JPH0365938A - Display device for camera - Google Patents

Abstract

PURPOSE:To obtain brightness in a superimposing display which is optimum for the brightness of an object by providing a display means which varies the brightness of a display element and specifying and setting the lighting time in modulating the luminance of the display element. CONSTITUTION:By selectively arranging a minute prism array 5a on a focusing plate 5, a display part such as the superimposing displays d1, d2 or d3 is allowed to brightly shine by the light source of an LED. In order to minutely and reasonably control the brightness of the superimposing display, on-time Tx for modulating the luminance is calculated based on formula I. In formula I, Ta means the maximum lighting time, (x) means the luminance of the object, L means the luminance of the object at the time when the lighting time Tx is the maximum one and gamma means a linearity constant. Thus, the comfortable superimposing display with high accuracy is accomplished.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device for controlling the brightness of so-called superimposed display, which is displayed overlaying a subject within the frame of a camera finder.

[Conventional technology]

Traditionally, information such as shutter speed and aperture value was displayed outside the frame screen in the viewfinder of a camera.
There was no selective display of what should be displayed within the frame screen, as in the case of autofocus distance measurement. Since the display device is outside the frame screen, the brightness control of the display outside the frame screen did not cause any visual problems even though it was quite rough.

[Problem that the invention is trying to solve]

However, in order to superimpose the display within the frame screen, the subject and display appear to overlap, so
It is necessary to display the image at a brightness that does not obscure the display from the brightness of the subject.

It is also a problem if the light is too bright and you feel uncomfortable when looking at the subject.

What is needed is a device that provides superimposed display brightness that is optimal for the brightness of the subject. The display brightness at which superimposed display can be visually determined to be appropriate for the brightness of the subject is surprisingly narrow, being only about 1 degree wide. We propose a superimpose control device that performs frequent control to fit within this range.

[Means to solve the problem]

In the present invention, in order to finely and rationally control the brightness of the superimposed display, the ON time of brightness modulation is calculated based on one simple formula, thereby achieving a highly accurate and comfortable superimposed display. I was able to make it happen.

〔Example〕

FIG. 1(a) is an explanatory diagram of the camera viewed from the side.

■ is the lens mount, 2 is the main mirror, 3 is the film surface,
4 is a prism for LED light projection, 5 is a focusing board, 6 is an information display device for displaying information outside the frame in the finder, 7 is a pentaprism, 8 is a photometric lens for the photometric sensor SPC, 9 is an eyepiece of the finder It's a lens.

The light that passes through the photographic lens (not shown) is rotated at 90° by the main mirror 2.
The light is deflected, reflected by the pentaprism 7, passes through the eyepiece 9, and reaches the human eye. Further, the light that has reached the matte surface of the focusing plate 5 is projected onto the photometric sensor SPC by the photometric lens 8. On the other hand, the light from the LED passes through the projection prism 4, is reflected by the main mirror 2, is bent vertically by the micro prism array in the display section of the focusing plate 5, passes through the pentaprism 7, passes through the eyepiece 9, and is directed to the eye. It will reach you.

By selectively arranging the micro prism array 5a on the focusing plate 5, display sections such as the superimposed displays dl, d2 and d3 in FIG. 2 can be brightly illuminated by the LED light source. Here, this is called superimposed display.

Since the superimposed display is displayed overlapping the subject within the viewfinder frame, the brightness must match the brightness of the subject visible in the viewfinder. It is also necessary to ensure that it does not occur.

In conventional displays, like the information display device 6, the actual display can be seen outside the frame, so it does not blend in with the subject, so it is sufficient to simply illuminate it appropriately. However, in superimpose, in order to track the brightness of the subject, it is necessary to change the brightness of the display within a dynamic range of about 20 stops, which is the photometric range of the camera.

Each area Zl-23 shown in Figure 2 is a photometric sensor SPC.
The photometric sensitivity distributions (photometric areas) are shown, and these include superimposed displays di to d3, each having a corresponding distribution.

