预热
介绍
让相机预热并达到热平衡状态可以提高应用的整体精度和成功率。本文将解释 Zivid 相机预热的原因和方法。
为什么需要预热
Zivid 相机内部含有主动电子元件（例如投影仪），在使用过程中会产生热量。内部升温会导致这些元件在温度变化时发生机械形变。
这些机械变化会导致基本光学组件发生微小的位移，从而在计算点云中点的位置时影响三角测量精度。由于每个内部组件可能处于许多未知的可能温度状态，因此相机的3D标定在加热或冷却阶段会不太准确。我们称这种现象为*预热漂移*。
建议控制相机温度并留出足够时间让所有组件达到稳定温度（热平衡）。因此，Zivid 3D标定可以识别并准确预测相机的物理状态并生成正确的点云。
备注
Zivid 相机使用 Thermal Stabilization（热稳定功能） 来保持稳定的温度，并减少预热的需要。
温度变化 - 相机 vs. 环境
预热测试表明，在最快的捕获周期（实时模式）下，Zivid 相机的内部温度可能会临时以每分钟 1.5 °C 的速度变化（10 分钟内升高 15 °C）。对于更典型的捕获周期，例如每 5 秒捕获一次，内部温度变化速度会慢两到三倍（每分钟 0.5 - 1 °C）。
另一方面，气温变化最快可达0.03 °C/min（例如6小时内增加10 °C）。这比预热期间相机中的临时温度变化慢两个数量级。
Zivid 相机采用了浮动温度标定技术，能够补偿环境温度的变化，从而在推荐的温度范围内确保性能稳定。经过充分预热并正确使用的相机，在整个规定的环境温度范围内均能保持稳定的性能表现。
何时进行预热
建议在以下情况下预热相机：
对误差要求很严格的应用，例如：
对于小于5毫米/距相机1米距离的抓取应用。
准确度误差要求 < 0.5% 的检测应用。
达到中等捕获周期（快于每10秒捕获一次）的应用。
在现场标定之前。
在手眼标定之前。
在运行生产之前。
相机还未连接到电源时，例如安装相机后。
当相机已开机但在过去20分钟内未捕获点云时，例如早上启动生产单元时。
如何进行预热
对相机进行预热时，请以固定的捕获周期连续捕获点云 10 分钟。
连接
第一步是连接相机。
Zivid::Application zivid;
std::cout << "Connecting to camera" << std::endl;
auto camera = zivid.connectCamera();
var zivid = new Zivid.NET.Application();
Console.WriteLine("Connecting to camera");
var camera = zivid.ConnectCamera();
设定捕获周期和设置
在预热期间，捕获周期应尽可能与实际应用中的捕获周期相似（料箱拾取、拆垛等）。
如果部署的相机每5秒进行一次捕获，它应该在预热阶段以相同的间隔进行捕获。如果生产中的相机没有稳定的捕获周期，那么预热阶段的捕获周期应该在极值之间，例如，如果它在实际应用中每5到11秒捕获一次，则应该在预热时每8秒捕获一次。如果实际应用中捕获之间的间隔超过10秒，则无需预热相机。
预热期间使用的相机设置也应尽可能与实际应用中的设置相似（预先配置，从 YML 文件或捕获助手加载）
const auto warmupTime = std::chrono::minutes(10);
const auto captureCycle = std::chrono::seconds{ captureCycleSeconds };
const auto settings = loadOrDefaultSettings(settingsPath);
var warmupTime = TimeSpan.FromMinutes(10);
var captureCycle = opts.CaptureCycle.HasValue ? TimeSpan.FromSeconds(opts.CaptureCycle.Value) : TimeSpan.FromSeconds(5);
var settings = LoadOrDefaultSettings(opts.SettingsPath);
加载或建议设置
Zivid::Settings loadOrDefaultSettings(const std::string &settingsPath)
{
if(!settingsPath.empty())
{
std::cout << "Loading settings from file" << std::endl;
return Zivid::Settings(settingsPath);
}
std::cout << "Using default 3D settings" << std::endl;
auto settings = Zivid::Settings{ Zivid::Settings::Acquisitions{ Zivid::Settings::Acquisition{} } };
return settings;
static Zivid.NET.Settings LoadOrDefaultSettings(string settingsPath)
{
if (settingsPath != null)
{
Console.WriteLine("Loading settings from file");
return new Zivid.NET.Settings(settingsPath);
}
Console.WriteLine("Using default 3D settings");
var settings = new Zivid.NET.Settings
{
Acquisitions = { new Zivid.NET.Settings.Acquisition { } }
};
return settings;
}
def _load_or_default_settings(settings_path: str) -> zivid.Settings:
"""Load settings from YML file or use default settings.
