc is applied to its collector through a resistor 21 and a focus display light emitting element 20. Further, a focus display sounding element 22 is connected in parallel with the series circuit of the resistor 21 and the light emitting element 20. The light emitting element 20 is formed of, for example, a light emitting diode, and the sound generating element 22 is formed of, for example, a ceramic piezoelectric element.

In the focus display device of the present invention having the electrical circuit configured as described above, when the focus detection device 2 outputs the state signal S ₁ as shown in FIG. 7A, the state signal S ₁ is inverted by the inverter 11, then the resistor 12 and capacitor 13
The potential signal _S4 at the other end of the capacitor 13 is charged and discharged by the CR timer circuit.
changes as shown in FIG. 7B. This signal S ₄
is input to the AND circuit 14 and the NOR circuit 15 together with the state signal _S1 , and the AND circuit 14
At the output end of the NOR circuit 15, output signals _S5 and _S6 as shown in FIG. 7C and D are obtained, respectively. Therefore, a focus display signal S ₃ as shown in FIG. 7E is obtained at the output terminal of the OR circuit 16 to which both signals S ₅ and S ₆ are input. Therefore, the AND circuit 1 is activated only while this focus display signal _S3 is at "H" level.
7, the oscillation output of the oscillation circuit 18 is applied to the base of the switching transistor 19, and the transistor 19 is repeatedly turned on and off. Therefore, the light emitting element 20 is intermittently energized,
The element 20 emits light to indicate the focused state, and a voltage is intermittently applied to the sound generating element 22, so that the element 22 produces a sound to indicate the focused state.

As described above, according to the present invention, the state signal output from the focus detection device is delayed by the delay circuit and then compared with the original state signal to extract the focus display signal. , it is possible to provide a very practical camera focus display device that can easily obtain a focus display signal.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the light receiving section and the focus detection device in the focus display device of the present invention, and FIGS. 2A to 2C are state diagrams showing the front focus state, the focus state, and the back focus state, respectively. , FIG. 3 is a diagram showing the output waveform of the focus detection device in each state shown in FIGS. 2A to C above, and FIG. 4 is a diagram showing the delay circuit and detection in the focus display device of the present invention. 5A to 5C are diagrams showing the output waveforms of each part in the electric circuit shown in FIG. 4 above, and FIG. 6 is a diagram showing the connection manner with the circuit shown in FIG. FIGS. 7A to 7E are electric circuit diagrams showing the delay circuit and detection circuit in more detail, and are diagrams showing output waveforms of each part in the electric circuit shown in FIG. 6. 2... Focus detection device, 5... Delay circuit, 6...
Exclusive OR circuit (detection circuit), 20... Light emitting element (display member), 22... Sound generating element (display member), S ₁
... Status signal, S ₂ , S ₄ ... Delayed signal, S ₃ ... Focus display signal.

Claims (1)

[Claims] 1. A focus detection device that outputs different status signals at near and far distances with the in-focus point as a boundary; and a focus detection device that delays the status signal output from the focus detection device for a certain period of time. a delay circuit; a detection circuit to which the delayed signal outputted from the delay circuit and the above-mentioned state signal are input, and outputs a focus display signal based on a mismatch between the two signals; 1. A focus display device for a camera, comprising: a display member for displaying focus comprising a sounding element driven by a focus display signal.