FIG. 3 shows a circuit diagram for realizing this embodiment.

ill+! corresponding to areas Zl to Z3! light sensor 5pcs
There are I~5PC3, each with a photometric amplifier AMPI~A.
MP3 and compression diodes DII-DI3 are connected, thereby photoelectrically converted and logarithmically compressed voltage is transmitted to inputs INI-IN3 of multiplexer MPX.

Furthermore, the input INN~ selected by the 5ELECT terminal signal
Any one of IN3 is transmitted from OUT to the A/D converter, and can be read by the central processing unit CPU (hereinafter simply abbreviated as CPU). The internal bus BUS of the microcomputer stores the CPU and programs (RO
M, random access memory RAM as a work area for calculations, non-volatile memory EEFROM to write adjustment data, etc., general-purpose input/output capacitor (PIO), counter/
A timer TIMER is connected, the CPU executes according to the ROM program, and each ROMSRAM, EEPRO
M,PIO,TIMER.

Access A/D converter etc. On the other hand, the LED corresponding to the superimposed display di-d3 in FIG.
1 to LED3, each of which has three constant current sources I1
Wait for 1 to 1:3 (i corresponds to LED1-LED3),
Each constant current source is configured to be enabled when the output B+1 of the register REG is High, and disabled when the output is Low.

The photometric circuit will be explained with reference to FIG.

There is a capacitor CI in the compression diode Dll.

As mentioned above, the superimposed display needs to track its brightness to the brightness of the subject in order to make it easier to see with the naked eye, but the brightness of the subject handled by the camera can be up to 20 steps. Therefore, if brightness modulation is used to ensure a wide dynamic range, the problem shown in (a) will occur.

In other words, in brightness modulation, a large current that is visible even under high brightness is used, the light is turned on for a short time under low brightness, and du
By reducing ty, the apparent brightness can be suppressed. Since the photocurrent 15PCI of the output of the photometric sensor 5pci increases greatly when this LED is lit, there is sufficient charge to charge the capacitor CI, so that an equilibrium state is quickly reached. However, even if the lights are turned off, the photocurrent depends on the brightness of the subject! ! lit”CI
Since the charge in the capacitor C1 is discharged by , especially in the case of a low-luminance object, even at time t, it is still not far from equilibrium.

(b) shows a small current, long-time lighting drive that appears to be the same as the drive in (a) with a large current, short-time lighting. At this time, the photocurrent I spc+ does not increase by that much due to the LED lighting, so it takes time to charge the capacitor CI, and the potential difference between the voltage Vl when the LED is lit and when it is not lit is not that large, so at time t. can already reach equilibrium.

Therefore, in order to ensure the brightness of the LED that tracks the brightness of the subject under low brightness, it is advantageous to control the LED drive current. However, it is difficult to ensure a wide dynamic range using only current, and on the other hand, it is difficult to achieve 20 steps of brightness modulation using only brightness modulation.

In super-imposed mode, the photometric sensor measures the subject's light. Since the super-imposed display is located within the sensitivity distribution, the amount of light from the display increases, and if the display and photometry are performed at the same time, the photometry output will output an erroneous signal, so it is essential to do it in a time-sharing manner. .

FIG. 6 shows the time-sharing relationship between photometry and superimpose display in this embodiment. t=o-Ta is the maximum time of the display section. t = T b - T c is the photometry interval. Photometry takes into account the flicker of artificial lighting, so considering the power frequency of 50 Hz or 60 Hz, it is approximately 8.3
It is desirable that the time is from ms to 10 ms. However, on the other hand, in order to prevent flickering of the superimpose display, the overall cycle Tc is set at a frequency above 50 Hz, that is, 20
ms or less is desirable. Therefore T LEDON-MA
X = Ta is 20 m s - 10 m s = 1
Within 0 ms.