Args:
settings_path: Path to the YML file that contains camera settings
Returns:
Camera Settings
"""
if settings_path:
print("Loading settings from file")
return zivid.Settings.load(Path(settings_path))
print("Using default 3D settings")
settings = zivid.Settings(acquisitions=[zivid.Settings.Acquisition()])
return settings
备注
这种预热方法利用投影仪作为加热元件，在稳定的捕获周期中对相机进行预热。投影仪开启时间与整个周期时间的比值称为占空比（duty cycle）。占空比不仅影响相机升温的速度，也决定了预热阶段结束后相机最终达到的稳态温度。
预热相机
要预热相机，请循环捕获3D点云10分钟，直到温度稳定。
std::cout << "Starting warm up for: " << warmupTime.count() << " minutes" << std::endl;
const auto beforeWarmup = SteadyClock::now();
while(SteadyClock::now() - beforeWarmup < warmupTime)
{
const auto beforeCapture = SteadyClock::now();
// Use the same capture method as you would use in production
// to get the most accurate results from warmup
camera.capture3D(settings);
const auto afterCapture = SteadyClock::now();
const auto captureTime = afterCapture - beforeCapture;
if(captureTime < captureCycle)
{
std::this_thread::sleep_for(captureCycle - captureTime);
}
else
{
std::cout << "Your capture time is longer than your desired capture cycle."
<< "Please increase the desired capture cycle." << std::endl;
}
const auto remainingTime = warmupTime - (SteadyClock::now() - beforeWarmup);
const auto remainingTimeMinutes = std::chrono::duration_cast<std::chrono::minutes>(remainingTime);
const auto remainingTimeSeconds =
std::chrono::duration_cast<std::chrono::seconds>(remainingTime - remainingTimeMinutes);
std::cout << "Remaining time: " << remainingTimeMinutes.count() << " minutes, "
<< remainingTimeSeconds.count() << " seconds." << std::endl;
}
std::cout << "Warm up completed" << std::endl;
DateTime beforeWarmup = DateTime.Now;
Console.WriteLine("Starting warm up for: {0} minutes", warmupTime.Minutes);
while (DateTime.Now.Subtract(beforeWarmup) < warmupTime)
{
var beforeCapture = DateTime.Now;
// Use the same capture method as you would use in production
// to get the most accurate results from warmup
using (camera.Capture3D(settings)) { }
var afterCapture = DateTime.Now;
var captureTime = afterCapture.Subtract(beforeCapture);
if (captureTime < captureCycle)
{
Thread.Sleep(captureCycle.Subtract(captureTime));
}
else
{
Console.WriteLine(
"Your capture time is longer than your desired capture cycle. Please increase the desired capture cycle.");
}
var remainingTime = warmupTime.Subtract(DateTime.Now.Subtract(beforeWarmup));
var remainingMinutes = Math.Floor(remainingTime.TotalMinutes);
var remainingSeconds = Math.Floor(remainingTime.TotalSeconds) % 60;
Console.WriteLine("Remaining time: {0} minutes, {1} seconds.", remainingMinutes, remainingSeconds);
}
Console.WriteLine("Warm up completed");
before_warmup = datetime.now()
print(f"Starting warmup for {warmup_time} minutes")
while (datetime.now() - before_warmup) < warmup_time:
before_capture = datetime.now()
# Use the same capture method as you would use in production
# to get the most accurate results from warmup
camera.capture_3d(settings)
after_capture = datetime.now()
duration = after_capture - before_capture
if duration.seconds <= capture_cycle.seconds:
sleep(capture_cycle.seconds - duration.seconds)
else:
print(
"Your capture time is longer than your desired capture cycle. \
Please increase the desired capture cycle."
)
remaining_time = warmup_time - (datetime.now() - before_warmup)
remaining_time_minutes = remaining_time.seconds // 60
remaining_time_seconds = remaining_time.seconds % 60
print(f"Remaining time: {remaining_time_minutes} minutes, {remaining_time_seconds} seconds.")
print("Warmup completed")
有关实现的示例，请参阅下面的完整预热代码示例。
/*
Short example of a basic way to warm up the camera with specified time and capture cycle.
For more information on warming up the camera, check out this tutorial:
https://support.zivid.com/en/latest/camera/academy/camera/warmup.html
*/
#include <Zivid/Zivid.h>
#include <clipp.h>
#include <chrono>
#include <iostream>
#include <thread>
using SteadyClock = std::chrono::steady_clock;
using Duration = std::chrono::nanoseconds;
namespace
{
Zivid::Settings loadOrDefaultSettings(const std::string &settingsPath)
{
if(!settingsPath.empty())
{
std::cout << "Loading settings from file" << std::endl;
return Zivid::Settings(settingsPath);
}
std::cout << "Using default 3D settings" << std::endl;
auto settings = Zivid::Settings{ Zivid::Settings::Acquisitions{ Zivid::Settings::Acquisition{} } };
return settings;
}
} // namespace
int main(int argc, char **argv)
{
try
{
std::string settingsPath;
size_t captureCycleSeconds = 5;
auto settingsOption = clipp::option("--settings-path")
& clipp::value("Path to the YML file that contains camera settings", settingsPath);
auto captureCycleOption =
clipp::option("--capture-cycle") & clipp::value("Capture cycle in seconds", captureCycleSeconds);
auto cli = (settingsOption, captureCycleOption);
if(!parse(argc, argv, cli))
{
auto fmt = clipp::doc_formatting{}.alternatives_min_split_size(1).surround_labels("\"", "\"");
std::cout << clipp::usage_lines(cli, "Warmup", fmt) << std::endl;
throw std::runtime_error{ "Invalid usage" };
}
Zivid::Application zivid;
std::cout << "Connecting to camera" << std::endl;
auto camera = zivid.connectCamera();
const auto warmupTime = std::chrono::minutes(10);
const auto captureCycle = std::chrono::seconds{ captureCycleSeconds };
const auto settings = loadOrDefaultSettings(settingsPath);
std::cout << "Starting warm up for: " << warmupTime.count() << " minutes" << std::endl;
const auto beforeWarmup = SteadyClock::now();
while(SteadyClock::now() - beforeWarmup < warmupTime)
{
const auto beforeCapture = SteadyClock::now();
// Use the same capture method as you would use in production
// to get the most accurate results from warmup
camera.capture3D(settings);
const auto afterCapture = SteadyClock::now();
const auto captureTime = afterCapture - beforeCapture;
if(captureTime < captureCycle)
{
std::this_thread::sleep_for(captureCycle - captureTime);
}
else
{
std::cout << "Your capture time is longer than your desired capture cycle."
<< "Please increase the desired capture cycle." << std::endl;
}
const auto remainingTime = warmupTime - (SteadyClock::now() - beforeWarmup);
const auto remainingTimeMinutes = std::chrono::duration_cast<std::chrono::minutes>(remainingTime);
const auto remainingTimeSeconds =
std::chrono::duration_cast<std::chrono::seconds>(remainingTime - remainingTimeMinutes);
std::cout << "Remaining time: " << remainingTimeMinutes.count() << " minutes, "
<< remainingTimeSeconds.count() << " seconds." << std::endl;
}
std::cout << "Warm up completed" << std::endl;
}
catch(const std::exception &e)
{
std::cerr << "Error: " << Zivid::toString(e) << std::endl;
std::cout << "Press enter to exit." << std::endl;
std::cin.get();
return EXIT_FAILURE;
}
return EXIT_SUCCESS;
}
}
catch (Exception ex)
{
Console.WriteLine("Error: " + ex.ToString());
return 1;
}
return 0;
}
static Zivid.NET.Settings LoadOrDefaultSettings(string settingsPath)
{
if (settingsPath != null)
{
Console.WriteLine("Loading settings from file");
return new Zivid.NET.Settings(settingsPath);
}
Console.WriteLine("Using default 3D settings");
var settings = new Zivid.NET.Settings
{
Acquisitions = { new Zivid.NET.Settings.Acquisition { } }
};
return settings;
}
/*
Short example of a basic way to warm up the camera with specified time and capture cycle.