In addition, as described above, in order to control the brightness of the display with a wide dynamic range that tracks the brightness of the subject, the drive shown in (b) in Figure 4 is performed, so the waiting time T wail of t = Ta - Tb is essential. This T LEIX
The sum of IN-MAX and T wail is 20 m s −1
The maximum value is 0 m s = 10 m s.

That is, as shown in FIG. 6, the period T that prevents flickering of the artificial light source when the superimpose display is off
Me. ,. After that, the Tx indicator is lit on the display section to be displayed at a brightness corresponding to the corresponding photometry output, and then the photometry circuit stabilizes at a voltage corresponding to the brightness of the subject. After waiting the waiting time T wail, photometry is repeated again.

Furthermore, by performing the brightness modulation of the display at this time in a front-aligned manner, a stable waiting time longer than the waiting time T Wai1 can be provided. FIG. 5 shows a graph of the brightness of an object and the corresponding drive current and drive time for superimposed display.

The horizontal axis is a logarithmic axis and indicates the brightness of the subject on the focusing plate 5. The vertical axis shows the drive current and LED lighting time T for superimposed display when driving as shown in FIG. 6.

As shown in FIG. 5, when the subject is bright, it is driven with a large current like l1nel, and as the subject becomes dark, the drive current is changed stepwise from medium current to small current. Also,
For brightness modulation, T,=T, it is necessary to exponentially shorten the driving time as the light becomes darker.

Current and driving time T corresponding to points a to f, respectively.

is shown in Figure 7. The height direction in FIG. 7 is the current, and the ON length corresponds to Tx.

The feature of this graph is that in general, when the brightness of the subject is halved (-steps darker), the lighting time of the superimpose display should also be halved, but in Figure 5, x
T when =20, =TI, but T when x=19
Not x f-T a/2. This depends on the driving time curve that is perceptually required by the human eye. Also,
l 1nel and I! Even if the current ratio of 1ne2 is 8 times, the human eye perceives the same brightness.l 1nel
The ratio of the drive times of and j' 1ne2 is not 1/8. This is because the relationship between LED current and light amount is not necessarily linear.

The drive time T determined from the above features is Tx-T8× (j=1 to 3).

2t l ILI-x) Here, γI (j=1 to 3) is l 1nel to f, respectively.
These are adjustment variables for each current of 1ne3. γj is LE
Although it varies depending on D, it is preferably about 0.4 to 0.8.

In addition, Ll (j=1 to 3) is when the brightness of the subject corresponding to point a, point C, and point e is made darker than point a, respectively.
6 points and 1g point along 1nel, and l 1 at 0 point
Move to ne2. Point g and point 0 are points that visually appear to have the same brightness. Similarly, l 1ne2. l 1n
Move to e3.

In this way, Ll, L2. La and γ1. γ2.
Just by using γ3 adjustment variables, human sensation and LED
Appropriate superimpose driving becomes possible by eliminating factors such as variations in characteristics, constant current, and LED light projection.

Furthermore, by using both duty drive and stepwise constant current drive, it is possible to easily cover a wide dynamic range required for superimposition.

Next, explanation will be given according to the flowchart (algorithm) shown in FIG.

5TOI, the main routine handles only photometry, calculation, and display, but if it is time-equivalent, it can be realized by interrupt processing using a timer, and it is also possible to coexist with other programs. Please keep this in mind. This main routine includes the LE that should be lit from the outside.
D information input/output capo) Through PIO, array LED
(i) It is assumed that i=1 to 3 are manually operated. Alternatively, as information on which LED should be lit based on the output information of other concurrent programs (for example, an autofocus program), settings are made such that if LED (t)i = 1 to 3 is 1, it will be lit, and if it is 0, it will be turned off. It is assumed that In addition, in the manufacturing process, the adjustment variable γin LI
+J=”~3 has already been written in the EEPROM.