For more information on warming up the camera, check out this tutorial:
https://support.zivid.com/en/latest/camera/academy/camera/warmup.html
*/
using CommandLine;
using System;
using System.Runtime.InteropServices;
using System.Threading;
using Duration = Zivid.NET.Duration;
class Program
{
public class Options
{
[Option('s', "settings-path", Required = false, HelpText = "Path to the YML file that contains camera settings.")]
public string SettingsPath { get; set; }
[Option('c', "capture-cycle", Required = false, HelpText = "Capture cycle in seconds.")]
public int? CaptureCycle { get; set; }
}
static int Main(string[] args)
{
return Parser.Default.ParseArguments<Options>(args)
.MapResult(
(Options opts) => RunWarmupWithOptionsAndReturnExitCode(opts),
errs => 1);
}
static int RunWarmupWithOptionsAndReturnExitCode(Options opts)
{
try
{
var zivid = new Zivid.NET.Application();
Console.WriteLine("Connecting to camera");
var camera = zivid.ConnectCamera();
var warmupTime = TimeSpan.FromMinutes(10);
var captureCycle = opts.CaptureCycle.HasValue ? TimeSpan.FromSeconds(opts.CaptureCycle.Value) : TimeSpan.FromSeconds(5);
var settings = LoadOrDefaultSettings(opts.SettingsPath);
DateTime beforeWarmup = DateTime.Now;
Console.WriteLine("Starting warm up for: {0} minutes", warmupTime.Minutes);
while (DateTime.Now.Subtract(beforeWarmup) < warmupTime)
{
var beforeCapture = DateTime.Now;
// Use the same capture method as you would use in production
// to get the most accurate results from warmup
using (camera.Capture3D(settings)) { }
var afterCapture = DateTime.Now;
var captureTime = afterCapture.Subtract(beforeCapture);
if (captureTime < captureCycle)
{
Thread.Sleep(captureCycle.Subtract(captureTime));
}
else
{
Console.WriteLine(
"Your capture time is longer than your desired capture cycle. Please increase the desired capture cycle.");
}
var remainingTime = warmupTime.Subtract(DateTime.Now.Subtract(beforeWarmup));
var remainingMinutes = Math.Floor(remainingTime.TotalMinutes);
var remainingSeconds = Math.Floor(remainingTime.TotalSeconds) % 60;
Console.WriteLine("Remaining time: {0} minutes, {1} seconds.", remainingMinutes, remainingSeconds);
}
Console.WriteLine("Warm up completed");
}
"""
Short example of a basic way to warm up the camera with specified time and capture cycle.
For more information on warming up the camera, check out this tutorial:
https://support.zivid.com/en/latest/camera/academy/camera/warmup.html
"""
import argparse
from datetime import datetime, timedelta
from pathlib import Path
from time import sleep
import zivid
def _options() -> argparse.Namespace:
"""Function to read user arguments.
Returns:
Arguments from user
"""
parser = argparse.ArgumentParser(description=__doc__)
parser.add_argument(
"--settings-path",
required=False,
help="Path to the YML file that contains camera settings",
)
parser.add_argument(
"--capture-cycle",
required=False,
type=float,
default=5.0,
help="Capture cycle in seconds",
)
return parser.parse_args()
def _load_or_default_settings(settings_path: str) -> zivid.Settings:
"""Load settings from YML file or use default settings.
Args:
settings_path: Path to the YML file that contains camera settings
Returns:
Camera Settings
"""
if settings_path:
print("Loading settings from file")
return zivid.Settings.load(Path(settings_path))
print("Using default 3D settings")
settings = zivid.Settings(acquisitions=[zivid.Settings.Acquisition()])
return settings
def _main() -> None:
user_options = _options()
app = zivid.Application()
print("Connecting to camera")
camera = app.connect_camera()
warmup_time = timedelta(minutes=10)
capture_cycle = timedelta(seconds=user_options.capture_cycle)
settings = _load_or_default_settings(user_options.settings_path)
before_warmup = datetime.now()
print(f"Starting warmup for {warmup_time} minutes")
while (datetime.now() - before_warmup) < warmup_time:
before_capture = datetime.now()
# Use the same capture method as you would use in production
# to get the most accurate results from warmup
camera.capture_3d(settings)
after_capture = datetime.now()
duration = after_capture - before_capture
if duration.seconds <= capture_cycle.seconds:
sleep(capture_cycle.seconds - duration.seconds)
else:
print(
"Your capture time is longer than your desired capture cycle. \
Please increase the desired capture cycle."
)
remaining_time = warmup_time - (datetime.now() - before_warmup)
remaining_time_minutes = remaining_time.seconds // 60
remaining_time_seconds = remaining_time.seconds % 60
print(f"Remaining time: {remaining_time_minutes} minutes, {remaining_time_seconds} seconds.")
print("Warmup completed")
if __name__ == "__main__":
_main()
如需预热相机，您可以运行我们的代码示例，同时需要提供循环时间和相机参数设置文件的路径。
示例: warmup.py
python /path/to/warmup.py --settings-path /path/to/settings.yml --capture-cycle 6.0