5TO2: CALL the photometry routine. The input variable is the number of photometry samplings N, and the output variable is the brightness AD at the focal plane of the subject in the sensitivity distribution of the three sensors.
(i) i=1 to 3. In the photometry routine, T m
In order to measure the average brightness at the time of easura, sampling is performed multiple times, and the photometric value AD (i) of each sensor is determined from the average value. Also, at this time, the superimpose display is off.

5TO3: CALL the brightness determination routine. As mentioned above, the superimposed display displays the object in the viewfinder frame, so it is not good if it is too bright or too dark. Therefore, as shown in Figure 2, the display section and
The photometric areas should be arranged accordingly. Therefore the LED
When lighting only I, it is necessary to determine the lighting brightness based on the photometric output of area zl, and this
, the same applies to LED3. However, if the LED
If more than one LED is turned on at the same time, and the brightness of each display differs due to the brightness of the corresponding subject, not only will control be complicated, but when you look at the viewfinder frame, the brightness of those LEDs will vary. You will notice the difference and feel uncomfortable.

When only one LED on the Super In-Bose is lit, the brightness of the display that should be lit for a given subject's brightness varies from person to person, and even if it is off by one degree, you won't notice a difference, but when two or more Humans are sensitive to differences in relative brightness when lights are on, and even the slightest difference can cause discomfort.

Therefore, L i g h t D E in step 3
In the F I N'E routine, when multiple lights are to be lit, the display is driven at the same brightness or almost the same brightness using the average value of the photometry output of the photometry area with the zone corresponding to the display to be turned on. The above problem is solved.

The input variables of this routine are the LEDs that indicate the LEDs to be lit (i) i = 1 to 3, and the photometric values AD of the three photometric sensors (i) i = 1 to 3° The output variables are the brightness to light the LEDs This is brightness information X on the focus board 5 for determining.

5TO4: Brightness information of the subject on the focus plane
As input, the current of the LED to be displayed is Current and d
Set the driving time width when driving UTY. The algorithm is basically the method shown in the graph of FIG.

5TO5: Display drive routine CAI, L. Input information is constant current value Current and duty driving time T8
, and an LED indicating the LED to be lit (i) i=1
~3.

5TO6: Wait for photometry to stabilize by waiting the Twait time. After this, the process returns to the photometry routine call of 5TO2.

Next, each subroutine will be explained.

5TII: Photometry routine, 5T12. First, since sampling photometry is performed to remove flicker from an artificial light source, the number of times sampling is performed is determined, and the sense T LOOP of each photometry is thereby determined. The photometry is averaged for each of the three sensors N times, so if the number of sensors is m, change 3 in the above formula to m, and fori of 5T17 = 1 +
03 should be set to fori=1+om.

5T13 to 5T15: Array SUM used temporally to calculate the average of three sensors N times (i) i=1 to
Clear 3.

5T18: To measure the i-th sensor, send the output to the select terminal of the multiplexer and select INi.

5T19: A/D converter converts the value to D
shall be.

5T20: SUM (i)=SUM (i) Repeat addition by ten.

5T21: Wait for Tt, oop obtained in 5T12.

5T16 - 5T23: Repeat s'ris - 5T21 in order and turn the whole thing N times, TOTALaXN
Perform sampling times. Therefore SUM (i)i=1
to 3, the AD value of the sensor corresponding to i is added N times.

8. Therefore, the N-time average photometric value of the sensor corresponding to i is each AD
(i) is input. That is, the brightness of the subject on the focusing plate 5 when the LED is turned off is included in AD (i) as a photometric value corresponding to each sensor.

5T27: Return to main routine 5T31: Light+DEFINE routine.

5T32 temporary variable S U M = b i t
= O.

5T33 to 5T37: The LED that should be lit is the LED
(i) = 1, and the LED that should not be lit is LED(i) = 0, so the LED that should be lit is
The number of D is counted using variable bits, and the photometric value AD(i) of the photometric sensor corresponding to the LED to be lit is added to obtain SUM.

5T38: When the LED to be lit is 0, bit=o, so in 5T39: "divisi or
5T40 to avoid byzeroJ errors
: JUMP to.

5T39: Photometry sensor 5 corresponding to the LED to be lit
T40. Return to main routine.

Sr11: Calculation routine.

5T52: Since γl to γ3 and Ll-L3 are stored in the EEFROM as adjustment data, these are read out.

5T53 to 5T60: In the graph of Figure 5, X is LIl
L2. The conditions for determining the relationship with L3 are as follows: j and T at that time are tabulated.

I will set it. For example, LEDI is connected to constant current source 2 (I!
1ne2), by setting B10 to High, the constant current source h2 becomes ONL, and the LEDl becomes 1ine2.
It is driven with a current corresponding to .

5T77: Wait for lighting time Tx.

5T78 to 5T82: By setting all B +1 = O, all LEDs including those turned on in 5T72 to 5T76 are turned off.

5T83. Wait for the time T, -T.

5T84: Return to the main routine Calculation results such as 0 or more are obtained from 5T53 to 5T60.

current=1 to 3 are l 1 of the graph in FIG. 5, respectively.
Corresponds to constant current of ne1 to ne3.

5T61: Return to main routine 0ST7
1: LED driving routine.

5T72 to 5T76: L corresponding to the LED that should be lit
While looking at the value of ED(i), set B++ in register REG.
Output 5TO6, 5T12, 5T21, 5T77.5T8
When performing step 3, the wait time should be set taking into account the delay caused by the execution time of each program, but
Here, for the sake of clarity, the program execution time is excluded from the calculations as it is negligibly short compared to the waiting time.

[Other Examples]

In the above embodiment, the on-time of brightness modulation for superimposed display is TX"" Ta X 2- y (L-m)
It is determined by calculating. However, in some cases, if the program area required for the calculation of 2-13L-〇 is too large, store calculation tables according to the above Tx formula in memory as multiple (x, Tx) tables in advance. By referring to the table, it is possible to obtain roughly the same effect as calculating the above-mentioned Tx formula.

Further, even in a general viewfinder display, by driving the display according to the above formula, it is possible to provide a more visually comfortable display brightness.

〔Effect of the invention〕

As explained above, by controlling the brightness of the superimposed display by modulating the brightness according to a simple formula, it is possible to provide a display that is visually comfortable and easy to distinguish, while also providing a display that is visually comfortable and easy to distinguish. By formulating display control for objects, process adjustments can be simplified,
Furthermore, reducing the number of adjustment variables has the effect of improving memory efficiency for storing adjustment data.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a camera as an embodiment of the present invention. FIG. 2 is an explanatory diagram showing an example of display on the finder. FIG. 3 is a schematic circuit configuration diagram of the camera of this embodiment. FIG. 4 is a diagram showing the photometry circuit and drive of this embodiment. FIG. 5 is a graph of the displayed drive current and drive time. FIG. 6 is an explanatory diagram showing the time-sharing relationship between display and photometry. FIG. 7 is an explanatory diagram showing the relationship between display-related current and driving time. Figure 8 is a flowchart. 5PCI~5PC3...Photometry sensor CPU...Central processing unit LEDI-LED3...LED (light emitting diode)
d1 to d3...Superimposed display Z1'=Z3
...Photometric sensitivity distribution (photometric area) C (L) Shaoku (b) Figure

Claims (1)

[Claims] (1) In a superimposed display that is superimposed on the subject image in the viewfinder, a brightness detection means for detecting the brightness of the subject; and in response to the subject brightness determined by the brightness detection means,
a display means for making the brightness of the display means variable; the lighting time T in the brightness modulation of the display element of the display means;
A camera display device characterized in that x is set as shown in the following equation. Tx=Ta×2^-^7^(^L^-^x^) Ta: Maximum lighting time, x: Subject brightness, L: Lighting time Subject brightness when Tx is the maximum lighting time γ: Linearity constant